objective c - Call Block_Release inside block to be released -

is possible release block inside itself? compiler it's fine, i'm not sure if @ runtime crash, since releases memory executed @ same time.

cancel_block_t somefunction(/*args*/){     __block bool canceled = no;     __block cancel_block_t cancel_block = block_copy(^{         canceled = yes;         block_release(cancel_block); //<-- can this?         cancel_block = null; //<-- can this?     });     // […]     return cancel_block; } 

would approach more safe?

 cancel_block_t somefunction(/*args*/){     __block bool canceled = no;     __block cancel_block_t cancel_block = block_copy(^{         canceled = yes;         dispatch_async(dispatch_time(dispatch_time_now, 0.001 * nsec_per_sec), dispatch_get_global_queue(dispatch_queue_priority_low, 0),^{             block_release(cancel_block);             cancel_block = null;         });     });     // […]     return cancel_block; } 

thanks help!

edit #1: corrected return type of function.

is non-arc code? arc automatically copy, retain, , release blocks.

anyway, not safe, @ least not always. i've seen crashes similar behavior. issue reference __block variable within same block object block_release() may deallocate. so, trying set variable can access memory after it's been freed (and maybe reused).

about function:

1) why return pointer block type? more normal function return block type (which reference). is, somefunction() should have return type of cancel_block_t, not cancel_block_t*. anyway, it's not safe take address of __block variable, since such variable can change location. starts life on stack gets moved heap.

2) normal semantics function returns block return autoreleased object. so, somefunction() should return [cancel_block autorelease]; (given it's been copied). caller responsible retaining if wants keep beyond current scope or autorelease pool. if it's submitted function (e.g. dispatch_async()), function responsible retaining it. in other words, memory management semantics same other object. block should not try release itself.