Question

Say I have a function pointer in C- library

int (*fptr)(void);

And I have a class in c++

class A { static int func(); }

I can do following and it will be safe on any platform

ftpr = A::func;

I would like for A::func() to return bool.

class A { static bool func(); }

and I do not mind casting

fptr = reinterpret_cast<int(*)()>(A::func);

But will it be safe on any platform? At the first glance it seems like it will (as long as sizeof(bool) <= sizeof(int)) but I am not so sure.

Answer 1

No, casting the function pointer is not safe. Calling a function via a function pointer of the wrong type yields undefined behavior.

If you need your C++ code to interoperate with C code, do not use the C++ bool type (or, for that matter, any other C++ types that C does not have) in your interface.