Function dispatch_block_perform 

pub unsafe extern "C" fn dispatch_block_perform(
    flags: dispatch_block_flags_t,
    block: dispatch_block_t,
)

Create, synchronously execute and release a dispatch block object from the specified block and flags.

Behaves identically to the sequence dispatch_block_t b = dispatch_block_create(flags, block); b(); Block_release(b); but may be implemented more efficiently internally by not requiring a copy to the heap of the specified block or the allocation of a new block object.

Parameter flags: Configuration flags for the temporary block object. The result of passing a value that is not a bitwise OR of flags from dispatch_block_flags_t is undefined.

Parameter block: The block to create the temporary block object from.