iPhone: I call protocol_conformsToProtocol function and it shows implicit declaration warning

I got 2 Protocol* object and want to check if they conform each other.

I use

BOOL protocol_conform开发者_StackOverflowsToProtocol(Protocol *proto, Protocol *other)

but it shows a warning

Implicit declaration of function 'protocol_conformsToProtocol'

What do I miss?

Are you including the right headers? I think protocol_conformsToProtocol is declared in <objc/runtime.h>.

#include <objc/runtime.h>