GCC Compiler Documentation

GNU Compiler Collection (GCC)

The GNU Compiler Collection (GCC) is a vital compiler system developed by the GNU Project. It supports a wide range of programming languages, including C, C++, Objective-C, Fortran, Ada, Go, and D. This documentation provides an overview of its features, usage, and common commands for developers working with these languages.

Key Features

• Extensive Language Support: Compiles numerous programming languages efficiently.
• Platform Independence: Runs on and generates code for a vast array of hardware architectures and operating systems.
• Optimization Capabilities: Offers sophisticated optimization techniques to improve code performance.
• Debugging Support: Integrates well with debuggers like GDB.
• Standards Compliance: Adheres to various language standards (e.g., ISO C++, ISO C).

Basic Usage

The fundamental command to compile a C source file (e.g., hello.c) into an executable is:

gcc hello.c -o hello
                

This command takes the source file hello.c and creates an executable file named hello. The -o flag specifies the output filename.

Common GCC Flags

GCC provides a rich set of flags to control the compilation process. Here are some frequently used ones:

Compilation Stages

• -E: Preprocess only. Stops after the preprocessing stage.
• -S: Compile only. Stops after the assembly stage.
• -c: Compile and assemble. Stops after the assembly stage.

Optimization Levels

• -O0: No optimization (default).
• -O1: Enable basic optimizations.
• -O2: Enable more optimizations.
• -O3: Enable aggressive optimizations.
• -Os: Optimize for size.
• -Ofast: Enable all -O3 optimizations plus potentially unsafe floating-point optimizations.

Debugging Information

• -g: Emit debugging information. This is crucial for using debuggers like GDB.
• -ggdb: Emit debugging information for GDB.

Warnings

• -Wall: Enable most warning messages.
• -Wextra: Enable additional warning messages not covered by -Wall.
• -Werror: Treat all warnings as errors.

Include Paths and Libraries

• -I /path/to/include: Add a directory to the search path for header files.
• -L /path/to/lib: Add a directory to the search path for libraries.
• -l library_name: Link with a specific library.

Example with Multiple Files and Libraries

Compiling a project with multiple source files (main.c, utils.c) and linking against a math library:

gcc main.c utils.c -I ./include -L ./lib -l mylib -o myprogram -O2 -Wall
                

Further Resources

• Official GCC Online Documentation
• GCC Man Page