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Editorial Team
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Asked: 2026-06-02T12:44:55+00:00

IN my C++ code I want to make use of a variable VarX in

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IN my C++ code I want to make use of a variable “VarX” in a file “B” which is actually modified in another file “A”.
So I had a look @ the following link & used extern concept.

How do I use extern to share variables between source files?

error LNK2005: “unsigned int VarX” (?VarX@@3IA) already defined in
***.obj.

My scenario is as follows:

File1.h
extern unsigned int VarX;

File2.cpp
#include File1.h
unsigned int VarX = 101;

File3.cpp
#include File1.h
unsigned int temp = VarX;

IMP NOTE: In the header file File1.h there are many other structure definitions and also many othe rdefinitions apart from the Extern definition.

Can someone help me in this. How shall I read the Value of VarX which is modified in File2.cpp in another File File3.cpp.

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1 Answer

  1. Editorial Team

    The problem isn’t accessibility, but a multiple definition. The error message is pretty clear, somewhere in the code you’re redefining VarX.

    Common causes can be:

    • invalid build – have you cleaned the build before compiling?
    • you have multiple unsigned int VarX = 101; or a unsigned int VarX; somewhere (in a header or an implementation file), without an extern declaration.
    • you #include "File2.cpp" somewhere in the code, causing it to be compiled multiple times.

    My bet is on the second possiblity.

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