From e2751e6ffc0c88e2c3b58418d708daee60b3c135 Mon Sep 17 00:00:00 2001
From: Peter Steinberger <me@petersteinberger.com>
Date: Thu, 5 Apr 2012 17:49:08 -0700
Subject: [PATCH] protect decrementActivityCount against integer underflow.

---
 AFNetworking/AFNetworkActivityIndicatorManager.m | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/AFNetworking/AFNetworkActivityIndicatorManager.m b/AFNetworking/AFNetworkActivityIndicatorManager.m
index 32dbbe0..3e36ba6 100644
--- a/AFNetworking/AFNetworkActivityIndicatorManager.m
+++ b/AFNetworking/AFNetworkActivityIndicatorManager.m
@@ -111,7 +111,11 @@ static NSTimeInterval const kAFNetworkActivityIndicatorInvisibilityDelay = 0.25;
 
 - (void)decrementActivityCount {
     [self willChangeValueForKey:@"activityCount"];
-    OSAtomicDecrement32((int32_t*)&_activityCount);
+    bool success;
+    do {
+        int32_t orig = _activityCount;
+        success = OSAtomicCompareAndSwap32(orig, MIN(orig - 1, orig), &_activityCount);
+    } while(!success);
     [self didChangeValueForKey:@"activityCount"];
     [self updateNetworkActivityIndicatorVisibilityDelayed];
 }