On Xcode, enabling Thread Sanitizer when running testposition breaks when moving either blue or green squares

[ericoporto]

In Xcode, you can enable a Thread Sanitizer by selecting it in Scheme->Edit Scheme, for the testposition running option. I created the Xcode project by using it's generator from CMake. I am using the prebuilt SDL2 framework from SDL releases.

I am using the CantinaBand60.wav file for testing.

testposition(2557,0x1ecc67ac0) malloc: nano zone abandoned due to inability to reserve vm space.
AddInstanceForFactory: No factory registered for id <CFUUID 0x10484e8c0> F8BB1C28-BAE8-11D6-9C31-00039315CD46
Now queueing '/Users/user/git/mojoAL-1/cmake-build-debugxcode/CantinaBand60.wav'...
==================
WARNING: ThreadSanitizer: data race (pid=2557)
  Read of size 1 at 0x00010a91005c by thread T5 (mutexes: write M0, write M1):
    #0 mix_source(ALCcontext_struct*, ALsource*, float*, int, char) <null> (libmojoal.dylib:arm64+0x3440c)
    #1 mix_context(ALCcontext_struct*, float*, int) <null> (libmojoal.dylib:arm64+0x3249c)
    #2 playback_device_callback(void*, unsigned char*, int) <null> (libmojoal.dylib:arm64+0x31f9c)
    #3 <null> <null> (SDL2:arm64+0x34128)

  Previous write of size 1 at 0x00010a91005c by main thread (mutexes: write M2):
    #0 _alSourcefv(unsigned int, int, float const*) <null> (libmojoal.dylib:arm64+0x2110c)
    #1 _alSource3f(unsigned int, int, float, float, float) <null> (libmojoal.dylib:arm64+0x214b8)
    #2 alSource3f <null> (libmojoal.dylib:arm64+0x213e0)
    #3 mainloop(SDL_Renderer*) <null> (testposition:arm64+0x1000062e4)
    #4 spatialize(SDL_Renderer*, char const*) <null> (testposition:arm64+0x100004868)
    #5 main <null> (testposition:arm64+0x100003a14)

  Location is heap block of size 15400 at 0x00010a910000 allocated by main thread:
    #0 calloc <null> (libclang_rt.tsan_osx_dynamic.dylib:arm64e+0x55c8c)
    #1 SDL_DYNAPI_entry <null> (SDL2:arm64+0xd75e0)
    #2 _alGenSources(int, unsigned int*) <null> (libmojoal.dylib:arm64+0x1d008)
    #3 alGenSources <null> (libmojoal.dylib:arm64+0x1bd60)
    #4 spatialize(SDL_Renderer*, char const*) <null> (testposition:arm64+0x100003c98)
    #5 main <null> (testposition:arm64+0x100003a14)

  Mutex M0 (0x00010465c6c0) created at:
    #0 pthread_mutex_init <null> (libclang_rt.tsan_osx_dynamic.dylib:arm64e+0x30e30)
    #1 SDL_DYNAPI_entry <null> (SDL2:arm64+0xe2f64)
    #2 alcCreateContext <null> (libmojoal.dylib:arm64+0x6738)
    #3 main <null> (testposition:arm64+0x1000036ac)

  Mutex M1 (0x00010465c380) created at:
    #0 pthread_mutex_init <null> (libclang_rt.tsan_osx_dynamic.dylib:arm64e+0x30e30)
    #1 SDL_DYNAPI_entry <null> (SDL2:arm64+0xe2f64)
    #2 alcCreateContext <null> (libmojoal.dylib:arm64+0x6738)
    #3 main <null> (testposition:arm64+0x1000036ac)

  Mutex M2 (0x00010465f2c0) created at:
    #0 pthread_mutex_init <null> (libclang_rt.tsan_osx_dynamic.dylib:arm64e+0x30e30)
    #1 SDL_DYNAPI_entry <null> (SDL2:arm64+0xe2f64)
    #2 prep_alc_device(char const*, char) <null> (libmojoal.dylib:arm64+0x5048)
    #3 alcOpenDevice <null> (libmojoal.dylib:arm64+0x4f80)
    #4 main <null> (testposition:arm64+0x1000035a0)

  Thread T5 (tid=34370, running) created by main thread at:
    #0 pthread_create <null> (libclang_rt.tsan_osx_dynamic.dylib:arm64e+0x2ffec)
    #1 <null> <null> (SDL2:arm64+0x24fe4)
    #2 alcCreateContext <null> (libmojoal.dylib:arm64+0x6738)
    #3 main <null> (testposition:arm64+0x1000036ac)

SUMMARY: ThreadSanitizer: data race (/Users/user/git/mojoAL-1/cmake-build-debugxcode/Debug/libmojoal.dylib:arm64+0x3440c) in mix_source(ALCcontext_struct*, ALsource*, float*, int, char)+0x2ac

Anyhow it reports a read of size 1 here

https://github.com/icculus/mojoAL/blob/1adfdf5cd5447c68e11b0ab9f74318a4e364e7c9/mojoal.c#L1939

While there is a write of size 1 here

https://github.com/icculus/mojoAL/blob/1adfdf5cd5447c68e11b0ab9f74318a4e364e7c9/mojoal.c#L3734

This appears fine.

I don't know how much of a real issue this is as the test appears to work correctly. Still decided to report just in case.