Function pointer equality in C

C 2011 (N1570 Committee Draft) 6.5.9 6: “Two pointers compare equal if and only if … both are pointers to the same … function …. So, yes, two pointers to the same function compare equal.

When the address of a function is taken in two different object modules, the compiler puts a placeholder in the object code. That placeholder is filled in when the object modules are linked into an executable or linked with a dynamic library at run-time.

For dynamic libraries, either the dynamic loader fills in all placeholders in the executable as necessary or the address of each function is actually the location of some stub code that jumps to the actual function, and a placeholder in or used by that stub code is filled in by the dynamic loader.

Additionally, note that an executable can contain more than one instance of a function. The compiler might insert the function inline in several places or might, for reasons of its own, include a specialization of the function as well as a general version. However, when the address of the function is taken, the compiler must provide the address of a single general version. (Or the compiler must ensure the program behaves as if that were done. E.g., if the compiler can detect that the program does not compare pointers, then it might, in theory, be able to use a different address for some instances of the address of the function.)