Multiple Definition Skill

Fixes linker errors where the same symbol is defined in multiple translation units.

Detection Patterns

• •multiple definition of 'X'
• •already defined in
• •duplicate symbol

Strategy

1. •Identify Symbol: Extract the duplicated symbol.
2. •Find Definitions: Locate all places where it's defined.
3. •Remove Duplicates: Keep one, remove or fix others.

Instructions

Step 1: Parse Error

From: multiple definition of 'globalVar'; first defined in a.o

Step 2: Common Causes & Fixes

Global variable in header:

// Wrong: header.h
int globalVar = 0;  // Defined in every .cpp that includes

// Fix Option 1: extern declaration
// header.h
extern int globalVar;
// source.cpp
int globalVar = 0;

// Fix Option 2: inline (C++17)
inline int globalVar = 0;

Function defined in header:

// Wrong
void foo() { ... }  // in header

// Fix: make inline
inline void foo() { ... }

Same source compiled twice: Check build file for duplicate source file entries.