Question

I have a basic question on function pointer.
In the below code snippet, how do I read this ”
*(FARPROC*)&pfn =“?

IFastString *CallCreateFastString(const char *psz) {

static IFastString * (*pfn)(const char *) = 0;

if (!pfn) {

const TCHAR szDll[] = _TEXT("FastString.DLL");

const char szFn[] = "CreateFastString";

HINSTANCE h = LoadLibrary(szDll);

if (h)

*(FARPROC*)&pfn = GetProcAddress(h, szFn);

}

return pfn ? pfn(psz) : 0;

}

Answer 1

This isn’t really about function pointers, but about casting in general.

Suppose pfn is of type T. Then &pfn is of type T*. This gets cast to FARPROC* by the cast expression (the stuff in the parentheses). Finally, this gets dereferenced, yielding a FARPROC&.

All in all this just means you’re treating pfn as if it were of type FARPROC and assign a value to it.

Here’s a generic example:

S make_an_S();

T x;
T * const px = &x;
S * const py = (S*)px;
*py = make_an_S();  // same as *(S*)&x = make_an_S();