Play with ARC variable lifetime qualifiers

unsafe.m

#import <Foundation/Foundation.h>

// clang -g -fobjc-arc -Wall -framework Foundation -o unsafe unsafe.m

@interface NSThing : NSObject
@end

@implementation NSThing

- (void) dealloc {
    NSLog (@"dealloc called for thing %p", self);
} // dealloc

@end // NSThing


int main (void) {

    {
        NSLog (@"Regular strong reference");
        NSThing *thisThing = [[NSThing alloc] init];
        NSThing *thatThing = thisThing;
        
        thisThing = nil;
        
        NSLog (@"that thing is %@", thatThing);
    }

    {
        NSLog (@"Regular weak reference");
        NSThing *thisThing = [[NSThing alloc] init];
        __weak NSThing *thatThing = thisThing;
        
        thisThing = nil;
        
        NSLog (@"that thing is %@", thatThing);
    }

    {
        NSLog (@"Unretained-unreleased reference");
        NSThing *thisThing = [[NSThing alloc] init];
        __unsafe_unretained NSThing *thatThing = thisThing;
        
        thisThing = nil;
        
        NSLog (@"that thing is %@", thatThing);
    }

#if BAD_PROGRAMMER_NO_COOKIE

    struct StructWithObject {
        NSThing *otherThing; // ARC forbids Objective-C objects in structs or unions
    };

#else

    struct StructWithObject {
        __unsafe_unretained NSThing *otherThing;
    };

#endif

    return 0;

} // main



#if 0

% ./unsafe
unsafe[44029:303] Regular strong reference
unsafe[44029:303] that thing is <NSThing: 0x7f9b93500340>
unsafe[44029:303] dealloc called for thing 0x7f9b93500340

unsafe[44029:303] Regular weak reference
unsafe[44029:303] dealloc called for thing 0x7f9b95000020
unsafe[44029:303] that thing is (null)

unsafe[44029:303] Unretained-unreleased reference
unsafe[44029:303] dealloc called for thing 0x7f9b95000020
unsafe[44029:303] that thing is <NSThing: 0x7f9b95000020>

#endif