🔧Connect multiple C++ Files

Here is how to connect multiple c++ file:

1KB

linker_example.zip

archive

Sample Code for linker using g++

Here is a code example using multiple files:

// File: math_operations.h
#ifndef MATH_OPERATIONS_H
#define MATH_OPERATIONS_H

// Function declarations
int add(int a, int b);
int subtract(int a, int b);

// Variable declaration with external linkage
extern int globalValue;

#endif // MATH_OPERATIONS_H

// File: math_operations.cpp
#include "math_operations.h"

// Function definitions
int add(int a, int b) {
    return a + b;
}

int subtract(int a, int b) {
    return a - b;
}

// Variable definition
int globalValue = 10;

// File: main.cpp
#include <iostream>
#include "math_operations.h"

int main() {
    std::cout << "Sum: " << add(5, 3) << std::endl;
    std::cout << "Difference: " << subtract(10, 4) << std::endl;
    std::cout << "Global value: " << globalValue << std::endl;
    return 0;
}

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Now, let's break down how these files are linked:

1. Header files and source files:

   • math_operations.h is a header file containing function declarations and an external variable declaration.

   • math_operations.cpp is a source file with the implementations of the functions declared in the header.

   • main.cpp is the main source file that uses the functions defined in math_operations.

2. #include directive:

   • math_operations.cpp includes math_operations.h to ensure the function implementations match the declarations.

   • main.cpp includes math_operations.h to access the function declarations and the external variable.

3. External linkage:

   • globalValue is declared with extern in the header, making it accessible across multiple files.

   • It's defined in math_operations.cpp and can be used in main.cpp.

4. Function declarations and definitions:

   • Functions are declared in math_operations.h and defined in math_operations.cpp.

   • This allows main.cpp to use these functions by including only the header file.

To compile and link these files, you would use a command like:

g++ main.cpp math_operations.cpp -o program

This compiles both source files and links them together into an executable named "program".

The #ifndef, #define, and #endif in the header file create an "include guard" to prevent multiple inclusions of the same header, which can cause compilation errors.