Why Am I Getting Error LNK2005: Multiple Definitions of \'k\' in My Win32 Console Application?

Error LNK2005: Multiple Definitions of 'k'

When developing a Win32 console application with multiple C source files, you may encounter error LNK2005, indicating that a variable has been defined multiple times.

Cause of the Error

In the given code, both A.cpp and B.cpp define a global variable named 'k'. This violates the C one definition rule, which states that each symbol (function, variable, etc.) must be defined only once in a program.

Resolving the Issue

There are several ways to resolve this error:

1. Using Nameless Namespace (for Variables Needed in Multiple Files)

If you need the same variable in both cpp files, use a nameless namespace to prevent multiple definitions:

<code class="cpp">namespace
{
    int k;
}</code>

2. Using 'extern' (for Variables Shared Across Files)

If you need to share a variable across multiple files, declare the variable as 'extern' in the header file and define it in only one cpp file:

<code class="cpp">// A.h
extern int k;

// A.cpp
int k = 0;

// B.cpp
#include "A.h"

// Use `k` anywhere in B.cpp</code>

By following these approaches, you can resolve error LNK2005 and ensure that each symbol is defined only once in your program.

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