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Command documentation sourced from the linux-command project This comprehensive command reference is part of the linux-command documentation project.

c++ - C++ Compiler

The c++ command is a compiler driver for the C++ programming language that invokes the underlying C++ compiler (typically GNU g++ or Clang). It serves as a frontend that processes C++ source files, handles preprocessing, compilation, assembly, and linking phases to produce executable programs, shared libraries, or object files. The c++ command supports modern C++ standards, extensive optimization options, debugging capabilities, and cross-compilation features, making it essential for C++ software development on Linux systems.

Basic Syntax​

c++ [OPTIONS] INPUT_FILES... [-o OUTPUT_FILE]
c++ -x c++ [OPTIONS] INPUT_FILES... [-o OUTPUT_FILE]
c++ -c [OPTIONS] SOURCE_FILES... [-o OBJECT_FILES]

Common Options​

Compilation Modes​

  • -c - Compile source files to object files, don't link
  • -S - Compile to assembly language, don't assemble
  • -E - Run preprocessor only, output to stdout
  • -o FILE - Specify output filename
  • -x LANGUAGE - Specify source language (c++, c, etc.)

Optimization Levels​

  • -O0 - No optimization (default)
  • -O1 - Basic optimization
  • -O2 - Standard optimization (recommended)
  • -O3 - Aggressive optimization
  • -Os - Optimize for size
  • -Oz - Aggressive size optimization
  • -Og - Optimizations that don't interfere with debugging
  • -Ofast - Fastest possible optimization (may violate standards)

Debugging Options​

  • -g - Generate debug information
  • -g0--g3 - Debug information levels
  • -ggdb - Generate gdb-specific debug info
  • -gdwarf - Use DWARF debug format
  • -p - Generate profiling information
  • -pg - Generate profiling for gprof

Warning Levels​

  • -Wall - Enable most warnings
  • -Wextra - Enable extra warnings
  • -Werror - Treat warnings as errors
  • -w - Suppress all warnings
  • -Wpedantic - Pedantic ISO C++ compliance warnings
  • -Weverything - Enable all possible warnings (Clang)

Language Standards​

  • -std=c++98 - ISO C++ 1998
  • -std=c++03 - ISO C++ 2003
  • -std=c++11 - ISO C++ 2011
  • -std=c++14 - ISO C++ 2014
  • -std=c++17 - ISO C++ 2017
  • -std=c++20 - ISO C++ 2020
  • -std=c++23 - ISO C++ 2023
  • -std=gnu++XX - GNU C++ dialect with extensions

Preprocessor Options​

  • -I DIR - Add directory to include search path
  • -D MACRO[=VALUE] - Define preprocessor macro
  • -U MACRO - Undefine preprocessor macro
  • -include FILE - Include file before compilation
  • -M - Generate makefile dependencies
  • -MM - Like -M but omit system headers

Linking Options​

  • -l LIBRARY - Link with library
  • -L DIR - Add directory to library search path
  • -static - Link statically
  • -shared - Create shared library
  • -fPIC - Generate position-independent code
  • -rpath PATH - Set runtime library search path

Usage Examples​

Basic Compilation​

Simple Program Compilation​

# Compile single source file to executable
c++ -o program program.cpp

# Compile with standard C++11
c++ -std=c++11 -o program program.cpp

# Compile with warnings and debugging
c++ -Wall -g -o program program.cpp

# Compile with optimization
c++ -O2 -o program program.cpp

Multiple Source Files​

# Compile multiple source files
c++ -o program main.cpp utils.cpp parser.cpp

# Compile with specific include directories
c++ -I./include -I./libs -o program main.cpp

# Compile with library linking
c++ -o program main.cpp -lssl -lcrypto -lpthread

Object File Generation​

# Compile to object files only
c++ -c main.cpp -o main.o
c++ -c utils.cpp -o utils.o
c++ -c parser.cpp -o parser.o

# Link object files into executable
c++ -o program main.o utils.o parser.o -lssl -lcrypto

# Compile multiple files to objects automatically
c++ -c *.cpp

Advanced Compilation​

Optimization Techniques​

# Maximum optimization for performance
c++ -O3 -march=native -o program program.cpp

# Optimize for specific architecture
c++ -O2 -march=haswell -mtune=generic -o program program.cpp

# Optimize for size
c++ -Os -o small_program program.cpp

# Profile-guided optimization
c++ -fprofile-generate -O2 -o program program.cpp
./program
c++ -fprofile-use -O2 -o program program.cpp

Debug Compilation​

# Full debug information
c++ -g3 -O0 -Wall -o debug_program program.cpp

# Debug with specific format
c++ -ggdb -O0 -o debug_program program.cpp

# Debug with sanitizers
c++ -g -fsanitize=address -o debug_program program.cpp
c++ -g -fsanitize=undefined -o debug_program program.cpp
c++ -g -fsanitize=thread -o debug_program program.cpp

# Debug with memory checker
c++ -g -DMEMCHECK -o debug_program program.cpp

Library Creation​

# Create static library
ar rcs libmystatic.a mycode1.o mycode2.o
c++ -o program main.cpp -L. -lmystatic

# Create shared library
c++ -fPIC -c mycode1.cpp -o mycode1.o
c++ -fPIC -c mycode2.cpp -o mycode2.o
c++ -shared -o libmyshared.so mycode1.o mycode2.o

# Link against shared library
c++ -o program main.cpp -L. -lmyshared

# Create shared library with soname
c++ -shared -Wl,-soname,libmyshared.so.1 -o libmyshared.so.1.0 mycode1.o mycode2.o

Preprocessor Usage​

Macro Definitions​

# Define macros at compile time
c++ -DDEBUG -DVERSION=\"1.0\" -o program program.cpp

# Conditional compilation
c++ -DNDEBUG -O2 -o release_program program.cpp
c++ -DDEBUG -g -o debug_program program.cpp

# Platform-specific compilation
c++ -DLINUX_BUILD -o program program.cpp
c++ -DWINDOWS_BUILD -o program.exe program.cpp

Include Path Management​

# Multiple include directories
c++ -I./include -I./external -I/usr/local/include -o program program.cpp

# System include paths
c++ -I/usr/include/opencv4 -o program program.cpp

# Relative and absolute paths
c++ -I../shared -I/opt/local/include -o program program.cpp

Linking and Libraries​

Static and Dynamic Linking​

# Static linking (create standalone executable)
c++ -static -o program program.cpp -lssl -lcrypto

# Dynamic linking (default)
c++ -o program program.cpp -lssl -lcrypto

# Mixed linking
c++ -o program program.cpp -Wl,-Bstatic -lssl -Wl,-Bdynamic -lcrypto

Library Search Paths​

# Add library search directories
c++ -L./lib -L/usr/local/lib -o program main.cpp -lmystuff

# Runtime library path (for shared libraries)
c++ -Wl,-rpath,'$ORIGIN' -o program program.cpp -lmylib
c++ -Wl,-rpath,/usr/local/lib -o program program.cpp -lmylib

# Multiple runtime paths
c++ -Wl,-rpath,/opt/lib -Wl,-rpath,/usr/local/lib -o program program.cpp

Specific Libraries​

# Math library
c++ -o math_program math.cpp -lm

# POSIX threads
c++ -o threaded_program threaded.cpp -lpthread

# OpenGL
c++ -o opengl_program opengl.cpp -lGL -lGLU -lglut

# SSL/TLS
c++ -o secure_program secure.cpp -lssl -lcrypto

# Boost
c++ -o boost_program boost.cpp -lboost_system -lboost_filesystem

Practical Examples​

Development Workflow​

Project Compilation​

# Typical project compilation
c++ -std=c++17 -Wall -Wextra -O2 \
    -I./include \
    -I./external/include \
    -o myapp \
    src/main.cpp \
    src/utils.cpp \
    src/network.cpp \
    -L./external/lib \
    -lboost_system \
    -lboost_filesystem \
    -lpthread

# Debug build for development
c++ -std=c++17 -Wall -Wextra -g3 -O0 \
    -DDEBUG \
    -fsanitize=address \
    -I./include \
    -o myapp_debug \
    src/*.cpp \
    -lpthread

Build System Integration​

# Makefile pattern for C++ compilation
# CXX = c++
# CXXFLAGS = -std=c++17 -Wall -Wextra -O2
# INCLUDES = -I./include
# LIBS = -lpthread
#
# all: program
#
# program: main.o utils.o
# 	$(CXX) $(CXXFLAGS) -o $@ $^ $(LIBS)
#
# %.o: %.cpp
# 	$(CXX) $(CXXFLAGS) $(INCLUDES) -c $< -o $@

Cross-Platform Development​

Platform-Specific Builds​

# Linux build with specific features
c++ -DLINUX_BUILD -std=c++17 -o program_linux program.cpp

# macOS build with frameworks
c++ -framework Foundation -framework CoreFoundation -o program_mac program.cpp

# Windows build (MinGW)
c++ -DWINDOWS_BUILD -static -o program.exe program.cpp -lws2_32

64-bit vs 32-bit Compilation​

# 64-bit compilation (default on modern systems)
c++ -m64 -o program_64 program.cpp

# 32-bit compilation
c++ -m32 -o program_32 program.cpp

# Architecture-specific optimization
c++ -march=x86-64 -mtune=generic -o program program.cpp
c++ -march=armv8-a -mtune=cortex-a72 -o program_arm program.cpp

Performance Optimization​

Aggressive Optimization​

# Maximum performance build
c++ -O3 -march=native -flto -DNDEBUG \
    -o fast_program program.cpp

# Link Time Optimization (LTO)
c++ -O3 -flto -c program.cpp -o program.o
c++ -O3 -flto -o program program.o

# Profile-guided optimization workflow
c++ -O2 -fprofile-generate -o program_profile program.cpp
./program_profile  # Run with representative input
c++ -O2 -fprofile-use -o program program.cpp

Vectorization and Parallelism​

# Enable auto-vectorization
c++ -O3 -ftree-vectorize -o vectorized_program program.cpp

# OpenMP support
c++ -fopenmp -o parallel_program parallel.cpp
export OMP_NUM_THREADS=4

# SIMD intrinsic support
c++ -mavx2 -mfma -o simd_program program.cpp

Advanced Features​

Template Instantiation​

# Explicit template instantiation
c++ -fvisibility-inlines-hidden -o template_program templates.cpp

# Debug templates with verbose output
c++ -ftemplate-backtrace-limit=0 -g -o template_debug templates.cpp

# Suppress template instantiation warnings
c++ -Wno-non-template-friend -o program program.cpp

Exception Handling​

# Enable exceptions (default)
c++ -fexceptions -o program program.cpp

# Disable exceptions for performance
c++ -fno-exceptions -o fast_program program.cpp

# Set exception handling model
c++ -fexceptions -fasync-unwind-tables -o program program.cpp

Advanced Usage​

Compiler-Specific Features​

GCC-Specific Options​

# GCC color diagnostics
c++ -fdiagnostics-color=auto -o program program.cpp

# GCC sanitizers
c++ -fsanitize=address,undefined -o program program.cpp

# GCC coverage analysis
c++ -fprofile-arcs -ftest-coverage -o program program.cpp
gcov program.cpp

# GCC time-trace (Clang also supports)
c++ -ftime-trace -o program program.cpp

Clang-Specific Options​

# Clang static analyzer
c++ -Xanalyzer -analyzer-output=text -o program program.cpp

# Clang tidy integration
c++ -Xclang -analyze -Xclang -analyzer-output=text -o program program.cpp

# Clang modules
c++ -fmodules -o program program.cpp

# Clang address sanitizer with debug info
c++ -g -fsanitize=address -fno-omit-frame-pointer -o program program.cpp

Build Automation​

Compilation Databases​

# Generate compilation database for IDEs
c++ -MJ compilation_database.json -c program.cpp -o program.o

# Bear tool integration
bear -- c++ -o program program.cpp

# CMake integration (CMake generates proper c++ commands)
mkdir build && cd build
cmake -DCMAKE_CXX_COMPILER=c++ ..
make

Dependency Generation​

# Generate makefile dependencies
c++ -M -MF deps.d program.cpp

# Generate dependencies without system headers
c++ -MM -MF deps.d program.cpp

# Include dependency files in Makefile
include deps.d

Specialized Compilation​

Embedded Systems​

# Freestanding environment compilation
c++ -ffreestanding -nostdlib -o firmware.elf firmware.cpp

# Cross-compilation for ARM
c++ -target arm-none-eabi -mcpu=cortex-m4 -o firmware.elf firmware.cpp

# Bare-metal compilation
c++ -ffreestanding -fno-exceptions -fno-rtti -o firmware.elf firmware.cpp

Kernel Development​

# Linux kernel module compilation
c++ -D__KERNEL__ -DMODULE -o kernel_module.o kernel_module.cpp

# Userspace kernel program
c++ -I./usr/include -o kernel_program kernel_program.cpp

Integration and Automation​

Build Scripts​

Automated Build Script​

#!/bin/bash
# Advanced C++ build script

set -e

# Configuration
SOURCE_DIR="src"
INCLUDE_DIR="include"
BUILD_DIR="build"
TARGET="myapp"
CXX="c++"
CXXFLAGS="-std=c++17 -Wall -Wextra -O2"
LIBS="-lpthread -lssl -lcrypto"

# Create build directory
mkdir -p "$BUILD_DIR"

# Compile source files
echo "Compiling source files..."
find "$SOURCE_DIR" -name "*.cpp" -exec "$CXX" $CXXFLAGS \
    -I"$INCLUDE_DIR" \
    -c {} -o "$BUILD_DIR"/{\//_}.o \;

# Link executable
echo "Linking executable..."
"$CXX" -o "$TARGET" "$BUILD_DIR"/*.o $LIBS

echo "Build completed successfully: $TARGET"

Testing Integration​

#!/bin/bash
# Build and test script

# Build test version
c++ -std=c++17 -Wall -Wextra -g -fsanitize=address \
    -DTEST_MODE \
    -o test_program \
    test/*.cpp src/*.cpp \
    -lgtest -lgtest_main -pthread

# Run tests
./test_program --gtest_output=xml:test_results.xml

# Generate coverage report
gcov test/*.cpp
lcov --capture --directory . --output-file coverage.info
genhtml coverage.info --output-directory coverage_html

Troubleshooting​

Common Issues​

Linking Errors​

# Undefined reference errors
# Solution: Check library order and include required libraries
c++ -o program main.cpp -lpthread -lssl -lcrypto

# Library not found errors
# Solution: Add library search paths
c++ -L./lib -L/usr/local/lib -o program main.cpp -lmylib

# Multiple definition errors
# Solution: Use inline or properly declare with extern
c++ -o program main.cpp utils.cpp -Wl,--allow-multiple-definition

Compilation Errors​

# Header file not found
# Solution: Add include directories
c++ -I./include -I/usr/local/include -o program program.cpp

# C++ standard not supported
# Solution: Use appropriate standard flag
c++ -std=c++14 -o program program.cpp

# Template instantiation errors
# Solution: Use explicit instantiation or export templates
c++ -fno-implicit-templates -o program program.cpp

Optimization Issues​

# Optimization breaks program
# Solution: Reduce optimization level or disable specific optimizations
c++ -O1 -fno-strict-aliasing -o program program.cpp

# Debug information missing
# Solution: Ensure debug flags are passed to all compilation stages
c++ -g -O0 -o program program.cpp
c++ -g -O0 -c utils.cpp -o utils.o
c++ -g -O0 -o program main.o utils.o

Performance Debugging​

Profiling Integration​

# Compile with profiling support
c++ -pg -O2 -o profiled_program program.cpp

# Run and generate profile
./profiled_program
gprof profiled_program gmon.out > profile_report.txt

# Remove profiling symbols
strip profiled_program

Memory Debugging​

# Valgrind integration
c++ -g -o valgrind_program program.cpp
valgrind --leak-check=full ./valgrind_program

# AddressSanitizer
c++ -g -fsanitize=address -o asan_program program.cpp
./asan_program

# UndefinedBehaviorSanitizer
c++ -g -fsanitize=undefined -o ubsan_program program.cpp
./ubsan_program
  • gcc - GNU C Compiler
  • g++ - GNU C++ Compiler
  • clang - Clang C Compiler
  • clang++ - Clang C++ Compiler
  • make - Build automation tool
  • cmake - Cross-platform build system
  • gdb - GNU Debugger
  • ld - GNU Linker
  • ar - Archive utility for static libraries
  • nm - Symbol table examination
  • objdump - Object file information display
  • readelf - ELF file information display

Best Practices​

  1. Always enable warnings (-Wall -Wextra) and fix all warning messages
  2. Use appropriate C++ standard (-std=c++17 or newer for modern features)
  3. Enable optimization (-O2 for release builds, -O0 for debugging)
  4. Include debug information (-g) for all builds intended for debugging
  5. Use position-independent code (-fPIC) for shared libraries
  6. Specify library dependencies explicitly and in correct order
  7. Use static analysis tools like Clang Static Analyzer or cppcheck
  8. Enable sanitizers during development for catching bugs early
  9. Consistent naming conventions for source files and output targets
  10. Version control your build scripts and compilation configurations

Performance Tips​

  1. Link Time Optimization (-flto) provides significant performance improvements
  2. Profile-guided optimization (-fprofile-generate/use) yields best results
  3. Architecture-specific flags (-march=native) improve local performance
  4. Thin LTO is faster than full LTO for large projects
  5. Incremental builds save compilation time during development
  6. Parallel compilation using make -j speeds up large builds
  7. Precompiled headers reduce compilation time for large headers
  8. Unity builds can improve compilation speed and optimization
  9. CCache can dramatically speed up rebuilds
  10. Avoid unnecessary template instantiation in translation units

The c++ command provides a comprehensive compilation solution for C++ development, supporting modern language standards, advanced optimization techniques, debugging capabilities, and cross-platform development. Its flexibility and power make it an essential tool for C++ programmers developing anything from simple utilities to complex, performance-critical applications.

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