Disable unused local typedefs warning

This triggers on gcc 4.8.4 for compile time asserts inside of functions

Fixes https://github.com/libsdl-org/SDL/issues/7732

Co-authored-by: Ozkan Sezer <sezeroz@gmail.com>

CMakeLists.txt

@@ -641,6 +641,11 @@ if(USE_GCC OR USE_CLANG OR USE_INTELCC)
     list(APPEND EXTRA_CFLAGS "-Wshadow")
   endif()
 
+  check_c_compiler_flag(-Wunused-local-typedefs HAVE_GCC_WUNUSED_LOCAL_TYPEDEFS)
+  if(HAVE_GCC_WUNUSED_LOCAL_TYPEDEFS)
+    list(APPEND EXTRA_CFLAGS "-Wno-unused-local-typedefs")
+  endif()
+
   if(APPLE)
     cmake_push_check_state(RESET)
     # FIXME: don't use deprecated declarations

configure

@@ -23225,6 +23225,41 @@ printf "%s\n" "$need_gcc_Wno_multichar" >&6; }
     fi
 }
 
+CheckUnusedLocalTypedefs()
+{
+    { printf "%s\n" "$as_me:${as_lineno-$LINENO}: checking for GCC -Wunused-local-typedefs option" >&5
+printf %s "checking for GCC -Wunused-local-typedefs option... " >&6; }
+    have_gcc_unused_local_typedefs=no
+
+    save_CFLAGS="$CFLAGS"
+    CFLAGS="$save_CFLAGS -Wunused-local-typedefs"
+    cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+
+    int x = 0;
+
+int
+main (void)
+{
+
+  ;
+  return 0;
+}
+_ACEOF
+if ac_fn_c_try_compile "$LINENO"
+then :
+  have_gcc_unused_local_typedefs=yes
+fi
+rm -f core conftest.err conftest.$ac_objext conftest.beam conftest.$ac_ext
+    { printf "%s\n" "$as_me:${as_lineno-$LINENO}: result: $have_gcc_unused_local_typedefs" >&5
+printf "%s\n" "$have_gcc_unused_local_typedefs" >&6; }
+    CFLAGS="$save_CFLAGS"
+
+    if test x$have_gcc_unused_local_typedefs = xyes; then
+        EXTRA_CFLAGS="$EXTRA_CFLAGS -Wno-unused-local-typedefs"
+    fi
+}
+
 CheckWayland()
 {
     # Check whether --enable-video-wayland was given.
@@ -28571,6 +28606,7 @@ printf "%s\n" "#define SDL_JOYSTICK_VIRTUAL 1" >>confdefs.h
 }
 
 CheckWarnAll
+CheckUnusedLocalTypedefs
 CheckNoStrictAliasing
 
 CheckEventSignals

configure.ac

@@ -1674,6 +1674,27 @@ dnl Haiku headers use multicharacter constants all over the place. Ignore these
     fi
 }
 
+dnl See if GCC's -Wunused-local-typedefs is supported and disable it
+dnl  because it triggers on gcc 4.8.4 for compile time asserts inside
+dnl  of functions.
+CheckUnusedLocalTypedefs()
+{
+    AC_MSG_CHECKING(for GCC -Wunused-local-typedefs option)
+    have_gcc_unused_local_typedefs=no
+
+    save_CFLAGS="$CFLAGS"
+    CFLAGS="$save_CFLAGS -Wunused-local-typedefs"
+    AC_COMPILE_IFELSE([AC_LANG_PROGRAM([[
+    int x = 0;
+    ]],[])], [have_gcc_unused_local_typedefs=yes],[])
+    AC_MSG_RESULT($have_gcc_unused_local_typedefs)
+    CFLAGS="$save_CFLAGS"
+
+    if test x$have_gcc_unused_local_typedefs = xyes; then
+        EXTRA_CFLAGS="$EXTRA_CFLAGS -Wno-unused-local-typedefs"
+    fi
+}
+
 dnl Check for Wayland
 CheckWayland()
 {
@@ -3746,6 +3767,7 @@ CheckVirtualJoystick()
 
 dnl Do this on all platforms, before everything else (other things might want to override it).
 CheckWarnAll
+CheckUnusedLocalTypedefs
 CheckNoStrictAliasing
 
 dnl Do this for every platform, but for some it doesn't mean anything, but better to catch it here anyhow.