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Editorial Team
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Asked: 2026-05-24T13:35:59+00:00

I’m experiencing a very strange (and annoying) linker error on my project. Say for

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I’m experiencing a very strange (and annoying) linker error on my project.

Say for example I have the file KernelExports.h:

#pragma once

extern "C"
{
    DWORD* KeTimeStampBundle;
    DWORD KeGetCurrentProcessType();
    //etc...
}

I then #include this in my stdafx.h and then add #include "stdafx.h" all all my *.cpp files. The problem is that now whenever I build I get a stream of linker errors: LNK2005: KeTimeStampBundle already defined in stdafx.obj. This should not be happening since the header file is only included in one file and is protected with include guards. The errors stop once I comment out the whole extern "C" block so I know that is what is causing the issue.

What’s even stranger is when I add all these source files to a new project it builds without any problems. I don’t see what the issue is here, can anyone enlighten me?

My IDE is Visual Studio 2008.

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1 Answer

  1. Editorial Team
    DWORD* KeTimeStampBundle;

    This does not declare a function. It declares and defines an object of type DWORD* named KeTimeStampBundle. If you include this header file in multiple source files, you will have multiple definitions of this object (one from each source file in which the header is included).

    Include guards and #pragma once ensure that something is only defined once in a given translation unit (source file). They have no effect on how things are defined across multiple translation units.

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