Possibly OP meant dlopen/dlsym on itself? But that's a stretch, and not really language feature...

And functions aren't guaranteed to be included in the binary unless you pass additional compiler flags with that strategy.

Very few things are guaranteed in C. If you want to guarantee the function exists let the operating system look up the function names by string for you.

Create a string, look up the address of a function in the library. Assign the address to a function pointer, call it.