GCC Compiler

g++ command is a GNU c++ compiler invocation command, which is used for preprocessing, compilation, assembly and linking of source code to generate an executable file. The different “options” of g++ command allow us to stop this process at the intermediate stage.

• Check g++ compiler version information:

g++ --version

• Compile a CPP file to generate executable target file: g++ file_name command is used to compile and create an executable file a.out (default target name). Example: Given a simple program to print “Hello Geek” on standard output with file name hello.cpp

#include <iostream>
int main() {
    std::cout << "Hello Geek\n"``;
    return 0;
}

g++ hello.cpp

This compiles and links hello.cpp to produce a default target executable file a.out in present working directory. To run this program, type ./a.out where ./ represents present working directory and a.out is the executable target file.

./a.out

• g++ -S file_name is used to only compile the file_name and not assembling or linking. It will generate a file_name.s assembly source file. Example:

g++ -S hello.cpp

• g++ -c file_name is used to only compile and assemble the file_name and not link the object code to produce executable file. It will generate a file_name.o object code file in present working directory. Example:

g++ -c hello.cpp

• g++ -o target_name file_name: Compiles and links file_name and generates executable target file with target_name (or a.out by default). Example:

g++ -o main.exe hello.cpp

• Compile and link multiple files: When the -c flag is used, it invokes the compiler stage which translates source code to object code. When the -o flag is used it links object code to create the executable file from file_name.o to a.out(default), multiples files may be passed together as arguments.

Example:

// hello.cpp
#include "helloWorld.h"
#include <iostream>
int main() {
    std::cout << "Hello Geek\n"``;
    helloWorld();
    return 0;
}

// helloWorld.cpp
#include <iostream>
void helloWorld() {
    std::cout << "Hello World\n"``;
}

g++ -c helloWorld.cpp hello.cpp

• It compiles and creates object code for the files helloWorld.cpp and hello.cpp to helloWorld.o and hello.o respectively.

g++ -o main.exe helloWorld.o hello.o

• It links the object codes helloWorld.o and hello.o to create an executable file main.exe

./main.exe

• It runs the executable file main.exe