Emscripten: Avoid SDL2 in JS global scope

After this fix, closure works with the LLVM wasm backend on SDL2.

src/audio/emscripten/SDL_emscriptenaudio.c

@@ -35,6 +35,7 @@ FeedAudioDevice(_THIS, const void *buf, const int buflen)
 {
     const int framelen = (SDL_AUDIO_BITSIZE(this->spec.format) / 8) * this->spec.channels;
     EM_ASM_ARGS({
+        var SDL2 = Module['SDL2'];
         var numChannels = SDL2.audio.currentOutputBuffer['numberOfChannels'];
         for (var c = 0; c < numChannels; ++c) {
             var channelData = SDL2.audio.currentOutputBuffer['getChannelData'](c);
@@ -100,6 +101,7 @@ HandleCaptureProcess(_THIS)
     }
 
     EM_ASM_ARGS({
+        var SDL2 = Module['SDL2'];
         var numChannels = SDL2.capture.currentCaptureBuffer.numberOfChannels;
         for (var c = 0; c < numChannels; ++c) {
             var channelData = SDL2.capture.currentCaptureBuffer.getChannelData(c);
@@ -145,6 +147,7 @@ static void
 EMSCRIPTENAUDIO_CloseDevice(_THIS)
 {
     EM_ASM_({
+        var SDL2 = Module['SDL2'];
         if ($0) {
             if (SDL2.capture.silenceTimer !== undefined) {
                 clearTimeout(SDL2.capture.silenceTimer);
@@ -196,11 +199,12 @@ EMSCRIPTENAUDIO_OpenDevice(_THIS, void *handle, const char *devname, int iscaptu
 
     /* based on parts of library_sdl.js */
 
-    /* create context (TODO: this puts stuff in the global namespace...)*/
+    /* create context */
     result = EM_ASM_INT({
-        if(typeof(SDL2) === 'undefined') {
-            SDL2 = {};
+        if(typeof(Module['SDL2']) === 'undefined') {
+            Module['SDL2'] = {};
         }
+        var SDL2 = Module['SDL2'];
         if (!$0) {
             SDL2.audio = {};
         } else {
@@ -249,7 +253,10 @@ EMSCRIPTENAUDIO_OpenDevice(_THIS, void *handle, const char *devname, int iscaptu
     this->hidden = (struct SDL_PrivateAudioData *)0x1;
 
     /* limit to native freq */
-    this->spec.freq = EM_ASM_INT_V({ return SDL2.audioContext.sampleRate; });
+    this->spec.freq = EM_ASM_INT_V({
+      var SDL2 = Module['SDL2'];
+      return SDL2.audioContext.sampleRate;
+    });
 
     SDL_CalculateAudioSpec(&this->spec);
 
@@ -271,6 +278,7 @@ EMSCRIPTENAUDIO_OpenDevice(_THIS, void *handle, const char *devname, int iscaptu
            to be honest. */
 
         EM_ASM_({
+            var SDL2 = Module['SDL2'];
             var have_microphone = function(stream) {
                 //console.log('SDL audio capture: we have a microphone! Replacing silence callback.');
                 if (SDL2.capture.silenceTimer !== undefined) {
@@ -313,6 +321,7 @@ EMSCRIPTENAUDIO_OpenDevice(_THIS, void *handle, const char *devname, int iscaptu
     } else {
         /* setup a ScriptProcessorNode */
         EM_ASM_ARGS({
+            var SDL2 = Module['SDL2'];
             SDL2.audio.scriptProcessorNode = SDL2.audioContext['createScriptProcessor']($1, 0, $0);
             SDL2.audio.scriptProcessorNode['onaudioprocess'] = function (e) {
                 if ((SDL2 === undefined) || (SDL2.audio === undefined)) { return; }