From 43e40ae84913738117f07c0764d9feae5ebaa7b1 Mon Sep 17 00:00:00 2001
From: Sam Lantinga <slouken@libsdl.org>
Date: Sat, 23 Aug 2014 10:57:26 -0700
Subject: [PATCH] Fixed bug 2690 - Floating point exception in Mix_Volume()

Francisco de la Pe?a

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

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.
---
 mixer.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/mixer.c b/mixer.c
index 2eaf1642..a1bc6916 100644
--- a/mixer.c
+++ b/mixer.c
@@ -320,7 +320,7 @@ static void mix_channels(void *udata, Uint8 *stream, int len)
     /* Mix any playing channels... */
     sdl_ticks = SDL_GetTicks();
     for ( i=0; i<num_channels; ++i ) {
-        if( ! mix_channel[i].paused ) {
+        if ( !mix_channel[i].paused ) {
             if ( mix_channel[i].expire > 0 && mix_channel[i].expire < sdl_ticks ) {
                 /* Expiration delay for that channel is reached */
                 mix_channel[i].playing = 0;
@@ -330,7 +330,7 @@ static void mix_channels(void *udata, Uint8 *stream, int len)
                 _Mix_channel_done_playing(i);
             } else if ( mix_channel[i].fading != MIX_NO_FADING ) {
                 Uint32 ticks = sdl_ticks - mix_channel[i].ticks_fade;
-                if( ticks > mix_channel[i].fade_length ) {
+                if ( ticks >= mix_channel[i].fade_length ) {
                     Mix_Volume(i, mix_channel[i].fade_volume_reset); /* Restore the volume */
                     if( mix_channel[i].fading == MIX_FADING_OUT ) {
                         mix_channel[i].playing = 0;
@@ -340,7 +340,7 @@ static void mix_channels(void *udata, Uint8 *stream, int len)
                     }
                     mix_channel[i].fading = MIX_NO_FADING;
                 } else {
-                    if( mix_channel[i].fading == MIX_FADING_OUT ) {
+                    if ( mix_channel[i].fading == MIX_FADING_OUT ) {
                         Mix_Volume(i, (mix_channel[i].fade_volume * (mix_channel[i].fade_length-ticks))
                                    / mix_channel[i].fade_length );
                     } else {
@@ -1094,7 +1094,7 @@ int Mix_FadeOutChannel(int which, int ms)
                 (mix_channel[which].fading != MIX_FADING_OUT) ) {
                 mix_channel[which].fade_volume = mix_channel[which].volume;
                 mix_channel[which].fading = MIX_FADING_OUT;
-                mix_channel[which].fade_length = ms;
+                mix_channel[which].fade_length = (Uint32)ms;
                 mix_channel[which].ticks_fade = SDL_GetTicks();
 
                 /* only change fade_volume_reset if we're not fading. */