Is there such a thing as a generic function pointer in C that can be assigned/casted to a more restrictive prototype?

Question

I have the need to dynamically link against a library at run-time and resolve a series of functions using dlsym. My first thought was to use an array of functio

Answer 1

dlsym returns a data pointer of type void *, but POSIX guarantees that this can be cast to a function pointer of the appropriate type:

Implementations supporting the XSI extension [...] require that an object of type void * can hold a pointer to a function. The result of converting a pointer to a function into a pointer to another data type (except void *) is still undefined, however.

Since Version 7 of POSIX, all implementations (not just XSI) are required to support the conversion.

Because conversion from a void * pointer to a function pointer via a direct cast can result in compiler warnings, older versions of POSIX recommend performing the conversion via aliasing:

int (*fptr)(int);
*(void **)(&fptr) = dlsym(handle, "my_function");

In the current version the recommendation is changed to:

int (*fptr)(int);
fptr = (int (*)(int))dlsym(handle, "my_function");