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c++visual-studio-2008scopeheader-filespragma

What is the scope of a pragma directive?

What is the scope of a pragma directive? For example, if I say #pragma warning(disable: 4996) in a header file A that is included from a different file B, will that also disable all those warnings inside B? Or should I enable the warning at the end of file A again?

Solution

  • It is till the end of the translation unit. Informally, a TU is the source file with its include files.

    The usual pattern is this:

    #pragma warning (push) //save
#pragma warning (disable: xxxx)
#pragma warning (disable: yyyy)
...

//code

#pragma warning (pop) //restore prev settings

    for example

    //A.h
#pragma once
#pragma warning (disable: 1234)
#include "b.h"

//b.h
#pragma once
//when included after a.h 1234 will be disabled

//c.cpp
#include "a.h" //warnings 1234 from b.h is disabled

//d.cpp
#include "b.h" //warnings 1234 from b.h are not disabled
#include "a.h"