Regarding the global namespace in C++

c++ namespaces global
user2058002 picture user2058002 · Oct 5, 2011 · Viewed 11k times · Source

In C++, should we be prepending stuff in the global namespace with ::?

For example, when using WinAPI, which is in C, should I do ::HANDLE instead of HANDLE, and ::LoadLibrary instead of LoadLibrary? What does C++ say about this? Is it generally a good idea, factoring in issues like readability and maintainability?

Answer

Armen Tsirunyan picture Armen Tsirunyan · Oct 5, 2011

Names in C++ can be qualified and unqualified. There are different rules for qualified and unqualified name lookup. ::HANDLE is a qualified name, whereas HANDLE is an unqualified name. Consider the following example:

#include <windows.h>

int main()
{
    int HANDLE;
    HANDLE x; //ERROR HANDLE IS NOT A TYPE
    ::HANDLE y; //OK, qualified name lookup finds the global HANDLE
}

I think that the desicion of choosing HANDLE vs. ::HANDLE is a matter of coding style. Of course, as my example suggests, there might be situations where qualifying is mandatory. So, you might as well use :: just in case, unless the syntax is somewhat disgusting for you.

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