[MacOS] Crash during debugging pointing to close audio code

[MrOnlineCoder]

This is very obscure and weird bug, therefore I am sorry I may not be able to provide full context needed to resolve it.

Almost every project with SDL3 + SDL_ttf + SDL_mixer + SDL_image crashes when debugged on MacOS, pointing to some code related to audio device closing (although call stack contains SDL_mixer too, it eventually points to SDL3 Audio API).

The code I use is basically pretty straightforward (error checking for all init and create calls is omitted, but it's present and I don't get any errors):

#include <SDL3/SDL.h>
#include <SDL3_image/SDL_image.h>
#include <SDL3_mixer/SDL_mixer.h>
#include <SDL3_ttf/SDL_ttf.h>

int main()
{
    SDL_Init(
        SDL_INIT_VIDEO | SDL_INIT_AUDIO | SDL_INIT_GAMEPAD);

    Mix_Init(MIX_INIT_OGG | MIX_INIT_MP3);

    SDL_AudioSpec audioSpec;
    audioSpec.channels = MIX_DEFAULT_CHANNELS;
    audioSpec.format = MIX_DEFAULT_FORMAT;
    audioSpec.freq = MIX_DEFAULT_FREQUENCY;

    Mix_OpenAudio(
        0, &audioSpec);

    TTF_Init();

    SDL_Window *window = SDL_CreateWindow(
        "App",
        1280,
        720, 0);

    SDL_Renderer *renderer = SDL_CreateRenderer(
        window,
        NULL);

    SDL_Event event;

    // create instances of textures, TTF_Fonts, etc...

    bool running = true;

    while (running)
    {
        while (SDL_PollEvent(&event))
        {
            if (event.type == SDL_EVENT_QUIT)
            {
                running = false;
                break;
            }

            // other event processing
        }

        // update logic

        SDL_RenderClear(renderer);

        // my rendering code

        SDL_RenderPresent(renderer);

        SDL_Delay(16);
    }

    // Free resources like textures, fonts, etc...

    SDL_DestroyRenderer(renderer);
    SDL_DestroyWindow(window);

    Mix_HaltMusic();
    Mix_CloseAudio();
    Mix_Quit();
    TTF_Quit();
    SDL_Quit();

    return 0;
}

The application runs well, but when I close it, I get a crash witht the following call stack on main thread:

__ulock_wait (@__ulock_wait:5)
_pthread_join (@_pthread_join:155)
SDL_SYS_WaitThread (/home/mronlinecoder/project/build/_deps/sdl3-src/src/thread/pthread/SDL_systhread.c:287)
SDL_WaitThread_REAL (/home/mronlinecoder/project/build/_deps/sdl3-src/src/thread/SDL_thread.c:466)
COREAUDIO_CloseDevice (/home/mronlinecoder/project/build/_deps/sdl3-src/src/audio/coreaudio/SDL_coreaudio.m:638)
ClosePhysicalAudioDevice (/home/mronlinecoder/project/build/_deps/sdl3-src/src/audio/SDL_audio.c:1596)
SDL_CloseAudioDevice_REAL (/home/mronlinecoder/project/build/_deps/sdl3-src/src/audio/SDL_audio.c:1629)
SDL_CloseAudioDevice (/home/mronlinecoder/project/build/_deps/sdl3-src/src/dynapi/SDL_dynapi_procs.h:102)
Mix_CloseAudio (/home/mronlinecoder/project/build/_deps/sdl3_mixer-src/src/mixer.c:1387)
main (/home/mronlinecoder/project/src/Main.cpp:68)
start (@start:622)

There is also an exception on system thread:

__cxa_throw (@__cxa_throw:3)
QueueAccessor::QueueAccessor(unsigned int, audit_token_t const*, bool) (@QueueAccessor::QueueAccessor(unsigned int, audit_token_t const*, bool):73)
AudioQueueInternalStop_Sync(unsigned int) (@AudioQueueInternalStop_Sync(unsigned int):13)
_dispatch_client_callout (@_dispatch_client_callout:8)
_dispatch_root_queue_drain (@_dispatch_root_queue_drain:219)
_dispatch_worker_thread2 (@_dispatch_worker_thread2:42)
_pthread_wqthread (@_pthread_wqthread:60)

When not debugged however, it seems to exit gracefully with 0 exit code.

Used platform and toolchain:

MacOS 14.6.1 (23G93) Darwin Kernel Version 23.6.0

Apple clang version 15.0.0 (clang-1500.3.9.4) Target: arm64-apple-darwin23.6.0 Thread model: posix InstalledDir: /Library/Developer/CommandLineTools/usr/bin

SDL: release-3.2.12 SDL_mixer: main branch latest commit (via FetchContent) SDL_image: main branch latest commit (via FetchContent)

Debugger used: lldb-1500.0.404.7 (launched via VSCode)

[icculus]

I'll try to reproduce this here.

For the second exception: CoreAudio tends to throw exceptions internally that it then catches itself, and Apple's debugger stops on these, but often they are harmless.

[MrOnlineCoder]

For the second exception: CoreAudio tends to throw exceptions internally that it then catches itself, and Apple's debugger stops on these, but often they are harmless.

This is interesting and valuable. Although as I understand, the Mix_CloseAudio triggers a wait or close on CoreAudio thread which gives an exception, but it happens very constintently every time, which is weird and just annoying. I don't know if I can safely add that to ignore list or it's really some problem. Probably the first, as no visible interruptions or problems occur during runtime until the app is closed.

[matthewkayin]

The info about the CoreAudio exceptions is good to know.

I've been having this same AudioQueueInternalStop_Sync crash on MacOS, clang 15, target arm64-apple-darwin23.5.0, SDL 3.2.12, not using SDL_mixer, just SDL3 audio. Happens only when debugging with lldb. If I debug with cppdbg, then the exception isn't caught.

I think I will consider these exceptions harmless for now.

[jawaidbazyar2]

Same issues here. Seems harmless but requires manual intervention to resume debugging execution.

[icculus]

Fwiw, I get CoreAudio debug logging from this test program when run under lldb, but the debugger doesn't halt. Not sure if this changed in a later Xcode or macOS release, or if something else is different.

2025-07-11 11:57:17.605733-0400 test[20678:53302325] [plugin] AddInstanceForFactory: No factory registered for id <CFUUID 0x6000033723a0> F8BB1C28-BAE8-11D6-9C31-00039315CD46
2025-07-11 11:57:17.686501-0400 test[20678:53302325]      HALDefaultDevice.cpp:742    Could not find default device for dIn
2025-07-11 11:57:20.419983-0400 test[20678:53302550] [AMCP]  68871          HALC_ProxyIOContext.cpp:1621  HALC_ProxyIOContext::IOWorkLoop: skipping cycle due to overload
2025-07-11 11:57:20.465678-0400 test[20678:53302550] [AMCP]  68871          HALC_ProxyIOContext.cpp:1621  HALC_ProxyIOContext::IOWorkLoop: skipping cycle due to overload
2025-07-11 11:57:20.617129-0400 test[20678:53302550] [AMCP]  68871          HALC_ProxyIOContext.cpp:1621  HALC_ProxyIOContext::IOWorkLoop: skipping cycle due to overload
2025-07-11 11:57:25.033405-0400 test[20678:53302540] [aqsrv]        AQ_Server_Common.h:48    Exception caught in AudioQueueInternalStop_Sync - error -66671

(including that "Exception caught" line.)

At any rate, this isn't a bug in SDL, as far as I can tell, so I'm closing for now.