How to use the command g++ (with examples)

The g++ command is part of the GNU Compiler Collection (GCC) and is used to compile C++ source files into executable binaries. It provides various options to customize the compilation process and generate optimized code.

Use case 1: Compile a source code file into an executable binary

Code:

g++ path/to/source.cpp -o path/to/output_executable

Motivation: The -o option specifies the output file name, allowing you to choose a custom name for the executable binary. This is useful when you want to provide a descriptive name for your compiled program.

Explanation:

• path/to/source.cpp is the path to the C++ source file you want to compile.
• -o path/to/output_executable specifies the output file path and name for the executable binary.

Example output:

No errors or warnings

Use case 2: Display common warnings

Code:

g++ path/to/source.cpp -Wall -o path/to/output_executable

Motivation: The -Wall option enables common warning messages during compilation. This can help you identify potential issues in your code and improve its quality.

Explanation:

• -Wall enables a set of common warning options.
• path/to/source.cpp is the path to the C++ source file you want to compile.
• -o path/to/output_executable specifies the output file path and name for the executable binary.

Example output:

warning: unused variable 'x' [-Wunused-variable]

Use case 3: Choose a language standard to compile for (C++98/C++11/C++14/C++17)

Code:

g++ path/to/source.cpp -std=c++98|c++11|c++14|c++17 -o path/to/output_executable

Motivation: The -std option allows you to specify the version of the C++ language standard to compile for. This is useful when you need to ensure compatibility with a specific version of the C++ standard.

Explanation:

• path/to/source.cpp is the path to the C++ source file you want to compile.
• -std=c++98|c++11|c++14|c++17 selects the C++ language standard to use.
• -o path/to/output_executable specifies the output file path and name for the executable binary.

Example output:

No errors or warnings

Use case 4: Include libraries located at a different path than the source file

Code:

g++ path/to/source.cpp -o path/to/output_executable -Ipath/to/header -Lpath/to/library -llibrary_name

Motivation: The -I option allows you to specify additional paths where header files are located, while the -L option allows you to specify additional paths where library files are located. This is useful when your source code depends on external libraries that are not in the default search paths.

Explanation:

• path/to/source.cpp is the path to the C++ source file you want to compile.
• -o path/to/output_executable specifies the output file path and name for the executable binary.
• -Ipath/to/header adds the path/to/header directory to the list of directories searched for header files.
• -Lpath/to/library adds the path/to/library directory to the list of directories searched for library files.
• -llibrary_name specifies the name of the library to link against.

Example output:

No errors or warnings

Use case 5: Compile and link multiple source code files into an executable binary

Code:

g++ -c path/to/source_1.cpp path/to/source_2.cpp ... && g++ -o path/to/output_executable path/to/source_1.o path/to/source_2.o ...

Motivation: When your program consists of multiple source code files, you need to compile and link them together to create an executable binary. The first command creates object files from the source files (-c option), and the second command links the object files into an executable binary.

Explanation:

• -c option specifies that only compilation should be performed, without linking.
• path/to/source_X.cpp is the path to each individual C++ source file you want to compile.
• path/to/source_X.o is the path to each individual object file generated from the source files.
• -o path/to/output_executable specifies the output file path and name for the executable binary.

Example output:

No errors or warnings

Use case 6: Optimize the compiled program for performance

Code:

g++ path/to/source.cpp -O1|2|3|fast -o path/to/output_executable

Motivation: The -O option allows you to enable different levels of optimization for the compiled program. Optimization can improve the performance of the program at the cost of longer compilation times.

Explanation:

• path/to/source.cpp is the path to the C++ source file you want to compile.
• -O1|2|3|fast selects a specific optimization level to apply during compilation.
• -o path/to/output_executable specifies the output file path and name for the executable binary.

Example output:

No errors or warnings

Use case 7: Display version

Code:

g++ --version

Motivation: The --version option allows you to quickly check the version of the g++ command installed on your system. This is useful to ensure that you have the correct version required for your project.

Example output:

g++ (GCC) 9.3.0

Conclusion:

The g++ command is a powerful tool for compiling C++ source code into executable binaries. It offers various options to customize the compilation process, optimize code, and include external libraries. With the examples provided, you should have a good starting point for using g++ and leveraging its functionality in your C++ projects.