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Editorial Team
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Asked: 2026-05-16T10:13:56+00:00

My target module is an executable to be built from X.cpp and Y.cpp ,

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My target module is an executable to be built from X.cpp and Y.cpp, both these two files need a common .h file:

extern HANDLE hPipe;
extern IMediaSample *pSave = NULL;

But when I build the module, I got an error saying :

Y.obj : error LNK2005: "struct IMediaSample * pSave" (?pSave@@3PAUIMediaSample@@A) already defined in X.obj

How to solve this issue?

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1 Answer

  1. Editorial Team
    extern IMediaSample *pSave = NULL;

    This is not just a declaration. This will define pSave to NULL. Since both .cpp include the .h, this variable will be defined in 2 translation units, which causes the conflict.

    You should just rewrite it as

    extern IMediaSample *pSave;

    in the .h, then add IMediaSample *pSave = NULL; in exactly one of the .cpps.

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