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Nope, they're an ObjectiveC object with some specialties at the compiler level. Google how they're implemented.

An objective-c object is just a pointer to a struct. You don't need the objective-c runtime to call a block.

Block_copy etc are implemented in libclosure which iirc does not require libobjc either. But of course if you ARE writing objc, they are valid objects and can be treated as such

Correct, the problem is to call the function you cannot treat it as a standard function since it's pointing to a struct, the struct does contain the actual function pointer but there is an implicit `this' first argument to that function pointer which has to be that struct itself. This means you cannot use the block in an API that explicitly requires a function pointer, instead the API must specifically be aware of the block and would need to support it.

It sounds like you could say it's ObjectiveC-compatible, not ObjectiveC per se. But it's an unimportant distinction.

Of course, there's no way around that except to write block variants for those functions. stdlib on osx for example has block variants of most functions that take function pointers (`man qsort_b` for an example)

But if you write your program to use blocks from the start, that's not a big problem.

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