Is it safe to remove these guards in header files of visual C++/MFC?

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I am porting some old legacy MFC apps in VC6++ and saw many these kinds of guards in the header files:

#if !defined(AFX_MOUSER_H__66D9BBF5_DD8D_11D4_B7C9_0050DAB84384__INCLUDED_)
#define AFX_MOUSER_H__66D9BBF5_DD8D_11D4_B7C9_0050DAB84384__INCLUDED_

// code snippet in between

#endif // !defined(AFX_MOUSER_H__66D9BBF5_DD8D_11D4_B7C9_0050DAB84384__INCLUDED_)

I know it is used by AppWizard to edit code. but now in Visual Studio 2017,
these kinds of tricks as guard statements are not used any more. I validated my understanding by creating a dialog based MFC app using AppWizard.

So is it safe for me to remove all old guards in .h header files?
Any advice and recommendation for doing this?

What I have tried:

did some simple tests on AppWizard generated demo app, it is okay.

Posted 8-Oct-20 9:09am

Southmountain

Updated 8-Oct-20 20:11pm

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2 solutions

Solution 2

As Richard noted, you cannot simply remove them, you have to replace them with the
#pragma once pragma.
To add my two cents to Richard's answer (GCC documentation):

#pragma once

If #pragma once is seen when scanning a header file, that file will never be read again, no matter what. It is a less-portable alternative to using '#ifndef' to guard the contents of header files against multiple inclusions.

Posted 8-Oct-20 20:11pm

CPallini

v2

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Southmountain 9-Oct-20 14:54pm

thank you for sharing this GCC tip!

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Richard MacCutchan · Accepted Answer · 2020-10-08T09:32:00

Solution 1

It is the old fashioned way of preventing header files from being included more than once. You can delete those lines and just add the following at the top of the file:

C++

#pragma once

Posted 8-Oct-20 9:32am

Richard MacCutchan

Updated 8-Oct-20 9:33am

v3

Comments

CPallini 9-Oct-20 2:07am

5.