Compiling C++ with `g++`

A simple guide to using g++, the default GNU compiler for C++ on macOS and Linux systems, to compile and run your code.

1. Basic Compilation

To compile a single C++ source file named main.cpp into an executable named a.out (the default):


                g++ main.cpp

To run the compiled program:


                ./a.out

2. Naming Your Executable

You can use the -o flag to specify a custom name for your compiled binary. This prevents multiple compilation runs from overwriting the generic a.out.


                g++ main.cpp -o my_program
./my_program

3. Enabling Warnings

It’s highly recommended to compile with warnings enabled. This helps catch potential bugs before they occur at runtime.


                g++ -Wall -Wextra main.cpp -o my_program

Warning Flags:

-Wall: Enables almost all warnings about constructions that some users consider questionable.
-Wextra: Enables some extra warning flags that are not enabled by -Wall.

4. Compiling Multiple Files

If your project spans multiple files (e.g., main.cpp, utils.cpp, math.cpp), you can compile them all together into a single executable:


                g++ main.cpp utils.cpp math.cpp -o my_app

5. Using Modern C++ Standards

By default, g++ may not use the latest C++ standard. If you want to use features from C++11, C++14, C++17, or C++20, specify the -std flag:


                # Compiling with C++17 standard
g++ -std=c++17 main.cpp -o my_app
 
# Compiling with C++20 standard
g++ -std=c++20 main.cpp -o my_app

Quick tip:

If you get errors about missing modern C++ features, double-check your -std flag. The default standard for g++ changes depending on the compiler version installed!

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