cmake

CMake

Purpose

Guide agents through modern (target-first) CMake for C/C++ projects: out-of-source builds, dependency management, generator selection, and integration with CI and IDEs.

Triggers

• "How do I write a CMakeLists.txt for my project?"
• "How do I add an external library with CMake?"
• "CMake can't find my package / library"
• "How do I enable sanitizers in CMake?"
• "How do I cross-compile with CMake?"
• "How do I use CMake Presets?"

Workflow

1. Modern CMake principles

• Define targets, not variables. Use target_* commands.
• Use PUBLIC/PRIVATE/INTERFACE to control property propagation.
• Never use include_directories() or link_libraries() (legacy).
• Minimum CMake version: cmake_minimum_required(VERSION 3.20) for most features.

2. Minimal project

cmake_minimum_required(VERSION 3.20)
project(MyApp VERSION 1.0 LANGUAGES C CXX)

set(CMAKE_C_STANDARD 11)
set(CMAKE_C_STANDARD_REQUIRED ON)
set(CMAKE_CXX_STANDARD 17)
set(CMAKE_CXX_STANDARD_REQUIRED ON)

add_executable(myapp
    src/main.c
    src/utils.c
)

target_include_directories(myapp PRIVATE include)
target_compile_options(myapp PRIVATE -Wall -Wextra)

3. Static / shared libraries

# Static library
add_library(mylib STATIC lib/foo.c lib/bar.c)
target_include_directories(mylib
    PUBLIC  include      # consumers get this include path
    PRIVATE src          # only mylib itself sees this
)

# Shared library
add_library(myshared SHARED lib/foo.c)
set_target_properties(myshared PROPERTIES
    VERSION   1.0.0
    SOVERSION 1
)

# Link executable against library
add_executable(myapp src/main.c)
target_link_libraries(myapp PRIVATE mylib)

4. Configure and build

# Out-of-source build (always do this)
cmake -S . -B build
cmake --build build

# With generator
cmake -S . -B build -G Ninja
cmake --build build -- -j$(nproc)

# Debug build
cmake -S . -B build-debug -DCMAKE_BUILD_TYPE=Debug
cmake --build build-debug

# Release
cmake -S . -B build-release -DCMAKE_BUILD_TYPE=Release
cmake --build build-release

# Install
cmake --install build --prefix /usr/local