# HG changeset patch
# User Sam Lantinga <slouken@libsdl.org>
# Date 1253518506 0
# Node ID 77f2f10b81a7bd4dd2c902d8565e8f2f68792179
# Parent  d390778b59c118eac0ba517049133c5c03704624
Fixed bug #570

SDL_SemWaitTimeout in src/thread/generic/SDL_syssem.c line 179 (SVN trunk):

--sem->count;

should be

if (retval == 0) {
    --sem->count;
}

Without this, sem->count will underflow on timeout effectively breaking the
semaphore. It appears that the implementation has been wrong since the initial
revision.

diff -r d390778b59c1 -r 77f2f10b81a7 src/thread/generic/SDL_syssem.c
--- a/src/thread/generic/SDL_syssem.c	Mon Sep 21 05:24:54 2009 +0000
+++ b/src/thread/generic/SDL_syssem.c	Mon Sep 21 07:35:06 2009 +0000
@@ -176,7 +176,9 @@
                                      sem->count_lock, timeout);
     }
     --sem->waiters_count;
-    --sem->count;
+    if (retval == 0) {
+        --sem->count;
+    }
     SDL_UnlockMutex(sem->count_lock);
 
     return retval;