How to write a pointer to std::cerr?

Given:

MY_CLASS* ptr = MY_CLASS::GetSomeInstance();

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

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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); 

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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.

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

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