Question

If I store a pointer to a function, and then at some later point during my program’s execution, compare it to the address of the same function, are the two addresses guaranteed to be equal.

E.g.

int foo(void){return 0;}
int (*foo_p)(void) = &foo;

assert(foo_p == &foo);

In the above code is the assertion always guaranteed to succeed? Are there any circumstances under which the address of a function can change?

Answer 1

Per 6.5.9:

Two pointers compare equal if and only if both are null pointers, both are pointers to the same object (including a pointer to an object and a subobject at its beginning) or function, both are pointers to one past the last element of the same array object, or one is a pointer to one past the end of one array object and the other is a pointer to the start of a different array object that happens to immediately follow the first array object in the address space.

(Boldface added for emphasis.)