How to avoid reference count underflow in _NSCFURLProtocolBridge in custom NSURLProtocol in GC environment

Question

The basics are I have a custom `NSURLProtocol`. In `startLoading`, `[self client]` is of type: ``` <_NSCFURLProtocolBridge> {NSURLProtocol, CFURLProtocol} ``` The problem is running this in a garbage-collected environment. Because I'm writing a screensaver, I'm forced to make it garbage-collected. However, the _NSCFURLProtocolBridge protocol seems to always throw: `malloc: reference count underflow for (memory_id_here), break on auto_refcount_underflow_error to debug` An example dump to the debug console is: `ScreenSaverEngine[1678:6807] client is <_NSCFURLProtocolBridge 0x20025ab00> {NSURLProtocol 0x200258ec0, CFURLProtocol 0x20029c400}` `ScreenSaverEngine(1678,0x102eda000) malloc: reference count underflow for 0x20025ab00, break on auto_refcount_underflow_error to debug.` You can see that the underflow occurs for `<_NSCFURLProtocolBridge 0x20025ab00>`. When I break on `auto_refcount_underflow_error`, it seems to stack-trace back up to `URLProtocolDidFinishLoading:` in: ``` id client…

Accepted Answer

Last WWDC we confirmed this bug with a webkit engineer, he could see the bug right there in the code so hopefully they'll fix it. The workaround is to CFRetain the client in the initWithRequest method.

```
- (id)initWithRequest:(NSURLRequest *)request cachedResponse:(NSCachedURLResponse *)cachedResponse client:(id <NSURLProtocolClient>)client
{
    // work around for NSURLProtocol bug
    // note that this leaks!
    CFRetain(client);

if (self = [super initWithRequest:request cachedResponse:cachedResponse client:client])
    {
    }

return self;
}
```

How to avoid reference count underflow in _NSCFURLProtocolBridge in custom NSURLProtocol in GC environment

Solution

Problem