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Bug 2690

Summary: Floating point exception in Mix_Volume()
Product: SDL_mixer Reporter: Francisco de la Peña <fran>
Component: miscAssignee: Ryan C. Gordon <icculus>
Status: RESOLVED FIXED QA Contact: Sam Lantinga <slouken>
Severity: normal    
Priority: P2    
Version: 2.0.0   
Hardware: x86_64   
OS: Linux   

Description Francisco de la Peña 2014-08-18 00:07:47 UTC 
This happens rarely under uncertain circunstances, as it doesn't crash always and does it randomly. Fortunately, I've got a backtrace when running a GDB session. Might be a divide by zero issue in SDL or SDL_mixer.

Program received signal SIGFPE, Arithmetic exception.
0x00000038e8c08a7d in mix_channels (udata=<optimized out>, stream=0x24e11b0 "", len=2048) at mixer.c:345
345	                        Mix_Volume(i, (mix_channel[i].fade_volume * ticks) / mix_channel[i].fade_length );
(gdb) bt f
#0  0x00000038e8c08a7d in mix_channels (udata=<optimized out>, stream=0x24e11b0 "", len=2048) at mixer.c:345
        ticks = 0
        mix_input = <optimized out>
        i = 0
        mixable = <optimized out>
        volume = <optimized out>
        sdl_ticks = 129373
#1  0x000000345d219e0b in SDL_RunAudio (devicep=devicep@entry=0x24df950)
    at /usr/src/debug/SDL2-2.0.3/src/audio/SDL_audio.c:483
        silence = 0
        device = 0x24df950
        stream = 0x24e11b0 ""
        stream_len = 2048
        udata = 0x0
        fill = 0x38e8c089b0 <mix_channels>
        delay = 11
#2  0x000000345d27764d in SDL_RunThread (data=0x25870d0) at /usr/src/debug/SDL2-2.0.3/src/thread/SDL_thread.c:282
        args = 0x25870d0
        userfunc = 0x345d219cb0 <SDL_RunAudio>
        userdata = 0x24df950
        thread = 0x2588a30
        statusloc = 0x2588a40
#3  0x000000345d2c2b29 in RunThread (data=<optimized out>)
    at /usr/src/debug/SDL2-2.0.3/src/thread/pthread/SDL_systhread.c:72
No locals.
#4  0x0000003bd6607f33 in start_thread (arg=0x7ffff1f26700) at pthread_create.c:309
        __res = <optimized out>
        pd = 0x7ffff1f26700
        now = <optimized out>
        unwind_buf = {cancel_jmp_buf = {{jmp_buf = {140737252583168, 8330904859251263453, 1, 38674912, 
                140737252583872, 140737252583168, -8330900440849889315, 8352766722943829981}, mask_was_saved = 0}}, 
---Type <return> to continue, or q <return> to quit---
          priv = {pad = {0x0, 0x0, 0x0, 0x0}, data = {prev = 0x0, cleanup = 0x0, canceltype = 0}}}
        not_first_call = <optimized out>
        pagesize_m1 = <optimized out>
        sp = <optimized out>
        freesize = <optimized out>
#5  0x0000003bd62f4ded in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:111
No locals.

Using SDL 2.0.3 and SDL_Mixer 2.0.0, PulseAudio, Fedora 20 x86_64 but looks like can be reproduced on other platforms.
Comment 1 Sam Lantinga 2014-08-23 17:57:53 UTC 
Nice catch!
https://hg.libsdl.org/SDL_mixer/rev/9599bb0ff844