Open Radar

 
18-Jun-2013 01:43 AM Rob Mayoff:
Summary:

Calling CFAllocatorSetDefault with anything but kCFAllocatorSystemDefault causes crashes.

Steps to Reproduce:

Call CFAllocatorSetDefault with any (valid) allocator.  Example:

int main(int argc, char *argv[])
{
    CFAllocatorSetDefault(kCFAllocatorMalloc);
    @autoreleasepool {
        return UIApplicationMain(argc, argv, nil, NSStringFromClass([AppDelegate class]));
    }
}

I have attached a test project with this code.  It crashes on both simulator and device.  Changing kCFAllocatorMalloc to kCFAllocatorSystemDefault removes the crash.

Expected Results:

Not crash.

Actual Results:

The app crashes soon after it changes the default allocator, the next time anything tries to create a Core Foundation object using NULL as the allocator.  The crash is in CFRetain, because CFRetain is being called with a NULL pointer.

Regression:

Notes:

The error is in _CFRuntimeCreateInstance.  When the allocator argument is NULL, and the current default allocator isn't the system default allocator, _CFRuntimeCreateInstance tries to retain the allocator.  But it just tries to retain the NULL instead of retaining the current default allocator.

See this stackoverflow question and my answer: http://stackoverflow.com/a/17138252/77567