Question

I created a function that accepts a function pointer, e.g.

typedef CString(*GetLabelFunc)(const CSomeObject* const pObject);

void DoSomething(GetLabelFunc funcGetLabel);

The function may receive a null pointer and will return an empty string in that case. This works perfectly fine in MSVC++ 2010 when using NULL and nullptr as parameter as well – but I do not consider a successful compilation a safe harbor in such special cases …

Now I wondered if passing nullptr is equivalent to NULL for function pointers. The reason why I am asking is that for instance void* does not accept function pointers (or it least it should not be used). So maybe there is a similar reason that nullptr should not be used for function pointers – meaning is it designed to work for object pointers only?

Answer 1

Yes, nullptr is specified to be convertible to the null pointer value for all pointer types, including function pointer types.

See [conv.ptr] 4.10/1 and [basic.compound] 3.9.2/3.