How to write a pointer to std::cerr?

Question

Given:

MY_CLASS* ptr = MY_CLASS::GetSomeInstance();

What is the correct way to output ptr to std::cerr , so I can log its value? Note I don't want to write the class, just the address.

Answer 1

operator<< is overloaded to take a const void* , so you can simply insert the pointer into the stream:

std::cerr << ptr;

The exception is that if the pointer is a const char* , it will be interpreted as a pointer to a C string. To print the pointer, you need to cast it explicitly to a const void* :

std::cerr << static_cast<const void*>(ptr); 

Answer 2

You can leverage boost format for printf like formatting:

std::cerr << format("%p", ptr) << endl;

%p formats pointer - should be portable between x86 and x64.

Answer 3

While using operator<< works, you could also use <cstdio> :

#include <cstdio>
...
MY_CLASS* ptr = MY_CLASS::GetSomeInstance();
fprintf(std::stderr, "Pointer address: %p", ptr);