# HG changeset patch
# User Sam Lantinga <slouken@libsdl.org>
# Date 1253518346 0
# Node ID 62e86ab81e3ceb5f0da6eac1f0be42a31e97be68
# Parent  453587d6dc8712f75acf5ff12470319312a2ddcb
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 453587d6dc87 -r 62e86ab81e3c src/thread/generic/SDL_syssem.c
--- a/src/thread/generic/SDL_syssem.c	Mon Sep 21 07:28:03 2009 +0000
+++ b/src/thread/generic/SDL_syssem.c	Mon Sep 21 07:32:26 2009 +0000
@@ -165,7 +165,9 @@
 		                             sem->count_lock, timeout);
 	}
 	--sem->waiters_count;
-	--sem->count;
+	if (retval == 0) {
+		--sem->count;
+	}
 	SDL_UnlockMutex(sem->count_lock);
 
 	return retval;