Linking global variables multiple times

[Vaclav_]

I really need some advice with this „problem“. I am rebuilding a class and according to the original its function is to act as „COM lookalike”Basically y a callback for DirectShow frame capture. The original uses global variables and there is the “problem”. No matter what I do the linker will complain about multiple definitions, but only on some variables. I have made sure the variables are unique and compiled only once, same as the header file, but it does not help. Here is the code: #ifndef _CALLBACK_GLOBALS #define _CALLBACK_GLOBALS #pragma message( "Compiling " __FILE__ ) #pragma message( "Last modified on " __TIMESTAMP__ ) BOOL g_bOneShot_CB = FALSE; DWORD g_dwGraphRegister_CB=0; // For running object table HWND g_hwnd_CB; // Structures typedef struct _callbackinfo_CB { double dblSampleTime; long lBufferSize; BYTE *pBuffer; BITMAPINFOHEADER bih; }CALLBACKINFO_CB; CALLBACKINFO_CB callback; // = {0}; #endif And here is a small sample of linker errors: _AVIFrame.obj : error LNK2005: "int g_bOneShot_CB" (?g_bOneShot_CB@@3HA) already defined in _Analysis_Contour.obj _AVIFrame.obj : error LNK2005: "struct _callbackinfo_CB callback" (?callback@@3U_callbackinfo_CB@@A) already defined in _Analysis_Contour.obj _Blob.obj : error LNK2005: "int g_bOneShot_CB" (?g_bOneShot_CB@@3HA) already defined in _Analysis_Contour.obj _Blob.obj : error LNK2005: "struct _callbackinfo_CB callback" (?callback@@3U_callbackinfo_CB@@A) already defined in _Analysis_Contour.obj _BlobTracker.obj : error LNK2005: "int g_bOneShot_CB" (?g_bOneShot_CB@@3HA) already defined in _Analysis_Contour.obj _BlobTracker.obj : error LNK2005: "struct _callbackinfo_CB callback" (?callback@@3U_callbackinfo_CB@@A) already defined in _Analysis_Contour.obj _ChildFrame_Tab.obj : error LNK2005: "int g_bOneShot_CB" (?g_bOneShot_CB@@3HA) already defined in _Analysis_Contour.obj _ChildFrame_Tab.obj : error LNK2005: "struct _callbackinfo_CB callback" (?callback@@3U_callbackinfo_CB@@A) already defined in _Analysis_Contour.obj _DocManager.obj : error LNK2005: "int g_bOneShot_CB" (?g_bOneShot_CB@@3HA) already defined in _Analysis_Contour.obj _DocManager.obj : error LNK2005: "struct _callbackinfo_CB callback" (?callback@@3U_callbackinfo_CB@@A) already defined in _Analysis_Contour.obj _DrawBitmap.obj : error LNK2005: "int g_bOneShot_CB" (?g_bOneShot_CB@@3HA) already defined in _Analysis_Contour.obj And here is sample usage STDMETHODIMP BufferCB( double dblSampleTime, BYTE * pBuffer, long lBufferSize

[David Crow]

Declare the global variables in the .h file like:

extern BOOL g_bOneShot_CB;
extern DWORD g_dwGraphRegister;

and then in the corresponding .cpp file, define them like:

g_bOneShot_CB = FALSE;
g_dwGraphRegister_CB = 0;

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[Vaclav_]

Thanks David, but I just found my stupid "problem". Or better yet, stupid found the problem! THe orignal has two classes in one cpp file, I really do not understand why people do that - it just makes things convoluted and does not save anything. I had the globals in my header file - mistake #1. After fixin that I had the header file in StdAfx and than BEFORE the globals - mistake #2 and #3. Now both compiler and linker are OK. Not the best solution, but now I can code! Cheers Vaclav