Comment by graphitemaster

The problem with clang blocks is they're represented as a Objective-C object, this makes them unusable in APIs that expect a function pointer, the only way you can cast them to a function pointer is to define the structure which represents the block and mmap executable code pages to marshal the call. Such a library exists that binds them to libffi here https://github.com/mikeash/MABlockClosure This feat alone makes blocks essentially useless unless your entire API is also block-based, as in T (^foo)(...) vs T(*foo)(...).