Experiment if __block causes a retain.

annti_blockSelf.m

// Run with:
//  clang -fobjc-arc -Wall -framework Foundation blockself.m && ./a.out

// Further reading:
// http://www.mikeash.com/pyblog/friday-qa-2009-08-14-practical-blocks.html
// http://clang.llvm.org/docs/AutomaticReferenceCounting.html#misc.blocks
// http://developer.apple.com/library/mac/#releasenotes/ObjectiveC/RN-TransitioningToARC/Introduction/Introduction.html

#import <Foundation/Foundation.h>

#pragma clang diagnostic ignored "-Warc-performSelector-leaks"

static SEL retainCount;

typedef void (^BlockType)();


int main(int argc, char *argv[])
{
    retainCount = sel_registerName("retainCount");
    
    @autoreleasepool
    {
        NSString *str = [NSString stringWithFormat:@"f%d", 0];
        printf("initial retainCount: %ld\n", (long)[str performSelector:retainCount]);

// This does retain:
#if 0
        BlockType block = ^()
        {
            printf("executed in block retainCount: %ld\n", (long)[str performSelector:retainCount]);
        };
        
        block();

// Only __unsafe_unretained does not retain in these cases:
#else
        __block NSString *selfStr = str;
        // __weak NSString *selfStr = str;
        // __unsafe_unretained NSString *selfStr = str;

        BlockType block = ^()
        {
            printf("executed in self block retainCount: %ld\n", (long)[selfStr performSelector:retainCount]);
        };
        
        block();
#endif        
        
        printf("final retainCount: %ld\n", (long)[str performSelector:retainCount]);
    }
}