Function pointers casting in C++

Question

I have a void pointer returned by dlsym(), I want to call the function pointed by the void pointer. So I do a type conversion by casting:

void *gptr = dlsym(         


        

Answer 1

You can cast dlsym to a function that returns the required pointer and then call it like this:

typedef void (*fptr)();
fptr my_fptr = reinterpret_cast(dlsym)(RTLD_DEFAULT, name);

PS. Casting a function pointer to a different function pointer and then calling it is undefined behavior (see point 7 in https://en.cppreference.com/w/cpp/language/reinterpret_cast) so it is better to cast the result of dlsym to uintptr_t and then to the required type:

fptr my_fptr = reinterpret_cast(reinterpret_cast(dlsym(RTLD_DEFAULT, name)));