I was thinking about calling conventions because std::free can use extern "C", but the function pointer declaration in C++ code points to an extern "C++" functi

I was thinking about calling conventions because std::free can use extern "C", but the function pointer declaration in C++ code points to an extern "C++" function, and the standard says these are two distinctive types. Are they guaranteed to be compatible - since they're only linkage specifiers, not calling conventions? I'm not sure. std::function would still work in this case because pointers to C functions have a normal operator().