clang format

Add optional "ident" argument to systemd sink constructor

.gitignore

@@ -1,4 +1,6 @@
 # Auto generated files
+[Dd]ebug/
+[Rr]elease/
 build/*
 *.slo
 *.lo
@@ -55,6 +57,7 @@ example/*
 
 # generated files
 generated
+version.rc
 
 # Cmake
 CMakeCache.txt
@@ -67,6 +70,8 @@ install_manifest.txt
 /tests/tests.VC.db
 /tests/tests
 /tests/logs/*
+spdlogConfig.cmake
+spdlogConfigVersion.cmake
 
 # idea
 .idea/
@@ -81,3 +86,7 @@ cmake-build-*/
 *.tcl
 *.user
 *.sln
+
+# macos
+*.DS_store
+*.xcodeproj/

.travis.yml

@@ -5,11 +5,11 @@
 sudo: required
 language: cpp
 
-# gcc t
-addons: &gcc48
+# gcc 4.9
+addons: &gcc49
   apt:
     packages:
-      - g++-4.8
+      - g++-4.9
     sources:
       - ubuntu-toolchain-r-test
 
@@ -29,6 +29,14 @@ addons: &gcc9
       - g++-9
     sources:
       - ubuntu-toolchain-r-test
+      
+# gcc 11.0
+addons: &gcc11
+  apt:
+    packages:
+      - g++-11
+    sources:
+      - ubuntu-toolchain-r-test
 
 
 # Clang 3.5
@@ -61,24 +69,33 @@ addons: &clang12
       - sourceline: "deb http://apt.llvm.org/bionic/ llvm-toolchain-bionic-12 main"
         key_url: "https://apt.llvm.org/llvm-snapshot.gpg.key"        
 
-
+env:
+  global:
+    - BUILD_EXAMPLE='ON'
+    
 matrix:
   include:
-    # Test gcc-4.8: C++11, Build=Release
-    - env: GCC_VERSION=4.8 BUILD_TYPE=Release CPP=11
+    # Test gcc-4.9: C++11, Build=Release
+    - env: GCC_VERSION=4.9 BUILD_TYPE=Release CPP=11 BUILD_EXAMPLE='OFF'
       os: linux
-      addons: *gcc48
+      addons: *gcc49
       
     # Test gcc-7: C++11, Build=Release
     - env: GCC_VERSION=7 BUILD_TYPE=Release CPP=11
       os: linux
       addons: *gcc7
       
-     # Test gcc-9: C++17, Build=Release
+    # Test gcc-9: C++17, Build=Release
     - env: GCC_VERSION=9 BUILD_TYPE=Release CPP=17
       os: linux
       addons: *gcc9
 
+    # Test gcc-11.0: C++20, Build=Debug
+    - env: GCC_VERSION=11 BUILD_TYPE=Debug CPP=20 ASAN=Off
+      os: linux
+      dist: bionic
+      addons: *gcc11
+      
     # Test clang-3.5: C++11, Build=Release
     - env: CLANG_VERSION=3.5 BUILD_TYPE=Release CPP=11
       os: linux
@@ -106,8 +123,8 @@ matrix:
       os: linux
       dist: bionic
       addons: *clang12
+          
                         
-
 before_script:
   - if [ -n "$GCC_VERSION" ]; then export CXX="g++-${GCC_VERSION}" CC="gcc-${GCC_VERSION}"; fi
   - if [ -n "$CLANG_VERSION" ]; then export CXX="clang++-${CLANG_VERSION}" CC="clang-${CLANG_VERSION}"; fi
@@ -125,8 +142,8 @@ script:
       --warn-uninitialized \
       -DCMAKE_BUILD_TYPE=$BUILD_TYPE \
       -DCMAKE_CXX_STANDARD=$CPP \
-      -DSPDLOG_BUILD_EXAMPLE=ON \
-      -DSPDLOG_BUILD_EXAMPLE_HO=ON \
+      -DSPDLOG_BUILD_EXAMPLE=$BUILD_EXAMPLE \
+      -DSPDLOG_BUILD_EXAMPLE_HO=$BUILD_EXAMPLE \
       -DSPDLOG_BUILD_WARNINGS=ON \
       -DSPDLOG_BUILD_BENCH=OFF \
       -DSPDLOG_BUILD_TESTS=ON \

CMakeLists.txt

@@ -1,6 +1,6 @@
 # Copyright(c) 2019 spdlog authors Distributed under the MIT License (http://opensource.org/licenses/MIT)
 
-cmake_minimum_required(VERSION 3.10)
+cmake_minimum_required(VERSION 3.10...3.21)
 
 # ---------------------------------------------------------------------------------------
 # Start spdlog project
@@ -15,13 +15,6 @@ message(STATUS "Build spdlog: ${SPDLOG_VERSION}")
 
 include(GNUInstallDirs)
 
-# ---------------------------------------------------------------------------------------
-# Set CMake policies to support later version behaviour
-# ---------------------------------------------------------------------------------------
-if(POLICY CMP0077)
-    cmake_policy(SET CMP0077 NEW) # option() honors variables already set
-endif()
-
 # ---------------------------------------------------------------------------------------
 # Set default build to release
 # ---------------------------------------------------------------------------------------
@@ -87,6 +80,7 @@ option(SPDLOG_BUILD_WARNINGS "Enable compiler warnings" OFF)
 
 # install options
 option(SPDLOG_INSTALL "Generate the install target" ${SPDLOG_MASTER_PROJECT})
+option(SPDLOG_USE_STD_FORMAT "Use std::format instead of fmt library. No compile-time format string checking." OFF)
 option(SPDLOG_FMT_EXTERNAL "Use external fmt library instead of bundled" OFF)
 option(SPDLOG_FMT_EXTERNAL_HO "Use external fmt header-only library instead of bundled" OFF)
 option(SPDLOG_NO_EXCEPTIONS "Compile with -fno-exceptions. Call abort() on any spdlog exceptions" OFF)
@@ -95,6 +89,14 @@ if(SPDLOG_FMT_EXTERNAL AND SPDLOG_FMT_EXTERNAL_HO)
     message(FATAL_ERROR "SPDLOG_FMT_EXTERNAL and SPDLOG_FMT_EXTERNAL_HO are mutually exclusive")
 endif()
 
+if(SPDLOG_USE_STD_FORMAT AND SPDLOG_FMT_EXTERNAL_HO)
+    message(FATAL_ERROR "SPDLOG_USE_STD_FORMAT and SPDLOG_FMT_EXTERNAL_HO are mutually exclusive")
+endif()
+
+if(SPDLOG_USE_STD_FORMAT AND SPDLOG_FMT_EXTERNAL)
+    message(FATAL_ERROR "SPDLOG_USE_STD_FORMAT and SPDLOG_FMT_EXTERNAL are mutually exclusive")
+endif()
+
 # misc tweakme options
 if(WIN32)
     option(SPDLOG_WCHAR_SUPPORT "Support wchar api" OFF)
@@ -137,7 +139,7 @@ message(STATUS "Build type: " ${CMAKE_BUILD_TYPE})
 # ---------------------------------------------------------------------------------------
 set(SPDLOG_SRCS src/spdlog.cpp src/stdout_sinks.cpp src/color_sinks.cpp src/file_sinks.cpp src/async.cpp src/cfg.cpp)
 
-if(NOT SPDLOG_FMT_EXTERNAL AND NOT SPDLOG_FMT_EXTERNAL_HO)
+if(NOT SPDLOG_USE_STD_FORMAT AND NOT SPDLOG_FMT_EXTERNAL AND NOT SPDLOG_FMT_EXTERNAL_HO)
     list(APPEND SPDLOG_SRCS src/fmt.cpp)
 endif()
 
@@ -152,7 +154,7 @@ if(SPDLOG_BUILD_SHARED OR BUILD_SHARED_LIBS)
         target_compile_options(spdlog PUBLIC $<$<AND:$<CXX_COMPILER_ID:MSVC>,$<NOT:$<COMPILE_LANGUAGE:CUDA>>>:/wd4251
                                              /wd4275>)
     endif()
-    if(NOT SPDLOG_FMT_EXTERNAL AND NOT SPDLOG_FMT_EXTERNAL_HO)
+    if(NOT SPDLOG_USE_STD_FORMAT AND NOT SPDLOG_FMT_EXTERNAL AND NOT SPDLOG_FMT_EXTERNAL_HO)
         target_compile_definitions(spdlog PRIVATE FMT_EXPORT PUBLIC FMT_SHARED)
     endif()
 else()
@@ -229,7 +231,8 @@ foreach(
     SPDLOG_NO_THREAD_ID
     SPDLOG_NO_TLS
     SPDLOG_NO_ATOMIC_LEVELS
-    SPDLOG_DISABLE_DEFAULT_LOGGER)
+    SPDLOG_DISABLE_DEFAULT_LOGGER
+    SPDLOG_USE_STD_FORMAT)
     if(${SPDLOG_OPTION})
         target_compile_definitions(spdlog PUBLIC ${SPDLOG_OPTION})
         target_compile_definitions(spdlog_header_only INTERFACE ${SPDLOG_OPTION})
@@ -287,7 +290,7 @@ if(SPDLOG_INSTALL)
         ARCHIVE DESTINATION ${CMAKE_INSTALL_LIBDIR}
         RUNTIME DESTINATION ${CMAKE_INSTALL_BINDIR})
 
-    if(NOT SPDLOG_FMT_EXTERNAL AND NOT SPDLOG_FMT_EXTERNAL_HO)
+    if(NOT SPDLOG_USE_STD_FORMAT AND NOT SPDLOG_FMT_EXTERNAL AND NOT SPDLOG_FMT_EXTERNAL_HO)
         install(DIRECTORY include/${PROJECT_NAME}/fmt/bundled/
                 DESTINATION "${CMAKE_INSTALL_INCLUDEDIR}/${PROJECT_NAME}/fmt/bundled/")
     endif()
@@ -307,7 +310,8 @@ if(SPDLOG_INSTALL)
     install(EXPORT spdlog DESTINATION ${export_dest_dir} NAMESPACE spdlog:: FILE ${config_targets_file})
 
     include(CMakePackageConfigHelpers)
-    configure_file("${project_config_in}" "${project_config_out}" @ONLY)
+    configure_package_config_file("${project_config_in}" "${project_config_out}"
+        INSTALL_DESTINATION ${export_dest_dir})
 
     write_basic_package_version_file("${version_config_file}" COMPATIBILITY SameMajorVersion)
     install(FILES "${project_config_out}" "${version_config_file}" DESTINATION "${export_dest_dir}")

README.md

@@ -1,10 +1,10 @@
 # spdlog
 
-Very fast, header-only/compiled, C++ logging library. [![Build Status](https://travis-ci.com/gabime/spdlog.svg?branch=v1.x)](https://travis-ci.com/gabime/spdlog)  [![Build status](https://ci.appveyor.com/api/projects/status/d2jnxclg20vd0o50?svg=true)](https://ci.appveyor.com/project/gabime/spdlog) [![Release](https://img.shields.io/github/release/gabime/spdlog.svg)](https://github.com/gabime/spdlog/releases/latest)
+Very fast, header-only/compiled, C++ logging library. [![Build Status](https://app.travis-ci.com/gabime/spdlog.svg?branch=v1.x)](https://app.travis-ci.com/gabime/spdlog)  [![Build status](https://ci.appveyor.com/api/projects/status/d2jnxclg20vd0o50?svg=true&branch=v1.x)](https://ci.appveyor.com/project/gabime/spdlog) [![Release](https://img.shields.io/github/release/gabime/spdlog.svg)](https://github.com/gabime/spdlog/releases/latest)
 
 ## Install 
 #### Header only version
-Copy the source [folder](https://github.com/gabime/spdlog/tree/v1.x/include/spdlog) to your build tree and use a C++11 compiler.
+Copy the include [folder](https://github.com/gabime/spdlog/tree/v1.x/include/spdlog) to your build tree and use a C++11 compiler.
 
 #### Static lib version (recommended - much faster compile times)
 ```console
@@ -22,9 +22,10 @@ $ cmake .. && make -j
  * Android
 
 ## Package managers:
+* Debian: `sudo apt install libspdlog-dev`
 * Homebrew: `brew install spdlog`
 * MacPorts: `sudo port install spdlog`
-* FreeBSD:  `cd /usr/ports/devel/spdlog/ && make install clean`
+* FreeBSD:  `pkg install spdlog`
 * Fedora: `dnf install spdlog`
 * Gentoo: `emerge dev-libs/spdlog`
 * Arch Linux: `pacman -S spdlog`
@@ -34,7 +35,6 @@ $ cmake .. && make -j
 * build2: ```depends: spdlog ^1.8.2```
 
 
-
 ## Features
 * Very fast (see [benchmarks](#benchmarks) below).
 * Headers only or compiled
@@ -144,7 +144,7 @@ void daily_example()
 #### Backtrace support
 ```c++
 // Debug messages can be stored in a ring buffer instead of being logged immediately.
-// This is useful in order to display debug logs only when really nededed (e.g. when error happens).
+// This is useful in order to display debug logs only when really needed (e.g. when error happens).
 // When needed, call dump_backtrace() to see them.
 
 spdlog::enable_backtrace(32); // Store the latest 32 messages in a buffer. Older messages will be dropped.
@@ -373,6 +373,35 @@ $ export SPDLOG_LEVEL=info,mylogger=trace
 $ ./example
 ```
 
+
+---
+#### Log file open/close event handlers
+```c++
+// You can get callbacks from spdlog before/after log file has been opened or closed. 
+// This is useful for cleanup procedures or for adding someting the start/end of the log files.
+void file_events_example()
+{
+    // pass the spdlog::file_event_handlers to file sinks for open/close log file notifications
+    spdlog::file_event_handlers handlers;
+    handlers.before_open = [](spdlog::filename_t filename) { spdlog::info("Before opening {}", filename); };
+    handlers.after_open = [](spdlog::filename_t filename, std::FILE *fstream) { fputs("After opening\n", fstream); };
+    handlers.before_close = [](spdlog::filename_t filename, std::FILE *fstream) { fputs("Before closing\n", fstream); };
+    handlers.after_close = [](spdlog::filename_t filename) { spdlog::info("After closing {}", filename); };
+    auto my_logger = spdlog::basic_logger_st("some_logger", "logs/events-sample.txt", true, handlers);        
+}
+```
+
+---
+#### Replace the Default Logger
+```c++
+void replace_default_logger_example()
+{
+    auto new_logger = spdlog::basic_logger_mt("new_default_logger", "logs/new-default-log.txt", true);
+    spdlog::set_default_logger(new_logger);
+    spdlog::info("new logger log message");
+}
+```
+
 ---
 ## Benchmarks
 

appveyor.yml

@@ -8,55 +8,91 @@ environment:
       WCHAR: 'OFF'
       WCHAR_FILES: 'OFF'
       BUILD_EXAMPLE: 'ON'
+      USE_STD_FORMAT: 'OFF'
+      CXX_STANDARD: 11
     - GENERATOR: '"Visual Studio 14 2015"'
       BUILD_TYPE: Release
       BUILD_SHARED: 'OFF'
       WCHAR: 'ON'
       WCHAR_FILES: 'OFF'
       BUILD_EXAMPLE: 'ON'
+      USE_STD_FORMAT: 'OFF'
+      CXX_STANDARD: 11
     - GENERATOR: '"Visual Studio 14 2015 Win64"'
       BUILD_TYPE: Debug
       BUILD_SHARED: 'OFF'
       WCHAR: 'ON'
       WCHAR_FILES: 'OFF'
       BUILD_EXAMPLE: 'ON'
+      USE_STD_FORMAT: 'OFF'
+      CXX_STANDARD: 11
     - GENERATOR: '"Visual Studio 14 2015 Win64"'
       BUILD_TYPE: Release
       BUILD_SHARED: 'OFF'
       WCHAR: 'ON'
       WCHAR_FILES: 'OFF'
       BUILD_EXAMPLE: 'ON'
+      USE_STD_FORMAT: 'OFF'
+      CXX_STANDARD: 11
     - GENERATOR: '"Visual Studio 15 2017 Win64"'
       BUILD_TYPE: Debug
       BUILD_SHARED: 'OFF'
       WCHAR: 'ON'
       WCHAR_FILES: 'OFF'
       BUILD_EXAMPLE: 'ON'
+      USE_STD_FORMAT: 'OFF'
+      CXX_STANDARD: 11
     - GENERATOR: '"Visual Studio 15 2017 Win64"'
       BUILD_TYPE: Release
       BUILD_SHARED: 'OFF'
       WCHAR: 'OFF'
       WCHAR_FILES: 'OFF'
       BUILD_EXAMPLE: 'ON'
+      USE_STD_FORMAT: 'OFF'
+      CXX_STANDARD: 11
     - GENERATOR: '"Visual Studio 15 2017 Win64"'
       BUILD_TYPE: Release
       BUILD_SHARED: 'ON'
       WCHAR: 'OFF'
       WCHAR_FILES: 'OFF'
       BUILD_EXAMPLE: 'ON'
+      USE_STD_FORMAT: 'OFF'
+      CXX_STANDARD: 11
     - GENERATOR: '"Visual Studio 15 2017 Win64"'
       BUILD_TYPE: Release
       BUILD_SHARED: 'ON'
       WCHAR: 'ON'
       WCHAR_FILES: 'ON'
       BUILD_EXAMPLE: 'OFF'
+      USE_STD_FORMAT: 'OFF'
+      CXX_STANDARD: 11
     - GENERATOR: '"Visual Studio 16 2019" -A x64'
       BUILD_TYPE: Release
       BUILD_SHARED: 'ON'
       WCHAR: 'OFF'
       WCHAR_FILES: 'OFF'
       BUILD_EXAMPLE: 'OFF'
+      USE_STD_FORMAT: 'OFF'
+      CXX_STANDARD: 17
       APPVEYOR_BUILD_WORKER_IMAGE: Visual Studio 2019
+    - GENERATOR: '"Visual Studio 17 2022" -A x64'
+      BUILD_TYPE: Release
+      BUILD_SHARED: 'ON'
+      WCHAR: 'OFF'
+      WCHAR_FILES: 'OFF'
+      BUILD_EXAMPLE: 'OFF'
+      USE_STD_FORMAT: 'ON'
+      CXX_STANDARD: 23 # std::format is only available with /std:c++latest at the moment.
+      APPVEYOR_BUILD_WORKER_IMAGE: Visual Studio 2022
+    - GENERATOR: '"Visual Studio 17 2022" -A x64'
+      BUILD_TYPE: Release
+      BUILD_SHARED: 'ON'
+      WCHAR: 'ON'
+      WCHAR_FILES: 'ON'
+      BUILD_EXAMPLE: 'OFF'
+      USE_STD_FORMAT: 'ON'
+      CXX_STANDARD: 23 # std::format is only available with /std:c++latest at the moment.
+      APPVEYOR_BUILD_WORKER_IMAGE: Visual Studio 2022
 build_script:
   - cmd: >-
       set
@@ -67,7 +103,7 @@ build_script:
 
       set PATH=%PATH%;C:\Program Files\Git\usr\bin
 
-      cmake -G %GENERATOR% -D CMAKE_BUILD_TYPE=%BUILD_TYPE% -D BUILD_SHARED_LIBS=%BUILD_SHARED% -D SPDLOG_WCHAR_SUPPORT=%WCHAR% -D SPDLOG_WCHAR_FILENAMES=%WCHAR_FILES% -D SPDLOG_BUILD_EXAMPLE=%BUILD_EXAMPLE% -D SPDLOG_BUILD_EXAMPLE_HO=%BUILD_EXAMPLE% -D SPDLOG_BUILD_TESTS=ON -D SPDLOG_BUILD_TESTS_HO=OFF -D SPDLOG_BUILD_WARNINGS=ON ..
+      cmake -G %GENERATOR% -D CMAKE_BUILD_TYPE=%BUILD_TYPE% -D BUILD_SHARED_LIBS=%BUILD_SHARED% -D SPDLOG_WCHAR_SUPPORT=%WCHAR% -D SPDLOG_WCHAR_FILENAMES=%WCHAR_FILES% -D SPDLOG_BUILD_EXAMPLE=%BUILD_EXAMPLE% -D SPDLOG_BUILD_EXAMPLE_HO=%BUILD_EXAMPLE% -D SPDLOG_BUILD_TESTS=ON -D SPDLOG_BUILD_TESTS_HO=OFF -D SPDLOG_BUILD_WARNINGS=ON -D SPDLOG_USE_STD_FORMAT=%USE_STD_FORMAT% -D CMAKE_CXX_STANDARD=%CXX_STANDARD% ..
 
       cmake --build . --config %BUILD_TYPE%
 

bench/CMakeLists.txt

@@ -16,10 +16,11 @@ if(NOT benchmark_FOUND)
         # User can fetch googlebenchmark
         message(STATUS "Downloading GoogleBenchmark")
         include(FetchContent)
-        set(BENCHMARK_ENABLE_GTEST_TESTS OFF CACHE INTERNAL "")
-        # Do not build and run googlebenchmark tests
-        FetchContent_Declare(googlebenchmark GIT_REPOSITORY https://github.com/google/benchmark.git GIT_TAG v1.5.2)
 
+        # disable tests  
+        set(BENCHMARK_ENABLE_TESTING OFF CACHE INTERNAL "")        
+        # Do not build and run googlebenchmark tests
+        FetchContent_Declare(googlebenchmark GIT_REPOSITORY https://github.com/google/benchmark.git GIT_TAG v1.6.0)
         FetchContent_MakeAvailable(googlebenchmark)
     else()
         message(FATAL_ERROR "GoogleBenchmark is missing. Use CMake >= 3.11 or download it")

bench/async_bench.cpp

@@ -10,7 +10,9 @@
 #include "spdlog/async.h"
 #include "spdlog/sinks/basic_file_sink.h"
 
-#ifdef SPDLOG_FMT_EXTERNAL
+#if defined(SPDLOG_USE_STD_FORMAT)
+#    include <format>
+#elif defined(SPDLOG_FMT_EXTERNAL)
 #    include <fmt/format.h>
 #else
 #    include "spdlog/fmt/bundled/format.h"
@@ -160,7 +162,7 @@ void thread_fun(std::shared_ptr<spdlog::logger> logger, int howmany)
 void bench_mt(int howmany, std::shared_ptr<spdlog::logger> logger, int thread_count)
 {
     using std::chrono::high_resolution_clock;
-    vector<thread> threads;
+    vector<std::thread> threads;
     auto start = high_resolution_clock::now();
 
     int msgs_per_thread = howmany / thread_count;

bench/bench.cpp

@@ -12,7 +12,9 @@
 #include "spdlog/sinks/null_sink.h"
 #include "spdlog/sinks/rotating_file_sink.h"
 
-#ifdef SPDLOG_FMT_EXTERNAL
+#if defined(SPDLOG_USE_STD_FORMAT)
+#    include <format>
+#elif defined(SPDLOG_FMT_EXTERNAL)
 #    include <fmt/locale.h>
 #else
 #    include "spdlog/fmt/bundled/format.h"
@@ -38,7 +40,7 @@ static const int max_threads = 1000;
 void bench_threaded_logging(size_t threads, int iters)
 {
     spdlog::info("**************************************************************");
-    spdlog::info(fmt::format(std::locale("en_US.UTF-8"), "Multi threaded: {:L} threads, {:L} messages", threads, iters));
+    spdlog::info(spdlog::fmt_lib::format(std::locale("en_US.UTF-8"), "Multi threaded: {:L} threads, {:L} messages", threads, iters));
     spdlog::info("**************************************************************");
 
     auto basic_mt = spdlog::basic_logger_mt("basic_mt", "logs/basic_mt.log", true);
@@ -74,7 +76,7 @@ void bench_threaded_logging(size_t threads, int iters)
 void bench_single_threaded(int iters)
 {
     spdlog::info("**************************************************************");
-    spdlog::info(fmt::format(std::locale("en_US.UTF-8"), "Single threaded: {} messages", iters));
+    spdlog::info(spdlog::fmt_lib::format(std::locale("en_US.UTF-8"), "Single threaded: {} messages", iters));
     spdlog::info("**************************************************************");
 
     auto basic_st = spdlog::basic_logger_st("basic_st", "logs/basic_st.log", true);
@@ -128,7 +130,7 @@ int main(int argc, char *argv[])
 
         if (threads > max_threads)
         {
-            throw std::runtime_error(fmt::format("Number of threads exceeds maximum({})", max_threads));
+            throw std::runtime_error(spdlog::fmt_lib::format("Number of threads exceeds maximum({})", max_threads));
         }
 
         bench_single_threaded(iters);
@@ -158,8 +160,8 @@ void bench(int howmany, std::shared_ptr<spdlog::logger> log)
     auto delta = high_resolution_clock::now() - start;
     auto delta_d = duration_cast<duration<double>>(delta).count();
 
-    spdlog::info(
-        fmt::format(std::locale("en_US.UTF-8"), "{:<30} Elapsed: {:0.2f} secs {:>16L}/sec", log->name(), delta_d, int(howmany / delta_d)));
+    spdlog::info(spdlog::fmt_lib::format(
+        std::locale("en_US.UTF-8"), "{:<30} Elapsed: {:0.2f} secs {:>16L}/sec", log->name(), delta_d, int(howmany / delta_d)));
     spdlog::drop(log->name());
 }
 
@@ -189,8 +191,8 @@ void bench_mt(int howmany, std::shared_ptr<spdlog::logger> log, size_t thread_co
 
     auto delta = high_resolution_clock::now() - start;
     auto delta_d = duration_cast<duration<double>>(delta).count();
-    spdlog::info(
-        fmt::format(std::locale("en_US.UTF-8"), "{:<30} Elapsed: {:0.2f} secs {:>16L}/sec", log->name(), delta_d, int(howmany / delta_d)));
+    spdlog::info(spdlog::fmt_lib::format(
+        std::locale("en_US.UTF-8"), "{:<30} Elapsed: {:0.2f} secs {:>16L}/sec", log->name(), delta_d, int(howmany / delta_d)));
     spdlog::drop(log->name());
 }
 

cmake/spdlogConfig.cmake.in

@@ -1,15 +1,20 @@
 # Copyright(c) 2019 spdlog authors
 # Distributed under the MIT License (http://opensource.org/licenses/MIT)
 
+@PACKAGE_INIT@
+
 find_package(Threads REQUIRED)
 
 set(SPDLOG_FMT_EXTERNAL @SPDLOG_FMT_EXTERNAL@)
+set(SPDLOG_FMT_EXTERNAL_HO @SPDLOG_FMT_EXTERNAL_HO@)
 set(config_targets_file @config_targets_file@)
 
-if(SPDLOG_FMT_EXTERNAL)
+if(SPDLOG_FMT_EXTERNAL OR SPDLOG_FMT_EXTERNAL_HO)
     include(CMakeFindDependencyMacro)
     find_dependency(fmt CONFIG)
 endif()
 
 
 include("${CMAKE_CURRENT_LIST_DIR}/${config_targets_file}")
+
+check_required_components(spdlog)

example/example.cpp

@@ -5,6 +5,7 @@
 // spdlog usage example
 
 #include <cstdio>
+#include <chrono>
 
 void load_levels_example();
 void stdout_logger_example();
@@ -13,13 +14,17 @@ void rotating_example();
 void daily_example();
 void async_example();
 void binary_example();
+void vector_example();
 void stopwatch_example();
 void trace_example();
 void multi_sink_example();
 void user_defined_example();
 void err_handler_example();
 void syslog_example();
+void udp_example();
 void custom_flags_example();
+void file_events_example();
+void replace_default_logger_example();
 
 #include "spdlog/spdlog.h"
 #include "spdlog/cfg/env.h"  // support for loading levels from the environment variable
@@ -69,12 +74,16 @@ int main(int, char *[])
         daily_example();
         async_example();
         binary_example();
+        vector_example();
         multi_sink_example();
         user_defined_example();
         err_handler_example();
         trace_example();
         stopwatch_example();
+        udp_example();
         custom_flags_example();
+        file_events_example();
+        replace_default_logger_example();
 
         // Flush all *registered* loggers using a worker thread every 3 seconds.
         // note: registered loggers *must* be thread safe for this to work correctly!
@@ -110,7 +119,7 @@ void stdout_logger_example()
 void basic_example()
 {
     // Create basic file logger (not rotated).
-    auto my_logger = spdlog::basic_logger_mt("file_logger", "logs/basic-log.txt");
+    auto my_logger = spdlog::basic_logger_mt("file_logger", "logs/basic-log.txt", true);
 }
 
 #include "spdlog/sinks/rotating_file_sink.h"
@@ -181,6 +190,21 @@ void binary_example()
     // logger->info("hexdump style, 20 chars per line {:a}", spdlog::to_hex(buf, 20));
 }
 
+// Log a vector of numbers
+#ifndef SPDLOG_USE_STD_FORMAT
+#    include "spdlog/fmt/ranges.h"
+void vector_example()
+{
+    std::vector<int> vec = {1, 2, 3};
+    spdlog::info("Vector example: {}", vec);
+}
+
+#else
+void vector_example() {}
+#endif
+
+// ! DSPDLOG_USE_STD_FORMAT
+
 // Compile time log levels.
 // define SPDLOG_ACTIVE_LEVEL to required level (e.g. SPDLOG_LEVEL_TRACE)
 void trace_example()
@@ -205,6 +229,15 @@ void stopwatch_example()
     spdlog::info("Stopwatch: {} seconds", sw);
 }
 
+#include "spdlog/sinks/udp_sink.h"
+void udp_example()
+{
+    spdlog::sinks::udp_sink_config cfg("127.0.0.1", 11091);
+    auto my_logger = spdlog::udp_logger_mt("udplog", cfg);
+    my_logger->set_level(spdlog::level::debug);
+    my_logger->info("hello world");
+}
+
 // A logger with multiple sinks (stdout and file) - each with a different format and log level.
 void multi_sink_example()
 {
@@ -221,20 +254,27 @@ void multi_sink_example()
     logger.info("this message should not appear in the console, only in the file");
 }
 
-// User defined types logging by implementing operator<<
+// User defined types logging
 struct my_type
 {
-    int i;
-    template<typename OStream>
-    friend OStream &operator<<(OStream &os, const my_type &c)
+    int i = 0;
+    explicit my_type(int i)
+        : i(i){};
+};
+
+namespace fmt_lib = spdlog::fmt_lib;
+template<>
+struct fmt_lib::formatter<my_type> : fmt_lib::formatter<std::string>
+{
+    auto format(my_type my, format_context &ctx) -> decltype(ctx.out())
     {
-        return os << "[my_type i=" << c.i << "]";
+        return fmt_lib::format_to(ctx.out(), "[my_type i={}]", my.i);
     }
 };
 
 void user_defined_example()
 {
-    spdlog::info("user defined type: {}", my_type{14});
+    spdlog::info("user defined type: {}", my_type(14));
 }
 
 // Custom error handler. Will be triggered on log failure.
@@ -290,5 +330,40 @@ void custom_flags_example()
     using spdlog::details::make_unique; // for pre c++14
     auto formatter = make_unique<spdlog::pattern_formatter>();
     formatter->add_flag<my_formatter_flag>('*').set_pattern("[%n] [%*] [%^%l%$] %v");
-    spdlog::set_formatter(std::move(formatter));
+    // set the new formatter using spdlog::set_formatter(formatter) or logger->set_formatter(formatter)
+    // spdlog::set_formatter(std::move(formatter));
+}
+
+void file_events_example()
+{
+    // pass the spdlog::file_event_handlers to file sinks for open/close log file notifications
+    spdlog::file_event_handlers handlers;
+    handlers.before_open = [](spdlog::filename_t filename) { spdlog::info("Before opening {}", filename); };
+    handlers.after_open = [](spdlog::filename_t filename, std::FILE *fstream) {
+        spdlog::info("After opening {}", filename);
+        fputs("After opening\n", fstream);
+    };
+    handlers.before_close = [](spdlog::filename_t filename, std::FILE *fstream) {
+        spdlog::info("Before closing {}", filename);
+        fputs("Before closing\n", fstream);
+    };
+    handlers.after_close = [](spdlog::filename_t filename) { spdlog::info("After closing {}", filename); };
+    auto file_sink = std::make_shared<spdlog::sinks::basic_file_sink_mt>("logs/events-sample.txt", true, handlers);
+    spdlog::logger my_logger("some_logger", file_sink);
+    my_logger.info("Some log line");
+}
+
+void replace_default_logger_example()
+{
+    // store the old logger so we don't break other examples.
+    auto old_logger = spdlog::default_logger();
+
+    auto new_logger = spdlog::basic_logger_mt("new_default_logger", "logs/new-default-log.txt", true);
+    spdlog::set_default_logger(new_logger);
+    spdlog::set_level(spdlog::level::info);
+    spdlog::debug("This message should not be displayed!");
+    spdlog::set_level(spdlog::level::trace);
+    spdlog::debug("This message should be displayed..");
+
+    spdlog::set_default_logger(old_logger);
 }

include/spdlog/async.h

@@ -35,7 +35,7 @@ template<async_overflow_policy OverflowPolicy = async_overflow_policy::block>
 struct async_factory_impl
 {
     template<typename Sink, typename... SinkArgs>
-    static std::shared_ptr<async_logger> create(std::string logger_name, SinkArgs &&...args)
+    static std::shared_ptr<async_logger> create(std::string logger_name, SinkArgs &&... args)
     {
         auto &registry_inst = details::registry::instance();
 
@@ -61,28 +61,34 @@ using async_factory = async_factory_impl<async_overflow_policy::block>;
 using async_factory_nonblock = async_factory_impl<async_overflow_policy::overrun_oldest>;
 
 template<typename Sink, typename... SinkArgs>
-inline std::shared_ptr<spdlog::logger> create_async(std::string logger_name, SinkArgs &&...sink_args)
+inline std::shared_ptr<spdlog::logger> create_async(std::string logger_name, SinkArgs &&... sink_args)
 {
     return async_factory::create<Sink>(std::move(logger_name), std::forward<SinkArgs>(sink_args)...);
 }
 
 template<typename Sink, typename... SinkArgs>
-inline std::shared_ptr<spdlog::logger> create_async_nb(std::string logger_name, SinkArgs &&...sink_args)
+inline std::shared_ptr<spdlog::logger> create_async_nb(std::string logger_name, SinkArgs &&... sink_args)
 {
     return async_factory_nonblock::create<Sink>(std::move(logger_name), std::forward<SinkArgs>(sink_args)...);
 }
 
 // set global thread pool.
-inline void init_thread_pool(size_t q_size, size_t thread_count, std::function<void()> on_thread_start)
+inline void init_thread_pool(
+    size_t q_size, size_t thread_count, std::function<void()> on_thread_start, std::function<void()> on_thread_stop)
 {
-    auto tp = std::make_shared<details::thread_pool>(q_size, thread_count, on_thread_start);
+    auto tp = std::make_shared<details::thread_pool>(q_size, thread_count, on_thread_start, on_thread_stop);
     details::registry::instance().set_tp(std::move(tp));
 }
 
-// set global thread pool.
+inline void init_thread_pool(size_t q_size, size_t thread_count, std::function<void()> on_thread_start)
+{
+    init_thread_pool(q_size, thread_count, on_thread_start, [] {});
+}
+
 inline void init_thread_pool(size_t q_size, size_t thread_count)
 {
-    init_thread_pool(q_size, thread_count, [] {});
+    init_thread_pool(
+        q_size, thread_count, [] {}, [] {});
 }
 
 // get the global thread pool.

include/spdlog/async_logger-inl.h

@@ -62,7 +62,7 @@ SPDLOG_INLINE void spdlog::async_logger::backend_sink_it_(const details::log_msg
             {
                 sink->log(msg);
             }
-            SPDLOG_LOGGER_CATCH()
+            SPDLOG_LOGGER_CATCH(msg.source)
         }
     }
 
@@ -80,7 +80,7 @@ SPDLOG_INLINE void spdlog::async_logger::backend_flush_()
         {
             sink->flush();
         }
-        SPDLOG_LOGGER_CATCH()
+        SPDLOG_LOGGER_CATCH(source_loc())
     }
 }
 

include/spdlog/common-inl.h

@@ -34,7 +34,7 @@ SPDLOG_INLINE spdlog::level::level_enum from_str(const std::string &name) SPDLOG
 {
     auto it = std::find(std::begin(level_string_views), std::end(level_string_views), name);
     if (it != std::end(level_string_views))
-        return static_cast<level::level_enum>(std::distance(std::begin(level_string_views), it));
+        return static_cast<level::level_enum>(it - std::begin(level_string_views));
 
     // check also for "warn" and "err" before giving up..
     if (name == "warn")
@@ -55,9 +55,13 @@ SPDLOG_INLINE spdlog_ex::spdlog_ex(std::string msg)
 
 SPDLOG_INLINE spdlog_ex::spdlog_ex(const std::string &msg, int last_errno)
 {
+#ifdef SPDLOG_USE_STD_FORMAT
+    msg_ = std::system_error(std::error_code(last_errno, std::generic_category()), msg).what();
+#else
     memory_buf_t outbuf;
     fmt::format_system_error(outbuf, last_errno, msg.c_str());
     msg_ = fmt::to_string(outbuf);
+#endif
 }
 
 SPDLOG_INLINE const char *spdlog_ex::what() const SPDLOG_NOEXCEPT

include/spdlog/common.h

@@ -14,16 +14,25 @@
 #include <string>
 #include <type_traits>
 #include <functional>
+#include <cstdio>
+
+#ifdef SPDLOG_USE_STD_FORMAT
+#    include <string_view>
+#endif
 
 #ifdef SPDLOG_COMPILED_LIB
 #    undef SPDLOG_HEADER_ONLY
-#    if defined(_WIN32) && defined(SPDLOG_SHARED_LIB)
-#        ifdef spdlog_EXPORTS
-#            define SPDLOG_API __declspec(dllexport)
-#        else
-#            define SPDLOG_API __declspec(dllimport)
+#    if defined(SPDLOG_SHARED_LIB)
+#        if defined(_WIN32)
+#            ifdef spdlog_EXPORTS
+#                define SPDLOG_API __declspec(dllexport)
+#            else // !spdlog_EXPORTS
+#                define SPDLOG_API __declspec(dllimport)
+#            endif
+#        else // !defined(_WIN32)
+#            define SPDLOG_API __attribute__((visibility("default")))
 #        endif
-#    else // !defined(_WIN32) || !defined(SPDLOG_SHARED_LIB)
+#    else // !defined(SPDLOG_SHARED_LIB)
 #        define SPDLOG_API
 #    endif
 #    define SPDLOG_INLINE
@@ -35,23 +44,30 @@
 
 #include <spdlog/fmt/fmt.h>
 
-// backward compatibility with fmt versions older than 8
-#if FMT_VERSION >= 80000
-#    define SPDLOG_FMT_RUNTIME(format_string) fmt::runtime(format_string)
-#    if defined(SPDLOG_WCHAR_FILENAMES) || defined(SPDLOG_WCHAR_TO_UTF8_SUPPORT)
-#        include <spdlog/fmt/xchar.h>
+#ifndef SPDLOG_USE_STD_FORMAT
+#    if FMT_VERSION >= 80000 // backward compatibility with fmt versions older than 8
+#        define SPDLOG_FMT_RUNTIME(format_string) fmt::runtime(format_string)
+#        if defined(SPDLOG_WCHAR_FILENAMES) || defined(SPDLOG_WCHAR_TO_UTF8_SUPPORT)
+#            include <spdlog/fmt/xchar.h>
+#        endif
+#    else
+#        define SPDLOG_FMT_RUNTIME(format_string) format_string
 #    endif
-#else
-#    define SPDLOG_FMT_RUNTIME(format_string) format_string
 #endif
 
-// visual studio upto 2013 does not support noexcept nor constexpr
+// visual studio up to 2013 does not support noexcept nor constexpr
 #if defined(_MSC_VER) && (_MSC_VER < 1900)
 #    define SPDLOG_NOEXCEPT _NOEXCEPT
 #    define SPDLOG_CONSTEXPR
+#    define SPDLOG_CONSTEXPR_FUNC
 #else
 #    define SPDLOG_NOEXCEPT noexcept
 #    define SPDLOG_CONSTEXPR constexpr
+#    if __cplusplus >= 201402L
+#        define SPDLOG_CONSTEXPR_FUNC constexpr
+#    else
+#        define SPDLOG_CONSTEXPR_FUNC
+#    endif
 #endif
 
 #if defined(__GNUC__) || defined(__clang__)
@@ -111,34 +127,65 @@ using log_clock = std::chrono::system_clock;
 using sink_ptr = std::shared_ptr<sinks::sink>;
 using sinks_init_list = std::initializer_list<sink_ptr>;
 using err_handler = std::function<void(const std::string &err_msg)>;
+#ifdef SPDLOG_USE_STD_FORMAT
+namespace fmt_lib = std;
+
+using string_view_t = std::string_view;
+using memory_buf_t = std::string;
+
+template<typename... Args>
+using format_string_t = std::string_view;
+
+template<class T, class Char = char>
+struct is_convertible_to_basic_format_string : std::integral_constant<bool, std::is_convertible<T, std::basic_string_view<Char>>::value>
+{};
+
+#    if defined(SPDLOG_WCHAR_FILENAMES) || defined(SPDLOG_WCHAR_TO_UTF8_SUPPORT)
+using wstring_view_t = std::wstring_view;
+using wmemory_buf_t = std::wstring;
+
+template<typename... Args>
+using wformat_string_t = std::wstring_view;
+#    endif
+
+#else // use fmt lib instead of std::format
+namespace fmt_lib = fmt;
+
 using string_view_t = fmt::basic_string_view<char>;
-using wstring_view_t = fmt::basic_string_view<wchar_t>;
 using memory_buf_t = fmt::basic_memory_buffer<char, 250>;
+
+template<typename... Args>
+using format_string_t = fmt::format_string<Args...>;
+
+template<class T>
+using remove_cvref_t = typename std::remove_cv<typename std::remove_reference<T>::type>::type;
+
+// clang doesn't like SFINAE disabled constructor in std::is_convertible<> so have to repeat the condition from basic_format_string here,
+// in addition, fmt::basic_runtime<Char> is only convertible to basic_format_string<Char> but not basic_string_view<Char>
+template<class T, class Char = char>
+struct is_convertible_to_basic_format_string
+    : std::integral_constant<bool,
+          std::is_convertible<T, fmt::basic_string_view<Char>>::value || std::is_same<remove_cvref_t<T>, fmt::basic_runtime<Char>>::value>
+{};
+
+#    if defined(SPDLOG_WCHAR_FILENAMES) || defined(SPDLOG_WCHAR_TO_UTF8_SUPPORT)
+using wstring_view_t = fmt::basic_string_view<wchar_t>;
 using wmemory_buf_t = fmt::basic_memory_buffer<wchar_t, 250>;
 
+template<typename... Args>
+using wformat_string_t = fmt::wformat_string<Args...>;
+#    endif
+#endif
+
 #ifdef SPDLOG_WCHAR_TO_UTF8_SUPPORT
 #    ifndef _WIN32
 #        error SPDLOG_WCHAR_TO_UTF8_SUPPORT only supported on windows
-#    else
-template<typename T>
-struct is_convertible_to_wstring_view : std::is_convertible<T, wstring_view_t>
-{};
-template<class T>
-struct is_convertible_to_wformat_string : std::is_convertible<T, fmt::wformat_string<>>
-{};
 #    endif // _WIN32
-#else
-template<typename>
-struct is_convertible_to_wstring_view : std::false_type
-{};
-template<class>
-struct is_convertible_to_wformat_string : std::false_type
-{};
-#endif // SPDLOG_WCHAR_TO_UTF8_SUPPORT
+#endif     // SPDLOG_WCHAR_TO_UTF8_SUPPORT
 
 template<class T>
-struct is_convertible_to_basic_format_string
-    : std::integral_constant<bool, std::is_convertible<const T &, fmt::format_string<>>::value || is_convertible_to_wformat_string<T>::value>
+struct is_convertible_to_any_format_string : std::integral_constant<bool, is_convertible_to_basic_format_string<T, char>::value ||
+                                                                              is_convertible_to_basic_format_string<T, wchar_t>::value>
 {};
 
 #if defined(SPDLOG_NO_ATOMIC_LEVELS)
@@ -161,7 +208,7 @@ using level_t = std::atomic<int>;
 
 // Log level enum
 namespace level {
-enum level_enum
+enum level_enum : int
 {
     trace = SPDLOG_LEVEL_TRACE,
     debug = SPDLOG_LEVEL_DEBUG,
@@ -173,13 +220,13 @@ enum level_enum
     n_levels
 };
 
-#define SPDLOG_LEVEL_NAME_TRACE string_view_t("trace", 5)
-#define SPDLOG_LEVEL_NAME_DEBUG string_view_t("debug", 5)
-#define SPDLOG_LEVEL_NAME_INFO string_view_t("info", 4)
-#define SPDLOG_LEVEL_NAME_WARNING string_view_t("warning", 7)
-#define SPDLOG_LEVEL_NAME_ERROR string_view_t("error", 5)
-#define SPDLOG_LEVEL_NAME_CRITICAL string_view_t("critical", 8)
-#define SPDLOG_LEVEL_NAME_OFF string_view_t("off", 3)
+#define SPDLOG_LEVEL_NAME_TRACE spdlog::string_view_t("trace", 5)
+#define SPDLOG_LEVEL_NAME_DEBUG spdlog::string_view_t("debug", 5)
+#define SPDLOG_LEVEL_NAME_INFO spdlog::string_view_t("info", 4)
+#define SPDLOG_LEVEL_NAME_WARNING spdlog::string_view_t("warning", 7)
+#define SPDLOG_LEVEL_NAME_ERROR spdlog::string_view_t("error", 5)
+#define SPDLOG_LEVEL_NAME_CRITICAL spdlog::string_view_t("critical", 8)
+#define SPDLOG_LEVEL_NAME_OFF spdlog::string_view_t("off", 3)
 
 #if !defined(SPDLOG_LEVEL_NAMES)
 #    define SPDLOG_LEVEL_NAMES                                                                                                             \
@@ -258,19 +305,52 @@ struct source_loc
     const char *funcname{nullptr};
 };
 
+struct file_event_handlers
+{
+    std::function<void(const filename_t &filename)> before_open;
+    std::function<void(const filename_t &filename, std::FILE *file_stream)> after_open;
+    std::function<void(const filename_t &filename, std::FILE *file_stream)> before_close;
+    std::function<void(const filename_t &filename)> after_close;
+    file_event_handlers()
+        : before_open{nullptr}
+        , after_open{nullptr}
+        , before_close{nullptr}
+        , after_close{nullptr}
+    {}
+};
+
 namespace details {
+
 // make_unique support for pre c++14
 
 #if __cplusplus >= 201402L // C++14 and beyond
+using std::enable_if_t;
 using std::make_unique;
 #else
+template<bool B, class T = void>
+using enable_if_t = typename std::enable_if<B, T>::type;
+
 template<typename T, typename... Args>
-std::unique_ptr<T> make_unique(Args &&...args)
+std::unique_ptr<T> make_unique(Args &&... args)
 {
     static_assert(!std::is_array<T>::value, "arrays not supported");
     return std::unique_ptr<T>(new T(std::forward<Args>(args)...));
 }
 #endif
+
+// to avoid useless casts (see https://github.com/nlohmann/json/issues/2893#issuecomment-889152324)
+template<typename T, typename U, enable_if_t<!std::is_same<T, U>::value, int> = 0>
+constexpr T conditional_static_cast(U value)
+{
+    return static_cast<T>(value);
+}
+
+template<typename T, typename U, enable_if_t<std::is_same<T, U>::value, int> = 0>
+constexpr T conditional_static_cast(U value)
+{
+    return value;
+}
+
 } // namespace details
 } // namespace spdlog
 

include/spdlog/details/file_helper-inl.h

@@ -20,6 +20,10 @@
 namespace spdlog {
 namespace details {
 
+SPDLOG_INLINE file_helper::file_helper(const file_event_handlers &event_handlers)
+    : event_handlers_(event_handlers)
+{}
+
 SPDLOG_INLINE file_helper::~file_helper()
 {
     close();
@@ -33,6 +37,10 @@ SPDLOG_INLINE void file_helper::open(const filename_t &fname, bool truncate)
     auto *mode = SPDLOG_FILENAME_T("ab");
     auto *trunc_mode = SPDLOG_FILENAME_T("wb");
 
+    if (event_handlers_.before_open)
+    {
+        event_handlers_.before_open(filename_);
+    }
     for (int tries = 0; tries < open_tries_; ++tries)
     {
         // create containing folder if not exists already.
@@ -52,6 +60,10 @@ SPDLOG_INLINE void file_helper::open(const filename_t &fname, bool truncate)
         }
         if (!os::fopen_s(&fd_, fname, mode))
         {
+            if (event_handlers_.after_open)
+            {
+                event_handlers_.after_open(filename_, fd_);
+            }
             return;
         }
 
@@ -72,15 +84,28 @@ SPDLOG_INLINE void file_helper::reopen(bool truncate)
 
 SPDLOG_INLINE void file_helper::flush()
 {
-    std::fflush(fd_);
+    if (std::fflush(fd_) != 0)
+    {
+        throw_spdlog_ex("Failed flush to file " + os::filename_to_str(filename_), errno);
+    }
 }
 
 SPDLOG_INLINE void file_helper::close()
 {
     if (fd_ != nullptr)
     {
+        if (event_handlers_.before_close)
+        {
+            event_handlers_.before_close(filename_, fd_);
+        }
+
         std::fclose(fd_);
         fd_ = nullptr;
+
+        if (event_handlers_.after_close)
+        {
+            event_handlers_.after_close(filename_);
+        }
     }
 }
 

include/spdlog/details/file_helper.h

@@ -16,7 +16,8 @@ namespace details {
 class SPDLOG_API file_helper
 {
 public:
-    explicit file_helper() = default;
+    file_helper() = default;
+    explicit file_helper(const file_event_handlers &event_handlers);
 
     file_helper(const file_helper &) = delete;
     file_helper &operator=(const file_helper &) = delete;
@@ -50,6 +51,7 @@ private:
     const unsigned int open_interval_ = 10;
     std::FILE *fd_{nullptr};
     filename_t filename_;
+    file_event_handlers event_handlers_;
 };
 } // namespace details
 } // namespace spdlog

include/spdlog/details/fmt_helper.h

@@ -8,6 +8,11 @@
 #include <spdlog/fmt/fmt.h>
 #include <spdlog/common.h>
 
+#ifdef SPDLOG_USE_STD_FORMAT
+#    include <charconv>
+#    include <limits>
+#endif
+
 // Some fmt helpers to efficiently format and pad ints and strings
 namespace spdlog {
 namespace details {
@@ -24,26 +29,73 @@ inline void append_string_view(spdlog::string_view_t view, memory_buf_t &dest)
     dest.append(buf_ptr, buf_ptr + view.size());
 }
 
+#ifdef SPDLOG_USE_STD_FORMAT
+template<typename T>
+inline void append_int(T n, memory_buf_t &dest)
+{
+    // Buffer should be large enough to hold all digits (digits10 + 1) and a sign
+    SPDLOG_CONSTEXPR const auto BUF_SIZE = std::numeric_limits<T>::digits10 + 2;
+    char buf[BUF_SIZE];
+
+    auto [ptr, ec] = std::to_chars(buf, buf + BUF_SIZE, n, 10);
+    if (ec == std::errc())
+    {
+        dest.append(buf, ptr);
+    }
+    else
+    {
+        throw_spdlog_ex("Failed to format int", static_cast<int>(ec));
+    }
+}
+#else
 template<typename T>
 inline void append_int(T n, memory_buf_t &dest)
 {
     fmt::format_int i(n);
     dest.append(i.data(), i.data() + i.size());
 }
+#endif
+
+template<typename T>
+SPDLOG_CONSTEXPR_FUNC unsigned int count_digits_fallback(T n)
+{
+    // taken from fmt: https://github.com/fmtlib/fmt/blob/8.0.1/include/fmt/format.h#L899-L912
+    unsigned int count = 1;
+    for (;;)
+    {
+        // Integer division is slow so do it for a group of four digits instead
+        // of for every digit. The idea comes from the talk by Alexandrescu
+        // "Three Optimization Tips for C++". See speed-test for a comparison.
+        if (n < 10)
+            return count;
+        if (n < 100)
+            return count + 1;
+        if (n < 1000)
+            return count + 2;
+        if (n < 10000)
+            return count + 3;
+        n /= 10000u;
+        count += 4;
+    }
+}
 
 template<typename T>
 inline unsigned int count_digits(T n)
 {
     using count_type = typename std::conditional<(sizeof(T) > sizeof(uint32_t)), uint64_t, uint32_t>::type;
+#ifdef SPDLOG_USE_STD_FORMAT
+    return count_digits_fallback(static_cast<count_type>(n));
+#else
     return static_cast<unsigned int>(fmt::
 // fmt 7.0.0 renamed the internal namespace to detail.
 // See: https://github.com/fmtlib/fmt/issues/1538
-#if FMT_VERSION < 70000
+#    if FMT_VERSION < 70000
             internal
-#else
+#    else
             detail
-#endif
+#    endif
         ::count_digits(static_cast<count_type>(n)));
+#endif
 }
 
 inline void pad2(int n, memory_buf_t &dest)
@@ -55,7 +107,7 @@ inline void pad2(int n, memory_buf_t &dest)
     }
     else // unlikely, but just in case, let fmt deal with it
     {
-        fmt::format_to(std::back_inserter(dest), SPDLOG_FMT_RUNTIME("{:02}"), n);
+        fmt_lib::format_to(std::back_inserter(dest), "{:02}", n);
     }
 }
 

include/spdlog/details/mpmc_blocking_q.h

@@ -49,7 +49,7 @@ public:
         push_cv_.notify_one();
     }
 
-    // try to dequeue item. if no item found. wait upto timeout and try again
+    // try to dequeue item. if no item found. wait up to timeout and try again
     // Return true, if succeeded dequeue item, false otherwise
     bool dequeue_for(T &popped_item, std::chrono::milliseconds wait_duration)
     {
@@ -87,7 +87,7 @@ public:
         push_cv_.notify_one();
     }
 
-    // try to dequeue item. if no item found. wait upto timeout and try again
+    // try to dequeue item. if no item found. wait up to timeout and try again
     // Return true, if succeeded dequeue item, false otherwise
     bool dequeue_for(T &popped_item, std::chrono::milliseconds wait_duration)
     {

include/spdlog/details/os-inl.h

@@ -46,7 +46,7 @@
 #        include <sys/syscall.h> //Use gettid() syscall under linux to get thread id
 
 #    elif defined(_AIX)
-#        include <pthread.h> // for pthread_getthreadid_np
+#        include <pthread.h> // for pthread_getthrds_np
 
 #    elif defined(__DragonFly__) || defined(__FreeBSD__)
 #        include <pthread_np.h> // for pthread_getthreadid_np
@@ -145,7 +145,7 @@ SPDLOG_INLINE bool fopen_s(FILE **fp, const filename_t &filename, const filename
     const int fd = ::open((filename.c_str()), O_CREAT | O_WRONLY | O_CLOEXEC | mode_flag, mode_t(0644));
     if (fd == -1)
     {
-        return false;
+        return true;
     }
     *fp = ::fdopen(fd, mode.c_str());
     if (*fp == nullptr)
@@ -230,8 +230,8 @@ SPDLOG_INLINE size_t filesize(FILE *f)
 #    endif
 
 #else // unix
-// OpenBSD doesn't compile with :: before the fileno(..)
-#    if defined(__OpenBSD__)
+// OpenBSD and AIX doesn't compile with :: before the fileno(..)
+#    if defined(__OpenBSD__) || defined(_AIX)
     int fd = fileno(f);
 #    else
     int fd = ::fileno(f);
@@ -305,7 +305,7 @@ SPDLOG_INLINE int utc_minutes_offset(const std::tm &tm)
                 ((local_year / 100 >> 2) - (gmt_year / 100 >> 2))
 
                 // + difference in years * 365 */
-                + (long int)(local_year - gmt_year) * 365);
+                + static_cast<long int>(local_year - gmt_year) * 365);
 
             long int hours = (24 * days) + (localtm.tm_hour - gmtm.tm_hour);
             long int mins = (60 * hours) + (localtm.tm_min - gmtm.tm_min);
@@ -336,7 +336,14 @@ SPDLOG_INLINE size_t _thread_id() SPDLOG_NOEXCEPT
 #        define SYS_gettid __NR_gettid
 #    endif
     return static_cast<size_t>(::syscall(SYS_gettid));
-#elif defined(_AIX) || defined(__DragonFly__) || defined(__FreeBSD__)
+#elif defined(_AIX)
+    struct __pthrdsinfo buf;
+    int reg_size = 0;
+    pthread_t pt = pthread_self();
+    int retval = pthread_getthrds_np(&pt, PTHRDSINFO_QUERY_TID, &buf, sizeof(buf), NULL, &reg_size);
+    int tid = (!retval) ? buf.__pi_tid : 0;
+    return static_cast<size_t>(tid);
+#elif defined(__DragonFly__) || defined(__FreeBSD__)
     return static_cast<size_t>(::pthread_getthreadid_np());
 #elif defined(__NetBSD__)
     return static_cast<size_t>(::_lwp_self());
@@ -381,7 +388,11 @@ SPDLOG_INLINE std::string filename_to_str(const filename_t &filename)
 {
     memory_buf_t buf;
     wstr_to_utf8buf(filename, buf);
+#    ifdef SPDLOG_USE_STD_FORMAT
+    return buf;
+#    else
     return fmt::to_string(buf);
+#    endif
 }
 #else
 SPDLOG_INLINE std::string filename_to_str(const filename_t &filename)
@@ -394,9 +405,9 @@ SPDLOG_INLINE int pid() SPDLOG_NOEXCEPT
 {
 
 #ifdef _WIN32
-    return static_cast<int>(::GetCurrentProcessId());
+    return conditional_static_cast<int>(::GetCurrentProcessId());
 #else
-    return static_cast<int>(::getpid());
+    return conditional_static_cast<int>(::getpid());
 #endif
 }
 
@@ -476,7 +487,7 @@ SPDLOG_INLINE void wstr_to_utf8buf(wstring_view_t wstr, memory_buf_t &target)
         }
     }
 
-    throw_spdlog_ex(fmt::format("WideCharToMultiByte failed. Last error: {}", ::GetLastError()));
+    throw_spdlog_ex(fmt_lib::format("WideCharToMultiByte failed. Last error: {}", ::GetLastError()));
 }
 
 SPDLOG_INLINE void utf8_to_wstrbuf(string_view_t str, wmemory_buf_t &target)
@@ -511,7 +522,7 @@ SPDLOG_INLINE void utf8_to_wstrbuf(string_view_t str, wmemory_buf_t &target)
         }
     }
 
-    throw_spdlog_ex(fmt::format("MultiByteToWideChar failed. Last error: {}", ::GetLastError()));
+    throw_spdlog_ex(fmt_lib::format("MultiByteToWideChar failed. Last error: {}", ::GetLastError()));
 }
 #endif // (defined(SPDLOG_WCHAR_TO_UTF8_SUPPORT) || defined(SPDLOG_WCHAR_FILENAMES)) && defined(_WIN32)
 
@@ -531,7 +542,7 @@ static SPDLOG_INLINE bool mkdir_(const filename_t &path)
 
 // create the given directory - and all directories leading to it
 // return true on success or if the directory already exists
-SPDLOG_INLINE bool create_dir(filename_t path)
+SPDLOG_INLINE bool create_dir(const filename_t &path)
 {
     if (path_exists(path))
     {
@@ -570,7 +581,7 @@ SPDLOG_INLINE bool create_dir(filename_t path)
 // "abc/" => "abc"
 // "abc" => ""
 // "abc///" => "abc//"
-SPDLOG_INLINE filename_t dir_name(filename_t path)
+SPDLOG_INLINE filename_t dir_name(const filename_t &path)
 {
     auto pos = path.find_last_of(folder_seps_filename);
     return pos != filename_t::npos ? path.substr(0, pos) : filename_t{};

include/spdlog/details/os.h

@@ -99,11 +99,11 @@ SPDLOG_API void utf8_to_wstrbuf(string_view_t str, wmemory_buf_t &target);
 // "abc/" => "abc"
 // "abc" => ""
 // "abc///" => "abc//"
-SPDLOG_API filename_t dir_name(filename_t path);
+SPDLOG_API filename_t dir_name(const filename_t &path);
 
 // Create a dir from the given path.
 // Return true if succeeded or if this dir already exists.
-SPDLOG_API bool create_dir(filename_t path);
+SPDLOG_API bool create_dir(const filename_t &path);
 
 // non thread safe, cross platform getenv/getenv_s
 // return empty string if field not found

include/spdlog/details/synchronous_factory.h

@@ -13,7 +13,7 @@ class logger;
 struct synchronous_factory
 {
     template<typename Sink, typename... SinkArgs>
-    static std::shared_ptr<spdlog::logger> create(std::string logger_name, SinkArgs &&...args)
+    static std::shared_ptr<spdlog::logger> create(std::string logger_name, SinkArgs &&... args)
     {
         auto sink = std::make_shared<Sink>(std::forward<SinkArgs>(args)...);
         auto new_logger = std::make_shared<spdlog::logger>(std::move(logger_name), std::move(sink));

include/spdlog/details/tcp_client-windows.h

@@ -25,20 +25,6 @@ class tcp_client
 {
     SOCKET socket_ = INVALID_SOCKET;
 
-    static bool winsock_initialized_()
-    {
-        SOCKET s = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);
-        if (s == INVALID_SOCKET)
-        {
-            return false;
-        }
-        else
-        {
-            closesocket(s);
-            return true;
-        }
-    }
-
     static void init_winsock_()
     {
         WSADATA wsaData;
@@ -52,13 +38,24 @@ class tcp_client
     static void throw_winsock_error_(const std::string &msg, int last_error)
     {
         char buf[512];
-        ::FormatMessage(FORMAT_MESSAGE_FROM_SYSTEM | FORMAT_MESSAGE_IGNORE_INSERTS, NULL, last_error,
+        ::FormatMessageA(FORMAT_MESSAGE_FROM_SYSTEM | FORMAT_MESSAGE_IGNORE_INSERTS, NULL, last_error,
             MAKELANGID(LANG_NEUTRAL, SUBLANG_DEFAULT), buf, (sizeof(buf) / sizeof(char)), NULL);
 
-        throw_spdlog_ex(fmt::format("tcp_sink - {}: {}", msg, buf));
+        throw_spdlog_ex(fmt_lib::format("tcp_sink - {}: {}", msg, buf));
     }
 
 public:
+    tcp_client()
+    {
+        init_winsock_();
+    }
+
+    ~tcp_client()
+    {
+        close();
+        ::WSACleanup();
+    }
+
     bool is_connected() const
     {
         return socket_ != INVALID_SOCKET;
@@ -68,7 +65,6 @@ public:
     {
         ::closesocket(socket_);
         socket_ = INVALID_SOCKET;
-        WSACleanup();
     }
 
     SOCKET fd() const
@@ -76,20 +72,9 @@ public:
         return socket_;
     }
 
-    ~tcp_client()
-    {
-        close();
-    }
-
     // try to connect or throw on failure
     void connect(const std::string &host, int port)
     {
-        // initialize winsock if needed
-        if (!winsock_initialized_())
-        {
-            init_winsock_();
-        }
-
         if (is_connected())
         {
             close();

include/spdlog/details/tcp_client.h

@@ -67,8 +67,7 @@ public:
         auto rv = ::getaddrinfo(host.c_str(), port_str.c_str(), &hints, &addrinfo_result);
         if (rv != 0)
         {
-            auto msg = fmt::format("::getaddrinfo failed: {}", gai_strerror(rv));
-            throw_spdlog_ex(msg);
+            throw_spdlog_ex(fmt_lib::format("::getaddrinfo failed: {}", gai_strerror(rv)));
         }
 
         // Try each address until we successfully connect(2).

include/spdlog/details/thread_pool-inl.h

@@ -13,7 +13,8 @@
 namespace spdlog {
 namespace details {
 
-SPDLOG_INLINE thread_pool::thread_pool(size_t q_max_items, size_t threads_n, std::function<void()> on_thread_start)
+SPDLOG_INLINE thread_pool::thread_pool(
+    size_t q_max_items, size_t threads_n, std::function<void()> on_thread_start, std::function<void()> on_thread_stop)
     : q_(q_max_items)
 {
     if (threads_n == 0 || threads_n > 1000)
@@ -23,15 +24,21 @@ SPDLOG_INLINE thread_pool::thread_pool(size_t q_max_items, size_t threads_n, std
     }
     for (size_t i = 0; i < threads_n; i++)
     {
-        threads_.emplace_back([this, on_thread_start] {
+        threads_.emplace_back([this, on_thread_start, on_thread_stop] {
             on_thread_start();
             this->thread_pool::worker_loop_();
+            on_thread_stop();
         });
     }
 }
 
+SPDLOG_INLINE thread_pool::thread_pool(size_t q_max_items, size_t threads_n, std::function<void()> on_thread_start)
+    : thread_pool(q_max_items, threads_n, on_thread_start, [] {})
+{}
+
 SPDLOG_INLINE thread_pool::thread_pool(size_t q_max_items, size_t threads_n)
-    : thread_pool(q_max_items, threads_n, [] {})
+    : thread_pool(
+          q_max_items, threads_n, [] {}, [] {})
 {}
 
 // message all threads to terminate gracefully join them

include/spdlog/details/thread_pool.h

@@ -27,7 +27,6 @@ enum class async_msg_type
     terminate
 };
 
-#include <spdlog/details/log_msg_buffer.h>
 // Async msg to move to/from the queue
 // Movable only. should never be copied
 struct async_msg : log_msg_buffer
@@ -85,10 +84,11 @@ public:
     using item_type = async_msg;
     using q_type = details::mpmc_blocking_queue<item_type>;
 
+    thread_pool(size_t q_max_items, size_t threads_n, std::function<void()> on_thread_start, std::function<void()> on_thread_stop);
     thread_pool(size_t q_max_items, size_t threads_n, std::function<void()> on_thread_start);
     thread_pool(size_t q_max_items, size_t threads_n);
 
-    // message all threads to terminate gracefully join them
+    // message all threads to terminate gracefully and join them
     ~thread_pool();
 
     thread_pool(const thread_pool &) = delete;

include/spdlog/details/udp_client-windows.h

@@ -0,0 +1,111 @@
+// Copyright(c) 2015-present, Gabi Melman & spdlog contributors.
+// Distributed under the MIT License (http://opensource.org/licenses/MIT)
+
+#pragma once
+
+// Helper RAII over winsock udp client socket.
+// Will throw on construction if socket creation failed.
+
+#include <spdlog/common.h>
+#include <spdlog/details/os.h>
+#include <spdlog/details/windows_include.h>
+#include <winsock2.h>
+#include <ws2tcpip.h>
+#include <stdlib.h>
+#include <stdio.h>
+#include <string>
+
+#pragma comment(lib, "Ws2_32.lib")
+#pragma comment(lib, "Mswsock.lib")
+#pragma comment(lib, "AdvApi32.lib")
+
+namespace spdlog {
+namespace details {
+class udp_client
+{
+    static constexpr int TX_BUFFER_SIZE = 1024 * 10;
+    SOCKET socket_ = INVALID_SOCKET;
+    sockaddr_in addr_ = {0};
+
+    static void init_winsock_()
+    {
+        WSADATA wsaData;
+        auto rv = ::WSAStartup(MAKEWORD(2, 2), &wsaData);
+        if (rv != 0)
+        {
+            throw_winsock_error_("WSAStartup failed", ::WSAGetLastError());
+        }
+    }
+
+    static void throw_winsock_error_(const std::string &msg, int last_error)
+    {
+        char buf[512];
+        ::FormatMessageA(FORMAT_MESSAGE_FROM_SYSTEM | FORMAT_MESSAGE_IGNORE_INSERTS, NULL, last_error,
+            MAKELANGID(LANG_NEUTRAL, SUBLANG_DEFAULT), buf, (sizeof(buf) / sizeof(char)), NULL);
+
+        throw_spdlog_ex(fmt_lib::format("udp_sink - {}: {}", msg, buf));
+    }
+
+    void cleanup_()
+    {
+        if (socket_ != INVALID_SOCKET)
+        {
+            ::closesocket(socket_);
+        }
+        socket_ = INVALID_SOCKET;
+        ::WSACleanup();
+    }
+
+public:
+    udp_client(const std::string &host, uint16_t port)
+    {
+        init_winsock_();
+
+        addr_.sin_family = PF_INET;
+        addr_.sin_port = htons(port);
+        addr_.sin_addr.s_addr = INADDR_ANY;
+        if (InetPtonA(PF_INET, host.c_str(), &addr_.sin_addr.s_addr) != 1)
+        {
+            int last_error = ::WSAGetLastError();
+            ::WSACleanup();
+            throw_winsock_error_("error: Invalid address!", last_error);
+        }
+
+        socket_ = ::socket(PF_INET, SOCK_DGRAM, 0);
+        if (socket_ == INVALID_SOCKET)
+        {
+            int last_error = ::WSAGetLastError();
+            ::WSACleanup();
+            throw_winsock_error_("error: Create Socket failed", last_error);
+        }
+
+        int option_value = TX_BUFFER_SIZE;
+        if (::setsockopt(socket_, SOL_SOCKET, SO_SNDBUF, reinterpret_cast<const char *>(&option_value), sizeof(option_value)) < 0)
+        {
+            int last_error = ::WSAGetLastError();
+            cleanup_();
+            throw_winsock_error_("error: setsockopt(SO_SNDBUF) Failed!", last_error);
+        }
+    }
+
+    ~udp_client()
+    {
+        cleanup_();
+    }
+
+    SOCKET fd() const
+    {
+        return socket_;
+    }
+
+    void send(const char *data, size_t n_bytes)
+    {
+        socklen_t tolen = sizeof(struct sockaddr);
+        if (::sendto(socket_, data, static_cast<int>(n_bytes), 0, (struct sockaddr *)&addr_, tolen) == -1)
+        {
+            throw_spdlog_ex("sendto(2) failed", errno);
+        }
+    }
+};
+} // namespace details
+} // namespace spdlog

include/spdlog/details/udp_client.h

@@ -0,0 +1,94 @@
+// Copyright(c) 2015-present, Gabi Melman & spdlog contributors.
+// Distributed under the MIT License (http://opensource.org/licenses/MIT)
+
+#pragma once
+
+// Helper RAII over unix udp client socket.
+// Will throw on construction if the socket creation failed.
+
+#ifdef _WIN32
+#    error "include udp_client-windows.h instead"
+#endif
+
+#include <spdlog/common.h>
+#include <spdlog/details/os.h>
+
+#include <sys/socket.h>
+#include <netinet/in.h>
+#include <arpa/inet.h>
+#include <unistd.h>
+#include <netdb.h>
+#include <netinet/udp.h>
+
+#include <string>
+
+namespace spdlog {
+namespace details {
+
+class udp_client
+{
+    static constexpr int TX_BUFFER_SIZE = 1024 * 10;
+    int socket_ = -1;
+    struct sockaddr_in sockAddr_;
+
+    void cleanup_()
+    {
+        if (socket_ != -1)
+        {
+            ::close(socket_);
+            socket_ = -1;
+        }
+    }
+
+public:
+    udp_client(const std::string &host, uint16_t port)
+    {
+        socket_ = ::socket(PF_INET, SOCK_DGRAM, 0);
+        if (socket_ < 0)
+        {
+            throw_spdlog_ex("error: Create Socket Failed!");
+        }
+
+        int option_value = TX_BUFFER_SIZE;
+        if (::setsockopt(socket_, SOL_SOCKET, SO_SNDBUF, reinterpret_cast<const char *>(&option_value), sizeof(option_value)) < 0)
+        {
+            cleanup_();
+            throw_spdlog_ex("error: setsockopt(SO_SNDBUF) Failed!");
+        }
+
+        sockAddr_.sin_family = AF_INET;
+        sockAddr_.sin_port = htons(port);
+
+        if (::inet_aton(host.c_str(), &sockAddr_.sin_addr) == 0)
+        {
+            cleanup_();
+            throw_spdlog_ex("error: Invalid address!");
+        }
+
+        ::memset(sockAddr_.sin_zero, 0x00, sizeof(sockAddr_.sin_zero));
+    }
+
+    ~udp_client()
+    {
+        cleanup_();
+    }
+
+    int fd() const
+    {
+        return socket_;
+    }
+
+    // Send exactly n_bytes of the given data.
+    // On error close the connection and throw.
+    void send(const char *data, size_t n_bytes)
+    {
+        ssize_t toslen = 0;
+        socklen_t tolen = sizeof(struct sockaddr);
+        if ((toslen = ::sendto(socket_, data, n_bytes, 0, (struct sockaddr *)&sockAddr_, tolen)) == -1)
+        {
+            throw_spdlog_ex("sendto(2) failed", errno);
+        }
+    }
+};
+} // namespace details
+} // namespace spdlog

include/spdlog/fmt/bin_to_hex.h

@@ -6,10 +6,19 @@
 #pragma once
 
 #include <cctype>
+#include <spdlog/common.h>
+
+#if defined(__has_include) && __has_include(<version>)
+#    include <version>
+#endif
+
+#if __cpp_lib_span >= 202002L
+#    include <span>
+#endif
 
 //
 // Support for logging binary data as hex
-// format flags, any combination of the followng:
+// format flags, any combination of the following:
 // {:X} - print in uppercase.
 // {:s} - don't separate each byte with space.
 // {:p} - don't print the position on each line start.
@@ -38,11 +47,12 @@ public:
         , size_per_line_(size_per_line)
     {}
 
-    It begin() const
+    // do not use begin() and end() to avoid collision with fmt/ranges
+    It get_begin() const
     {
         return begin_;
     }
-    It end() const
+    It get_end() const
     {
         return end_;
     }
@@ -66,6 +76,20 @@ inline details::dump_info<typename Container::const_iterator> to_hex(const Conta
     return details::dump_info<Iter>(std::begin(container), std::end(container), size_per_line);
 }
 
+#if __cpp_lib_span >= 202002L
+
+template<typename Value, size_t Extent>
+inline details::dump_info<typename std::span<Value, Extent>::iterator> to_hex(
+    const std::span<Value, Extent> &container, size_t size_per_line = 32)
+{
+    using Container = std::span<Value, Extent>;
+    static_assert(sizeof(typename Container::value_type) == 1, "sizeof(Container::value_type) != 1");
+    using Iter = typename Container::iterator;
+    return details::dump_info<Iter>(std::begin(container), std::end(container), size_per_line);
+}
+
+#endif
+
 // create dump_info from ranges
 template<typename It>
 inline details::dump_info<It> to_hex(const It range_begin, const It range_end, size_t size_per_line = 32)
@@ -75,10 +99,16 @@ inline details::dump_info<It> to_hex(const It range_begin, const It range_end, s
 
 } // namespace spdlog
 
-namespace fmt {
+namespace
+#ifdef SPDLOG_USE_STD_FORMAT
+    std
+#else
+    fmt
+#endif
+{
 
 template<typename T>
-struct formatter<spdlog::details::dump_info<T>>
+struct formatter<spdlog::details::dump_info<T>, char>
 {
     const char delimiter = ' ';
     bool put_newlines = true;
@@ -89,7 +119,7 @@ struct formatter<spdlog::details::dump_info<T>>
 
     // parse the format string flags
     template<typename ParseContext>
-    FMT_CONSTEXPR auto parse(ParseContext &ctx) -> decltype(ctx.begin())
+    SPDLOG_CONSTEXPR_FUNC auto parse(ParseContext &ctx) -> decltype(ctx.begin())
     {
         auto it = ctx.begin();
         while (it != ctx.end() && *it != '}')
@@ -130,21 +160,21 @@ struct formatter<spdlog::details::dump_info<T>>
         SPDLOG_CONSTEXPR const char *hex_lower = "0123456789abcdef";
         const char *hex_chars = use_uppercase ? hex_upper : hex_lower;
 
-#if FMT_VERSION < 60000
+#if !defined(SPDLOG_USE_STD_FORMAT) && FMT_VERSION < 60000
         auto inserter = ctx.begin();
 #else
         auto inserter = ctx.out();
 #endif
 
         int size_per_line = static_cast<int>(the_range.size_per_line());
-        auto start_of_line = the_range.begin();
-        for (auto i = the_range.begin(); i != the_range.end(); i++)
+        auto start_of_line = the_range.get_begin();
+        for (auto i = the_range.get_begin(); i != the_range.get_end(); i++)
         {
             auto ch = static_cast<unsigned char>(*i);
 
-            if (put_newlines && (i == the_range.begin() || i - start_of_line >= size_per_line))
+            if (put_newlines && (i == the_range.get_begin() || i - start_of_line >= size_per_line))
             {
-                if (show_ascii && i != the_range.begin())
+                if (show_ascii && i != the_range.get_begin())
                 {
                     *inserter++ = delimiter;
                     *inserter++ = delimiter;
@@ -155,7 +185,7 @@ struct formatter<spdlog::details::dump_info<T>>
                     }
                 }
 
-                put_newline(inserter, static_cast<size_t>(i - the_range.begin()));
+                put_newline(inserter, static_cast<size_t>(i - the_range.get_begin()));
 
                 // put first byte without delimiter in front of it
                 *inserter++ = hex_chars[(ch >> 4) & 0x0f];
@@ -174,9 +204,9 @@ struct formatter<spdlog::details::dump_info<T>>
         }
         if (show_ascii) // add ascii to last line
         {
-            if (the_range.end() - the_range.begin() > size_per_line)
+            if (the_range.get_end() - the_range.get_begin() > size_per_line)
             {
-                auto blank_num = size_per_line - (the_range.end() - start_of_line);
+                auto blank_num = size_per_line - (the_range.get_end() - start_of_line);
                 while (blank_num-- > 0)
                 {
                     *inserter++ = delimiter;
@@ -189,7 +219,7 @@ struct formatter<spdlog::details::dump_info<T>>
             }
             *inserter++ = delimiter;
             *inserter++ = delimiter;
-            for (auto j = start_of_line; j != the_range.end(); j++)
+            for (auto j = start_of_line; j != the_range.get_end(); j++)
             {
                 auto pc = static_cast<unsigned char>(*j);
                 *inserter++ = std::isprint(pc) ? static_cast<char>(*j) : '.';
@@ -209,8 +239,8 @@ struct formatter<spdlog::details::dump_info<T>>
 
         if (put_positions)
         {
-            fmt::format_to(inserter, "{:04X}: ", pos);
+            spdlog::fmt_lib::format_to(inserter, "{:04X}: ", pos);
         }
     }
 };
-} // namespace fmt
+} // namespace std

include/spdlog/fmt/bundled/args.h

@@ -143,6 +143,8 @@ class dynamic_format_arg_store
   }
 
  public:
+  constexpr dynamic_format_arg_store() = default;
+
   /**
     \rst
     Adds an argument into the dynamic store for later passing to a formatting

include/spdlog/fmt/bundled/color.h

@@ -185,9 +185,13 @@ enum class terminal_color : uint8_t {
 
 enum class emphasis : uint8_t {
   bold = 1,
-  italic = 1 << 1,
-  underline = 1 << 2,
-  strikethrough = 1 << 3
+  faint = 1 << 1,
+  italic = 1 << 2,
+  underline = 1 << 3,
+  blink = 1 << 4,
+  reverse = 1 << 5,
+  conceal = 1 << 6,
+  strikethrough = 1 << 7,
 };
 
 // rgb is a struct for red, green and blue colors.
@@ -409,16 +413,18 @@ template <typename Char> struct ansi_color_escape {
     buffer[19] = static_cast<Char>(0);
   }
   FMT_CONSTEXPR ansi_color_escape(emphasis em) FMT_NOEXCEPT {
-    uint8_t em_codes[4] = {};
-    uint8_t em_bits = static_cast<uint8_t>(em);
-    if (em_bits & static_cast<uint8_t>(emphasis::bold)) em_codes[0] = 1;
-    if (em_bits & static_cast<uint8_t>(emphasis::italic)) em_codes[1] = 3;
-    if (em_bits & static_cast<uint8_t>(emphasis::underline)) em_codes[2] = 4;
-    if (em_bits & static_cast<uint8_t>(emphasis::strikethrough))
-      em_codes[3] = 9;
+    uint8_t em_codes[num_emphases] = {};
+    if (has_emphasis(em, emphasis::bold)) em_codes[0] = 1;
+    if (has_emphasis(em, emphasis::faint)) em_codes[1] = 2;
+    if (has_emphasis(em, emphasis::italic)) em_codes[2] = 3;
+    if (has_emphasis(em, emphasis::underline)) em_codes[3] = 4;
+    if (has_emphasis(em, emphasis::blink)) em_codes[4] = 5;
+    if (has_emphasis(em, emphasis::reverse)) em_codes[5] = 7;
+    if (has_emphasis(em, emphasis::conceal)) em_codes[6] = 8;
+    if (has_emphasis(em, emphasis::strikethrough)) em_codes[7] = 9;
 
     size_t index = 0;
-    for (int i = 0; i < 4; ++i) {
+    for (size_t i = 0; i < num_emphases; ++i) {
       if (!em_codes[i]) continue;
       buffer[index++] = static_cast<Char>('\x1b');
       buffer[index++] = static_cast<Char>('[');
@@ -435,7 +441,8 @@ template <typename Char> struct ansi_color_escape {
   }
 
  private:
-  Char buffer[7u + 3u * 4u + 1u];
+  static constexpr size_t num_emphases = 8;
+  Char buffer[7u + 3u * num_emphases + 1u];
 
   static FMT_CONSTEXPR void to_esc(uint8_t c, Char* out,
                                    char delimiter) FMT_NOEXCEPT {
@@ -444,6 +451,10 @@ template <typename Char> struct ansi_color_escape {
     out[2] = static_cast<Char>('0' + c % 10);
     out[3] = static_cast<Char>(delimiter);
   }
+  static FMT_CONSTEXPR bool has_emphasis(emphasis em,
+                                         emphasis mask) FMT_NOEXCEPT {
+    return static_cast<uint8_t>(em) & static_cast<uint8_t>(mask);
+  }
 };
 
 template <typename Char>

include/spdlog/fmt/bundled/compile.h

@@ -156,7 +156,7 @@ struct is_compiled_string : std::is_base_of<compiled_string, S> {};
     std::string s = fmt::format(FMT_COMPILE("{}"), 42);
   \endrst
  */
-#ifdef __cpp_if_constexpr
+#if defined(__cpp_if_constexpr) && defined(__cpp_return_type_deduction)
 #  define FMT_COMPILE(s) \
     FMT_STRING_IMPL(s, fmt::detail::compiled_string, explicit)
 #else
@@ -179,7 +179,7 @@ const T& first(const T& value, const Tail&...) {
   return value;
 }
 
-#ifdef __cpp_if_constexpr
+#if defined(__cpp_if_constexpr) && defined(__cpp_return_type_deduction)
 template <typename... Args> struct type_list {};
 
 // Returns a reference to the argument at index N from [first, rest...].
@@ -190,7 +190,7 @@ constexpr const auto& get([[maybe_unused]] const T& first,
   if constexpr (N == 0)
     return first;
   else
-    return get<N - 1>(rest...);
+    return detail::get<N - 1>(rest...);
 }
 
 template <typename Char, typename... Args>
@@ -202,7 +202,8 @@ constexpr int get_arg_index_by_name(basic_string_view<Char> name,
 template <int N, typename> struct get_type_impl;
 
 template <int N, typename... Args> struct get_type_impl<N, type_list<Args...>> {
-  using type = remove_cvref_t<decltype(get<N>(std::declval<Args>()...))>;
+  using type =
+      remove_cvref_t<decltype(detail::get<N>(std::declval<Args>()...))>;
 };
 
 template <int N, typename T>
@@ -242,7 +243,7 @@ template <typename Char> struct code_unit {
 // This ensures that the argument type is convertible to `const T&`.
 template <typename T, int N, typename... Args>
 constexpr const T& get_arg_checked(const Args&... args) {
-  const auto& arg = get<N>(args...);
+  const auto& arg = detail::get<N>(args...);
   if constexpr (detail::is_named_arg<remove_cvref_t<decltype(arg)>>()) {
     return arg.value;
   } else {
@@ -289,7 +290,7 @@ template <typename Char> struct runtime_named_field {
   constexpr OutputIt format(OutputIt out, const Args&... args) const {
     bool found = (try_format_argument(out, name, args) || ...);
     if (!found) {
-      throw format_error("argument with specified name is not found");
+      FMT_THROW(format_error("argument with specified name is not found"));
     }
     return out;
   }
@@ -399,7 +400,9 @@ template <typename Char> struct arg_id_handler {
     return 0;
   }
 
-  constexpr void on_error(const char* message) { throw format_error(message); }
+  constexpr void on_error(const char* message) {
+    FMT_THROW(format_error(message));
+  }
 };
 
 template <typename Char> struct parse_arg_id_result {
@@ -451,7 +454,7 @@ constexpr auto compile_format_string(S format_str) {
   constexpr auto str = basic_string_view<char_type>(format_str);
   if constexpr (str[POS] == '{') {
     if constexpr (POS + 1 == str.size())
-      throw format_error("unmatched '{' in format string");
+      FMT_THROW(format_error("unmatched '{' in format string"));
     if constexpr (str[POS + 1] == '{') {
       return parse_tail<Args, POS + 2, ID>(make_text(str, POS, 1), format_str);
     } else if constexpr (str[POS + 1] == '}' || str[POS + 1] == ':') {
@@ -500,7 +503,7 @@ constexpr auto compile_format_string(S format_str) {
     }
   } else if constexpr (str[POS] == '}') {
     if constexpr (POS + 1 == str.size())
-      throw format_error("unmatched '}' in format string");
+      FMT_THROW(format_error("unmatched '}' in format string"));
     return parse_tail<Args, POS + 2, ID>(make_text(str, POS, 1), format_str);
   } else {
     constexpr auto end = parse_text(str, POS + 1);
@@ -527,12 +530,12 @@ constexpr auto compile(S format_str) {
     return result;
   }
 }
-#endif  // __cpp_if_constexpr
+#endif  // defined(__cpp_if_constexpr) && defined(__cpp_return_type_deduction)
 }  // namespace detail
 
 FMT_MODULE_EXPORT_BEGIN
 
-#ifdef __cpp_if_constexpr
+#if defined(__cpp_if_constexpr) && defined(__cpp_return_type_deduction)
 
 template <typename CompiledFormat, typename... Args,
           typename Char = typename CompiledFormat::char_type,

include/spdlog/fmt/bundled/fmt.license.rst

@@ -0,0 +1,27 @@
+Copyright (c) 2012 - present, Victor Zverovich
+
+Permission is hereby granted, free of charge, to any person obtaining
+a copy of this software and associated documentation files (the
+"Software"), to deal in the Software without restriction, including
+without limitation the rights to use, copy, modify, merge, publish,
+distribute, sublicense, and/or sell copies of the Software, and to
+permit persons to whom the Software is furnished to do so, subject to
+the following conditions:
+
+The above copyright notice and this permission notice shall be
+included in all copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
+LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
+OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+
+--- Optional exception to the license ---
+
+As an exception, if, as a result of your compiling your source code, portions
+of this Software are embedded into a machine-executable object form of such
+source code, you may redistribute such embedded portions in such object form
+without including the above copyright and permission notices.

include/spdlog/fmt/bundled/format-inl.h

@@ -40,6 +40,10 @@ FMT_FUNC void assert_fail(const char* file, int line, const char* message) {
   std::terminate();
 }
 
+FMT_FUNC void throw_format_error(const char* message) {
+  FMT_THROW(format_error(message));
+}
+
 #ifndef _MSC_VER
 #  define FMT_SNPRINTF snprintf
 #else  // _MSC_VER
@@ -145,141 +149,13 @@ template <> FMT_FUNC int count_digits<4>(detail::fallback_uintptr n) {
   return i >= 0 ? i * char_digits + count_digits<4, unsigned>(n.value[i]) : 1;
 }
 
-#if __cplusplus < 201703L
-template <typename T> constexpr const char basic_data<T>::digits[][2];
-template <typename T> constexpr const char basic_data<T>::hex_digits[];
-template <typename T> constexpr const char basic_data<T>::signs[];
-template <typename T> constexpr const unsigned basic_data<T>::prefixes[];
-template <typename T> constexpr const char basic_data<T>::left_padding_shifts[];
-template <typename T>
-constexpr const char basic_data<T>::right_padding_shifts[];
-#endif
+// log10(2) = 0x0.4d104d427de7fbcc...
+static constexpr uint64_t log10_2_significand = 0x4d104d427de7fbcc;
 
-template <typename T> struct bits {
-  static FMT_CONSTEXPR_DECL const int value =
-      static_cast<int>(sizeof(T) * std::numeric_limits<unsigned char>::digits);
-};
-
-class fp;
-template <int SHIFT = 0> fp normalize(fp value);
-
-// Lower (upper) boundary is a value half way between a floating-point value
-// and its predecessor (successor). Boundaries have the same exponent as the
-// value so only significands are stored.
-struct boundaries {
-  uint64_t lower;
-  uint64_t upper;
-};
-
-// A handmade floating-point number f * pow(2, e).
-class fp {
- private:
-  using significand_type = uint64_t;
-
-  template <typename Float>
-  using is_supported_float = bool_constant<sizeof(Float) == sizeof(uint64_t) ||
-                                           sizeof(Float) == sizeof(uint32_t)>;
-
- public:
-  significand_type f;
-  int e;
-
-  // All sizes are in bits.
-  // Subtract 1 to account for an implicit most significant bit in the
-  // normalized form.
-  static FMT_CONSTEXPR_DECL const int double_significand_size =
-      std::numeric_limits<double>::digits - 1;
-  static FMT_CONSTEXPR_DECL const uint64_t implicit_bit =
-      1ULL << double_significand_size;
-  static FMT_CONSTEXPR_DECL const int significand_size =
-      bits<significand_type>::value;
-
-  fp() : f(0), e(0) {}
-  fp(uint64_t f_val, int e_val) : f(f_val), e(e_val) {}
-
-  // Constructs fp from an IEEE754 double. It is a template to prevent compile
-  // errors on platforms where double is not IEEE754.
-  template <typename Double> explicit fp(Double d) { assign(d); }
-
-  // Assigns d to this and return true iff predecessor is closer than successor.
-  template <typename Float, FMT_ENABLE_IF(is_supported_float<Float>::value)>
-  bool assign(Float d) {
-    // Assume float is in the format [sign][exponent][significand].
-    using limits = std::numeric_limits<Float>;
-    const int float_significand_size = limits::digits - 1;
-    const int exponent_size =
-        bits<Float>::value - float_significand_size - 1;  // -1 for sign
-    const uint64_t float_implicit_bit = 1ULL << float_significand_size;
-    const uint64_t significand_mask = float_implicit_bit - 1;
-    const uint64_t exponent_mask = (~0ULL >> 1) & ~significand_mask;
-    const int exponent_bias = (1 << exponent_size) - limits::max_exponent - 1;
-    constexpr bool is_double = sizeof(Float) == sizeof(uint64_t);
-    auto u = bit_cast<conditional_t<is_double, uint64_t, uint32_t>>(d);
-    f = u & significand_mask;
-    int biased_e =
-        static_cast<int>((u & exponent_mask) >> float_significand_size);
-    // Predecessor is closer if d is a normalized power of 2 (f == 0) other than
-    // the smallest normalized number (biased_e > 1).
-    bool is_predecessor_closer = f == 0 && biased_e > 1;
-    if (biased_e != 0)
-      f += float_implicit_bit;
-    else
-      biased_e = 1;  // Subnormals use biased exponent 1 (min exponent).
-    e = biased_e - exponent_bias - float_significand_size;
-    return is_predecessor_closer;
-  }
-
-  template <typename Float, FMT_ENABLE_IF(!is_supported_float<Float>::value)>
-  bool assign(Float) {
-    *this = fp();
-    return false;
-  }
-};
-
-// Normalizes the value converted from double and multiplied by (1 << SHIFT).
-template <int SHIFT> fp normalize(fp value) {
-  // Handle subnormals.
-  const auto shifted_implicit_bit = fp::implicit_bit << SHIFT;
-  while ((value.f & shifted_implicit_bit) == 0) {
-    value.f <<= 1;
-    --value.e;
-  }
-  // Subtract 1 to account for hidden bit.
-  const auto offset =
-      fp::significand_size - fp::double_significand_size - SHIFT - 1;
-  value.f <<= offset;
-  value.e -= offset;
-  return value;
-}
-
-inline bool operator==(fp x, fp y) { return x.f == y.f && x.e == y.e; }
-
-// Computes lhs * rhs / pow(2, 64) rounded to nearest with half-up tie breaking.
-inline uint64_t multiply(uint64_t lhs, uint64_t rhs) {
-#if FMT_USE_INT128
-  auto product = static_cast<__uint128_t>(lhs) * rhs;
-  auto f = static_cast<uint64_t>(product >> 64);
-  return (static_cast<uint64_t>(product) & (1ULL << 63)) != 0 ? f + 1 : f;
-#else
-  // Multiply 32-bit parts of significands.
-  uint64_t mask = (1ULL << 32) - 1;
-  uint64_t a = lhs >> 32, b = lhs & mask;
-  uint64_t c = rhs >> 32, d = rhs & mask;
-  uint64_t ac = a * c, bc = b * c, ad = a * d, bd = b * d;
-  // Compute mid 64-bit of result and round.
-  uint64_t mid = (bd >> 32) + (ad & mask) + (bc & mask) + (1U << 31);
-  return ac + (ad >> 32) + (bc >> 32) + (mid >> 32);
-#endif
-}
-
-inline fp operator*(fp x, fp y) { return {multiply(x.f, y.f), x.e + y.e + 64}; }
-
-// Returns a cached power of 10 `c_k = c_k.f * pow(2, c_k.e)` such that its
-// (binary) exponent satisfies `min_exponent <= c_k.e <= min_exponent + 28`.
-inline fp get_cached_power(int min_exponent, int& pow10_exponent) {
+template <typename T = void> struct basic_impl_data {
   // Normalized 64-bit significands of pow(10, k), for k = -348, -340, ..., 340.
   // These are generated by support/compute-powers.py.
-  static constexpr const uint64_t pow10_significands[] = {
+  static constexpr uint64_t pow10_significands[87] = {
       0xfa8fd5a0081c0288, 0xbaaee17fa23ebf76, 0x8b16fb203055ac76,
       0xcf42894a5dce35ea, 0x9a6bb0aa55653b2d, 0xe61acf033d1a45df,
       0xab70fe17c79ac6ca, 0xff77b1fcbebcdc4f, 0xbe5691ef416bd60c,
@@ -311,9 +187,13 @@ inline fp get_cached_power(int min_exponent, int& pow10_exponent) {
       0x9e19db92b4e31ba9, 0xeb96bf6ebadf77d9, 0xaf87023b9bf0ee6b,
   };
 
+#if FMT_GCC_VERSION && FMT_GCC_VERSION < 409
+#  pragma GCC diagnostic push
+#  pragma GCC diagnostic ignored "-Wnarrowing"
+#endif
   // Binary exponents of pow(10, k), for k = -348, -340, ..., 340, corresponding
   // to significands above.
-  static constexpr const int16_t pow10_exponents[] = {
+  static constexpr int16_t pow10_exponents[87] = {
       -1220, -1193, -1166, -1140, -1113, -1087, -1060, -1034, -1007, -980, -954,
       -927,  -901,  -874,  -847,  -821,  -794,  -768,  -741,  -715,  -688, -661,
       -635,  -608,  -582,  -555,  -529,  -502,  -475,  -449,  -422,  -396, -369,
@@ -322,11 +202,137 @@ inline fp get_cached_power(int min_exponent, int& pow10_exponent) {
       242,   269,   295,   322,   348,   375,   402,   428,   455,   481,  508,
       534,   561,   588,   614,   641,   667,   694,   720,   747,   774,  800,
       827,   853,   880,   907,   933,   960,   986,   1013,  1039,  1066};
+#if FMT_GCC_VERSION && FMT_GCC_VERSION < 409
+#  pragma GCC diagnostic pop
+#endif
 
+  static constexpr uint64_t power_of_10_64[20] = {
+      1, FMT_POWERS_OF_10(1ULL), FMT_POWERS_OF_10(1000000000ULL),
+      10000000000000000000ULL};
+};
+
+// This is a struct rather than an alias to avoid shadowing warnings in gcc.
+struct impl_data : basic_impl_data<> {};
+
+#if __cplusplus < 201703L
+template <typename T>
+constexpr uint64_t basic_impl_data<T>::pow10_significands[];
+template <typename T> constexpr int16_t basic_impl_data<T>::pow10_exponents[];
+template <typename T> constexpr uint64_t basic_impl_data<T>::power_of_10_64[];
+#endif
+
+template <typename T> struct bits {
+  static FMT_CONSTEXPR_DECL const int value =
+      static_cast<int>(sizeof(T) * std::numeric_limits<unsigned char>::digits);
+};
+
+// Returns the number of significand bits in Float excluding the implicit bit.
+template <typename Float> constexpr int num_significand_bits() {
+  // Subtract 1 to account for an implicit most significant bit in the
+  // normalized form.
+  return std::numeric_limits<Float>::digits - 1;
+}
+
+// A floating-point number f * pow(2, e).
+struct fp {
+  uint64_t f;
+  int e;
+
+  static constexpr const int num_significand_bits = bits<decltype(f)>::value;
+
+  constexpr fp() : f(0), e(0) {}
+  constexpr fp(uint64_t f_val, int e_val) : f(f_val), e(e_val) {}
+
+  // Constructs fp from an IEEE754 floating-point number. It is a template to
+  // prevent compile errors on systems where n is not IEEE754.
+  template <typename Float> explicit FMT_CONSTEXPR fp(Float n) { assign(n); }
+
+  template <typename Float>
+  using is_supported = bool_constant<sizeof(Float) == sizeof(uint64_t) ||
+                                     sizeof(Float) == sizeof(uint32_t)>;
+
+  // Assigns d to this and return true iff predecessor is closer than successor.
+  template <typename Float, FMT_ENABLE_IF(is_supported<Float>::value)>
+  FMT_CONSTEXPR bool assign(Float n) {
+    // Assume float is in the format [sign][exponent][significand].
+    const int num_float_significand_bits =
+        detail::num_significand_bits<Float>();
+    const uint64_t implicit_bit = 1ULL << num_float_significand_bits;
+    const uint64_t significand_mask = implicit_bit - 1;
+    constexpr bool is_double = sizeof(Float) == sizeof(uint64_t);
+    auto u = bit_cast<conditional_t<is_double, uint64_t, uint32_t>>(n);
+    f = u & significand_mask;
+    const uint64_t exponent_mask = (~0ULL >> 1) & ~significand_mask;
+    int biased_e =
+        static_cast<int>((u & exponent_mask) >> num_float_significand_bits);
+    // The predecessor is closer if n is a normalized power of 2 (f == 0) other
+    // than the smallest normalized number (biased_e > 1).
+    bool is_predecessor_closer = f == 0 && biased_e > 1;
+    if (biased_e != 0)
+      f += implicit_bit;
+    else
+      biased_e = 1;  // Subnormals use biased exponent 1 (min exponent).
+    const int exponent_bias = std::numeric_limits<Float>::max_exponent - 1;
+    e = biased_e - exponent_bias - num_float_significand_bits;
+    return is_predecessor_closer;
+  }
+
+  template <typename Float, FMT_ENABLE_IF(!is_supported<Float>::value)>
+  bool assign(Float) {
+    FMT_ASSERT(false, "");
+    return false;
+  }
+};
+
+// Normalizes the value converted from double and multiplied by (1 << SHIFT).
+template <int SHIFT = 0> FMT_CONSTEXPR fp normalize(fp value) {
+  // Handle subnormals.
+  const uint64_t implicit_bit = 1ULL << num_significand_bits<double>();
+  const auto shifted_implicit_bit = implicit_bit << SHIFT;
+  while ((value.f & shifted_implicit_bit) == 0) {
+    value.f <<= 1;
+    --value.e;
+  }
+  // Subtract 1 to account for hidden bit.
+  const auto offset =
+      fp::num_significand_bits - num_significand_bits<double>() - SHIFT - 1;
+  value.f <<= offset;
+  value.e -= offset;
+  return value;
+}
+
+inline bool operator==(fp x, fp y) { return x.f == y.f && x.e == y.e; }
+
+// Computes lhs * rhs / pow(2, 64) rounded to nearest with half-up tie breaking.
+FMT_CONSTEXPR inline uint64_t multiply(uint64_t lhs, uint64_t rhs) {
+#if FMT_USE_INT128
+  auto product = static_cast<__uint128_t>(lhs) * rhs;
+  auto f = static_cast<uint64_t>(product >> 64);
+  return (static_cast<uint64_t>(product) & (1ULL << 63)) != 0 ? f + 1 : f;
+#else
+  // Multiply 32-bit parts of significands.
+  uint64_t mask = (1ULL << 32) - 1;
+  uint64_t a = lhs >> 32, b = lhs & mask;
+  uint64_t c = rhs >> 32, d = rhs & mask;
+  uint64_t ac = a * c, bc = b * c, ad = a * d, bd = b * d;
+  // Compute mid 64-bit of result and round.
+  uint64_t mid = (bd >> 32) + (ad & mask) + (bc & mask) + (1U << 31);
+  return ac + (ad >> 32) + (bc >> 32) + (mid >> 32);
+#endif
+}
+
+FMT_CONSTEXPR inline fp operator*(fp x, fp y) {
+  return {multiply(x.f, y.f), x.e + y.e + 64};
+}
+
+// Returns a cached power of 10 `c_k = c_k.f * pow(2, c_k.e)` such that its
+// (binary) exponent satisfies `min_exponent <= c_k.e <= min_exponent + 28`.
+FMT_CONSTEXPR inline fp get_cached_power(int min_exponent,
+                                         int& pow10_exponent) {
   const int shift = 32;
-  const auto significand = static_cast<int64_t>(data::log10_2_significand);
+  const auto significand = static_cast<int64_t>(log10_2_significand);
   int index = static_cast<int>(
-      ((min_exponent + fp::significand_size - 1) * (significand >> shift) +
+      ((min_exponent + fp::num_significand_bits - 1) * (significand >> shift) +
        ((int64_t(1) << shift) - 1))  // ceil
       >> 32                          // arithmetic shift
   );
@@ -336,7 +342,8 @@ inline fp get_cached_power(int min_exponent, int& pow10_exponent) {
   const int dec_exp_step = 8;
   index = (index - first_dec_exp - 1) / dec_exp_step + 1;
   pow10_exponent = first_dec_exp + index * dec_exp_step;
-  return {pow10_significands[index], pow10_exponents[index]};
+  return {impl_data::pow10_significands[index],
+          impl_data::pow10_exponents[index]};
 }
 
 // A simple accumulator to hold the sums of terms in bigint::square if uint128_t
@@ -345,14 +352,16 @@ struct accumulator {
   uint64_t lower;
   uint64_t upper;
 
-  accumulator() : lower(0), upper(0) {}
-  explicit operator uint32_t() const { return static_cast<uint32_t>(lower); }
+  constexpr accumulator() : lower(0), upper(0) {}
+  constexpr explicit operator uint32_t() const {
+    return static_cast<uint32_t>(lower);
+  }
 
-  void operator+=(uint64_t n) {
+  FMT_CONSTEXPR void operator+=(uint64_t n) {
     lower += n;
     if (lower < n) ++upper;
   }
-  void operator>>=(int shift) {
+  FMT_CONSTEXPR void operator>>=(int shift) {
     FMT_ASSERT(shift == 32, "");
     (void)shift;
     lower = (upper << 32) | (lower >> 32);
@@ -370,27 +379,31 @@ class bigint {
   basic_memory_buffer<bigit, bigits_capacity> bigits_;
   int exp_;
 
-  bigit operator[](int index) const { return bigits_[to_unsigned(index)]; }
-  bigit& operator[](int index) { return bigits_[to_unsigned(index)]; }
+  FMT_CONSTEXPR20 bigit operator[](int index) const {
+    return bigits_[to_unsigned(index)];
+  }
+  FMT_CONSTEXPR20 bigit& operator[](int index) {
+    return bigits_[to_unsigned(index)];
+  }
 
   static FMT_CONSTEXPR_DECL const int bigit_bits = bits<bigit>::value;
 
   friend struct formatter<bigint>;
 
-  void subtract_bigits(int index, bigit other, bigit& borrow) {
+  FMT_CONSTEXPR20 void subtract_bigits(int index, bigit other, bigit& borrow) {
     auto result = static_cast<double_bigit>((*this)[index]) - other - borrow;
     (*this)[index] = static_cast<bigit>(result);
     borrow = static_cast<bigit>(result >> (bigit_bits * 2 - 1));
   }
 
-  void remove_leading_zeros() {
+  FMT_CONSTEXPR20 void remove_leading_zeros() {
     int num_bigits = static_cast<int>(bigits_.size()) - 1;
     while (num_bigits > 0 && (*this)[num_bigits] == 0) --num_bigits;
     bigits_.resize(to_unsigned(num_bigits + 1));
   }
 
   // Computes *this -= other assuming aligned bigints and *this >= other.
-  void subtract_aligned(const bigint& other) {
+  FMT_CONSTEXPR20 void subtract_aligned(const bigint& other) {
     FMT_ASSERT(other.exp_ >= exp_, "unaligned bigints");
     FMT_ASSERT(compare(*this, other) >= 0, "");
     bigit borrow = 0;
@@ -401,7 +414,7 @@ class bigint {
     remove_leading_zeros();
   }
 
-  void multiply(uint32_t value) {
+  FMT_CONSTEXPR20 void multiply(uint32_t value) {
     const double_bigit wide_value = value;
     bigit carry = 0;
     for (size_t i = 0, n = bigits_.size(); i < n; ++i) {
@@ -412,7 +425,7 @@ class bigint {
     if (carry != 0) bigits_.push_back(carry);
   }
 
-  void multiply(uint64_t value) {
+  FMT_CONSTEXPR20 void multiply(uint64_t value) {
     const bigit mask = ~bigit(0);
     const double_bigit lower = value & mask;
     const double_bigit upper = value >> bigit_bits;
@@ -430,14 +443,16 @@ class bigint {
   }
 
  public:
-  bigint() : exp_(0) {}
+  FMT_CONSTEXPR20 bigint() : exp_(0) {}
   explicit bigint(uint64_t n) { assign(n); }
-  ~bigint() { FMT_ASSERT(bigits_.capacity() <= bigits_capacity, ""); }
+  FMT_CONSTEXPR20 ~bigint() {
+    FMT_ASSERT(bigits_.capacity() <= bigits_capacity, "");
+  }
 
   bigint(const bigint&) = delete;
   void operator=(const bigint&) = delete;
 
-  void assign(const bigint& other) {
+  FMT_CONSTEXPR20 void assign(const bigint& other) {
     auto size = other.bigits_.size();
     bigits_.resize(size);
     auto data = other.bigits_.data();
@@ -445,7 +460,7 @@ class bigint {
     exp_ = other.exp_;
   }
 
-  void assign(uint64_t n) {
+  FMT_CONSTEXPR20 void assign(uint64_t n) {
     size_t num_bigits = 0;
     do {
       bigits_[num_bigits++] = n & ~bigit(0);
@@ -455,9 +470,11 @@ class bigint {
     exp_ = 0;
   }
 
-  int num_bigits() const { return static_cast<int>(bigits_.size()) + exp_; }
+  FMT_CONSTEXPR20 int num_bigits() const {
+    return static_cast<int>(bigits_.size()) + exp_;
+  }
 
-  FMT_NOINLINE bigint& operator<<=(int shift) {
+  FMT_NOINLINE FMT_CONSTEXPR20 bigint& operator<<=(int shift) {
     FMT_ASSERT(shift >= 0, "");
     exp_ += shift / bigit_bits;
     shift %= bigit_bits;
@@ -472,13 +489,13 @@ class bigint {
     return *this;
   }
 
-  template <typename Int> bigint& operator*=(Int value) {
+  template <typename Int> FMT_CONSTEXPR20 bigint& operator*=(Int value) {
     FMT_ASSERT(value > 0, "");
     multiply(uint32_or_64_or_128_t<Int>(value));
     return *this;
   }
 
-  friend int compare(const bigint& lhs, const bigint& rhs) {
+  friend FMT_CONSTEXPR20 int compare(const bigint& lhs, const bigint& rhs) {
     int num_lhs_bigits = lhs.num_bigits(), num_rhs_bigits = rhs.num_bigits();
     if (num_lhs_bigits != num_rhs_bigits)
       return num_lhs_bigits > num_rhs_bigits ? 1 : -1;
@@ -495,8 +512,8 @@ class bigint {
   }
 
   // Returns compare(lhs1 + lhs2, rhs).
-  friend int add_compare(const bigint& lhs1, const bigint& lhs2,
-                         const bigint& rhs) {
+  friend FMT_CONSTEXPR20 int add_compare(const bigint& lhs1, const bigint& lhs2,
+                                         const bigint& rhs) {
     int max_lhs_bigits = (std::max)(lhs1.num_bigits(), lhs2.num_bigits());
     int num_rhs_bigits = rhs.num_bigits();
     if (max_lhs_bigits + 1 < num_rhs_bigits) return -1;
@@ -519,7 +536,7 @@ class bigint {
   }
 
   // Assigns pow(10, exp) to this bigint.
-  void assign_pow10(int exp) {
+  FMT_CONSTEXPR20 void assign_pow10(int exp) {
     FMT_ASSERT(exp >= 0, "");
     if (exp == 0) return assign(1);
     // Find the top bit.
@@ -538,7 +555,7 @@ class bigint {
     *this <<= exp;  // Multiply by pow(2, exp) by shifting.
   }
 
-  void square() {
+  FMT_CONSTEXPR20 void square() {
     int num_bigits = static_cast<int>(bigits_.size());
     int num_result_bigits = 2 * num_bigits;
     basic_memory_buffer<bigit, bigits_capacity> n(std::move(bigits_));
@@ -569,7 +586,7 @@ class bigint {
 
   // If this bigint has a bigger exponent than other, adds trailing zero to make
   // exponents equal. This simplifies some operations such as subtraction.
-  void align(const bigint& other) {
+  FMT_CONSTEXPR20 void align(const bigint& other) {
     int exp_difference = exp_ - other.exp_;
     if (exp_difference <= 0) return;
     int num_bigits = static_cast<int>(bigits_.size());
@@ -582,7 +599,7 @@ class bigint {
 
   // Divides this bignum by divisor, assigning the remainder to this and
   // returning the quotient.
-  int divmod_assign(const bigint& divisor) {
+  FMT_CONSTEXPR20 int divmod_assign(const bigint& divisor) {
     FMT_ASSERT(this != &divisor, "");
     if (compare(*this, divisor) < 0) return 0;
     FMT_ASSERT(divisor.bigits_[divisor.bigits_.size() - 1u] != 0, "");
@@ -602,8 +619,9 @@ enum class round_direction { unknown, up, down };
 // some number v and the error, returns whether v should be rounded up, down, or
 // whether the rounding direction can't be determined due to error.
 // error should be less than divisor / 2.
-inline round_direction get_round_direction(uint64_t divisor, uint64_t remainder,
-                                           uint64_t error) {
+FMT_CONSTEXPR inline round_direction get_round_direction(uint64_t divisor,
+                                                         uint64_t remainder,
+                                                         uint64_t error) {
   FMT_ASSERT(remainder < divisor, "");  // divisor - remainder won't overflow.
   FMT_ASSERT(error < divisor, "");      // divisor - error won't overflow.
   FMT_ASSERT(error < divisor - error, "");  // error * 2 won't overflow.
@@ -626,19 +644,52 @@ enum result {
 };
 }
 
-inline uint64_t power_of_10_64(int exp) {
-  static constexpr const uint64_t data[] = {1, FMT_POWERS_OF_10(1),
-                                            FMT_POWERS_OF_10(1000000000ULL),
-                                            10000000000000000000ULL};
-  return data[exp];
-}
+struct gen_digits_handler {
+  char* buf;
+  int size;
+  int precision;
+  int exp10;
+  bool fixed;
+
+  FMT_CONSTEXPR digits::result on_digit(char digit, uint64_t divisor,
+                                        uint64_t remainder, uint64_t error,
+                                        bool integral) {
+    FMT_ASSERT(remainder < divisor, "");
+    buf[size++] = digit;
+    if (!integral && error >= remainder) return digits::error;
+    if (size < precision) return digits::more;
+    if (!integral) {
+      // Check if error * 2 < divisor with overflow prevention.
+      // The check is not needed for the integral part because error = 1
+      // and divisor > (1 << 32) there.
+      if (error >= divisor || error >= divisor - error) return digits::error;
+    } else {
+      FMT_ASSERT(error == 1 && divisor > 2, "");
+    }
+    auto dir = get_round_direction(divisor, remainder, error);
+    if (dir != round_direction::up)
+      return dir == round_direction::down ? digits::done : digits::error;
+    ++buf[size - 1];
+    for (int i = size - 1; i > 0 && buf[i] > '9'; --i) {
+      buf[i] = '0';
+      ++buf[i - 1];
+    }
+    if (buf[0] > '9') {
+      buf[0] = '1';
+      if (fixed)
+        buf[size++] = '0';
+      else
+        ++exp10;
+    }
+    return digits::done;
+  }
+};
 
 // Generates output using the Grisu digit-gen algorithm.
 // error: the size of the region (lower, upper) outside of which numbers
 // definitely do not round to value (Delta in Grisu3).
-template <typename Handler>
-FMT_INLINE digits::result grisu_gen_digits(fp value, uint64_t error, int& exp,
-                                           Handler& handler) {
+FMT_INLINE FMT_CONSTEXPR20 digits::result grisu_gen_digits(
+    fp value, uint64_t error, int& exp, gen_digits_handler& handler) {
   const fp one(1ULL << -value.e, value.e);
   // The integral part of scaled value (p1 in Grisu) = value / one. It cannot be
   // zero because it contains a product of two 64-bit numbers with MSB set (due
@@ -649,10 +700,28 @@ FMT_INLINE digits::result grisu_gen_digits(fp value, uint64_t error, int& exp,
   // The fractional part of scaled value (p2 in Grisu) c = value % one.
   uint64_t fractional = value.f & (one.f - 1);
   exp = count_digits(integral);  // kappa in Grisu.
-  // Divide by 10 to prevent overflow.
-  auto result = handler.on_start(power_of_10_64(exp - 1) << -one.e,
-                                 value.f / 10, error * 10, exp);
-  if (result != digits::more) return result;
+  // Non-fixed formats require at least one digit and no precision adjustment.
+  if (handler.fixed) {
+    // Adjust fixed precision by exponent because it is relative to decimal
+    // point.
+    int precision_offset = exp + handler.exp10;
+    if (precision_offset > 0 &&
+        handler.precision > max_value<int>() - precision_offset) {
+      FMT_THROW(format_error("number is too big"));
+    }
+    handler.precision += precision_offset;
+    // Check if precision is satisfied just by leading zeros, e.g.
+    // format("{:.2f}", 0.001) gives "0.00" without generating any digits.
+    if (handler.precision <= 0) {
+      if (handler.precision < 0) return digits::done;
+      // Divide by 10 to prevent overflow.
+      uint64_t divisor = impl_data::power_of_10_64[exp - 1] << -one.e;
+      auto dir = get_round_direction(divisor, value.f / 10, error * 10);
+      if (dir == round_direction::unknown) return digits::error;
+      handler.buf[handler.size++] = dir == round_direction::up ? '1' : '0';
+      return digits::done;
+    }
+  }
   // Generate digits for the integral part. This can produce up to 10 digits.
   do {
     uint32_t digit = 0;
@@ -699,9 +768,9 @@ FMT_INLINE digits::result grisu_gen_digits(fp value, uint64_t error, int& exp,
     }
     --exp;
     auto remainder = (static_cast<uint64_t>(integral) << -one.e) + fractional;
-    result = handler.on_digit(static_cast<char>('0' + digit),
-                              power_of_10_64(exp) << -one.e, remainder, error,
-                              exp, true);
+    auto result = handler.on_digit(static_cast<char>('0' + digit),
+                                   impl_data::power_of_10_64[exp] << -one.e,
+                                   remainder, error, true);
     if (result != digits::more) return result;
   } while (exp > 0);
   // Generate digits for the fractional part.
@@ -711,69 +780,11 @@ FMT_INLINE digits::result grisu_gen_digits(fp value, uint64_t error, int& exp,
     char digit = static_cast<char>('0' + (fractional >> -one.e));
     fractional &= one.f - 1;
     --exp;
-    result = handler.on_digit(digit, one.f, fractional, error, exp, false);
+    auto result = handler.on_digit(digit, one.f, fractional, error, false);
     if (result != digits::more) return result;
   }
 }
 
-// The fixed precision digit handler.
-struct fixed_handler {
-  char* buf;
-  int size;
-  int precision;
-  int exp10;
-  bool fixed;
-
-  digits::result on_start(uint64_t divisor, uint64_t remainder, uint64_t error,
-                          int& exp) {
-    // Non-fixed formats require at least one digit and no precision adjustment.
-    if (!fixed) return digits::more;
-    // Adjust fixed precision by exponent because it is relative to decimal
-    // point.
-    precision += exp + exp10;
-    // Check if precision is satisfied just by leading zeros, e.g.
-    // format("{:.2f}", 0.001) gives "0.00" without generating any digits.
-    if (precision > 0) return digits::more;
-    if (precision < 0) return digits::done;
-    auto dir = get_round_direction(divisor, remainder, error);
-    if (dir == round_direction::unknown) return digits::error;
-    buf[size++] = dir == round_direction::up ? '1' : '0';
-    return digits::done;
-  }
-
-  digits::result on_digit(char digit, uint64_t divisor, uint64_t remainder,
-                          uint64_t error, int, bool integral) {
-    FMT_ASSERT(remainder < divisor, "");
-    buf[size++] = digit;
-    if (!integral && error >= remainder) return digits::error;
-    if (size < precision) return digits::more;
-    if (!integral) {
-      // Check if error * 2 < divisor with overflow prevention.
-      // The check is not needed for the integral part because error = 1
-      // and divisor > (1 << 32) there.
-      if (error >= divisor || error >= divisor - error) return digits::error;
-    } else {
-      FMT_ASSERT(error == 1 && divisor > 2, "");
-    }
-    auto dir = get_round_direction(divisor, remainder, error);
-    if (dir != round_direction::up)
-      return dir == round_direction::down ? digits::done : digits::error;
-    ++buf[size - 1];
-    for (int i = size - 1; i > 0 && buf[i] > '9'; --i) {
-      buf[i] = '0';
-      ++buf[i - 1];
-    }
-    if (buf[0] > '9') {
-      buf[0] = '1';
-      if (fixed)
-        buf[size++] = '0';
-      else
-        ++exp10;
-    }
-    return digits::done;
-  }
-};
-
 // A 128-bit integer type used internally,
 struct uint128_wrapper {
   uint128_wrapper() = default;
@@ -897,8 +908,7 @@ inline uint64_t umul96_lower64(uint32_t x, uint64_t y) FMT_NOEXCEPT {
 inline int floor_log10_pow2(int e) FMT_NOEXCEPT {
   FMT_ASSERT(e <= 1700 && e >= -1700, "too large exponent");
   const int shift = 22;
-  return (e * static_cast<int>(data::log10_2_significand >> (64 - shift))) >>
-         shift;
+  return (e * static_cast<int>(log10_2_significand >> (64 - shift))) >> shift;
 }
 
 // Various fast log computations.
@@ -916,8 +926,7 @@ inline int floor_log10_pow2_minus_log10_4_over_3(int e) FMT_NOEXCEPT {
   FMT_ASSERT(e <= 1700 && e >= -1700, "too large exponent");
   const uint64_t log10_4_over_3_fractional_digits = 0x1ffbfc2bbc780375;
   const int shift_amount = 22;
-  return (e * static_cast<int>(data::log10_2_significand >>
-                               (64 - shift_amount)) -
+  return (e * static_cast<int>(log10_2_significand >> (64 - shift_amount)) -
           static_cast<int>(log10_4_over_3_fractional_digits >>
                            (64 - shift_amount))) >>
          shift_amount;
@@ -1042,7 +1051,7 @@ template <> struct cache_accessor<float> {
   static uint64_t get_cached_power(int k) FMT_NOEXCEPT {
     FMT_ASSERT(k >= float_info<float>::min_k && k <= float_info<float>::max_k,
                "k is out of range");
-    constexpr const uint64_t pow10_significands[] = {
+    static constexpr const uint64_t pow10_significands[] = {
         0x81ceb32c4b43fcf5, 0xa2425ff75e14fc32, 0xcad2f7f5359a3b3f,
         0xfd87b5f28300ca0e, 0x9e74d1b791e07e49, 0xc612062576589ddb,
         0xf79687aed3eec552, 0x9abe14cd44753b53, 0xc16d9a0095928a28,
@@ -2210,24 +2219,21 @@ small_divisor_case_label:
 }
 }  // namespace dragonbox
 
-// Formats value using a variation of the Fixed-Precision Positive
-// Floating-Point Printout ((FPP)^2) algorithm by Steele & White:
+// Formats a floating-point number using a variation of the Fixed-Precision
+// Positive Floating-Point Printout ((FPP)^2) algorithm by Steele & White:
 // https://fmt.dev/papers/p372-steele.pdf.
-template <typename Double>
-void fallback_format(Double d, int num_digits, bool binary32, buffer<char>& buf,
-                     int& exp10) {
+FMT_CONSTEXPR20 inline void format_dragon(fp value, bool is_predecessor_closer,
+                                          int num_digits, buffer<char>& buf,
+                                          int& exp10) {
   bigint numerator;    // 2 * R in (FPP)^2.
   bigint denominator;  // 2 * S in (FPP)^2.
   // lower and upper are differences between value and corresponding boundaries.
   bigint lower;             // (M^- in (FPP)^2).
   bigint upper_store;       // upper's value if different from lower.
   bigint* upper = nullptr;  // (M^+ in (FPP)^2).
-  fp value;
   // Shift numerator and denominator by an extra bit or two (if lower boundary
   // is closer) to make lower and upper integers. This eliminates multiplication
   // by 2 during later computations.
-  const bool is_predecessor_closer =
-      binary32 ? value.assign(static_cast<float>(d)) : value.assign(d);
   int shift = is_predecessor_closer ? 2 : 1;
   uint64_t significand = value.f << shift;
   if (value.e >= 0) {
@@ -2297,9 +2303,9 @@ void fallback_format(Double d, int num_digits, bool binary32, buffer<char>& buf,
   // Generate the given number of digits.
   exp10 -= num_digits - 1;
   if (num_digits == 0) {
-    buf.try_resize(1);
     denominator *= 10;
-    buf[0] = add_compare(numerator, numerator, denominator) > 0 ? '1' : '0';
+    auto digit = add_compare(numerator, numerator, denominator) > 0 ? '1' : '0';
+    buf.push_back(digit);
     return;
   }
   buf.try_resize(to_unsigned(num_digits));
@@ -2330,9 +2336,12 @@ void fallback_format(Double d, int num_digits, bool binary32, buffer<char>& buf,
   buf[num_digits - 1] = static_cast<char>('0' + digit);
 }
 
-template <typename T>
-int format_float(T value, int precision, float_specs specs, buffer<char>& buf) {
-  static_assert(!std::is_same<T, float>::value, "");
+template <typename Float>
+FMT_HEADER_ONLY_CONSTEXPR20 int format_float(Float value, int precision,
+                                             float_specs specs,
+                                             buffer<char>& buf) {
+  // float is passed as double to reduce the number of instantiations.
+  static_assert(!std::is_same<Float, float>::value, "");
   FMT_ASSERT(value >= 0, "value is negative");
 
   const bool fixed = specs.format == float_format::fixed;
@@ -2342,13 +2351,13 @@ int format_float(T value, int precision, float_specs specs, buffer<char>& buf) {
       return 0;
     }
     buf.try_resize(to_unsigned(precision));
-    std::uninitialized_fill_n(buf.data(), precision, '0');
+    fill_n(buf.data(), precision, '0');
     return -precision;
   }
 
-  if (!specs.use_grisu) return snprintf_float(value, precision, specs, buf);
+  if (specs.fallback) return snprintf_float(value, precision, specs, buf);
 
-  if (precision < 0) {
+  if (!is_constant_evaluated() && precision < 0) {
     // Use Dragonbox for the shortest format.
     if (specs.binary32) {
       auto dec = dragonbox::to_decimal(static_cast<float>(value));
@@ -2360,26 +2369,37 @@ int format_float(T value, int precision, float_specs specs, buffer<char>& buf) {
     return dec.exponent;
   }
 
-  // Use Grisu + Dragon4 for the given precision:
-  // https://www.cs.tufts.edu/~nr/cs257/archive/florian-loitsch/printf.pdf.
   int exp = 0;
-  const int min_exp = -60;  // alpha in Grisu.
-  int cached_exp10 = 0;     // K in Grisu.
-  fp normalized = normalize(fp(value));
-  const auto cached_pow = get_cached_power(
-      min_exp - (normalized.e + fp::significand_size), cached_exp10);
-  normalized = normalized * cached_pow;
-  // Limit precision to the maximum possible number of significant digits in an
-  // IEEE754 double because we don't need to generate zeros.
-  const int max_double_digits = 767;
-  if (precision > max_double_digits) precision = max_double_digits;
-  fixed_handler handler{buf.data(), 0, precision, -cached_exp10, fixed};
-  if (grisu_gen_digits(normalized, 1, exp, handler) == digits::error) {
-    exp += handler.size - cached_exp10 - 1;
-    fallback_format(value, handler.precision, specs.binary32, buf, exp);
-  } else {
-    exp += handler.exp10;
-    buf.try_resize(to_unsigned(handler.size));
+  bool use_dragon = true;
+  if (is_fast_float<Float>()) {
+    // Use Grisu + Dragon4 for the given precision:
+    // https://www.cs.tufts.edu/~nr/cs257/archive/florian-loitsch/printf.pdf.
+    const int min_exp = -60;  // alpha in Grisu.
+    int cached_exp10 = 0;     // K in Grisu.
+    fp normalized = normalize(fp(value));
+    const auto cached_pow = get_cached_power(
+        min_exp - (normalized.e + fp::num_significand_bits), cached_exp10);
+    normalized = normalized * cached_pow;
+    gen_digits_handler handler{buf.data(), 0, precision, -cached_exp10, fixed};
+    if (grisu_gen_digits(normalized, 1, exp, handler) != digits::error &&
+        !is_constant_evaluated()) {
+      exp += handler.exp10;
+      buf.try_resize(to_unsigned(handler.size));
+      use_dragon = false;
+    } else {
+      exp += handler.size - cached_exp10 - 1;
+      precision = handler.precision;
+    }
+  }
+  if (use_dragon) {
+    auto f = fp();
+    bool is_predecessor_closer =
+        specs.binary32 ? f.assign(static_cast<float>(value)) : f.assign(value);
+    // Limit precision to the maximum possible number of significant digits in
+    // an IEEE754 double because we don't need to generate zeros.
+    const int max_double_digits = 767;
+    if (precision > max_double_digits) precision = max_double_digits;
+    format_dragon(f, is_predecessor_closer, precision, buf, exp);
   }
   if (!fixed && !specs.showpoint) {
     // Remove trailing zeros.
@@ -2391,7 +2411,7 @@ int format_float(T value, int precision, float_specs specs, buffer<char>& buf) {
     buf.try_resize(num_digits);
   }
   return exp;
-}  // namespace detail
+}
 
 template <typename T>
 int snprintf_float(T value, int precision, float_specs specs,
@@ -2525,8 +2545,8 @@ template <> struct formatter<detail::bigint> {
 };
 
 FMT_FUNC detail::utf8_to_utf16::utf8_to_utf16(string_view s) {
-  for_each_codepoint(s, [this](uint32_t cp, int error) {
-    if (error != 0) FMT_THROW(std::runtime_error("invalid utf8"));
+  for_each_codepoint(s, [this](uint32_t cp, string_view) {
+    if (cp == invalid_code_point) FMT_THROW(std::runtime_error("invalid utf8"));
     if (cp <= 0xFFFF) {
       buffer_.push_back(static_cast<wchar_t>(cp));
     } else {
@@ -2534,6 +2554,7 @@ FMT_FUNC detail::utf8_to_utf16::utf8_to_utf16(string_view s) {
       buffer_.push_back(static_cast<wchar_t>(0xD800 + (cp >> 10)));
       buffer_.push_back(static_cast<wchar_t>(0xDC00 + (cp & 0x3FF)));
     }
+    return true;
   });
   buffer_.push_back(0);
 }
@@ -2549,15 +2570,17 @@ FMT_FUNC void format_system_error(detail::buffer<char>& out, int error_code,
   format_error_code(out, error_code, message);
 }
 
-FMT_FUNC void detail::error_handler::on_error(const char* message) {
-  FMT_THROW(format_error(message));
-}
-
 FMT_FUNC void report_system_error(int error_code,
                                   const char* message) FMT_NOEXCEPT {
   report_error(format_system_error, error_code, message);
 }
 
+// DEPRECATED!
+// This function is defined here and not inline for ABI compatiblity.
+FMT_FUNC void detail::error_handler::on_error(const char* message) {
+  throw_format_error(message);
+}
+
 FMT_FUNC std::string vformat(string_view fmt, format_args args) {
   // Don't optimize the "{}" case to keep the binary size small and because it
   // can be better optimized in fmt::format anyway.

include/spdlog/fmt/bundled/os.h

@@ -21,17 +21,20 @@
 
 #include "format.h"
 
+#ifndef FMT_USE_FCNTL
 // UWP doesn't provide _pipe.
-#if FMT_HAS_INCLUDE("winapifamily.h")
-#  include <winapifamily.h>
-#endif
-#if (FMT_HAS_INCLUDE(<fcntl.h>) || defined(__APPLE__) || \
-     defined(__linux__)) &&                              \
-    (!defined(WINAPI_FAMILY) || (WINAPI_FAMILY == WINAPI_FAMILY_DESKTOP_APP))
-#  include <fcntl.h>  // for O_RDONLY
-#  define FMT_USE_FCNTL 1
-#else
-#  define FMT_USE_FCNTL 0
+#  if FMT_HAS_INCLUDE("winapifamily.h")
+#    include <winapifamily.h>
+#  endif
+#  if (FMT_HAS_INCLUDE(<fcntl.h>) || defined(__APPLE__) || \
+       defined(__linux__)) &&                              \
+      (!defined(WINAPI_FAMILY) ||                          \
+       (WINAPI_FAMILY == WINAPI_FAMILY_DESKTOP_APP))
+#    include <fcntl.h>  // for O_RDONLY
+#    define FMT_USE_FCNTL 1
+#  else
+#    define FMT_USE_FCNTL 0
+#  endif
 #endif
 
 #ifndef FMT_POSIX
@@ -390,23 +393,26 @@ struct ostream_params {
       : ostream_params(params...) {
     this->buffer_size = bs.value;
   }
+
+// Intel has a bug that results in failure to deduce a constructor
+// for empty parameter packs.
+#  if defined(__INTEL_COMPILER) && __INTEL_COMPILER < 2000
+  ostream_params(int new_oflag) : oflag(new_oflag) {}
+  ostream_params(detail::buffer_size bs) : buffer_size(bs.value) {}
+#  endif
 };
 
 FMT_END_DETAIL_NAMESPACE
 
-constexpr detail::buffer_size buffer_size;
+// Added {} below to work around default constructor error known to
+// occur in Xcode versions 7.2.1 and 8.2.1.
+constexpr detail::buffer_size buffer_size{};
 
 /** A fast output stream which is not thread-safe. */
 class FMT_API ostream final : private detail::buffer<char> {
  private:
   file file_;
 
-  void flush() {
-    if (size() == 0) return;
-    file_.write(data(), size());
-    clear();
-  }
-
   void grow(size_t) override;
 
   ostream(cstring_view path, const detail::ostream_params& params)
@@ -426,6 +432,12 @@ class FMT_API ostream final : private detail::buffer<char> {
     delete[] data();
   }
 
+  void flush() {
+    if (size() == 0) return;
+    file_.write(data(), size());
+    clear();
+  }
+
   template <typename... T>
   friend ostream output_file(cstring_view path, T... params);
 
@@ -500,7 +512,7 @@ class locale {
 
   // Converts string to floating-point number and advances str past the end
   // of the parsed input.
-  double strtod(const char*& str) const {
+  FMT_DEPRECATED double strtod(const char*& str) const {
     char* end = nullptr;
     double result = strtod_l(str, &end, locale_);
     str = end;

include/spdlog/fmt/bundled/ostream.h

@@ -14,73 +14,20 @@
 
 FMT_BEGIN_NAMESPACE
 
-template <typename Char> class basic_printf_parse_context;
 template <typename OutputIt, typename Char> class basic_printf_context;
 
 namespace detail {
 
-template <class Char> class formatbuf : public std::basic_streambuf<Char> {
- private:
-  using int_type = typename std::basic_streambuf<Char>::int_type;
-  using traits_type = typename std::basic_streambuf<Char>::traits_type;
-
-  buffer<Char>& buffer_;
-
- public:
-  formatbuf(buffer<Char>& buf) : buffer_(buf) {}
-
- protected:
-  // The put-area is actually always empty. This makes the implementation
-  // simpler and has the advantage that the streambuf and the buffer are always
-  // in sync and sputc never writes into uninitialized memory. The obvious
-  // disadvantage is that each call to sputc always results in a (virtual) call
-  // to overflow. There is no disadvantage here for sputn since this always
-  // results in a call to xsputn.
-
-  int_type overflow(int_type ch = traits_type::eof()) FMT_OVERRIDE {
-    if (!traits_type::eq_int_type(ch, traits_type::eof()))
-      buffer_.push_back(static_cast<Char>(ch));
-    return ch;
-  }
-
-  std::streamsize xsputn(const Char* s, std::streamsize count) FMT_OVERRIDE {
-    buffer_.append(s, s + count);
-    return count;
-  }
-};
-
-struct converter {
-  template <typename T, FMT_ENABLE_IF(is_integral<T>::value)> converter(T);
-};
-
-template <typename Char> struct test_stream : std::basic_ostream<Char> {
- private:
-  void_t<> operator<<(converter);
-};
-
-// Hide insertion operators for built-in types.
-template <typename Char, typename Traits>
-void_t<> operator<<(std::basic_ostream<Char, Traits>&, Char);
-template <typename Char, typename Traits>
-void_t<> operator<<(std::basic_ostream<Char, Traits>&, char);
-template <typename Traits>
-void_t<> operator<<(std::basic_ostream<char, Traits>&, char);
-template <typename Traits>
-void_t<> operator<<(std::basic_ostream<char, Traits>&, signed char);
-template <typename Traits>
-void_t<> operator<<(std::basic_ostream<char, Traits>&, unsigned char);
-
-// Checks if T has a user-defined operator<< (e.g. not a member of
-// std::ostream).
-template <typename T, typename Char> class is_streamable {
+// Checks if T has a user-defined operator<<.
+template <typename T, typename Char, typename Enable = void>
+class is_streamable {
  private:
   template <typename U>
-  static bool_constant<!std::is_same<decltype(std::declval<test_stream<Char>&>()
-                                              << std::declval<U>()),
-                                     void_t<>>::value>
-  test(int);
+  static auto test(int)
+      -> bool_constant<sizeof(std::declval<std::basic_ostream<Char>&>()
+                              << std::declval<U>()) != 0>;
 
-  template <typename> static std::false_type test(...);
+  template <typename> static auto test(...) -> std::false_type;
 
   using result = decltype(test<T>(0));
 
@@ -90,7 +37,21 @@ template <typename T, typename Char> class is_streamable {
   static const bool value = result::value;
 };
 
+// Formatting of built-in types and arrays is intentionally disabled because
+// it's handled by standard (non-ostream) formatters.
+template <typename T, typename Char>
+struct is_streamable<
+    T, Char,
+    enable_if_t<
+        std::is_arithmetic<T>::value || std::is_array<T>::value ||
+        std::is_pointer<T>::value || std::is_same<T, char8_type>::value ||
+        std::is_same<T, std::basic_string<Char>>::value ||
+        std::is_same<T, std_string_view<Char>>::value ||
+        (std::is_convertible<T, int>::value && !std::is_enum<T>::value)>>
+    : std::false_type {};
+
 // Write the content of buf to os.
+// It is a separate function rather than a part of vprint to simplify testing.
 template <typename Char>
 void write_buffer(std::basic_ostream<Char>& os, buffer<Char>& buf) {
   const Char* buf_data = buf.data();
@@ -108,8 +69,8 @@ void write_buffer(std::basic_ostream<Char>& os, buffer<Char>& buf) {
 template <typename Char, typename T>
 void format_value(buffer<Char>& buf, const T& value,
                   locale_ref loc = locale_ref()) {
-  formatbuf<Char> format_buf(buf);
-  std::basic_ostream<Char> output(&format_buf);
+  auto&& format_buf = formatbuf<std::basic_streambuf<Char>>(buf);
+  auto&& output = std::basic_ostream<Char>(&format_buf);
 #if !defined(FMT_STATIC_THOUSANDS_SEPARATOR)
   if (loc) output.imbue(loc.get<std::locale>());
 #endif
@@ -122,29 +83,22 @@ void format_value(buffer<Char>& buf, const T& value,
 template <typename T, typename Char>
 struct fallback_formatter<T, Char, enable_if_t<is_streamable<T, Char>::value>>
     : private formatter<basic_string_view<Char>, Char> {
-  FMT_CONSTEXPR auto parse(basic_format_parse_context<Char>& ctx)
-      -> decltype(ctx.begin()) {
-    return formatter<basic_string_view<Char>, Char>::parse(ctx);
-  }
-  template <typename ParseCtx,
-            FMT_ENABLE_IF(std::is_same<
-                          ParseCtx, basic_printf_parse_context<Char>>::value)>
-  auto parse(ParseCtx& ctx) -> decltype(ctx.begin()) {
-    return ctx.begin();
-  }
+  using formatter<basic_string_view<Char>, Char>::parse;
 
   template <typename OutputIt>
   auto format(const T& value, basic_format_context<OutputIt, Char>& ctx)
       -> OutputIt {
-    basic_memory_buffer<Char> buffer;
+    auto buffer = basic_memory_buffer<Char>();
     format_value(buffer, value, ctx.locale());
-    basic_string_view<Char> str(buffer.data(), buffer.size());
-    return formatter<basic_string_view<Char>, Char>::format(str, ctx);
+    return formatter<basic_string_view<Char>, Char>::format(
+        {buffer.data(), buffer.size()}, ctx);
   }
+
+  // DEPRECATED!
   template <typename OutputIt>
   auto format(const T& value, basic_printf_context<OutputIt, Char>& ctx)
       -> OutputIt {
-    basic_memory_buffer<Char> buffer;
+    auto buffer = basic_memory_buffer<Char>();
     format_value(buffer, value, ctx.locale());
     return std::copy(buffer.begin(), buffer.end(), ctx.out());
   }
@@ -155,7 +109,7 @@ FMT_MODULE_EXPORT
 template <typename Char>
 void vprint(std::basic_ostream<Char>& os, basic_string_view<Char> format_str,
             basic_format_args<buffer_context<type_identity_t<Char>>> args) {
-  basic_memory_buffer<Char> buffer;
+  auto buffer = basic_memory_buffer<Char>();
   detail::vformat_to(buffer, format_str, args);
   detail::write_buffer(os, buffer);
 }

include/spdlog/fmt/bundled/printf.h

@@ -233,7 +233,7 @@ class printf_arg_formatter : public arg_formatter<Char> {
 
   OutputIt write_null_pointer(bool is_string = false) {
     auto s = this->specs;
-    s.type = 0;
+    s.type = presentation_type::none;
     return write_bytes(this->out, is_string ? "(null)" : "(nil)", s);
   }
 
@@ -249,8 +249,10 @@ class printf_arg_formatter : public arg_formatter<Char> {
     // std::is_same instead.
     if (std::is_same<T, Char>::value) {
       format_specs fmt_specs = this->specs;
-      if (fmt_specs.type && fmt_specs.type != 'c')
+      if (fmt_specs.type != presentation_type::none &&
+          fmt_specs.type != presentation_type::chr) {
         return (*this)(static_cast<int>(value));
+      }
       fmt_specs.sign = sign::none;
       fmt_specs.alt = false;
       fmt_specs.fill[0] = ' ';  // Ignore '0' flag for char types.
@@ -271,13 +273,13 @@ class printf_arg_formatter : public arg_formatter<Char> {
   /** Formats a null-terminated C string. */
   OutputIt operator()(const char* value) {
     if (value) return base::operator()(value);
-    return write_null_pointer(this->specs.type != 'p');
+    return write_null_pointer(this->specs.type != presentation_type::pointer);
   }
 
   /** Formats a null-terminated wide C string. */
   OutputIt operator()(const wchar_t* value) {
     if (value) return base::operator()(value);
-    return write_null_pointer(this->specs.type != 'p');
+    return write_null_pointer(this->specs.type != presentation_type::pointer);
   }
 
   OutputIt operator()(basic_string_view<Char> value) {
@@ -490,13 +492,13 @@ void vprintf(buffer<Char>& buf, basic_string_view<Char> format,
 
     // Parse type.
     if (it == end) FMT_THROW(format_error("invalid format string"));
-    specs.type = static_cast<char>(*it++);
+    char type = static_cast<char>(*it++);
     if (arg.is_integral()) {
       // Normalize type.
-      switch (specs.type) {
+      switch (type) {
       case 'i':
       case 'u':
-        specs.type = 'd';
+        type = 'd';
         break;
       case 'c':
         visit_format_arg(
@@ -505,6 +507,9 @@ void vprintf(buffer<Char>& buf, basic_string_view<Char> format,
         break;
       }
     }
+    specs.type = parse_presentation_type(type);
+    if (specs.type == presentation_type::none)
+      parse_ctx.on_error("invalid type specifier");
 
     start = it;
 

include/spdlog/fmt/bundled/ranges.h

@@ -13,37 +13,13 @@
 #define FMT_RANGES_H_
 
 #include <initializer_list>
+#include <tuple>
 #include <type_traits>
 
 #include "format.h"
 
 FMT_BEGIN_NAMESPACE
 
-template <typename Char, typename Enable = void> struct formatting_range {
-#ifdef FMT_DEPRECATED_BRACED_RANGES
-  Char prefix = '{';
-  Char postfix = '}';
-#else
-  Char prefix = '[';
-  Char postfix = ']';
-#endif
-
-  template <typename ParseContext>
-  FMT_CONSTEXPR auto parse(ParseContext& ctx) -> decltype(ctx.begin()) {
-    return ctx.begin();
-  }
-};
-
-template <typename Char, typename Enable = void> struct formatting_tuple {
-  Char prefix = '(';
-  Char postfix = ')';
-
-  template <typename ParseContext>
-  FMT_CONSTEXPR auto parse(ParseContext& ctx) -> decltype(ctx.begin()) {
-    return ctx.begin();
-  }
-};
-
 namespace detail {
 
 template <typename RangeT, typename OutputIterator>
@@ -71,7 +47,7 @@ OutputIterator copy(wchar_t ch, OutputIterator out) {
   return out;
 }
 
-/// Return true value if T has std::string interface, like std::string_view.
+// Returns true if T has a std::string-like interface, like std::string_view.
 template <typename T> class is_std_string_like {
   template <typename U>
   static auto check(U* p)
@@ -80,12 +56,40 @@ template <typename T> class is_std_string_like {
 
  public:
   static FMT_CONSTEXPR_DECL const bool value =
-      is_string<T>::value || !std::is_void<decltype(check<T>(nullptr))>::value;
+      is_string<T>::value ||
+      std::is_convertible<T, std_string_view<char>>::value ||
+      !std::is_void<decltype(check<T>(nullptr))>::value;
 };
 
 template <typename Char>
 struct is_std_string_like<fmt::basic_string_view<Char>> : std::true_type {};
 
+template <typename T> class is_map {
+  template <typename U> static auto check(U*) -> typename U::mapped_type;
+  template <typename> static void check(...);
+
+ public:
+#ifdef FMT_FORMAT_MAP_AS_LIST
+  static FMT_CONSTEXPR_DECL const bool value = false;
+#else
+  static FMT_CONSTEXPR_DECL const bool value =
+      !std::is_void<decltype(check<T>(nullptr))>::value;
+#endif
+};
+
+template <typename T> class is_set {
+  template <typename U> static auto check(U*) -> typename U::key_type;
+  template <typename> static void check(...);
+
+ public:
+#ifdef FMT_FORMAT_SET_AS_LIST
+  static FMT_CONSTEXPR_DECL const bool value = false;
+#else
+  static FMT_CONSTEXPR_DECL const bool value =
+      !std::is_void<decltype(check<T>(nullptr))>::value && !is_map<T>::value;
+#endif
+};
+
 template <typename... Ts> struct conditional_helper {};
 
 template <typename T, typename _ = void> struct is_range_ : std::false_type {};
@@ -143,16 +147,16 @@ struct has_mutable_begin_end : std::false_type {};
 
 template <typename T>
 struct has_const_begin_end<
-    T, void_t<decltype(detail::range_begin(
-                  std::declval<const remove_cvref_t<T>&>())),
-              decltype(detail::range_begin(
-                  std::declval<const remove_cvref_t<T>&>()))>>
+    T,
+    void_t<
+        decltype(detail::range_begin(std::declval<const remove_cvref_t<T>&>())),
+        decltype(detail::range_end(std::declval<const remove_cvref_t<T>&>()))>>
     : std::true_type {};
 
 template <typename T>
 struct has_mutable_begin_end<
     T, void_t<decltype(detail::range_begin(std::declval<T>())),
-              decltype(detail::range_begin(std::declval<T>())),
+              decltype(detail::range_end(std::declval<T>())),
               enable_if_t<std::is_copy_constructible<T>::value>>>
     : std::true_type {};
 
@@ -160,34 +164,10 @@ template <typename T>
 struct is_range_<T, void>
     : std::integral_constant<bool, (has_const_begin_end<T>::value ||
                                     has_mutable_begin_end<T>::value)> {};
-
-template <typename T, typename Enable = void> struct range_to_view;
-template <typename T>
-struct range_to_view<T, enable_if_t<has_const_begin_end<T>::value>> {
-  struct view_t {
-    const T* m_range_ptr;
-
-    auto begin() const FMT_DECLTYPE_RETURN(detail::range_begin(*m_range_ptr));
-    auto end() const FMT_DECLTYPE_RETURN(detail::range_end(*m_range_ptr));
-  };
-  static auto view(const T& range) -> view_t { return {&range}; }
-};
-
-template <typename T>
-struct range_to_view<T, enable_if_t<!has_const_begin_end<T>::value &&
-                                    has_mutable_begin_end<T>::value>> {
-  struct view_t {
-    T m_range_copy;
-
-    auto begin() FMT_DECLTYPE_RETURN(detail::range_begin(m_range_copy));
-    auto end() FMT_DECLTYPE_RETURN(detail::range_end(m_range_copy));
-  };
-  static auto view(const T& range) -> view_t { return {range}; }
-};
 #  undef FMT_DECLTYPE_RETURN
 #endif
 
-/// tuple_size and tuple_element check.
+// tuple_size and tuple_element check.
 template <typename T> class is_tuple_like_ {
   template <typename U>
   static auto check(U* p) -> decltype(std::tuple_size<U>::value, int());
@@ -251,16 +231,295 @@ template <typename OutputIt> OutputIt write_delimiter(OutputIt out) {
   return out;
 }
 
-template <
-    typename Char, typename OutputIt, typename Arg,
-    FMT_ENABLE_IF(is_std_string_like<typename std::decay<Arg>::type>::value)>
-OutputIt write_range_entry(OutputIt out, const Arg& v) {
+struct singleton {
+  unsigned char upper;
+  unsigned char lower_count;
+};
+
+inline auto is_printable(uint16_t x, const singleton* singletons,
+                         size_t singletons_size,
+                         const unsigned char* singleton_lowers,
+                         const unsigned char* normal, size_t normal_size)
+    -> bool {
+  auto upper = x >> 8;
+  auto lower_start = 0;
+  for (size_t i = 0; i < singletons_size; ++i) {
+    auto s = singletons[i];
+    auto lower_end = lower_start + s.lower_count;
+    if (upper < s.upper) break;
+    if (upper == s.upper) {
+      for (auto j = lower_start; j < lower_end; ++j) {
+        if (singleton_lowers[j] == (x & 0xff)) return false;
+      }
+    }
+    lower_start = lower_end;
+  }
+
+  auto xsigned = static_cast<int>(x);
+  auto current = true;
+  for (size_t i = 0; i < normal_size; ++i) {
+    auto v = static_cast<int>(normal[i]);
+    auto len = (v & 0x80) != 0 ? (v & 0x7f) << 8 | normal[++i] : v;
+    xsigned -= len;
+    if (xsigned < 0) break;
+    current = !current;
+  }
+  return current;
+}
+
+// Returns true iff the code point cp is printable.
+// This code is generated by support/printable.py.
+inline auto is_printable(uint32_t cp) -> bool {
+  static constexpr singleton singletons0[] = {
+      {0x00, 1},  {0x03, 5},  {0x05, 6},  {0x06, 3},  {0x07, 6},  {0x08, 8},
+      {0x09, 17}, {0x0a, 28}, {0x0b, 25}, {0x0c, 20}, {0x0d, 16}, {0x0e, 13},
+      {0x0f, 4},  {0x10, 3},  {0x12, 18}, {0x13, 9},  {0x16, 1},  {0x17, 5},
+      {0x18, 2},  {0x19, 3},  {0x1a, 7},  {0x1c, 2},  {0x1d, 1},  {0x1f, 22},
+      {0x20, 3},  {0x2b, 3},  {0x2c, 2},  {0x2d, 11}, {0x2e, 1},  {0x30, 3},
+      {0x31, 2},  {0x32, 1},  {0xa7, 2},  {0xa9, 2},  {0xaa, 4},  {0xab, 8},
+      {0xfa, 2},  {0xfb, 5},  {0xfd, 4},  {0xfe, 3},  {0xff, 9},
+  };
+  static constexpr unsigned char singletons0_lower[] = {
+      0xad, 0x78, 0x79, 0x8b, 0x8d, 0xa2, 0x30, 0x57, 0x58, 0x8b, 0x8c, 0x90,
+      0x1c, 0x1d, 0xdd, 0x0e, 0x0f, 0x4b, 0x4c, 0xfb, 0xfc, 0x2e, 0x2f, 0x3f,
+      0x5c, 0x5d, 0x5f, 0xb5, 0xe2, 0x84, 0x8d, 0x8e, 0x91, 0x92, 0xa9, 0xb1,
+      0xba, 0xbb, 0xc5, 0xc6, 0xc9, 0xca, 0xde, 0xe4, 0xe5, 0xff, 0x00, 0x04,
+      0x11, 0x12, 0x29, 0x31, 0x34, 0x37, 0x3a, 0x3b, 0x3d, 0x49, 0x4a, 0x5d,
+      0x84, 0x8e, 0x92, 0xa9, 0xb1, 0xb4, 0xba, 0xbb, 0xc6, 0xca, 0xce, 0xcf,
+      0xe4, 0xe5, 0x00, 0x04, 0x0d, 0x0e, 0x11, 0x12, 0x29, 0x31, 0x34, 0x3a,
+      0x3b, 0x45, 0x46, 0x49, 0x4a, 0x5e, 0x64, 0x65, 0x84, 0x91, 0x9b, 0x9d,
+      0xc9, 0xce, 0xcf, 0x0d, 0x11, 0x29, 0x45, 0x49, 0x57, 0x64, 0x65, 0x8d,
+      0x91, 0xa9, 0xb4, 0xba, 0xbb, 0xc5, 0xc9, 0xdf, 0xe4, 0xe5, 0xf0, 0x0d,
+      0x11, 0x45, 0x49, 0x64, 0x65, 0x80, 0x84, 0xb2, 0xbc, 0xbe, 0xbf, 0xd5,
+      0xd7, 0xf0, 0xf1, 0x83, 0x85, 0x8b, 0xa4, 0xa6, 0xbe, 0xbf, 0xc5, 0xc7,
+      0xce, 0xcf, 0xda, 0xdb, 0x48, 0x98, 0xbd, 0xcd, 0xc6, 0xce, 0xcf, 0x49,
+      0x4e, 0x4f, 0x57, 0x59, 0x5e, 0x5f, 0x89, 0x8e, 0x8f, 0xb1, 0xb6, 0xb7,
+      0xbf, 0xc1, 0xc6, 0xc7, 0xd7, 0x11, 0x16, 0x17, 0x5b, 0x5c, 0xf6, 0xf7,
+      0xfe, 0xff, 0x80, 0x0d, 0x6d, 0x71, 0xde, 0xdf, 0x0e, 0x0f, 0x1f, 0x6e,
+      0x6f, 0x1c, 0x1d, 0x5f, 0x7d, 0x7e, 0xae, 0xaf, 0xbb, 0xbc, 0xfa, 0x16,
+      0x17, 0x1e, 0x1f, 0x46, 0x47, 0x4e, 0x4f, 0x58, 0x5a, 0x5c, 0x5e, 0x7e,
+      0x7f, 0xb5, 0xc5, 0xd4, 0xd5, 0xdc, 0xf0, 0xf1, 0xf5, 0x72, 0x73, 0x8f,
+      0x74, 0x75, 0x96, 0x2f, 0x5f, 0x26, 0x2e, 0x2f, 0xa7, 0xaf, 0xb7, 0xbf,
+      0xc7, 0xcf, 0xd7, 0xdf, 0x9a, 0x40, 0x97, 0x98, 0x30, 0x8f, 0x1f, 0xc0,
+      0xc1, 0xce, 0xff, 0x4e, 0x4f, 0x5a, 0x5b, 0x07, 0x08, 0x0f, 0x10, 0x27,
+      0x2f, 0xee, 0xef, 0x6e, 0x6f, 0x37, 0x3d, 0x3f, 0x42, 0x45, 0x90, 0x91,
+      0xfe, 0xff, 0x53, 0x67, 0x75, 0xc8, 0xc9, 0xd0, 0xd1, 0xd8, 0xd9, 0xe7,
+      0xfe, 0xff,
+  };
+  static constexpr singleton singletons1[] = {
+      {0x00, 6},  {0x01, 1}, {0x03, 1},  {0x04, 2}, {0x08, 8},  {0x09, 2},
+      {0x0a, 5},  {0x0b, 2}, {0x0e, 4},  {0x10, 1}, {0x11, 2},  {0x12, 5},
+      {0x13, 17}, {0x14, 1}, {0x15, 2},  {0x17, 2}, {0x19, 13}, {0x1c, 5},
+      {0x1d, 8},  {0x24, 1}, {0x6a, 3},  {0x6b, 2}, {0xbc, 2},  {0xd1, 2},
+      {0xd4, 12}, {0xd5, 9}, {0xd6, 2},  {0xd7, 2}, {0xda, 1},  {0xe0, 5},
+      {0xe1, 2},  {0xe8, 2}, {0xee, 32}, {0xf0, 4}, {0xf8, 2},  {0xf9, 2},
+      {0xfa, 2},  {0xfb, 1},
+  };
+  static constexpr unsigned char singletons1_lower[] = {
+      0x0c, 0x27, 0x3b, 0x3e, 0x4e, 0x4f, 0x8f, 0x9e, 0x9e, 0x9f, 0x06, 0x07,
+      0x09, 0x36, 0x3d, 0x3e, 0x56, 0xf3, 0xd0, 0xd1, 0x04, 0x14, 0x18, 0x36,
+      0x37, 0x56, 0x57, 0x7f, 0xaa, 0xae, 0xaf, 0xbd, 0x35, 0xe0, 0x12, 0x87,
+      0x89, 0x8e, 0x9e, 0x04, 0x0d, 0x0e, 0x11, 0x12, 0x29, 0x31, 0x34, 0x3a,
+      0x45, 0x46, 0x49, 0x4a, 0x4e, 0x4f, 0x64, 0x65, 0x5c, 0xb6, 0xb7, 0x1b,
+      0x1c, 0x07, 0x08, 0x0a, 0x0b, 0x14, 0x17, 0x36, 0x39, 0x3a, 0xa8, 0xa9,
+      0xd8, 0xd9, 0x09, 0x37, 0x90, 0x91, 0xa8, 0x07, 0x0a, 0x3b, 0x3e, 0x66,
+      0x69, 0x8f, 0x92, 0x6f, 0x5f, 0xee, 0xef, 0x5a, 0x62, 0x9a, 0x9b, 0x27,
+      0x28, 0x55, 0x9d, 0xa0, 0xa1, 0xa3, 0xa4, 0xa7, 0xa8, 0xad, 0xba, 0xbc,
+      0xc4, 0x06, 0x0b, 0x0c, 0x15, 0x1d, 0x3a, 0x3f, 0x45, 0x51, 0xa6, 0xa7,
+      0xcc, 0xcd, 0xa0, 0x07, 0x19, 0x1a, 0x22, 0x25, 0x3e, 0x3f, 0xc5, 0xc6,
+      0x04, 0x20, 0x23, 0x25, 0x26, 0x28, 0x33, 0x38, 0x3a, 0x48, 0x4a, 0x4c,
+      0x50, 0x53, 0x55, 0x56, 0x58, 0x5a, 0x5c, 0x5e, 0x60, 0x63, 0x65, 0x66,
+      0x6b, 0x73, 0x78, 0x7d, 0x7f, 0x8a, 0xa4, 0xaa, 0xaf, 0xb0, 0xc0, 0xd0,
+      0xae, 0xaf, 0x79, 0xcc, 0x6e, 0x6f, 0x93,
+  };
+  static constexpr unsigned char normal0[] = {
+      0x00, 0x20, 0x5f, 0x22, 0x82, 0xdf, 0x04, 0x82, 0x44, 0x08, 0x1b, 0x04,
+      0x06, 0x11, 0x81, 0xac, 0x0e, 0x80, 0xab, 0x35, 0x28, 0x0b, 0x80, 0xe0,
+      0x03, 0x19, 0x08, 0x01, 0x04, 0x2f, 0x04, 0x34, 0x04, 0x07, 0x03, 0x01,
+      0x07, 0x06, 0x07, 0x11, 0x0a, 0x50, 0x0f, 0x12, 0x07, 0x55, 0x07, 0x03,
+      0x04, 0x1c, 0x0a, 0x09, 0x03, 0x08, 0x03, 0x07, 0x03, 0x02, 0x03, 0x03,
+      0x03, 0x0c, 0x04, 0x05, 0x03, 0x0b, 0x06, 0x01, 0x0e, 0x15, 0x05, 0x3a,
+      0x03, 0x11, 0x07, 0x06, 0x05, 0x10, 0x07, 0x57, 0x07, 0x02, 0x07, 0x15,
+      0x0d, 0x50, 0x04, 0x43, 0x03, 0x2d, 0x03, 0x01, 0x04, 0x11, 0x06, 0x0f,
+      0x0c, 0x3a, 0x04, 0x1d, 0x25, 0x5f, 0x20, 0x6d, 0x04, 0x6a, 0x25, 0x80,
+      0xc8, 0x05, 0x82, 0xb0, 0x03, 0x1a, 0x06, 0x82, 0xfd, 0x03, 0x59, 0x07,
+      0x15, 0x0b, 0x17, 0x09, 0x14, 0x0c, 0x14, 0x0c, 0x6a, 0x06, 0x0a, 0x06,
+      0x1a, 0x06, 0x59, 0x07, 0x2b, 0x05, 0x46, 0x0a, 0x2c, 0x04, 0x0c, 0x04,
+      0x01, 0x03, 0x31, 0x0b, 0x2c, 0x04, 0x1a, 0x06, 0x0b, 0x03, 0x80, 0xac,
+      0x06, 0x0a, 0x06, 0x21, 0x3f, 0x4c, 0x04, 0x2d, 0x03, 0x74, 0x08, 0x3c,
+      0x03, 0x0f, 0x03, 0x3c, 0x07, 0x38, 0x08, 0x2b, 0x05, 0x82, 0xff, 0x11,
+      0x18, 0x08, 0x2f, 0x11, 0x2d, 0x03, 0x20, 0x10, 0x21, 0x0f, 0x80, 0x8c,
+      0x04, 0x82, 0x97, 0x19, 0x0b, 0x15, 0x88, 0x94, 0x05, 0x2f, 0x05, 0x3b,
+      0x07, 0x02, 0x0e, 0x18, 0x09, 0x80, 0xb3, 0x2d, 0x74, 0x0c, 0x80, 0xd6,
+      0x1a, 0x0c, 0x05, 0x80, 0xff, 0x05, 0x80, 0xdf, 0x0c, 0xee, 0x0d, 0x03,
+      0x84, 0x8d, 0x03, 0x37, 0x09, 0x81, 0x5c, 0x14, 0x80, 0xb8, 0x08, 0x80,
+      0xcb, 0x2a, 0x38, 0x03, 0x0a, 0x06, 0x38, 0x08, 0x46, 0x08, 0x0c, 0x06,
+      0x74, 0x0b, 0x1e, 0x03, 0x5a, 0x04, 0x59, 0x09, 0x80, 0x83, 0x18, 0x1c,
+      0x0a, 0x16, 0x09, 0x4c, 0x04, 0x80, 0x8a, 0x06, 0xab, 0xa4, 0x0c, 0x17,
+      0x04, 0x31, 0xa1, 0x04, 0x81, 0xda, 0x26, 0x07, 0x0c, 0x05, 0x05, 0x80,
+      0xa5, 0x11, 0x81, 0x6d, 0x10, 0x78, 0x28, 0x2a, 0x06, 0x4c, 0x04, 0x80,
+      0x8d, 0x04, 0x80, 0xbe, 0x03, 0x1b, 0x03, 0x0f, 0x0d,
+  };
+  static constexpr unsigned char normal1[] = {
+      0x5e, 0x22, 0x7b, 0x05, 0x03, 0x04, 0x2d, 0x03, 0x66, 0x03, 0x01, 0x2f,
+      0x2e, 0x80, 0x82, 0x1d, 0x03, 0x31, 0x0f, 0x1c, 0x04, 0x24, 0x09, 0x1e,
+      0x05, 0x2b, 0x05, 0x44, 0x04, 0x0e, 0x2a, 0x80, 0xaa, 0x06, 0x24, 0x04,
+      0x24, 0x04, 0x28, 0x08, 0x34, 0x0b, 0x01, 0x80, 0x90, 0x81, 0x37, 0x09,
+      0x16, 0x0a, 0x08, 0x80, 0x98, 0x39, 0x03, 0x63, 0x08, 0x09, 0x30, 0x16,
+      0x05, 0x21, 0x03, 0x1b, 0x05, 0x01, 0x40, 0x38, 0x04, 0x4b, 0x05, 0x2f,
+      0x04, 0x0a, 0x07, 0x09, 0x07, 0x40, 0x20, 0x27, 0x04, 0x0c, 0x09, 0x36,
+      0x03, 0x3a, 0x05, 0x1a, 0x07, 0x04, 0x0c, 0x07, 0x50, 0x49, 0x37, 0x33,
+      0x0d, 0x33, 0x07, 0x2e, 0x08, 0x0a, 0x81, 0x26, 0x52, 0x4e, 0x28, 0x08,
+      0x2a, 0x56, 0x1c, 0x14, 0x17, 0x09, 0x4e, 0x04, 0x1e, 0x0f, 0x43, 0x0e,
+      0x19, 0x07, 0x0a, 0x06, 0x48, 0x08, 0x27, 0x09, 0x75, 0x0b, 0x3f, 0x41,
+      0x2a, 0x06, 0x3b, 0x05, 0x0a, 0x06, 0x51, 0x06, 0x01, 0x05, 0x10, 0x03,
+      0x05, 0x80, 0x8b, 0x62, 0x1e, 0x48, 0x08, 0x0a, 0x80, 0xa6, 0x5e, 0x22,
+      0x45, 0x0b, 0x0a, 0x06, 0x0d, 0x13, 0x39, 0x07, 0x0a, 0x36, 0x2c, 0x04,
+      0x10, 0x80, 0xc0, 0x3c, 0x64, 0x53, 0x0c, 0x48, 0x09, 0x0a, 0x46, 0x45,
+      0x1b, 0x48, 0x08, 0x53, 0x1d, 0x39, 0x81, 0x07, 0x46, 0x0a, 0x1d, 0x03,
+      0x47, 0x49, 0x37, 0x03, 0x0e, 0x08, 0x0a, 0x06, 0x39, 0x07, 0x0a, 0x81,
+      0x36, 0x19, 0x80, 0xb7, 0x01, 0x0f, 0x32, 0x0d, 0x83, 0x9b, 0x66, 0x75,
+      0x0b, 0x80, 0xc4, 0x8a, 0xbc, 0x84, 0x2f, 0x8f, 0xd1, 0x82, 0x47, 0xa1,
+      0xb9, 0x82, 0x39, 0x07, 0x2a, 0x04, 0x02, 0x60, 0x26, 0x0a, 0x46, 0x0a,
+      0x28, 0x05, 0x13, 0x82, 0xb0, 0x5b, 0x65, 0x4b, 0x04, 0x39, 0x07, 0x11,
+      0x40, 0x05, 0x0b, 0x02, 0x0e, 0x97, 0xf8, 0x08, 0x84, 0xd6, 0x2a, 0x09,
+      0xa2, 0xf7, 0x81, 0x1f, 0x31, 0x03, 0x11, 0x04, 0x08, 0x81, 0x8c, 0x89,
+      0x04, 0x6b, 0x05, 0x0d, 0x03, 0x09, 0x07, 0x10, 0x93, 0x60, 0x80, 0xf6,
+      0x0a, 0x73, 0x08, 0x6e, 0x17, 0x46, 0x80, 0x9a, 0x14, 0x0c, 0x57, 0x09,
+      0x19, 0x80, 0x87, 0x81, 0x47, 0x03, 0x85, 0x42, 0x0f, 0x15, 0x85, 0x50,
+      0x2b, 0x80, 0xd5, 0x2d, 0x03, 0x1a, 0x04, 0x02, 0x81, 0x70, 0x3a, 0x05,
+      0x01, 0x85, 0x00, 0x80, 0xd7, 0x29, 0x4c, 0x04, 0x0a, 0x04, 0x02, 0x83,
+      0x11, 0x44, 0x4c, 0x3d, 0x80, 0xc2, 0x3c, 0x06, 0x01, 0x04, 0x55, 0x05,
+      0x1b, 0x34, 0x02, 0x81, 0x0e, 0x2c, 0x04, 0x64, 0x0c, 0x56, 0x0a, 0x80,
+      0xae, 0x38, 0x1d, 0x0d, 0x2c, 0x04, 0x09, 0x07, 0x02, 0x0e, 0x06, 0x80,
+      0x9a, 0x83, 0xd8, 0x08, 0x0d, 0x03, 0x0d, 0x03, 0x74, 0x0c, 0x59, 0x07,
+      0x0c, 0x14, 0x0c, 0x04, 0x38, 0x08, 0x0a, 0x06, 0x28, 0x08, 0x22, 0x4e,
+      0x81, 0x54, 0x0c, 0x15, 0x03, 0x03, 0x05, 0x07, 0x09, 0x19, 0x07, 0x07,
+      0x09, 0x03, 0x0d, 0x07, 0x29, 0x80, 0xcb, 0x25, 0x0a, 0x84, 0x06,
+  };
+  auto lower = static_cast<uint16_t>(cp);
+  if (cp < 0x10000) {
+    return is_printable(lower, singletons0,
+                        sizeof(singletons0) / sizeof(*singletons0),
+                        singletons0_lower, normal0, sizeof(normal0));
+  }
+  if (cp < 0x20000) {
+    return is_printable(lower, singletons1,
+                        sizeof(singletons1) / sizeof(*singletons1),
+                        singletons1_lower, normal1, sizeof(normal1));
+  }
+  if (0x2a6de <= cp && cp < 0x2a700) return false;
+  if (0x2b735 <= cp && cp < 0x2b740) return false;
+  if (0x2b81e <= cp && cp < 0x2b820) return false;
+  if (0x2cea2 <= cp && cp < 0x2ceb0) return false;
+  if (0x2ebe1 <= cp && cp < 0x2f800) return false;
+  if (0x2fa1e <= cp && cp < 0x30000) return false;
+  if (0x3134b <= cp && cp < 0xe0100) return false;
+  if (0xe01f0 <= cp && cp < 0x110000) return false;
+  return cp < 0x110000;
+}
+
+inline auto needs_escape(uint32_t cp) -> bool {
+  return cp < 0x20 || cp == 0x7f || cp == '"' || cp == '\\' ||
+         !is_printable(cp);
+}
+
+template <typename Char> struct find_escape_result {
+  const Char* begin;
+  const Char* end;
+  uint32_t cp;
+};
+
+template <typename Char>
+auto find_escape(const Char* begin, const Char* end)
+    -> find_escape_result<Char> {
+  for (; begin != end; ++begin) {
+    auto cp = static_cast<typename std::make_unsigned<Char>::type>(*begin);
+    if (sizeof(Char) == 1 && cp >= 0x80) continue;
+    if (needs_escape(cp)) return {begin, begin + 1, cp};
+  }
+  return {begin, nullptr, 0};
+}
+
+inline auto find_escape(const char* begin, const char* end)
+    -> find_escape_result<char> {
+  if (!is_utf8()) return find_escape<char>(begin, end);
+  auto result = find_escape_result<char>{end, nullptr, 0};
+  for_each_codepoint(string_view(begin, to_unsigned(end - begin)),
+                     [&](uint32_t cp, string_view sv) {
+                       if (needs_escape(cp)) {
+                         result = {sv.begin(), sv.end(), cp};
+                         return false;
+                       }
+                       return true;
+                     });
+  return result;
+}
+
+template <typename Char, typename OutputIt>
+auto write_range_entry(OutputIt out, basic_string_view<Char> str) -> OutputIt {
   *out++ = '"';
-  out = write<Char>(out, v);
+  auto begin = str.begin(), end = str.end();
+  do {
+    auto escape = find_escape(begin, end);
+    out = copy_str<Char>(begin, escape.begin, out);
+    begin = escape.end;
+    if (!begin) break;
+    auto c = static_cast<Char>(escape.cp);
+    switch (escape.cp) {
+    case '\n':
+      *out++ = '\\';
+      c = 'n';
+      break;
+    case '\r':
+      *out++ = '\\';
+      c = 'r';
+      break;
+    case '\t':
+      *out++ = '\\';
+      c = 't';
+      break;
+    case '"':
+      FMT_FALLTHROUGH;
+    case '\\':
+      *out++ = '\\';
+      break;
+    default:
+      if (is_utf8()) {
+        if (escape.cp < 0x100) {
+          out = format_to(out, "\\x{:02x}", escape.cp);
+          continue;
+        }
+        if (escape.cp < 0x10000) {
+          out = format_to(out, "\\u{:04x}", escape.cp);
+          continue;
+        }
+        if (escape.cp < 0x110000) {
+          out = format_to(out, "\\U{:08x}", escape.cp);
+          continue;
+        }
+      }
+      for (Char escape_char : basic_string_view<Char>(
+               escape.begin, to_unsigned(escape.end - escape.begin))) {
+        out = format_to(
+            out, "\\x{:02x}",
+            static_cast<typename std::make_unsigned<Char>::type>(escape_char));
+      }
+      continue;
+    }
+    *out++ = c;
+  } while (begin != end);
   *out++ = '"';
   return out;
 }
 
+template <typename Char, typename OutputIt, typename T,
+          FMT_ENABLE_IF(std::is_convertible<T, std_string_view<char>>::value)>
+inline auto write_range_entry(OutputIt out, const T& str) -> OutputIt {
+  auto sv = std_string_view<Char>(str);
+  return write_range_entry<Char>(out, basic_string_view<Char>(sv));
+}
+
 template <typename Char, typename OutputIt, typename Arg,
           FMT_ENABLE_IF(std::is_same<Arg, Char>::value)>
 OutputIt write_range_entry(OutputIt out, const Arg v) {
@@ -288,43 +547,37 @@ template <typename T> struct is_tuple_like {
 template <typename TupleT, typename Char>
 struct formatter<TupleT, Char, enable_if_t<fmt::is_tuple_like<TupleT>::value>> {
  private:
-  // C++11 generic lambda for format()
+  // C++11 generic lambda for format().
   template <typename FormatContext> struct format_each {
     template <typename T> void operator()(const T& v) {
       if (i > 0) out = detail::write_delimiter(out);
       out = detail::write_range_entry<Char>(out, v);
       ++i;
     }
-    formatting_tuple<Char>& formatting;
-    size_t& i;
-    typename std::add_lvalue_reference<
-        decltype(std::declval<FormatContext>().out())>::type out;
+    int i;
+    typename FormatContext::iterator& out;
   };
 
  public:
-  formatting_tuple<Char> formatting;
-
   template <typename ParseContext>
   FMT_CONSTEXPR auto parse(ParseContext& ctx) -> decltype(ctx.begin()) {
-    return formatting.parse(ctx);
+    return ctx.begin();
   }
 
   template <typename FormatContext = format_context>
   auto format(const TupleT& values, FormatContext& ctx) -> decltype(ctx.out()) {
     auto out = ctx.out();
-    size_t i = 0;
-
-    detail::copy(formatting.prefix, out);
-    detail::for_each(values, format_each<FormatContext>{formatting, i, out});
-    detail::copy(formatting.postfix, out);
-
-    return ctx.out();
+    *out++ = '(';
+    detail::for_each(values, format_each<FormatContext>{0, out});
+    *out++ = ')';
+    return out;
   }
 };
 
 template <typename T, typename Char> struct is_range {
   static FMT_CONSTEXPR_DECL const bool value =
       detail::is_range_<T>::value && !detail::is_std_string_like<T>::value &&
+      !detail::is_map<T>::value &&
       !std::is_convertible<T, std::basic_string<Char>>::value &&
       !std::is_constructible<detail::std_string_view<Char>, T>::value;
 };
@@ -334,32 +587,80 @@ struct formatter<
     T, Char,
     enable_if_t<
         fmt::is_range<T, Char>::value
-// Workaround a bug in MSVC 2017 and earlier.
-#if !FMT_MSC_VER || FMT_MSC_VER >= 1927
-        && (has_formatter<detail::value_type<T>, format_context>::value ||
+// Workaround a bug in MSVC 2019 and earlier.
+#if !FMT_MSC_VER
+        && (is_formattable<detail::value_type<T>, Char>::value ||
             detail::has_fallback_formatter<detail::value_type<T>, Char>::value)
 #endif
         >> {
-  formatting_range<Char> formatting;
-
   template <typename ParseContext>
   FMT_CONSTEXPR auto parse(ParseContext& ctx) -> decltype(ctx.begin()) {
-    return formatting.parse(ctx);
+    return ctx.begin();
   }
 
-  template <typename FormatContext>
-  typename FormatContext::iterator format(const T& values, FormatContext& ctx) {
-    auto out = detail::copy(formatting.prefix, ctx.out());
-    size_t i = 0;
-    auto view = detail::range_to_view<T>::view(values);
-    auto it = view.begin();
-    auto end = view.end();
+  template <
+      typename FormatContext, typename U,
+      FMT_ENABLE_IF(
+          std::is_same<U, conditional_t<detail::has_const_begin_end<T>::value,
+                                        const T, T>>::value)>
+  auto format(U& range, FormatContext& ctx) -> decltype(ctx.out()) {
+#ifdef FMT_DEPRECATED_BRACED_RANGES
+    Char prefix = '{';
+    Char postfix = '}';
+#else
+    Char prefix = detail::is_set<T>::value ? '{' : '[';
+    Char postfix = detail::is_set<T>::value ? '}' : ']';
+#endif
+    auto out = ctx.out();
+    *out++ = prefix;
+    int i = 0;
+    auto it = std::begin(range);
+    auto end = std::end(range);
     for (; it != end; ++it) {
       if (i > 0) out = detail::write_delimiter(out);
       out = detail::write_range_entry<Char>(out, *it);
       ++i;
     }
-    return detail::copy(formatting.postfix, out);
+    *out++ = postfix;
+    return out;
+  }
+};
+
+template <typename T, typename Char>
+struct formatter<
+    T, Char,
+    enable_if_t<
+        detail::is_map<T>::value
+// Workaround a bug in MSVC 2019 and earlier.
+#if !FMT_MSC_VER
+        && (is_formattable<detail::value_type<T>, Char>::value ||
+            detail::has_fallback_formatter<detail::value_type<T>, Char>::value)
+#endif
+        >> {
+  template <typename ParseContext>
+  FMT_CONSTEXPR auto parse(ParseContext& ctx) -> decltype(ctx.begin()) {
+    return ctx.begin();
+  }
+
+  template <
+      typename FormatContext, typename U,
+      FMT_ENABLE_IF(
+          std::is_same<U, conditional_t<detail::has_const_begin_end<T>::value,
+                                        const T, T>>::value)>
+  auto format(U& map, FormatContext& ctx) -> decltype(ctx.out()) {
+    auto out = ctx.out();
+    *out++ = '{';
+    int i = 0;
+    for (const auto& item : map) {
+      if (i > 0) out = detail::write_delimiter(out);
+      out = detail::write_range_entry<Char>(out, item.first);
+      *out++ = ':';
+      *out++ = ' ';
+      out = detail::write_range_entry<Char>(out, item.second);
+      ++i;
+    }
+    *out++ = '}';
+    return out;
   }
 };
 
@@ -374,46 +675,70 @@ template <typename Char, typename... T> struct tuple_join_view : detail::view {
 template <typename Char, typename... T>
 using tuple_arg_join = tuple_join_view<Char, T...>;
 
+// Define FMT_TUPLE_JOIN_SPECIFIERS to enable experimental format specifiers
+// support in tuple_join. It is disabled by default because of issues with
+// the dynamic width and precision.
+#ifndef FMT_TUPLE_JOIN_SPECIFIERS
+#  define FMT_TUPLE_JOIN_SPECIFIERS 0
+#endif
+
 template <typename Char, typename... T>
 struct formatter<tuple_join_view<Char, T...>, Char> {
   template <typename ParseContext>
   FMT_CONSTEXPR auto parse(ParseContext& ctx) -> decltype(ctx.begin()) {
-    return ctx.begin();
+    return do_parse(ctx, std::integral_constant<size_t, sizeof...(T)>());
   }
 
   template <typename FormatContext>
-  auto format(const tuple_join_view<Char, T...>& value, FormatContext& ctx) ->
-      typename FormatContext::iterator {
-    return format(value, ctx, detail::make_index_sequence<sizeof...(T)>{});
+  auto format(const tuple_join_view<Char, T...>& value,
+              FormatContext& ctx) const -> typename FormatContext::iterator {
+    return do_format(value, ctx,
+                     std::integral_constant<size_t, sizeof...(T)>());
   }
 
  private:
-  template <typename FormatContext, size_t... N>
-  auto format(const tuple_join_view<Char, T...>& value, FormatContext& ctx,
-              detail::index_sequence<N...>) ->
-      typename FormatContext::iterator {
-    using std::get;
-    return format_args(value, ctx, get<N>(value.tuple)...);
+  std::tuple<formatter<typename std::decay<T>::type, Char>...> formatters_;
+
+  template <typename ParseContext>
+  FMT_CONSTEXPR auto do_parse(ParseContext& ctx,
+                              std::integral_constant<size_t, 0>)
+      -> decltype(ctx.begin()) {
+    return ctx.begin();
+  }
+
+  template <typename ParseContext, size_t N>
+  FMT_CONSTEXPR auto do_parse(ParseContext& ctx,
+                              std::integral_constant<size_t, N>)
+      -> decltype(ctx.begin()) {
+    auto end = ctx.begin();
+#if FMT_TUPLE_JOIN_SPECIFIERS
+    end = std::get<sizeof...(T) - N>(formatters_).parse(ctx);
+    if (N > 1) {
+      auto end1 = do_parse(ctx, std::integral_constant<size_t, N - 1>());
+      if (end != end1)
+        FMT_THROW(format_error("incompatible format specs for tuple elements"));
+    }
+#endif
+    return end;
   }
 
   template <typename FormatContext>
-  auto format_args(const tuple_join_view<Char, T...>&, FormatContext& ctx) ->
+  auto do_format(const tuple_join_view<Char, T...>&, FormatContext& ctx,
+                 std::integral_constant<size_t, 0>) const ->
       typename FormatContext::iterator {
-    // NOTE: for compilers that support C++17, this empty function instantiation
-    // can be replaced with a constexpr branch in the variadic overload.
     return ctx.out();
   }
 
-  template <typename FormatContext, typename Arg, typename... Args>
-  auto format_args(const tuple_join_view<Char, T...>& value, FormatContext& ctx,
-                   const Arg& arg, const Args&... args) ->
+  template <typename FormatContext, size_t N>
+  auto do_format(const tuple_join_view<Char, T...>& value, FormatContext& ctx,
+                 std::integral_constant<size_t, N>) const ->
       typename FormatContext::iterator {
-    using base = formatter<typename std::decay<Arg>::type, Char>;
-    auto out = base().format(arg, ctx);
-    if (sizeof...(Args) > 0) {
+    auto out = std::get<sizeof...(T) - N>(formatters_)
+                   .format(std::get<sizeof...(T) - N>(value.tuple), ctx);
+    if (N > 1) {
       out = std::copy(value.sep.begin(), value.sep.end(), out);
       ctx.advance_to(out);
-      return format_args(value, ctx, args...);
+      return do_format(value, ctx, std::integral_constant<size_t, N - 1>());
     }
     return out;
   }

include/spdlog/fmt/bundled/xchar.h

@@ -5,8 +5,8 @@
 //
 // For the license information refer to format.h.
 
-#ifndef FMT_WCHAR_H_
-#define FMT_WCHAR_H_
+#ifndef FMT_XCHAR_H_
+#define FMT_XCHAR_H_
 
 #include <cwchar>
 #include <tuple>
@@ -217,11 +217,11 @@ inline void vprint(wstring_view fmt, wformat_args args) {
 
 template <typename... T>
 void print(std::FILE* f, wformat_string<T...> fmt, T&&... args) {
-  return vprint(f, wstring_view(fmt), make_wformat_args(args...));
+  return vprint(f, wstring_view(fmt), fmt::make_wformat_args(args...));
 }
 
 template <typename... T> void print(wformat_string<T...> fmt, T&&... args) {
-  return vprint(wstring_view(fmt), make_wformat_args(args...));
+  return vprint(wstring_view(fmt), fmt::make_wformat_args(args...));
 }
 
 /**
@@ -233,4 +233,4 @@ template <typename T> inline auto to_wstring(const T& value) -> std::wstring {
 FMT_MODULE_EXPORT_END
 FMT_END_NAMESPACE
 
-#endif  // FMT_WCHAR_H_
+#endif  // FMT_XCHAR_H_

include/spdlog/fmt/chrono.h

@@ -8,13 +8,15 @@
 // include bundled or external copy of fmtlib's chrono support
 //
 
-#if !defined(SPDLOG_FMT_EXTERNAL)
-#    ifdef SPDLOG_HEADER_ONLY
-#        ifndef FMT_HEADER_ONLY
-#            define FMT_HEADER_ONLY
+#if !defined(SPDLOG_USE_STD_FORMAT)
+#    if !defined(SPDLOG_FMT_EXTERNAL)
+#        ifdef SPDLOG_HEADER_ONLY
+#            ifndef FMT_HEADER_ONLY
+#                define FMT_HEADER_ONLY
+#            endif
 #        endif
+#        include <spdlog/fmt/bundled/chrono.h>
+#    else
+#        include <fmt/chrono.h>
 #    endif
-#    include <spdlog/fmt/bundled/chrono.h>
-#else
-#    include <fmt/chrono.h>
 #endif

include/spdlog/fmt/compile.h

@@ -5,16 +5,18 @@
 
 #pragma once
 //
-// include bundled or external copy of fmtlib's ostream support
+// include bundled or external copy of fmtlib's compile-time support
 //
 
-#if !defined(SPDLOG_FMT_EXTERNAL)
-#    ifdef SPDLOG_HEADER_ONLY
-#        ifndef FMT_HEADER_ONLY
-#            define FMT_HEADER_ONLY
+#if !defined(SPDLOG_USE_STD_FORMAT)
+#    if !defined(SPDLOG_FMT_EXTERNAL)
+#        ifdef SPDLOG_HEADER_ONLY
+#            ifndef FMT_HEADER_ONLY
+#                define FMT_HEADER_ONLY
+#            endif
 #        endif
+#        include <spdlog/fmt/bundled/compile.h>
+#    else
+#        include <fmt/compile.h>
 #    endif
-#    include <spdlog/fmt/bundled/compile.h>
-#else
-#    include <fmt/compile.h>
 #endif

include/spdlog/fmt/fmt.h

@@ -10,7 +10,9 @@
 // By default spdlog include its own copy.
 //
 
-#if !defined(SPDLOG_FMT_EXTERNAL)
+#if defined(SPDLOG_USE_STD_FORMAT) // SPDLOG_USE_STD_FORMAT is defined - use std::format
+#    include <format>
+#elif !defined(SPDLOG_FMT_EXTERNAL)
 #    if !defined(SPDLOG_COMPILED_LIB) && !defined(FMT_HEADER_ONLY)
 #        define FMT_HEADER_ONLY
 #    endif

include/spdlog/fmt/ostr.h

@@ -8,13 +8,15 @@
 // include bundled or external copy of fmtlib's ostream support
 //
 
-#if !defined(SPDLOG_FMT_EXTERNAL)
-#    ifdef SPDLOG_HEADER_ONLY
-#        ifndef FMT_HEADER_ONLY
-#            define FMT_HEADER_ONLY
+#if !defined(SPDLOG_USE_STD_FORMAT)
+#    if !defined(SPDLOG_FMT_EXTERNAL)
+#        ifdef SPDLOG_HEADER_ONLY
+#            ifndef FMT_HEADER_ONLY
+#                define FMT_HEADER_ONLY
+#            endif
 #        endif
+#        include <spdlog/fmt/bundled/ostream.h>
+#    else
+#        include <fmt/ostream.h>
 #    endif
-#    include <spdlog/fmt/bundled/ostream.h>
-#else
-#    include <fmt/ostream.h>
 #endif

include/spdlog/fmt/ranges.h

@@ -0,0 +1,22 @@
+//
+// Copyright(c) 2016 Gabi Melman.
+// Distributed under the MIT License (http://opensource.org/licenses/MIT)
+//
+
+#pragma once
+//
+// include bundled or external copy of fmtlib's ranges support
+//
+
+#if !defined(SPDLOG_USE_STD_FORMAT)
+#    if !defined(SPDLOG_FMT_EXTERNAL)
+#        ifdef SPDLOG_HEADER_ONLY
+#            ifndef FMT_HEADER_ONLY
+#                define FMT_HEADER_ONLY
+#            endif
+#        endif
+#        include <spdlog/fmt/bundled/ranges.h>
+#    else
+#        include <fmt/ranges.h>
+#    endif
+#endif

include/spdlog/fmt/xchar.h

@@ -5,16 +5,18 @@
 
 #pragma once
 //
-// include bundled or external copy of fmtlib's ostream support
+// include bundled or external copy of fmtlib's xchar support
 //
 
-#if !defined(SPDLOG_FMT_EXTERNAL)
-#    ifdef SPDLOG_HEADER_ONLY
-#        ifndef FMT_HEADER_ONLY
-#            define FMT_HEADER_ONLY
+#if !defined(SPDLOG_USE_STD_FORMAT)
+#    if !defined(SPDLOG_FMT_EXTERNAL)
+#        ifdef SPDLOG_HEADER_ONLY
+#            ifndef FMT_HEADER_ONLY
+#                define FMT_HEADER_ONLY
+#            endif
 #        endif
+#        include <spdlog/fmt/bundled/xchar.h>
+#    else
+#        include <fmt/xchar.h>
 #    endif
-#    include <spdlog/fmt/bundled/xchar.h>
-#else
-#    include <fmt/xchar.h>
 #endif

include/spdlog/fwd.h

@@ -11,4 +11,8 @@ namespace sinks {
 class sink;
 }
 
+namespace level {
+enum level_enum : int;
+}
+
 } // namespace spdlog

include/spdlog/logger-inl.h

@@ -185,7 +185,7 @@ SPDLOG_INLINE void logger::sink_it_(const details::log_msg &msg)
             {
                 sink->log(msg);
             }
-            SPDLOG_LOGGER_CATCH()
+            SPDLOG_LOGGER_CATCH(msg.source)
         }
     }
 
@@ -203,7 +203,7 @@ SPDLOG_INLINE void logger::flush_()
         {
             sink->flush();
         }
-        SPDLOG_LOGGER_CATCH()
+        SPDLOG_LOGGER_CATCH(source_loc())
     }
 }
 

include/spdlog/logger.h

@@ -28,10 +28,17 @@
 #include <vector>
 
 #ifndef SPDLOG_NO_EXCEPTIONS
-#    define SPDLOG_LOGGER_CATCH()                                                                                                          \
+#    define SPDLOG_LOGGER_CATCH(location)                                                                                                  \
         catch (const std::exception &ex)                                                                                                   \
         {                                                                                                                                  \
-            err_handler_(ex.what());                                                                                                       \
+            if (location.filename)                                                                                                         \
+            {                                                                                                                              \
+                err_handler_(fmt_lib::format("{} [{}({})]", ex.what(), location.filename, location.line));                                 \
+            }                                                                                                                              \
+            else                                                                                                                           \
+            {                                                                                                                              \
+                err_handler_(ex.what());                                                                                                   \
+            }                                                                                                                              \
         }                                                                                                                                  \
         catch (...)                                                                                                                        \
         {                                                                                                                                  \
@@ -39,7 +46,7 @@
             throw;                                                                                                                         \
         }
 #else
-#    define SPDLOG_LOGGER_CATCH()
+#    define SPDLOG_LOGGER_CATCH(location)
 #endif
 
 namespace spdlog {
@@ -78,13 +85,13 @@ public:
     void swap(spdlog::logger &other) SPDLOG_NOEXCEPT;
 
     template<typename... Args>
-    void log(source_loc loc, level::level_enum lvl, fmt::format_string<Args...> fmt, Args &&...args)
+    void log(source_loc loc, level::level_enum lvl, format_string_t<Args...> fmt, Args &&... args)
     {
         log_(loc, lvl, fmt, std::forward<Args>(args)...);
     }
 
     template<typename... Args>
-    void log(level::level_enum lvl, fmt::format_string<Args...> fmt, Args &&...args)
+    void log(level::level_enum lvl, format_string_t<Args...> fmt, Args &&... args)
     {
         log(source_loc{}, lvl, fmt, std::forward<Args>(args)...);
     }
@@ -95,17 +102,8 @@ public:
         log(source_loc{}, lvl, msg);
     }
 
-    // T can be statically converted to string_view
-    template<class T, typename std::enable_if<std::is_convertible<const T &, spdlog::string_view_t>::value, int>::type = 0>
-    void log(source_loc loc, level::level_enum lvl, const T &msg)
-    {
-        log(loc, lvl, string_view_t{msg});
-    }
-
-    // T cannot be statically converted to neither string_view, nor wstring_view and nor format string
-    template<class T, typename std::enable_if<!std::is_convertible<const T &, spdlog::string_view_t>::value &&
-                                                  !is_convertible_to_basic_format_string<const T &>::value,
-                          int>::type = 0>
+    // T cannot be statically converted to format string (including string_view/wstring_view)
+    template<class T, typename std::enable_if<!is_convertible_to_any_format_string<const T &>::value, int>::type = 0>
     void log(source_loc loc, level::level_enum lvl, const T &msg)
     {
         log(loc, lvl, "{}", msg);
@@ -143,86 +141,121 @@ public:
     }
 
     template<typename... Args>
-    void trace(fmt::format_string<Args...> fmt, Args &&...args)
+    void trace(format_string_t<Args...> fmt, Args &&... args)
     {
         log(level::trace, fmt, std::forward<Args>(args)...);
     }
 
     template<typename... Args>
-    void debug(fmt::format_string<Args...> fmt, Args &&...args)
+    void debug(format_string_t<Args...> fmt, Args &&... args)
     {
         log(level::debug, fmt, std::forward<Args>(args)...);
     }
 
     template<typename... Args>
-    void info(fmt::format_string<Args...> fmt, Args &&...args)
+    void info(format_string_t<Args...> fmt, Args &&... args)
     {
         log(level::info, fmt, std::forward<Args>(args)...);
     }
 
     template<typename... Args>
-    void warn(fmt::format_string<Args...> fmt, Args &&...args)
+    void warn(format_string_t<Args...> fmt, Args &&... args)
     {
         log(level::warn, fmt, std::forward<Args>(args)...);
     }
 
     template<typename... Args>
-    void error(fmt::format_string<Args...> fmt, Args &&...args)
+    void error(format_string_t<Args...> fmt, Args &&... args)
     {
         log(level::err, fmt, std::forward<Args>(args)...);
     }
 
     template<typename... Args>
-    void critical(fmt::format_string<Args...> fmt, Args &&...args)
+    void critical(format_string_t<Args...> fmt, Args &&... args)
     {
         log(level::critical, fmt, std::forward<Args>(args)...);
     }
 
 #ifdef SPDLOG_WCHAR_TO_UTF8_SUPPORT
     template<typename... Args>
-    void log(level::level_enum lvl, fmt::wformat_string<Args...> fmt, Args &&...args)
-    {
-        log(source_loc{}, lvl, fmt, std::forward<Args>(args)...);
-    }
-
-    template<typename... Args>
-    void log(source_loc loc, level::level_enum lvl, fmt::wformat_string<Args...> fmt, Args &&...args)
+    void log(source_loc loc, level::level_enum lvl, wformat_string_t<Args...> fmt, Args &&... args)
     {
         log_(loc, lvl, fmt, std::forward<Args>(args)...);
     }
 
     template<typename... Args>
-    void trace(fmt::wformat_string<Args...> fmt, Args &&...args)
+    void log(level::level_enum lvl, wformat_string_t<Args...> fmt, Args &&... args)
+    {
+        log(source_loc{}, lvl, fmt, std::forward<Args>(args)...);
+    }
+
+    void log(log_clock::time_point log_time, source_loc loc, level::level_enum lvl, wstring_view_t msg)
+    {
+        bool log_enabled = should_log(lvl);
+        bool traceback_enabled = tracer_.enabled();
+        if (!log_enabled && !traceback_enabled)
+        {
+            return;
+        }
+
+        memory_buf_t buf;
+        details::os::wstr_to_utf8buf(wstring_view_t(msg.data(), msg.size()), buf);
+        details::log_msg log_msg(log_time, loc, name_, lvl, string_view_t(buf.data(), buf.size()));
+        log_it_(log_msg, log_enabled, traceback_enabled);
+    }
+
+    void log(source_loc loc, level::level_enum lvl, wstring_view_t msg)
+    {
+        bool log_enabled = should_log(lvl);
+        bool traceback_enabled = tracer_.enabled();
+        if (!log_enabled && !traceback_enabled)
+        {
+            return;
+        }
+
+        memory_buf_t buf;
+        details::os::wstr_to_utf8buf(wstring_view_t(msg.data(), msg.size()), buf);
+        details::log_msg log_msg(loc, name_, lvl, string_view_t(buf.data(), buf.size()));
+        log_it_(log_msg, log_enabled, traceback_enabled);
+    }
+
+    void log(level::level_enum lvl, wstring_view_t msg)
+    {
+        log(source_loc{}, lvl, msg);
+    }
+
+    template<typename... Args>
+    void trace(wformat_string_t<Args...> fmt, Args &&... args)
     {
         log(level::trace, fmt, std::forward<Args>(args)...);
     }
 
     template<typename... Args>
-    void debug(fmt::wformat_string<Args...> fmt, Args &&...args)
+    void debug(wformat_string_t<Args...> fmt, Args &&... args)
     {
         log(level::debug, fmt, std::forward<Args>(args)...);
     }
 
     template<typename... Args>
-    void info(fmt::wformat_string<Args...> fmt, Args &&...args)
+    void info(wformat_string_t<Args...> fmt, Args &&... args)
     {
         log(level::info, fmt, std::forward<Args>(args)...);
     }
 
     template<typename... Args>
-    void warn(fmt::wformat_string<Args...> fmt, Args &&...args)
+    void warn(wformat_string_t<Args...> fmt, Args &&... args)
     {
         log(level::warn, fmt, std::forward<Args>(args)...);
     }
 
     template<typename... Args>
-    void error(fmt::wformat_string<Args...> fmt, Args &&...args)
+    void error(wformat_string_t<Args...> fmt, Args &&... args)
     {
         log(level::err, fmt, std::forward<Args>(args)...);
     }
 
     template<typename... Args>
-    void critical(fmt::wformat_string<Args...> fmt, Args &&...args)
+    void critical(wformat_string_t<Args...> fmt, Args &&... args)
     {
         log(level::critical, fmt, std::forward<Args>(args)...);
     }
@@ -320,7 +353,7 @@ protected:
 
     // common implementation for after templated public api has been resolved
     template<typename... Args>
-    void log_(source_loc loc, level::level_enum lvl, string_view_t fmt, Args &&...args)
+    void log_(source_loc loc, level::level_enum lvl, string_view_t fmt, Args &&... args)
     {
         bool log_enabled = should_log(lvl);
         bool traceback_enabled = tracer_.enabled();
@@ -330,17 +363,21 @@ protected:
         }
         SPDLOG_TRY
         {
+#ifdef SPDLOG_USE_STD_FORMAT
+            memory_buf_t buf = std::vformat(fmt, std::make_format_args(std::forward<Args>(args)...));
+#else
             memory_buf_t buf;
-            fmt::detail::vformat_to(buf, fmt, fmt::make_format_args(args...));
+            fmt::detail::vformat_to(buf, fmt, fmt::make_format_args(std::forward<Args>(args)...));
+#endif
             details::log_msg log_msg(loc, name_, lvl, string_view_t(buf.data(), buf.size()));
             log_it_(log_msg, log_enabled, traceback_enabled);
         }
-        SPDLOG_LOGGER_CATCH()
+        SPDLOG_LOGGER_CATCH(loc)
     }
 
 #ifdef SPDLOG_WCHAR_TO_UTF8_SUPPORT
     template<typename... Args>
-    void log_(source_loc loc, level::level_enum lvl, wstring_view_t fmt, Args &&...args)
+    void log_(source_loc loc, level::level_enum lvl, wstring_view_t fmt, Args &&... args)
     {
         bool log_enabled = should_log(lvl);
         bool traceback_enabled = tracer_.enabled();
@@ -351,14 +388,19 @@ protected:
         SPDLOG_TRY
         {
             // format to wmemory_buffer and convert to utf8
-            fmt::wmemory_buffer wbuf;
-            fmt::detail::vformat_to(wbuf, fmt, fmt::make_format_args<fmt::wformat_context>(args...));
+            ;
+#    ifdef SPDLOG_USE_STD_FORMAT
+            wmemory_buf_t wbuf = std::vformat(fmt, std::make_wformat_args(std::forward<Args>(args)...));
+#    else
+            wmemory_buf_t wbuf;
+            fmt::detail::vformat_to(wbuf, fmt, fmt::make_format_args<fmt::wformat_context>(std::forward<Args>(args)...));
+#    endif
             memory_buf_t buf;
             details::os::wstr_to_utf8buf(wstring_view_t(wbuf.data(), wbuf.size()), buf);
             details::log_msg log_msg(loc, name_, lvl, string_view_t(buf.data(), buf.size()));
             log_it_(log_msg, log_enabled, traceback_enabled);
         }
-        SPDLOG_LOGGER_CATCH()
+        SPDLOG_LOGGER_CATCH(loc)
     }
 
     // T can be statically converted to wstring_view, and no formatting needed.
@@ -378,7 +420,7 @@ protected:
             details::log_msg log_msg(loc, name_, lvl, string_view_t(buf.data(), buf.size()));
             log_it_(log_msg, log_enabled, traceback_enabled);
         }
-        SPDLOG_LOGGER_CATCH()
+        SPDLOG_LOGGER_CATCH(loc)
     }
 
 #endif // SPDLOG_WCHAR_TO_UTF8_SUPPORT

include/spdlog/pattern_formatter-inl.h

@@ -766,6 +766,7 @@ public:
     {
         if (msg.source.empty())
         {
+            ScopedPadder p(0, padinfo_, dest);
             return;
         }
 
@@ -800,6 +801,7 @@ public:
     {
         if (msg.source.empty())
         {
+            ScopedPadder p(0, padinfo_, dest);
             return;
         }
         size_t text_size = padinfo_.enabled() ? std::char_traits<char>::length(msg.source.filename) : 0;
@@ -846,6 +848,7 @@ public:
     {
         if (msg.source.empty())
         {
+            ScopedPadder p(0, padinfo_, dest);
             return;
         }
         auto filename = basename(msg.source.filename);
@@ -867,6 +870,7 @@ public:
     {
         if (msg.source.empty())
         {
+            ScopedPadder p(0, padinfo_, dest);
             return;
         }
 
@@ -889,6 +893,7 @@ public:
     {
         if (msg.source.empty())
         {
+            ScopedPadder p(0, padinfo_, dest);
             return;
         }
         size_t text_size = padinfo_.enabled() ? std::char_traits<char>::length(msg.source.funcname) : 0;
@@ -1019,6 +1024,7 @@ SPDLOG_INLINE pattern_formatter::pattern_formatter(
     : pattern_(std::move(pattern))
     , eol_(std::move(eol))
     , pattern_time_type_(time_type)
+    , need_localtime_(false)
     , last_log_secs_(0)
     , custom_handlers_(std::move(custom_user_flags))
 {
@@ -1031,6 +1037,7 @@ SPDLOG_INLINE pattern_formatter::pattern_formatter(pattern_time_type time_type,
     : pattern_("%+")
     , eol_(std::move(eol))
     , pattern_time_type_(time_type)
+    , need_localtime_(true)
     , last_log_secs_(0)
 {
     std::memset(&cached_tm_, 0, sizeof(cached_tm_));
@@ -1049,11 +1056,14 @@ SPDLOG_INLINE std::unique_ptr<formatter> pattern_formatter::clone() const
 
 SPDLOG_INLINE void pattern_formatter::format(const details::log_msg &msg, memory_buf_t &dest)
 {
-    auto secs = std::chrono::duration_cast<std::chrono::seconds>(msg.time.time_since_epoch());
-    if (secs != last_log_secs_)
+    if (need_localtime_)
     {
-        cached_tm_ = get_time_(msg);
-        last_log_secs_ = secs;
+        const auto secs = std::chrono::duration_cast<std::chrono::seconds>(msg.time.time_since_epoch());
+        if (secs != last_log_secs_)
+        {
+            cached_tm_ = get_time_(msg);
+            last_log_secs_ = secs;
+        }
     }
 
     for (auto &f : formatters_)
@@ -1067,6 +1077,7 @@ SPDLOG_INLINE void pattern_formatter::format(const details::log_msg &msg, memory
 SPDLOG_INLINE void pattern_formatter::set_pattern(std::string pattern)
 {
     pattern_ = std::move(pattern);
+    need_localtime_ = false;
     compile_pattern_(pattern_);
 }
 
@@ -1097,6 +1108,7 @@ SPDLOG_INLINE void pattern_formatter::handle_flag_(char flag, details::padding_i
     {
     case ('+'): // default formatter
         formatters_.push_back(details::make_unique<details::full_formatter>(padding));
+        need_localtime_ = true;
         break;
 
     case 'n': // logger name
@@ -1121,60 +1133,74 @@ SPDLOG_INLINE void pattern_formatter::handle_flag_(char flag, details::padding_i
 
     case ('a'): // weekday
         formatters_.push_back(details::make_unique<details::a_formatter<Padder>>(padding));
+        need_localtime_ = true;
         break;
 
     case ('A'): // short weekday
         formatters_.push_back(details::make_unique<details::A_formatter<Padder>>(padding));
+        need_localtime_ = true;
         break;
 
     case ('b'):
     case ('h'): // month
         formatters_.push_back(details::make_unique<details::b_formatter<Padder>>(padding));
+        need_localtime_ = true;
         break;
 
     case ('B'): // short month
         formatters_.push_back(details::make_unique<details::B_formatter<Padder>>(padding));
+        need_localtime_ = true;
         break;
 
     case ('c'): // datetime
         formatters_.push_back(details::make_unique<details::c_formatter<Padder>>(padding));
+        need_localtime_ = true;
         break;
 
     case ('C'): // year 2 digits
         formatters_.push_back(details::make_unique<details::C_formatter<Padder>>(padding));
+        need_localtime_ = true;
         break;
 
     case ('Y'): // year 4 digits
         formatters_.push_back(details::make_unique<details::Y_formatter<Padder>>(padding));
+        need_localtime_ = true;
         break;
 
     case ('D'):
     case ('x'): // datetime MM/DD/YY
         formatters_.push_back(details::make_unique<details::D_formatter<Padder>>(padding));
+        need_localtime_ = true;
         break;
 
     case ('m'): // month 1-12
         formatters_.push_back(details::make_unique<details::m_formatter<Padder>>(padding));
+        need_localtime_ = true;
         break;
 
     case ('d'): // day of month 1-31
         formatters_.push_back(details::make_unique<details::d_formatter<Padder>>(padding));
+        need_localtime_ = true;
         break;
 
     case ('H'): // hours 24
         formatters_.push_back(details::make_unique<details::H_formatter<Padder>>(padding));
+        need_localtime_ = true;
         break;
 
     case ('I'): // hours 12
         formatters_.push_back(details::make_unique<details::I_formatter<Padder>>(padding));
+        need_localtime_ = true;
         break;
 
     case ('M'): // minutes
         formatters_.push_back(details::make_unique<details::M_formatter<Padder>>(padding));
+        need_localtime_ = true;
         break;
 
     case ('S'): // seconds
         formatters_.push_back(details::make_unique<details::S_formatter<Padder>>(padding));
+        need_localtime_ = true;
         break;
 
     case ('e'): // milliseconds
@@ -1195,23 +1221,28 @@ SPDLOG_INLINE void pattern_formatter::handle_flag_(char flag, details::padding_i
 
     case ('p'): // am/pm
         formatters_.push_back(details::make_unique<details::p_formatter<Padder>>(padding));
+        need_localtime_ = true;
         break;
 
     case ('r'): // 12 hour clock 02:55:02 pm
         formatters_.push_back(details::make_unique<details::r_formatter<Padder>>(padding));
+        need_localtime_ = true;
         break;
 
     case ('R'): // 24-hour HH:MM time
         formatters_.push_back(details::make_unique<details::R_formatter<Padder>>(padding));
+        need_localtime_ = true;
         break;
 
     case ('T'):
     case ('X'): // ISO 8601 time format (HH:MM:SS)
         formatters_.push_back(details::make_unique<details::T_formatter<Padder>>(padding));
+        need_localtime_ = true;
         break;
 
     case ('z'): // timezone
         formatters_.push_back(details::make_unique<details::z_formatter<Padder>>(padding));
+        need_localtime_ = true;
         break;
 
     case ('P'): // pid
@@ -1342,7 +1373,6 @@ SPDLOG_INLINE details::padding_info pattern_formatter::handle_padspec_(std::stri
     {
         truncate = false;
     }
-
     return details::padding_info{std::min<size_t>(width, max_width), side, truncate};
 }
 

include/spdlog/pattern_formatter.h

@@ -68,7 +68,7 @@ class SPDLOG_API custom_flag_formatter : public details::flag_formatter
 public:
     virtual std::unique_ptr<custom_flag_formatter> clone() const = 0;
 
-    void set_padding_info(details::padding_info padding)
+    void set_padding_info(const details::padding_info &padding)
     {
         flag_formatter::padinfo_ = padding;
     }
@@ -92,7 +92,7 @@ public:
     void format(const details::log_msg &msg, memory_buf_t &dest) override;
 
     template<typename T, typename... Args>
-    pattern_formatter &add_flag(char flag, Args &&...args)
+    pattern_formatter &add_flag(char flag, Args &&... args)
     {
         custom_handlers_[flag] = details::make_unique<T>(std::forward<Args>(args)...);
         return *this;
@@ -103,6 +103,7 @@ private:
     std::string pattern_;
     std::string eol_;
     pattern_time_type pattern_time_type_;
+    bool need_localtime_;
     std::tm cached_tm_;
     std::chrono::seconds last_log_secs_;
     std::vector<std::unique_ptr<details::flag_formatter>> formatters_;

include/spdlog/sinks/ansicolor_sink-inl.h

@@ -34,7 +34,7 @@ template<typename ConsoleMutex>
 SPDLOG_INLINE void ansicolor_sink<ConsoleMutex>::set_color(level::level_enum color_level, string_view_t color)
 {
     std::lock_guard<mutex_t> lock(mutex_);
-    colors_[color_level] = to_string_(color);
+    colors_[static_cast<size_t>(color_level)] = to_string_(color);
 }
 
 template<typename ConsoleMutex>
@@ -52,7 +52,7 @@ SPDLOG_INLINE void ansicolor_sink<ConsoleMutex>::log(const details::log_msg &msg
         // before color range
         print_range_(formatted, 0, msg.color_range_start);
         // in color range
-        print_ccode_(colors_[msg.level]);
+        print_ccode_(colors_[static_cast<size_t>(msg.level)]);
         print_range_(formatted, msg.color_range_start, msg.color_range_end);
         print_ccode_(reset);
         // after color range

include/spdlog/sinks/base_sink.h

@@ -16,7 +16,7 @@
 namespace spdlog {
 namespace sinks {
 template<typename Mutex>
-class base_sink : public sink
+class SPDLOG_API base_sink : public sink
 {
 public:
     base_sink();
@@ -37,7 +37,7 @@ public:
 protected:
     // sink formatter
     std::unique_ptr<spdlog::formatter> formatter_;
-    mutable Mutex mutex_;
+    Mutex mutex_;
 
     virtual void sink_it_(const details::log_msg &msg) = 0;
     virtual void flush_() = 0;

include/spdlog/sinks/basic_file_sink-inl.h

@@ -14,7 +14,8 @@ namespace spdlog {
 namespace sinks {
 
 template<typename Mutex>
-SPDLOG_INLINE basic_file_sink<Mutex>::basic_file_sink(const filename_t &filename, bool truncate)
+SPDLOG_INLINE basic_file_sink<Mutex>::basic_file_sink(const filename_t &filename, bool truncate, const file_event_handlers &event_handlers)
+    : file_helper_{event_handlers}
 {
     file_helper_.open(filename, truncate);
 }

include/spdlog/sinks/basic_file_sink.h

@@ -20,7 +20,7 @@ template<typename Mutex>
 class basic_file_sink final : public base_sink<Mutex>
 {
 public:
-    explicit basic_file_sink(const filename_t &filename, bool truncate = false);
+    explicit basic_file_sink(const filename_t &filename, bool truncate = false, const file_event_handlers &event_handlers = {});
     const filename_t &filename() const;
 
 protected:
@@ -40,15 +40,17 @@ using basic_file_sink_st = basic_file_sink<details::null_mutex>;
 // factory functions
 //
 template<typename Factory = spdlog::synchronous_factory>
-inline std::shared_ptr<logger> basic_logger_mt(const std::string &logger_name, const filename_t &filename, bool truncate = false)
+inline std::shared_ptr<logger> basic_logger_mt(
+    const std::string &logger_name, const filename_t &filename, bool truncate = false, const file_event_handlers &event_handlers = {})
 {
-    return Factory::template create<sinks::basic_file_sink_mt>(logger_name, filename, truncate);
+    return Factory::template create<sinks::basic_file_sink_mt>(logger_name, filename, truncate, event_handlers);
 }
 
 template<typename Factory = spdlog::synchronous_factory>
-inline std::shared_ptr<logger> basic_logger_st(const std::string &logger_name, const filename_t &filename, bool truncate = false)
+inline std::shared_ptr<logger> basic_logger_st(
+    const std::string &logger_name, const filename_t &filename, bool truncate = false, const file_event_handlers &event_handlers = {})
 {
-    return Factory::template create<sinks::basic_file_sink_st>(logger_name, filename, truncate);
+    return Factory::template create<sinks::basic_file_sink_st>(logger_name, filename, truncate, event_handlers);
 }
 
 } // namespace spdlog

include/spdlog/sinks/daily_file_sink.h

@@ -32,7 +32,7 @@ struct daily_filename_calculator
     {
         filename_t basename, ext;
         std::tie(basename, ext) = details::file_helper::split_by_extension(filename);
-        return fmt::format(
+        return fmt_lib::format(
             SPDLOG_FILENAME_T("{}_{:04d}-{:02d}-{:02d}{}"), basename, now_tm.tm_year + 1900, now_tm.tm_mon + 1, now_tm.tm_mday, ext);
     }
 };
@@ -48,14 +48,62 @@ struct daily_filename_format_calculator
 {
     static filename_t calc_filename(const filename_t &filename, const tm &now_tm)
     {
+#ifdef SPDLOG_USE_STD_FORMAT
+        // adapted from fmtlib: https://github.com/fmtlib/fmt/blob/8.0.1/include/fmt/chrono.h#L522-L546
+
+        filename_t tm_format;
+        tm_format.append(filename);
+        // By appending an extra space we can distinguish an empty result that
+        // indicates insufficient buffer size from a guaranteed non-empty result
+        // https://github.com/fmtlib/fmt/issues/2238
+        tm_format.push_back(' ');
+
+        const size_t MIN_SIZE = 10;
+        filename_t buf;
+        buf.resize(MIN_SIZE);
+        for (;;)
+        {
+            size_t count = strftime(buf.data(), buf.size(), tm_format.c_str(), &now_tm);
+            if (count != 0)
+            {
+                // Remove the extra space.
+                buf.resize(count - 1);
+                break;
+            }
+            buf.resize(buf.size() * 2);
+        }
+
+        return buf;
+#else
         // generate fmt datetime format string, e.g. {:%Y-%m-%d}.
         filename_t fmt_filename = fmt::format(SPDLOG_FILENAME_T("{{:{}}}"), filename);
-#if defined(_MSC_VER) && defined(SPDLOG_WCHAR_FILENAMES) // for some reason msvc doesnt allow fmt::runtime(..) with wchar here
+#    if defined(_MSC_VER) && defined(SPDLOG_WCHAR_FILENAMES) // for some reason msvc doesn't allow fmt::runtime(..) with wchar here
         return fmt::format(fmt_filename, now_tm);
-#else
+#    else
         return fmt::format(SPDLOG_FMT_RUNTIME(fmt_filename), now_tm);
+#    endif
 #endif
     }
+
+private:
+#if defined __GNUC__
+#    pragma GCC diagnostic push
+#    pragma GCC diagnostic ignored "-Wformat-nonliteral"
+#endif
+
+    static size_t strftime(char *str, size_t count, const char *format, const std::tm *time)
+    {
+        return std::strftime(str, count, format, time);
+    }
+
+    static size_t strftime(wchar_t *str, size_t count, const wchar_t *format, const std::tm *time)
+    {
+        return std::wcsftime(str, count, format, time);
+    }
+
+#if defined(__GNUC__)
+#    pragma GCC diagnostic pop
+#endif
 };
 
 /*
@@ -68,10 +116,12 @@ class daily_file_sink final : public base_sink<Mutex>
 {
 public:
     // create daily file sink which rotates on given time
-    daily_file_sink(filename_t base_filename, int rotation_hour, int rotation_minute, bool truncate = false, uint16_t max_files = 0)
+    daily_file_sink(filename_t base_filename, int rotation_hour, int rotation_minute, bool truncate = false, uint16_t max_files = 0,
+        const file_event_handlers &event_handlers = {})
         : base_filename_(std::move(base_filename))
         , rotation_h_(rotation_hour)
         , rotation_m_(rotation_minute)
+        , file_helper_{event_handlers}
         , truncate_(truncate)
         , max_files_(max_files)
         , filenames_q_()
@@ -213,30 +263,32 @@ using daily_file_format_sink_st = daily_file_sink<details::null_mutex, daily_fil
 // factory functions
 //
 template<typename Factory = spdlog::synchronous_factory>
-inline std::shared_ptr<logger> daily_logger_mt(
-    const std::string &logger_name, const filename_t &filename, int hour = 0, int minute = 0, bool truncate = false, uint16_t max_files = 0)
+inline std::shared_ptr<logger> daily_logger_mt(const std::string &logger_name, const filename_t &filename, int hour = 0, int minute = 0,
+    bool truncate = false, uint16_t max_files = 0, const file_event_handlers &event_handlers = {})
 {
-    return Factory::template create<sinks::daily_file_sink_mt>(logger_name, filename, hour, minute, truncate, max_files);
+    return Factory::template create<sinks::daily_file_sink_mt>(logger_name, filename, hour, minute, truncate, max_files, event_handlers);
 }
 
 template<typename Factory = spdlog::synchronous_factory>
-inline std::shared_ptr<logger> daily_logger_format_mt(
-    const std::string &logger_name, const filename_t &filename, int hour = 0, int minute = 0, bool truncate = false, uint16_t max_files = 0)
+inline std::shared_ptr<logger> daily_logger_format_mt(const std::string &logger_name, const filename_t &filename, int hour = 0,
+    int minute = 0, bool truncate = false, uint16_t max_files = 0, const file_event_handlers &event_handlers = {})
 {
-    return Factory::template create<sinks::daily_file_format_sink_mt>(logger_name, filename, hour, minute, truncate, max_files);
+    return Factory::template create<sinks::daily_file_format_sink_mt>(
+        logger_name, filename, hour, minute, truncate, max_files, event_handlers);
 }
 
 template<typename Factory = spdlog::synchronous_factory>
-inline std::shared_ptr<logger> daily_logger_st(
-    const std::string &logger_name, const filename_t &filename, int hour = 0, int minute = 0, bool truncate = false, uint16_t max_files = 0)
+inline std::shared_ptr<logger> daily_logger_st(const std::string &logger_name, const filename_t &filename, int hour = 0, int minute = 0,
+    bool truncate = false, uint16_t max_files = 0, const file_event_handlers &event_handlers = {})
 {
-    return Factory::template create<sinks::daily_file_sink_st>(logger_name, filename, hour, minute, truncate, max_files);
+    return Factory::template create<sinks::daily_file_sink_st>(logger_name, filename, hour, minute, truncate, max_files, event_handlers);
 }
 
 template<typename Factory = spdlog::synchronous_factory>
-inline std::shared_ptr<logger> daily_logger_format_st(
-    const std::string &logger_name, const filename_t &filename, int hour = 0, int minute = 0, bool truncate = false, uint16_t max_files = 0)
+inline std::shared_ptr<logger> daily_logger_format_st(const std::string &logger_name, const filename_t &filename, int hour = 0,
+    int minute = 0, bool truncate = false, uint16_t max_files = 0, const file_event_handlers &event_handlers = {})
 {
-    return Factory::template create<sinks::daily_file_format_sink_st>(logger_name, filename, hour, minute, truncate, max_files);
+    return Factory::template create<sinks::daily_file_format_sink_st>(
+        logger_name, filename, hour, minute, truncate, max_files, event_handlers);
 }
 } // namespace spdlog

include/spdlog/sinks/hourly_file_sink.h

@@ -31,7 +31,7 @@ struct hourly_filename_calculator
     {
         filename_t basename, ext;
         std::tie(basename, ext) = details::file_helper::split_by_extension(filename);
-        return fmt::format(SPDLOG_FILENAME_T("{}_{:04d}{:02d}{:02d}_{:02d}{}"), basename, now_tm.tm_year + 1900, now_tm.tm_mon + 1,
+        return fmt_lib::format(SPDLOG_FILENAME_T("{}_{:04d}-{:02d}-{:02d}_{:02d}{}"), basename, now_tm.tm_year + 1900, now_tm.tm_mon + 1,
             now_tm.tm_mday, now_tm.tm_hour, ext);
     }
 };
@@ -46,8 +46,10 @@ class hourly_file_sink final : public base_sink<Mutex>
 {
 public:
     // create hourly file sink which rotates on given time
-    hourly_file_sink(filename_t base_filename, bool truncate = false, uint16_t max_files = 0)
+    hourly_file_sink(
+        filename_t base_filename, bool truncate = false, uint16_t max_files = 0, const file_event_handlers &event_handlers = {})
         : base_filename_(std::move(base_filename))
+        , file_helper_{event_handlers}
         , truncate_(truncate)
         , max_files_(max_files)
         , filenames_q_()
@@ -179,16 +181,16 @@ using hourly_file_sink_st = hourly_file_sink<details::null_mutex>;
 // factory functions
 //
 template<typename Factory = spdlog::synchronous_factory>
-inline std::shared_ptr<logger> hourly_logger_mt(
-    const std::string &logger_name, const filename_t &filename, bool truncate = false, uint16_t max_files = 0)
+inline std::shared_ptr<logger> hourly_logger_mt(const std::string &logger_name, const filename_t &filename, bool truncate = false,
+    uint16_t max_files = 0, const file_event_handlers &event_handlers = {})
 {
-    return Factory::template create<sinks::hourly_file_sink_mt>(logger_name, filename, truncate, max_files);
+    return Factory::template create<sinks::hourly_file_sink_mt>(logger_name, filename, truncate, max_files, event_handlers);
 }
 
 template<typename Factory = spdlog::synchronous_factory>
-inline std::shared_ptr<logger> hourly_logger_st(
-    const std::string &logger_name, const filename_t &filename, bool truncate = false, uint16_t max_files = 0)
+inline std::shared_ptr<logger> hourly_logger_st(const std::string &logger_name, const filename_t &filename, bool truncate = false,
+    uint16_t max_files = 0, const file_event_handlers &event_handlers = {})
 {
-    return Factory::template create<sinks::hourly_file_sink_st>(logger_name, filename, truncate, max_files);
+    return Factory::template create<sinks::hourly_file_sink_st>(logger_name, filename, truncate, max_files, event_handlers);
 }
 } // namespace spdlog

include/spdlog/sinks/mongo_sink.h

@@ -33,7 +33,7 @@ public:
     {
         try
         {
-            client_ = std::make_unique<mongocxx::client>(mongocxx::uri{uri});
+            client_ = spdlog::details::make_unique<mongocxx::client>(mongocxx::uri{uri});
             db_name_ = db_name;
             coll_name_ = collection_name;
         }
@@ -72,6 +72,7 @@ private:
     std::string coll_name_;
     std::unique_ptr<mongocxx::client> client_ = nullptr;
 };
+template<>
 mongocxx::instance mongo_sink<std::mutex>::instance_{};
 
 #include "spdlog/details/null_mutex.h"

include/spdlog/sinks/msvc_sink.h

@@ -30,7 +30,11 @@ protected:
     {
         memory_buf_t formatted;
         base_sink<Mutex>::formatter_->format(msg, formatted);
+#    ifdef SPDLOG_USE_STD_FORMAT
+        OutputDebugStringA(formatted.c_str());
+#    else
         OutputDebugStringA(fmt::to_string(formatted).c_str());
+#    endif
     }
 
     void flush_() override {}

include/spdlog/sinks/qt_sinks.h

@@ -4,7 +4,7 @@
 #pragma once
 
 //
-// Custom sink for QPlainTextEdit or QTextEdit and its children(QTextBrowser...
+// Custom sink for QPlainTextEdit or QTextEdit and its childs(QTextBrowser...
 // etc) Building and using requires Qt library.
 //
 
@@ -13,96 +13,25 @@
 #include "spdlog/details/synchronous_factory.h"
 #include "spdlog/sinks/base_sink.h"
 
-#include <QObject>
-#include <QPlainTextEdit>
 #include <QTextEdit>
-
-namespace _spdlog_p {
-namespace _sinks_p {
-//
-// Private class for QTextEdit and its derivatives
-//
-class qtextedit_sink_p : public QObject
-{
-    Q_OBJECT
-public:
-    qtextedit_sink_p(QTextEdit *textedit = nullptr)
-    {
-        if (textedit != nullptr)
-        {
-            textedit_ = textedit;
-            connect(this, &qtextedit_sink_p::append_text, textedit_, &QTextEdit::append);
-        }
-    }
-
-    ~qtextedit_sink_p() {}
-
-    void append(const spdlog::string_view_t &str)
-    {
-        emit append_text(QString::fromUtf8(str.data(), static_cast<int>(str.size() - 2)));
-    }
-
-signals:
-    void append_text(const QString &);
-
-private:
-    QTextEdit *textedit_ = nullptr;
-};
+#include <QPlainTextEdit>
 
 //
-// Private class for QPlainTextEdit
-//
-class qplaintextedit_sink_p : public QObject
-{
-    Q_OBJECT
-public:
-    qplaintextedit_sink_p(QPlainTextEdit *textedit = nullptr)
-    {
-        if (textedit != nullptr)
-        {
-            textedit_ = textedit;
-            connect(this, &qplaintextedit_sink_p::append_text, textedit_, &QPlainTextEdit::appendPlainText);
-        }
-    }
-
-    ~qplaintextedit_sink_p() {}
-
-    void append(const spdlog::string_view_t &str)
-    {
-        emit append_text(QString::fromUtf8(str.data(), static_cast<int>(str.size() - 2)));
-    }
-
-signals:
-    void append_text(const QString &);
-
-private:
-    QPlainTextEdit *textedit_ = nullptr;
-};
-} // namespace _sinks_p
-} // namespace _spdlog_p
-
-//
-// qtextedit_sink class
+// qt_sink class
 //
 namespace spdlog {
 namespace sinks {
 template<typename Mutex>
-class qtextedit_sink : public base_sink<Mutex>
+class qt_sink : public base_sink<Mutex>
 {
 public:
-    qtextedit_sink(QTextEdit *textedit = nullptr)
+    qt_sink(QObject *qt_object, const std::string &meta_method)
     {
-        if (textedit != nullptr)
-        {
-            textedit_p = std::make_shared<_spdlog_p::_sinks_p::qtextedit_sink_p>(textedit);
-        }
-        else
-        {
-            throw spdlog_ex("Error opening QTextEdit");
-        }
+        qt_object_ = qt_object;
+        meta_method_ = meta_method;
     }
 
-    ~qtextedit_sink()
+    ~qt_sink()
     {
         flush_();
     }
@@ -112,89 +41,62 @@ protected:
     {
         memory_buf_t formatted;
         base_sink<Mutex>::formatter_->format(msg, formatted);
-        string_view_t str_v = string_view_t(formatted.data(), formatted.size());
-        textedit_p->append(str_v);
+        string_view_t str = string_view_t(formatted.data(), formatted.size());
+        QMetaObject::invokeMethod(qt_object_, meta_method_.c_str(), Qt::AutoConnection,
+            Q_ARG(QString, QString::fromUtf8(str.data(), static_cast<int>(str.size())).trimmed()));
     }
 
     void flush_() override {}
 
 private:
-    std::shared_ptr<_spdlog_p::_sinks_p::qtextedit_sink_p> textedit_p = nullptr;
-};
-
-//
-// qplaintextedit_sink class
-//
-template<typename Mutex>
-class qplaintextedit_sink : public base_sink<Mutex>
-{
-public:
-    qplaintextedit_sink(QPlainTextEdit *textedit = nullptr)
-    {
-        if (textedit != nullptr)
-        {
-            textedit_p = std::make_shared<_spdlog_p::_sinks_p::qplaintextedit_sink_p>(textedit);
-        }
-        else
-        {
-            throw spdlog_ex("Error opening QPlainTextEdit");
-        }
-    }
-
-    ~qplaintextedit_sink()
-    {
-        flush_();
-    }
-
-protected:
-    void sink_it_(const details::log_msg &msg) override
-    {
-        memory_buf_t formatted;
-        base_sink<Mutex>::formatter_->format(msg, formatted);
-        string_view_t str_v = string_view_t(formatted.data(), formatted.size());
-        textedit_p->append(str_v);
-    }
-
-    void flush_() override {}
-
-private:
-    std::shared_ptr<_spdlog_p::_sinks_p::qplaintextedit_sink_p> textedit_p = nullptr;
+    QObject *qt_object_ = nullptr;
+    std::string meta_method_;
 };
 
 #include "spdlog/details/null_mutex.h"
 #include <mutex>
-using qtextedit_sink_mt = qtextedit_sink<std::mutex>;
-using qtextedit_sink_st = qtextedit_sink<spdlog::details::null_mutex>;
-
-using qplaintextedit_sink_mt = qplaintextedit_sink<std::mutex>;
-using qplaintextedit_sink_st = qplaintextedit_sink<spdlog::details::null_mutex>;
-
+using qt_sink_mt = qt_sink<std::mutex>;
+using qt_sink_st = qt_sink<spdlog::details::null_mutex>;
 } // namespace sinks
 
 //
 // Factory functions
 //
 template<typename Factory = spdlog::synchronous_factory>
-inline std::shared_ptr<logger> qtextedit_logger_mt(const std::string &logger_name, QTextEdit *qtextedit = nullptr)
+inline std::shared_ptr<logger> qt_logger_mt(const std::string &logger_name, QTextEdit *qt_object, const std::string &meta_method = "append")
 {
-    return Factory::template create<sinks::qtextedit_sink_mt>(logger_name, qtextedit);
+    return Factory::template create<sinks::qt_sink_mt>(logger_name, qt_object, meta_method);
 }
 
 template<typename Factory = spdlog::synchronous_factory>
-inline std::shared_ptr<logger> qtextedit_logger_st(const std::string &logger_name, QTextEdit *qtextedit = nullptr)
+inline std::shared_ptr<logger> qt_logger_st(const std::string &logger_name, QTextEdit *qt_object, const std::string &meta_method = "append")
 {
-    return Factory::template create<sinks::qtextedit_sink_st>(logger_name, qtextedit);
+    return Factory::template create<sinks::qt_sink_st>(logger_name, qt_object, meta_method);
 }
 
 template<typename Factory = spdlog::synchronous_factory>
-inline std::shared_ptr<logger> qplaintextedit_logger_mt(const std::string &logger_name, QPlainTextEdit *qplaintextedit = nullptr)
+inline std::shared_ptr<logger> qt_logger_mt(
+    const std::string &logger_name, QPlainTextEdit *qt_object, const std::string &meta_method = "appendPlainText")
 {
-    return Factory::template create<sinks::qplaintextedit_sink_mt>(logger_name, qplaintextedit);
+    return Factory::template create<sinks::qt_sink_mt>(logger_name, qt_object, meta_method);
 }
 
 template<typename Factory = spdlog::synchronous_factory>
-inline std::shared_ptr<logger> qplaintextedit_logger_st(const std::string &logger_name, QPlainTextEdit *qplaintextedit = nullptr)
+inline std::shared_ptr<logger> qt_logger_st(
+    const std::string &logger_name, QPlainTextEdit *qt_object, const std::string &meta_method = "appendPlainText")
 {
-    return Factory::template create<sinks::qplaintextedit_sink_st>(logger_name, qplaintextedit);
+    return Factory::template create<sinks::qt_sink_st>(logger_name, qt_object, meta_method);
+}
+
+template<typename Factory = spdlog::synchronous_factory>
+inline std::shared_ptr<logger> qt_logger_mt(const std::string &logger_name, QObject *qt_object, const std::string &meta_method)
+{
+    return Factory::template create<sinks::qt_sink_mt>(logger_name, qt_object, meta_method);
+}
+
+template<typename Factory = spdlog::synchronous_factory>
+inline std::shared_ptr<logger> qt_logger_st(const std::string &logger_name, QObject *qt_object, const std::string &meta_method)
+{
+    return Factory::template create<sinks::qt_sink_st>(logger_name, qt_object, meta_method);
 }
 } // namespace spdlog

include/spdlog/sinks/ringbuffer_sink.h

@@ -50,7 +50,11 @@ public:
         {
             memory_buf_t formatted;
             base_sink<Mutex>::formatter_->format(q_.at(i), formatted);
+#ifdef SPDLOG_USE_STD_FORMAT
+            ret.push_back(std::move(formatted));
+#else
             ret.push_back(fmt::to_string(formatted));
+#endif
         }
         return ret;
     }

include/spdlog/sinks/rotating_file_sink-inl.h

@@ -25,16 +25,27 @@ namespace sinks {
 
 template<typename Mutex>
 SPDLOG_INLINE rotating_file_sink<Mutex>::rotating_file_sink(
-    filename_t base_filename, std::size_t max_size, std::size_t max_files, bool rotate_on_open)
+    filename_t base_filename, std::size_t max_size, std::size_t max_files, bool rotate_on_open, const file_event_handlers &event_handlers)
     : base_filename_(std::move(base_filename))
     , max_size_(max_size)
     , max_files_(max_files)
+    , file_helper_{event_handlers}
 {
+    if (max_size == 0)
+    {
+        throw_spdlog_ex("rotating sink constructor: max_size arg cannot be zero");
+    }
+
+    if (max_files > 200000)
+    {
+        throw_spdlog_ex("rotating sink constructor: max_files arg cannot exceed 200000");
+    }
     file_helper_.open(calc_filename(base_filename_, 0));
     current_size_ = file_helper_.size(); // expensive. called only once
     if (rotate_on_open && current_size_ > 0)
     {
         rotate_();
+        current_size_ = 0;
     }
 }
 
@@ -50,7 +61,7 @@ SPDLOG_INLINE filename_t rotating_file_sink<Mutex>::calc_filename(const filename
 
     filename_t basename, ext;
     std::tie(basename, ext) = details::file_helper::split_by_extension(filename);
-    return fmt::format(SPDLOG_FILENAME_T("{}.{}{}"), basename, index, ext);
+    return fmt_lib::format(SPDLOG_FILENAME_T("{}.{}{}"), basename, index, ext);
 }
 
 template<typename Mutex>
@@ -65,13 +76,22 @@ SPDLOG_INLINE void rotating_file_sink<Mutex>::sink_it_(const details::log_msg &m
 {
     memory_buf_t formatted;
     base_sink<Mutex>::formatter_->format(msg, formatted);
-    current_size_ += formatted.size();
-    if (current_size_ > max_size_)
+    auto new_size = current_size_ + formatted.size();
+
+    // rotate if the new estimated file size exceeds max size.
+    // rotate only if the real size > 0 to better deal with full disk (see issue #2261).
+    // we only check the real size when new_size > max_size_ because it is relatively expensive.
+    if (new_size > max_size_)
     {
-        rotate_();
-        current_size_ = formatted.size();
+        file_helper_.flush();
+        if (file_helper_.size() > 0)
+        {
+            rotate_();
+            new_size = formatted.size();
+        }
     }
     file_helper_.write(formatted);
+    current_size_ = new_size;
 }
 
 template<typename Mutex>
@@ -90,6 +110,7 @@ SPDLOG_INLINE void rotating_file_sink<Mutex>::rotate_()
 {
     using details::os::filename_to_str;
     using details::os::path_exists;
+
     file_helper_.close();
     for (auto i = max_files_; i > 0; --i)
     {

include/spdlog/sinks/rotating_file_sink.h

@@ -22,7 +22,8 @@ template<typename Mutex>
 class rotating_file_sink final : public base_sink<Mutex>
 {
 public:
-    rotating_file_sink(filename_t base_filename, std::size_t max_size, std::size_t max_files, bool rotate_on_open = false);
+    rotating_file_sink(filename_t base_filename, std::size_t max_size, std::size_t max_files, bool rotate_on_open = false,
+        const file_event_handlers &event_handlers = {});
     static filename_t calc_filename(const filename_t &filename, std::size_t index);
     filename_t filename();
 
@@ -59,17 +60,19 @@ using rotating_file_sink_st = rotating_file_sink<details::null_mutex>;
 //
 
 template<typename Factory = spdlog::synchronous_factory>
-inline std::shared_ptr<logger> rotating_logger_mt(
-    const std::string &logger_name, const filename_t &filename, size_t max_file_size, size_t max_files, bool rotate_on_open = false)
+inline std::shared_ptr<logger> rotating_logger_mt(const std::string &logger_name, const filename_t &filename, size_t max_file_size,
+    size_t max_files, bool rotate_on_open = false, const file_event_handlers &event_handlers = {})
 {
-    return Factory::template create<sinks::rotating_file_sink_mt>(logger_name, filename, max_file_size, max_files, rotate_on_open);
+    return Factory::template create<sinks::rotating_file_sink_mt>(
+        logger_name, filename, max_file_size, max_files, rotate_on_open, event_handlers);
 }
 
 template<typename Factory = spdlog::synchronous_factory>
-inline std::shared_ptr<logger> rotating_logger_st(
-    const std::string &logger_name, const filename_t &filename, size_t max_file_size, size_t max_files, bool rotate_on_open = false)
+inline std::shared_ptr<logger> rotating_logger_st(const std::string &logger_name, const filename_t &filename, size_t max_file_size,
+    size_t max_files, bool rotate_on_open = false, const file_event_handlers &event_handlers = {})
 {
-    return Factory::template create<sinks::rotating_file_sink_st>(logger_name, filename, max_file_size, max_files, rotate_on_open);
+    return Factory::template create<sinks::rotating_file_sink_st>(
+        logger_name, filename, max_file_size, max_files, rotate_on_open, event_handlers);
 }
 } // namespace spdlog
 

include/spdlog/sinks/stdout_sinks-inl.h

@@ -16,7 +16,7 @@
 // so instead we use ::FileWrite
 #    include <spdlog/details/windows_include.h>
 
-#    ifndef _USING_V110_SDK71_ // fileapi.h doesnt exist in winxp
+#    ifndef _USING_V110_SDK71_ // fileapi.h doesn't exist in winxp
 #        include <fileapi.h>   // WriteFile (..)
 #    endif
 
@@ -37,7 +37,7 @@ SPDLOG_INLINE stdout_sink_base<ConsoleMutex>::stdout_sink_base(FILE *file)
 #ifdef _WIN32
     // get windows handle from the FILE* object
 
-    handle_ = (HANDLE)::_get_osfhandle(::_fileno(file_));
+    handle_ = reinterpret_cast<HANDLE>(::_get_osfhandle(::_fileno(file_)));
 
     // don't throw to support cases where no console is attached,
     // and let the log method to do nothing if (handle_ == INVALID_HANDLE_VALUE).
@@ -60,7 +60,7 @@ SPDLOG_INLINE void stdout_sink_base<ConsoleMutex>::log(const details::log_msg &m
     std::lock_guard<mutex_t> lock(mutex_);
     memory_buf_t formatted;
     formatter_->format(msg, formatted);
-    ::fflush(file_); // flush in case there is somthing in this file_ already
+    ::fflush(file_); // flush in case there is something in this file_ already
     auto size = static_cast<DWORD>(formatted.size());
     DWORD bytes_written = 0;
     bool ok = ::WriteFile(handle_, formatted.data(), size, &bytes_written, nullptr) != 0;

include/spdlog/sinks/systemd_sink.h

@@ -18,16 +18,15 @@ namespace sinks {
 
 /**
  * Sink that write to systemd journal using the `sd_journal_send()` library call.
- *
- * Locking is not needed, as `sd_journal_send()` itself is thread-safe.
  */
 template<typename Mutex>
 class systemd_sink : public base_sink<Mutex>
 {
 public:
-    //
-    systemd_sink()
-        : syslog_levels_{{/* spdlog::level::trace      */ LOG_DEBUG,
+    systemd_sink(std::string ident = "", bool enable_formatting = false)
+        : ident_{std::move(ident)}
+        , enable_formatting_{enable_formatting}
+        , syslog_levels_{{/* spdlog::level::trace      */ LOG_DEBUG,
               /* spdlog::level::debug      */ LOG_DEBUG,
               /* spdlog::level::info       */ LOG_INFO,
               /* spdlog::level::warn       */ LOG_WARNING,
@@ -42,31 +41,46 @@ public:
     systemd_sink &operator=(const systemd_sink &) = delete;
 
 protected:
+    const std::string ident_;
+    bool enable_formatting_ = false;
     using levels_array = std::array<int, 7>;
     levels_array syslog_levels_;
 
     void sink_it_(const details::log_msg &msg) override
     {
         int err;
+        string_view_t payload;
+        memory_buf_t formatted;
+        if (enable_formatting_)
+        {
+            base_sink<Mutex>::formatter_->format(msg, formatted);
+            payload = string_view_t(formatted.data(), formatted.size());
+        }
+        else
+        {
+            payload = msg.payload;
+        }
 
-        size_t length = msg.payload.size();
+        size_t length = payload.size();
         // limit to max int
         if (length > static_cast<size_t>(std::numeric_limits<int>::max()))
         {
             length = static_cast<size_t>(std::numeric_limits<int>::max());
         }
 
+        const string_view_t syslog_identifier = ident_.empty() ? msg.logger_name : ident_;
+
         // Do not send source location if not available
         if (msg.source.empty())
         {
             // Note: function call inside '()' to avoid macro expansion
-            err = (sd_journal_send)("MESSAGE=%.*s", static_cast<int>(length), msg.payload.data(), "PRIORITY=%d", syslog_level(msg.level),
-                "SYSLOG_IDENTIFIER=%.*s", static_cast<int>(msg.logger_name.size()), msg.logger_name.data(), nullptr);
+            err = (sd_journal_send)("MESSAGE=%.*s", static_cast<int>(length), payload.data(), "PRIORITY=%d", syslog_level(msg.level),
+                "SYSLOG_IDENTIFIER=%.*s", static_cast<int>(syslog_identifier.size()), syslog_identifier.data(), nullptr);
         }
         else
         {
-            err = (sd_journal_send)("MESSAGE=%.*s", static_cast<int>(length), msg.payload.data(), "PRIORITY=%d", syslog_level(msg.level),
-                "SYSLOG_IDENTIFIER=%.*s", static_cast<int>(msg.logger_name.size()), msg.logger_name.data(), "CODE_FILE=%s",
+            err = (sd_journal_send)("MESSAGE=%.*s", static_cast<int>(length), payload.data(), "PRIORITY=%d", syslog_level(msg.level),
+                "SYSLOG_IDENTIFIER=%.*s", static_cast<int>(syslog_identifier.size()), syslog_identifier.data(), "CODE_FILE=%s",
                 msg.source.filename, "CODE_LINE=%d", msg.source.line, "CODE_FUNC=%s", msg.source.funcname, nullptr);
         }
 
@@ -90,14 +104,16 @@ using systemd_sink_st = systemd_sink<details::null_mutex>;
 
 // Create and register a syslog logger
 template<typename Factory = spdlog::synchronous_factory>
-inline std::shared_ptr<logger> systemd_logger_mt(const std::string &logger_name)
+inline std::shared_ptr<logger> systemd_logger_mt(
+    const std::string &logger_name, const std::string &ident = "", bool enable_formatting = false)
 {
-    return Factory::template create<sinks::systemd_sink_mt>(logger_name);
+    return Factory::template create<sinks::systemd_sink_mt>(logger_name, ident, enable_formatting);
 }
 
 template<typename Factory = spdlog::synchronous_factory>
-inline std::shared_ptr<logger> systemd_logger_st(const std::string &logger_name)
+inline std::shared_ptr<logger> systemd_logger_st(
+    const std::string &logger_name, const std::string &ident = "", bool enable_formatting = false)
 {
-    return Factory::template create<sinks::systemd_sink_st>(logger_name);
+    return Factory::template create<sinks::systemd_sink_st>(logger_name, ident, enable_formatting);
 }
 } // namespace spdlog

include/spdlog/sinks/udp_sink.h

@@ -0,0 +1,74 @@
+// Copyright(c) 2015-present, Gabi Melman & spdlog contributors.
+// Distributed under the MIT License (http://opensource.org/licenses/MIT)
+
+#pragma once
+
+#include <spdlog/common.h>
+#include <spdlog/sinks/base_sink.h>
+#include <spdlog/details/null_mutex.h>
+#ifdef _WIN32
+#    include <spdlog/details/udp_client-windows.h>
+#else
+#    include <spdlog/details/udp_client.h>
+#endif
+
+#include <mutex>
+#include <string>
+#include <chrono>
+#include <functional>
+
+// Simple udp client sink
+// Sends formatted log via udp
+
+namespace spdlog {
+namespace sinks {
+
+struct udp_sink_config
+{
+    std::string server_host;
+    uint16_t server_port;
+
+    udp_sink_config(std::string host, uint16_t port)
+        : server_host{std::move(host)}
+        , server_port{port}
+    {}
+};
+
+template<typename Mutex>
+class udp_sink : public spdlog::sinks::base_sink<Mutex>
+{
+public:
+    // host can be hostname or ip address
+    explicit udp_sink(udp_sink_config sink_config)
+        : client_{sink_config.server_host, sink_config.server_port}
+    {}
+
+    ~udp_sink() override = default;
+
+protected:
+    void sink_it_(const spdlog::details::log_msg &msg) override
+    {
+        spdlog::memory_buf_t formatted;
+        spdlog::sinks::base_sink<Mutex>::formatter_->format(msg, formatted);
+        client_.send(formatted.data(), formatted.size());
+    }
+
+    void flush_() override {}
+    details::udp_client client_;
+};
+
+using udp_sink_mt = udp_sink<std::mutex>;
+using udp_sink_st = udp_sink<spdlog::details::null_mutex>;
+
+} // namespace sinks
+
+//
+// factory functions
+//
+template<typename Factory = spdlog::synchronous_factory>
+inline std::shared_ptr<logger> udp_logger_mt(const std::string &logger_name, sinks::udp_sink_config skin_config)
+{
+    return Factory::template create<sinks::udp_sink_mt>(logger_name, skin_config);
+}
+
+} // namespace spdlog

include/spdlog/sinks/win_eventlog_sink.h

@@ -47,6 +47,24 @@ namespace win_eventlog {
 
 namespace internal {
 
+struct local_alloc_t
+{
+    HLOCAL hlocal_;
+
+    SPDLOG_CONSTEXPR local_alloc_t() SPDLOG_NOEXCEPT : hlocal_(nullptr) {}
+
+    local_alloc_t(local_alloc_t const &) = delete;
+    local_alloc_t &operator=(local_alloc_t const &) = delete;
+
+    ~local_alloc_t() SPDLOG_NOEXCEPT
+    {
+        if (hlocal_)
+        {
+            LocalFree(hlocal_);
+        }
+    }
+};
+
 /** Windows error */
 struct win32_error : public spdlog_ex
 {
@@ -55,22 +73,17 @@ struct win32_error : public spdlog_ex
     {
         std::string system_message;
 
-        LPSTR format_message_result{};
+        local_alloc_t format_message_result{};
         auto format_message_succeeded =
             ::FormatMessageA(FORMAT_MESSAGE_ALLOCATE_BUFFER | FORMAT_MESSAGE_FROM_SYSTEM | FORMAT_MESSAGE_IGNORE_INSERTS, nullptr,
-                error_code, MAKELANGID(LANG_NEUTRAL, SUBLANG_DEFAULT), (LPSTR)&format_message_result, 0, nullptr);
+                error_code, MAKELANGID(LANG_NEUTRAL, SUBLANG_DEFAULT), (LPSTR)&format_message_result.hlocal_, 0, nullptr);
 
-        if (format_message_succeeded && format_message_result)
+        if (format_message_succeeded && format_message_result.hlocal_)
         {
-            system_message = fmt::format(" ({})", format_message_result);
+            system_message = fmt_lib::format(" ({})", (LPSTR)format_message_result.hlocal_);
         }
 
-        if (format_message_result)
-        {
-            LocalFree((HLOCAL)format_message_result);
-        }
-
-        return fmt::format("{}: {}{}", user_message, error_code, system_message);
+        return fmt_lib::format("{}: {}{}", user_message, error_code, system_message);
     }
 
     explicit win32_error(std::string const &func_name, DWORD error = GetLastError())

include/spdlog/spdlog.h

@@ -31,7 +31,7 @@ using default_factory = synchronous_factory;
 // Example:
 //   spdlog::create<daily_file_sink_st>("logger_name", "dailylog_filename", 11, 59);
 template<typename Sink, typename... SinkArgs>
-inline std::shared_ptr<spdlog::logger> create(std::string logger_name, SinkArgs &&...sink_args)
+inline std::shared_ptr<spdlog::logger> create(std::string logger_name, SinkArgs &&... sink_args)
 {
     return default_factory::create<Sink>(std::move(logger_name), std::forward<SinkArgs>(sink_args)...);
 }
@@ -128,49 +128,49 @@ SPDLOG_API spdlog::logger *default_logger_raw();
 SPDLOG_API void set_default_logger(std::shared_ptr<spdlog::logger> default_logger);
 
 template<typename... Args>
-inline void log(source_loc source, level::level_enum lvl, fmt::format_string<Args...> fmt, Args &&...args)
+inline void log(source_loc source, level::level_enum lvl, format_string_t<Args...> fmt, Args &&... args)
 {
     default_logger_raw()->log(source, lvl, fmt, std::forward<Args>(args)...);
 }
 
 template<typename... Args>
-inline void log(level::level_enum lvl, fmt::format_string<Args...> fmt, Args &&...args)
+inline void log(level::level_enum lvl, format_string_t<Args...> fmt, Args &&... args)
 {
     default_logger_raw()->log(source_loc{}, lvl, fmt, std::forward<Args>(args)...);
 }
 
 template<typename... Args>
-inline void trace(fmt::format_string<Args...> fmt, Args &&...args)
+inline void trace(format_string_t<Args...> fmt, Args &&... args)
 {
     default_logger_raw()->trace(fmt, std::forward<Args>(args)...);
 }
 
 template<typename... Args>
-inline void debug(fmt::format_string<Args...> fmt, Args &&...args)
+inline void debug(format_string_t<Args...> fmt, Args &&... args)
 {
     default_logger_raw()->debug(fmt, std::forward<Args>(args)...);
 }
 
 template<typename... Args>
-inline void info(fmt::format_string<Args...> fmt, Args &&...args)
+inline void info(format_string_t<Args...> fmt, Args &&... args)
 {
     default_logger_raw()->info(fmt, std::forward<Args>(args)...);
 }
 
 template<typename... Args>
-inline void warn(fmt::format_string<Args...> fmt, Args &&...args)
+inline void warn(format_string_t<Args...> fmt, Args &&... args)
 {
     default_logger_raw()->warn(fmt, std::forward<Args>(args)...);
 }
 
 template<typename... Args>
-inline void error(fmt::format_string<Args...> fmt, Args &&...args)
+inline void error(format_string_t<Args...> fmt, Args &&... args)
 {
     default_logger_raw()->error(fmt, std::forward<Args>(args)...);
 }
 
 template<typename... Args>
-inline void critical(fmt::format_string<Args...> fmt, Args &&...args)
+inline void critical(format_string_t<Args...> fmt, Args &&... args)
 {
     default_logger_raw()->critical(fmt, std::forward<Args>(args)...);
 }
@@ -189,49 +189,49 @@ inline void log(level::level_enum lvl, const T &msg)
 
 #ifdef SPDLOG_WCHAR_TO_UTF8_SUPPORT
 template<typename... Args>
-inline void log(source_loc source, level::level_enum lvl, fmt::wformat_string<Args...> fmt, Args &&...args)
+inline void log(source_loc source, level::level_enum lvl, wformat_string_t<Args...> fmt, Args &&... args)
 {
     default_logger_raw()->log(source, lvl, fmt, std::forward<Args>(args)...);
 }
 
 template<typename... Args>
-inline void log(level::level_enum lvl, fmt::wformat_string<Args...> fmt, Args &&...args)
+inline void log(level::level_enum lvl, wformat_string_t<Args...> fmt, Args &&... args)
 {
     default_logger_raw()->log(source_loc{}, lvl, fmt, std::forward<Args>(args)...);
 }
 
 template<typename... Args>
-inline void trace(fmt::wformat_string<Args...> fmt, Args &&...args)
+inline void trace(wformat_string_t<Args...> fmt, Args &&... args)
 {
     default_logger_raw()->trace(fmt, std::forward<Args>(args)...);
 }
 
 template<typename... Args>
-inline void debug(fmt::wformat_string<Args...> fmt, Args &&...args)
+inline void debug(wformat_string_t<Args...> fmt, Args &&... args)
 {
     default_logger_raw()->debug(fmt, std::forward<Args>(args)...);
 }
 
 template<typename... Args>
-inline void info(fmt::wformat_string<Args...> fmt, Args &&...args)
+inline void info(wformat_string_t<Args...> fmt, Args &&... args)
 {
     default_logger_raw()->info(fmt, std::forward<Args>(args)...);
 }
 
 template<typename... Args>
-inline void warn(fmt::wformat_string<Args...> fmt, Args &&...args)
+inline void warn(wformat_string_t<Args...> fmt, Args &&... args)
 {
     default_logger_raw()->warn(fmt, std::forward<Args>(args)...);
 }
 
 template<typename... Args>
-inline void error(fmt::wformat_string<Args...> fmt, Args &&...args)
+inline void error(wformat_string_t<Args...> fmt, Args &&... args)
 {
     default_logger_raw()->error(fmt, std::forward<Args>(args)...);
 }
 
 template<typename... Args>
-inline void critical(fmt::wformat_string<Args...> fmt, Args &&...args)
+inline void critical(wformat_string_t<Args...> fmt, Args &&... args)
 {
     default_logger_raw()->critical(fmt, std::forward<Args>(args)...);
 }

include/spdlog/stopwatch.h

@@ -42,13 +42,20 @@ public:
 
     void reset()
     {
-        start_tp_ = clock ::now();
+        start_tp_ = clock::now();
     }
 };
 } // namespace spdlog
 
 // Support for fmt formatting  (e.g. "{:012.9}" or just "{}")
-namespace fmt {
+namespace
+#ifdef SPDLOG_USE_STD_FORMAT
+    std
+#else
+    fmt
+#endif
+{
+
 template<>
 struct formatter<spdlog::stopwatch> : formatter<double>
 {
@@ -58,4 +65,4 @@ struct formatter<spdlog::stopwatch> : formatter<double>
         return formatter<double>::format(sw.elapsed().count(), ctx);
     }
 };
-} // namespace fmt
+} // namespace std

include/spdlog/tweakme.h

@@ -74,6 +74,13 @@
 // #define SPDLOG_FMT_EXTERNAL
 ///////////////////////////////////////////////////////////////////////////////
 
+///////////////////////////////////////////////////////////////////////////////
+// Uncomment to use C++20 std::format instead of fmt. This removes compile
+// time checking of format strings, but doesn't depend on the fmt library.
+//
+// #define SPDLOG_USE_STD_FORMAT
+///////////////////////////////////////////////////////////////////////////////
+
 ///////////////////////////////////////////////////////////////////////////////
 // Uncomment to enable wchar_t support (convert to utf8)
 //
@@ -89,8 +96,7 @@
 ///////////////////////////////////////////////////////////////////////////////
 // Uncomment to customize level names (e.g. "MY TRACE")
 //
-// #define SPDLOG_LEVEL_NAMES { "MY TRACE", "MY DEBUG", "MY INFO", "MY WARNING",
-// "MY ERROR", "MY CRITICAL", "OFF" }
+// #define SPDLOG_LEVEL_NAMES { "MY TRACE", "MY DEBUG", "MY INFO", "MY WARNING", "MY ERROR", "MY CRITICAL", "OFF" }
 ///////////////////////////////////////////////////////////////////////////////
 
 ///////////////////////////////////////////////////////////////////////////////
@@ -120,5 +126,9 @@
 // __PRETTY_FUNCTION__ might be nicer in clang/gcc, and __FUNCTION__ in msvc.
 // Defaults to __FUNCTION__ (should work on all compilers) if not defined.
 //
-// #define SPDLOG_FUNCTION __PRETTY_FUNCTION__
+// #ifdef __PRETTY_FUNCTION__
+// # define SPDLOG_FUNCTION __PRETTY_FUNCTION__
+// #else
+// # define SPDLOG_FUNCTION __FUNCTION__
+// #endif
 ///////////////////////////////////////////////////////////////////////////////

include/spdlog/version.h

@@ -4,7 +4,7 @@
 #pragma once
 
 #define SPDLOG_VER_MAJOR 1
-#define SPDLOG_VER_MINOR 9
+#define SPDLOG_VER_MINOR 10
 #define SPDLOG_VER_PATCH 0
 
 #define SPDLOG_VERSION (SPDLOG_VER_MAJOR * 10000 + SPDLOG_VER_MINOR * 100 + SPDLOG_VER_PATCH)

src/fmt.cpp

@@ -6,12 +6,54 @@
 #    error Please define SPDLOG_COMPILED_LIB to compile this file.
 #endif
 
-#if !defined(SPDLOG_FMT_EXTERNAL)
+#if !defined(SPDLOG_FMT_EXTERNAL) && !defined(SPDLOG_USE_STD_FORMAT)
 #    include <spdlog/fmt/bundled/format-inl.h>
 
 FMT_BEGIN_NAMESPACE
 namespace detail {
 
+// DEPRECATED!
+template<typename T = void>
+struct basic_data
+{
+    FMT_API static constexpr const char digits[100][2] = {{'0', '0'}, {'0', '1'}, {'0', '2'}, {'0', '3'}, {'0', '4'}, {'0', '5'},
+        {'0', '6'}, {'0', '7'}, {'0', '8'}, {'0', '9'}, {'1', '0'}, {'1', '1'}, {'1', '2'}, {'1', '3'}, {'1', '4'}, {'1', '5'}, {'1', '6'},
+        {'1', '7'}, {'1', '8'}, {'1', '9'}, {'2', '0'}, {'2', '1'}, {'2', '2'}, {'2', '3'}, {'2', '4'}, {'2', '5'}, {'2', '6'}, {'2', '7'},
+        {'2', '8'}, {'2', '9'}, {'3', '0'}, {'3', '1'}, {'3', '2'}, {'3', '3'}, {'3', '4'}, {'3', '5'}, {'3', '6'}, {'3', '7'}, {'3', '8'},
+        {'3', '9'}, {'4', '0'}, {'4', '1'}, {'4', '2'}, {'4', '3'}, {'4', '4'}, {'4', '5'}, {'4', '6'}, {'4', '7'}, {'4', '8'}, {'4', '9'},
+        {'5', '0'}, {'5', '1'}, {'5', '2'}, {'5', '3'}, {'5', '4'}, {'5', '5'}, {'5', '6'}, {'5', '7'}, {'5', '8'}, {'5', '9'}, {'6', '0'},
+        {'6', '1'}, {'6', '2'}, {'6', '3'}, {'6', '4'}, {'6', '5'}, {'6', '6'}, {'6', '7'}, {'6', '8'}, {'6', '9'}, {'7', '0'}, {'7', '1'},
+        {'7', '2'}, {'7', '3'}, {'7', '4'}, {'7', '5'}, {'7', '6'}, {'7', '7'}, {'7', '8'}, {'7', '9'}, {'8', '0'}, {'8', '1'}, {'8', '2'},
+        {'8', '3'}, {'8', '4'}, {'8', '5'}, {'8', '6'}, {'8', '7'}, {'8', '8'}, {'8', '9'}, {'9', '0'}, {'9', '1'}, {'9', '2'}, {'9', '3'},
+        {'9', '4'}, {'9', '5'}, {'9', '6'}, {'9', '7'}, {'9', '8'}, {'9', '9'}};
+    FMT_API static constexpr const char hex_digits[] = "0123456789abcdef";
+    FMT_API static constexpr const char signs[4] = {0, '-', '+', ' '};
+    FMT_API static constexpr const char left_padding_shifts[5] = {31, 31, 0, 1, 0};
+    FMT_API static constexpr const char right_padding_shifts[5] = {0, 31, 0, 1, 0};
+    FMT_API static constexpr const unsigned prefixes[4] = {0, 0, 0x1000000u | '+', 0x1000000u | ' '};
+};
+
+#    ifdef FMT_SHARED
+// Required for -flto, -fivisibility=hidden and -shared to work
+extern template struct basic_data<void>;
+#    endif
+
+#    if __cplusplus < 201703L
+// DEPRECATED! These are here only for ABI compatiblity.
+template<typename T>
+constexpr const char basic_data<T>::digits[][2];
+template<typename T>
+constexpr const char basic_data<T>::hex_digits[];
+template<typename T>
+constexpr const char basic_data<T>::signs[];
+template<typename T>
+constexpr const char basic_data<T>::left_padding_shifts[];
+template<typename T>
+constexpr const char basic_data<T>::right_padding_shifts[];
+template<typename T>
+constexpr const unsigned basic_data<T>::prefixes[];
+#    endif
+
 template<typename T>
 int format_float(char *buf, std::size_t size, const char *format, int precision, T value)
 {

tests/test_async.cpp

@@ -51,7 +51,7 @@ TEST_CASE("discard policy using factory ", "[async]")
 
     auto logger = spdlog::create_async_nb<spdlog::sinks::test_sink_mt>("as2");
     auto test_sink = std::static_pointer_cast<spdlog::sinks::test_sink_mt>(logger->sinks()[0]);
-    test_sink->set_delay(std::chrono::milliseconds(1));
+    test_sink->set_delay(std::chrono::milliseconds(3));
 
     for (size_t i = 0; i < messages; i++)
     {
@@ -166,7 +166,7 @@ TEST_CASE("to_file", "[async]")
     require_message_count(TEST_FILENAME, messages);
     auto contents = file_contents(TEST_FILENAME);
     using spdlog::details::os::default_eol;
-    REQUIRE(ends_with(contents, fmt::format("Hello message #1023{}", default_eol)));
+    REQUIRE(ends_with(contents, spdlog::fmt_lib::format("Hello message #1023{}", default_eol)));
 }
 
 TEST_CASE("to_file multi-workers", "[async]")

tests/test_daily_logger.cpp

@@ -3,7 +3,11 @@
  */
 #include "includes.h"
 
+#ifdef SPDLOG_USE_STD_FORMAT
+using filename_memory_buf_t = std::basic_string<spdlog::filename_t::value_type>;
+#else
 using filename_memory_buf_t = fmt::basic_memory_buffer<spdlog::filename_t::value_type, 250>;
+#endif
 
 TEST_CASE("daily_logger with dateonly calculator", "[daily_logger]")
 {
@@ -15,7 +19,7 @@ TEST_CASE("daily_logger with dateonly calculator", "[daily_logger]")
     spdlog::filename_t basename = SPDLOG_FILENAME_T("test_logs/daily_dateonly");
     std::tm tm = spdlog::details::os::localtime();
     filename_memory_buf_t w;
-    fmt::format_to(
+    spdlog::fmt_lib::format_to(
         std::back_inserter(w), SPDLOG_FILENAME_T("{}_{:04d}-{:02d}-{:02d}"), basename, tm.tm_year + 1900, tm.tm_mon + 1, tm.tm_mday);
 
     auto logger = spdlog::create<sink_type>("logger", basename, 0, 0);
@@ -28,10 +32,19 @@ TEST_CASE("daily_logger with dateonly calculator", "[daily_logger]")
 
 #ifdef SPDLOG_WCHAR_FILENAMES
     spdlog::memory_buf_t buf;
+#    ifdef SPDLOG_USE_STD_FORMAT
+    spdlog::details::os::wstr_to_utf8buf(w, buf);
+    auto &filename = buf;
+#    else
     spdlog::details::os::wstr_to_utf8buf(fmt::to_string(w), buf);
     auto filename = fmt::to_string(buf);
+#    endif
 #else
+#    ifdef SPDLOG_USE_STD_FORMAT
+    auto &filename = w;
+#    else
     auto filename = fmt::to_string(w);
+#    endif
 #endif
     require_message_count(filename, 10);
 }
@@ -41,9 +54,13 @@ struct custom_daily_file_name_calculator
     static spdlog::filename_t calc_filename(const spdlog::filename_t &basename, const tm &now_tm)
     {
         filename_memory_buf_t w;
-        fmt::format_to(std::back_inserter(w), SPDLOG_FILENAME_T("{}{:04d}{:02d}{:02d}"), basename, now_tm.tm_year + 1900, now_tm.tm_mon + 1,
-            now_tm.tm_mday);
+        spdlog::fmt_lib::format_to(std::back_inserter(w), SPDLOG_FILENAME_T("{}{:04d}{:02d}{:02d}"), basename, now_tm.tm_year + 1900,
+            now_tm.tm_mon + 1, now_tm.tm_mday);
+#ifdef SPDLOG_USE_STD_FORMAT
+        return w;
+#else
         return fmt::to_string(w);
+#endif
     }
 };
 
@@ -57,7 +74,7 @@ TEST_CASE("daily_logger with custom calculator", "[daily_logger]")
     spdlog::filename_t basename = SPDLOG_FILENAME_T("test_logs/daily_dateonly");
     std::tm tm = spdlog::details::os::localtime();
     filename_memory_buf_t w;
-    fmt::format_to(
+    spdlog::fmt_lib::format_to(
         std::back_inserter(w), SPDLOG_FILENAME_T("{}{:04d}{:02d}{:02d}"), basename, tm.tm_year + 1900, tm.tm_mon + 1, tm.tm_mday);
 
     auto logger = spdlog::create<sink_type>("logger", basename, 0, 0);
@@ -70,10 +87,19 @@ TEST_CASE("daily_logger with custom calculator", "[daily_logger]")
 
 #ifdef SPDLOG_WCHAR_FILENAMES
     spdlog::memory_buf_t buf;
+#    ifdef SPDLOG_USE_STD_FORMAT
+    spdlog::details::os::wstr_to_utf8buf(w, buf);
+    auto &filename = buf;
+#    else
     spdlog::details::os::wstr_to_utf8buf(fmt::to_string(w), buf);
     auto filename = fmt::to_string(buf);
+#    endif
 #else
+#    ifdef SPDLOG_USE_STD_FORMAT
+    auto &filename = w;
+#    else
     auto filename = fmt::to_string(w);
+#    endif
 #endif
     require_message_count(filename, 10);
 }
@@ -118,6 +144,16 @@ TEST_CASE("daily_file_sink::daily_filename_calculator", "[daily_file_sink]]")
 }
 #endif
 
+TEST_CASE("daily_file_sink::daily_filename_format_calculator", "[daily_file_sink]]")
+{
+    std::tm tm = spdlog::details::os::localtime();
+    // example-YYYY-MM-DD.log
+    auto filename = spdlog::sinks::daily_filename_format_calculator::calc_filename(SPDLOG_FILENAME_T("example-%Y-%m-%d.log"), tm);
+
+    REQUIRE(filename ==
+            spdlog::fmt_lib::format(SPDLOG_FILENAME_T("example-{:04d}-{:02d}-{:02d}.log"), tm.tm_year + 1900, tm.tm_mon + 1, tm.tm_mday));
+}
+
 /* Test removal of old files */
 static spdlog::details::log_msg create_msg(std::chrono::seconds offset)
 {
@@ -165,4 +201,4 @@ TEST_CASE("daily_logger rotate", "[daily_file_sink]")
     test_rotate(days_to_run, 10, 10);
     test_rotate(days_to_run, 11, 10);
     test_rotate(days_to_run, 20, 10);
-}
+}

tests/test_errors.cpp

@@ -29,12 +29,16 @@ TEST_CASE("default_error_handler", "[errors]]")
 
     auto logger = spdlog::create<spdlog::sinks::basic_file_sink_mt>("test-error", filename, true);
     logger->set_pattern("%v");
+#ifdef SPDLOG_USE_STD_FORMAT
+    logger->info("Test message {} {}", 1);
+#else
     logger->info(fmt::runtime("Test message {} {}"), 1);
+#endif
     logger->info("Test message {}", 2);
     logger->flush();
 
     using spdlog::details::os::default_eol;
-    REQUIRE(file_contents(SIMPLE_LOG) == fmt::format("Test message 2{}", default_eol));
+    REQUIRE(file_contents(SIMPLE_LOG) == spdlog::fmt_lib::format("Test message 2{}", default_eol));
     REQUIRE(count_lines(SIMPLE_LOG) == 1);
 }
 
@@ -49,7 +53,11 @@ TEST_CASE("custom_error_handler", "[errors]]")
     logger->set_error_handler([=](const std::string &) { throw custom_ex(); });
     logger->info("Good message #1");
 
+#ifdef SPDLOG_USE_STD_FORMAT
+    REQUIRE_THROWS_AS(logger->info("Bad format msg {} {}", "xxx"), custom_ex);
+#else
     REQUIRE_THROWS_AS(logger->info(fmt::runtime("Bad format msg {} {}"), "xxx"), custom_ex);
+#endif
     logger->info("Good message #2");
     require_message_count(SIMPLE_LOG, 2);
 }
@@ -88,7 +96,11 @@ TEST_CASE("async_error_handler", "[errors]]")
             ofs << err_msg;
         });
         logger->info("Good message #1");
+#ifdef SPDLOG_USE_STD_FORMAT
+        logger->info("Bad format msg {} {}", "xxx");
+#else
         logger->info(fmt::runtime("Bad format msg {} {}"), "xxx");
+#endif
         logger->info("Good message #2");
         spdlog::drop("logger"); // force logger to drain the queue and shutdown
     }

tests/test_file_helper.cpp

@@ -10,7 +10,7 @@ using spdlog::details::file_helper;
 static void write_with_helper(file_helper &helper, size_t howmany)
 {
     spdlog::memory_buf_t formatted;
-    fmt::format_to(std::back_inserter(formatted), "{}", std::string(howmany, '1'));
+    spdlog::fmt_lib::format_to(std::back_inserter(formatted), "{}", std::string(howmany, '1'));
     helper.write(formatted);
     helper.flush();
 }
@@ -99,3 +99,70 @@ TEST_CASE("file_helper_split_by_extension", "[file_helper::split_by_extension()]
     test_split_ext(SPDLOG_FILENAME_T("."), SPDLOG_FILENAME_T("."), SPDLOG_FILENAME_T(""));
     test_split_ext(SPDLOG_FILENAME_T("..txt"), SPDLOG_FILENAME_T("."), SPDLOG_FILENAME_T(".txt"));
 }
+
+TEST_CASE("file_event_handlers", "[file_helper]")
+{
+    enum class flags
+    {
+        before_open,
+        after_open,
+        before_close,
+        after_close
+    };
+    prepare_logdir();
+
+    spdlog::filename_t test_filename = SPDLOG_FILENAME_T(TEST_FILENAME);
+    // define event handles that update vector of flags when called
+    std::vector<flags> events;
+    spdlog::file_event_handlers handlers;
+    handlers.before_open = [&](spdlog::filename_t filename) {
+        REQUIRE(filename == test_filename);
+        events.push_back(flags::before_open);
+    };
+    handlers.after_open = [&](spdlog::filename_t filename, std::FILE *fstream) {
+        REQUIRE(filename == test_filename);
+        REQUIRE(fstream);
+        fputs("after_open\n", fstream);
+        events.push_back(flags::after_open);
+    };
+    handlers.before_close = [&](spdlog::filename_t filename, std::FILE *fstream) {
+        REQUIRE(filename == test_filename);
+        REQUIRE(fstream);
+        fputs("before_close\n", fstream);
+        events.push_back(flags::before_close);
+    };
+    handlers.after_close = [&](spdlog::filename_t filename) {
+        REQUIRE(filename == test_filename);
+        events.push_back(flags::after_close);
+    };
+    {
+        spdlog::details::file_helper helper{handlers};
+        REQUIRE(events.empty());
+
+        helper.open(test_filename);
+        REQUIRE(events == std::vector<flags>{flags::before_open, flags::after_open});
+
+        events.clear();
+        helper.close();
+        REQUIRE(events == std::vector<flags>{flags::before_close, flags::after_close});
+        REQUIRE(file_contents(TEST_FILENAME) == "after_open\nbefore_close\n");
+
+        helper.reopen(true);
+        events.clear();
+    }
+    // make sure that the file_helper destrcutor calls the close callbacks if needed
+    REQUIRE(events == std::vector<flags>{flags::before_close, flags::after_close});
+    REQUIRE(file_contents(TEST_FILENAME) == "after_open\nbefore_close\n");
+}
+
+TEST_CASE("file_helper_open", "[file_helper]")
+{
+    prepare_logdir();
+    spdlog::filename_t target_filename = SPDLOG_FILENAME_T(TEST_FILENAME);
+    file_helper helper;
+    helper.open(target_filename);
+    helper.close();
+
+    target_filename += SPDLOG_FILENAME_T("/invalid");
+    REQUIRE_THROWS_AS(helper.open(target_filename), spdlog::spdlog_ex);
+}

tests/test_file_logging.cpp

@@ -20,7 +20,7 @@ TEST_CASE("simple_file_logger", "[simple_logger]]")
     logger->flush();
     require_message_count(SIMPLE_LOG, 2);
     using spdlog::details::os::default_eol;
-    REQUIRE(file_contents(SIMPLE_LOG) == fmt::format("Test message 1{}Test message 2{}", default_eol, default_eol));
+    REQUIRE(file_contents(SIMPLE_LOG) == spdlog::fmt_lib::format("Test message 1{}Test message 2{}", default_eol, default_eol));
 }
 
 TEST_CASE("flush_on", "[flush_on]]")
@@ -41,7 +41,7 @@ TEST_CASE("flush_on", "[flush_on]]")
     require_message_count(SIMPLE_LOG, 3);
     using spdlog::details::os::default_eol;
     REQUIRE(file_contents(SIMPLE_LOG) ==
-            fmt::format("Should not be flushed{}Test message 1{}Test message 2{}", default_eol, default_eol, default_eol));
+            spdlog::fmt_lib::format("Should not be flushed{}Test message 1{}Test message 2{}", default_eol, default_eol, default_eol));
 }
 
 TEST_CASE("rotating_file_logger1", "[rotating_logger]]")
@@ -98,3 +98,12 @@ TEST_CASE("rotating_file_logger2", "[rotating_logger]]")
     REQUIRE(get_filesize(ROTATING_LOG) <= max_size);
     REQUIRE(get_filesize(ROTATING_LOG ".1") <= max_size);
 }
+
+// test that passing max_size=0 throws
+TEST_CASE("rotating_file_logger3", "[rotating_logger]]")
+{
+    prepare_logdir();
+    size_t max_size = 0;
+    spdlog::filename_t basename = SPDLOG_FILENAME_T(ROTATING_LOG);
+    REQUIRE_THROWS_AS(spdlog::rotating_logger_mt("logger", basename, max_size, 0), spdlog::spdlog_ex);
+}

tests/test_fmt_helper.cpp

@@ -8,28 +8,48 @@ void test_pad2(int n, const char *expected)
 {
     memory_buf_t buf;
     spdlog::details::fmt_helper::pad2(n, buf);
+
+#ifdef SPDLOG_USE_STD_FORMAT
+    REQUIRE(buf == expected);
+#else
     REQUIRE(fmt::to_string(buf) == expected);
+#endif
 }
 
 void test_pad3(uint32_t n, const char *expected)
 {
     memory_buf_t buf;
     spdlog::details::fmt_helper::pad3(n, buf);
+
+#ifdef SPDLOG_USE_STD_FORMAT
+    REQUIRE(buf == expected);
+#else
     REQUIRE(fmt::to_string(buf) == expected);
+#endif
 }
 
 void test_pad6(std::size_t n, const char *expected)
 {
     memory_buf_t buf;
     spdlog::details::fmt_helper::pad6(n, buf);
+
+#ifdef SPDLOG_USE_STD_FORMAT
+    REQUIRE(buf == expected);
+#else
     REQUIRE(fmt::to_string(buf) == expected);
+#endif
 }
 
 void test_pad9(std::size_t n, const char *expected)
 {
     memory_buf_t buf;
     spdlog::details::fmt_helper::pad9(n, buf);
+
+#ifdef SPDLOG_USE_STD_FORMAT
+    REQUIRE(buf == expected);
+#else
     REQUIRE(fmt::to_string(buf) == expected);
+#endif
 }
 
 TEST_CASE("pad2", "[fmt_helper]")

tests/test_macros.cpp

@@ -25,9 +25,10 @@ TEST_CASE("debug and trace w/o format string", "[macros]]")
     logger->flush();
 
     using spdlog::details::os::default_eol;
-    REQUIRE(ends_with(file_contents(TEST_FILENAME), fmt::format("Test message 2{}", default_eol)));
+    REQUIRE(ends_with(file_contents(TEST_FILENAME), spdlog::fmt_lib::format("Test message 2{}", default_eol)));
     REQUIRE(count_lines(TEST_FILENAME) == 1);
 
+    auto orig_default_logger = spdlog::default_logger();
     spdlog::set_default_logger(logger);
 
     SPDLOG_TRACE("Test message 3");
@@ -35,7 +36,8 @@ TEST_CASE("debug and trace w/o format string", "[macros]]")
     logger->flush();
 
     require_message_count(TEST_FILENAME, 2);
-    REQUIRE(ends_with(file_contents(TEST_FILENAME), fmt::format("Test message 4{}", default_eol)));
+    REQUIRE(ends_with(file_contents(TEST_FILENAME), spdlog::fmt_lib::format("Test message 4{}", default_eol)));
+    spdlog::set_default_logger(std::move(orig_default_logger));
 }
 
 TEST_CASE("disable param evaluation", "[macros]")
@@ -50,13 +52,3 @@ TEST_CASE("pass logger pointer", "[macros]")
     SPDLOG_LOGGER_TRACE(&ref, "Test message 1");
     SPDLOG_LOGGER_DEBUG(&ref, "Test message 2");
 }
-
-// ensure that even if right macro level is on- don't evaluate if the logger's level is not high enough
-// TEST_CASE("disable param evaluation2", "[macros]")
-//{
-//    auto logger = std::make_shared<spdlog::logger>("test-macro");
-//    logger->set_level(spdlog::level::off);
-//    int x = 0;
-//    SPDLOG_LOGGER_DEBUG(logger, "Test message {}", ++x);
-//    REQUIRE(x == 0);
-//}

tests/test_pattern_formatter.cpp

@@ -5,7 +5,7 @@ using spdlog::memory_buf_t;
 
 // log to str and return it
 template<typename... Args>
-static std::string log_to_str(const std::string &msg, const Args &...args)
+static std::string log_to_str(const std::string &msg, const Args &... args)
 {
     std::ostringstream oss;
     auto oss_sink = std::make_shared<spdlog::sinks::ostream_sink_mt>(oss);
@@ -64,7 +64,7 @@ TEST_CASE("color range test1", "[pattern_formatter]")
     auto formatter = std::make_shared<spdlog::pattern_formatter>("%^%v%$", spdlog::pattern_time_type::local, "\n");
 
     memory_buf_t buf;
-    fmt::format_to(std::back_inserter(buf), "Hello");
+    spdlog::fmt_lib::format_to(std::back_inserter(buf), "Hello");
     memory_buf_t formatted;
     std::string logger_name = "test";
     spdlog::details::log_msg msg(logger_name, spdlog::level::info, spdlog::string_view_t(buf.data(), buf.size()));
@@ -273,7 +273,11 @@ TEST_CASE("clone-default-formatter", "[pattern_formatter]")
     formatter_1->format(msg, formatted_1);
     formatter_2->format(msg, formatted_2);
 
+#ifdef SPDLOG_USE_STD_FORMAT
+    REQUIRE(formatted_1 == formatted_2);
+#else
     REQUIRE(fmt::to_string(formatted_1) == fmt::to_string(formatted_2));
+#endif
 }
 
 TEST_CASE("clone-default-formatter2", "[pattern_formatter]")
@@ -288,7 +292,11 @@ TEST_CASE("clone-default-formatter2", "[pattern_formatter]")
     formatter_1->format(msg, formatted_1);
     formatter_2->format(msg, formatted_2);
 
+#ifdef SPDLOG_USE_STD_FORMAT
+    REQUIRE(formatted_1 == formatted_2);
+#else
     REQUIRE(fmt::to_string(formatted_1) == fmt::to_string(formatted_2));
+#endif
 }
 
 TEST_CASE("clone-formatter", "[pattern_formatter]")
@@ -302,7 +310,12 @@ TEST_CASE("clone-formatter", "[pattern_formatter]")
     memory_buf_t formatted_2;
     formatter_1->format(msg, formatted_1);
     formatter_2->format(msg, formatted_2);
+
+#ifdef SPDLOG_USE_STD_FORMAT
+    REQUIRE(formatted_1 == formatted_2);
+#else
     REQUIRE(fmt::to_string(formatted_1) == fmt::to_string(formatted_2));
+#endif
 }
 
 TEST_CASE("clone-formatter-2", "[pattern_formatter]")
@@ -317,7 +330,12 @@ TEST_CASE("clone-formatter-2", "[pattern_formatter]")
     memory_buf_t formatted_2;
     formatter_1->format(msg, formatted_1);
     formatter_2->format(msg, formatted_2);
+
+#ifdef SPDLOG_USE_STD_FORMAT
+    REQUIRE(formatted_1 == formatted_2);
+#else
     REQUIRE(fmt::to_string(formatted_1) == fmt::to_string(formatted_2));
+#endif
 }
 
 class custom_test_flag : public spdlog::custom_flag_formatter
@@ -362,9 +380,15 @@ TEST_CASE("clone-custom_formatter", "[pattern_formatter]")
     formatter_1->format(msg, formatted_1);
     formatter_2->format(msg, formatted_2);
 
-    auto expected = fmt::format("[logger-name] [custom_output] some message{}", spdlog::details::os::default_eol);
+    auto expected = spdlog::fmt_lib::format("[logger-name] [custom_output] some message{}", spdlog::details::os::default_eol);
+
+#ifdef SPDLOG_USE_STD_FORMAT
+    REQUIRE(formatted_1 == expected);
+    REQUIRE(formatted_2 == expected);
+#else
     REQUIRE(fmt::to_string(formatted_1) == expected);
     REQUIRE(fmt::to_string(formatted_2) == expected);
+#endif
 }
 
 //
@@ -385,7 +409,12 @@ TEST_CASE("short filename formatter-1", "[pattern_formatter]")
     spdlog::source_loc source_loc{test_path, 123, "some_func()"};
     spdlog::details::log_msg msg(source_loc, "logger-name", spdlog::level::info, "Hello");
     formatter.format(msg, formatted);
+
+#ifdef SPDLOG_USE_STD_FORMAT
+    REQUIRE(formatted == "myfile.cpp");
+#else
     REQUIRE(fmt::to_string(formatted) == "myfile.cpp");
+#endif
 }
 
 TEST_CASE("short filename formatter-2", "[pattern_formatter]")
@@ -396,7 +425,12 @@ TEST_CASE("short filename formatter-2", "[pattern_formatter]")
     spdlog::source_loc source_loc{"myfile.cpp", 123, "some_func()"};
     spdlog::details::log_msg msg(source_loc, "logger-name", spdlog::level::info, "Hello");
     formatter.format(msg, formatted);
+
+#ifdef SPDLOG_USE_STD_FORMAT
+    REQUIRE(formatted == "myfile.cpp:123");
+#else
     REQUIRE(fmt::to_string(formatted) == "myfile.cpp:123");
+#endif
 }
 
 TEST_CASE("short filename formatter-3", "[pattern_formatter]")
@@ -407,7 +441,12 @@ TEST_CASE("short filename formatter-3", "[pattern_formatter]")
     spdlog::source_loc source_loc{"", 123, "some_func()"};
     spdlog::details::log_msg msg(source_loc, "logger-name", spdlog::level::info, "Hello");
     formatter.format(msg, formatted);
+
+#ifdef SPDLOG_USE_STD_FORMAT
+    REQUIRE(formatted == " Hello");
+#else
     REQUIRE(fmt::to_string(formatted) == " Hello");
+#endif
 }
 
 TEST_CASE("full filename formatter", "[pattern_formatter]")
@@ -418,7 +457,12 @@ TEST_CASE("full filename formatter", "[pattern_formatter]")
     spdlog::source_loc source_loc{test_path, 123, "some_func()"};
     spdlog::details::log_msg msg(source_loc, "logger-name", spdlog::level::info, "Hello");
     formatter.format(msg, formatted);
+
+#ifdef SPDLOG_USE_STD_FORMAT
+    REQUIRE(formatted == test_path);
+#else
     REQUIRE(fmt::to_string(formatted) == test_path);
+#endif
 }
 
 TEST_CASE("custom flags", "[pattern_formatter]")
@@ -430,8 +474,13 @@ TEST_CASE("custom flags", "[pattern_formatter]")
 
     spdlog::details::log_msg msg(spdlog::source_loc{}, "logger-name", spdlog::level::info, "some message");
     formatter->format(msg, formatted);
-    auto expected = fmt::format("[logger-name] [custom1] [custom2] some message{}", spdlog::details::os::default_eol);
+    auto expected = spdlog::fmt_lib::format("[logger-name] [custom1] [custom2] some message{}", spdlog::details::os::default_eol);
+
+#ifdef SPDLOG_USE_STD_FORMAT
+    REQUIRE(formatted == expected);
+#else
     REQUIRE(fmt::to_string(formatted) == expected);
+#endif
 }
 
 TEST_CASE("custom flags-padding", "[pattern_formatter]")
@@ -443,8 +492,13 @@ TEST_CASE("custom flags-padding", "[pattern_formatter]")
 
     spdlog::details::log_msg msg(spdlog::source_loc{}, "logger-name", spdlog::level::info, "some message");
     formatter->format(msg, formatted);
-    auto expected = fmt::format("[logger-name] [custom1] [     custom2] some message{}", spdlog::details::os::default_eol);
+    auto expected = spdlog::fmt_lib::format("[logger-name] [custom1] [     custom2] some message{}", spdlog::details::os::default_eol);
+
+#ifdef SPDLOG_USE_STD_FORMAT
+    REQUIRE(formatted == expected);
+#else
     REQUIRE(fmt::to_string(formatted) == expected);
+#endif
 }
 
 TEST_CASE("custom flags-exception", "[pattern_formatter]")