Question

Say SomeStruct is defined as:

struct SomeStruct {
    int member;
};

What does these means?

1. &SomeStruct::member
2. int SomeStruct::*

I encounter this, tried to output its type info but still cannot figure out the meaning. Below is a working example:

#include <iostream>
#include <typeinfo>
using namespace std;
struct SomeStruct {
    int member;
};


int main(int argc, const char *argv[])
{
  cout << typeid(&SomeStruct::member).name() << endl;
  cout << typeid(int SomeStruct::*).name() << endl;
  return 0;
}

Compiled by i686-apple-darwin10-gcc-4.2.1 (GCC) 4.2.1 (Apple Inc. build 5664) on my MBP, the output is:

M10SomeStructi
M10SomeStructi

Answer 1

int SomeStruct::* is called a “pointer to member”, in this case, a pointer to a member of SomeStruct. This is NOT strictly a pointer to a member function (although this is the most common use of this syntax).

&SomeStruct::member is a reference to the member member of SomeStruct.

See this related question

If you’d like some more complete information on the topic, here’s a decent article on the topic.

And, the obligatory section on the topic in the C++ FAQ lite.