cmkr.build - Modern CMake with TOML

cmkr (pronounced "cmaker") is a modern build system that parses cmake.toml files and generates idiomatic CMakeLists.txt. It simplifies CMake by using TOML syntax while maintaining full CMake compatibility.

Quick Start - New Project Setup

1. Bootstrap cmkr in Your Project

bash

# Download the bootstrap script
curl https://raw.githubusercontent.com/build-cpp/cmkr/main/cmake/cmkr.cmake -o cmkr.cmake

# Run the bootstrap (downloads cmkr and generates initial files)
cmake -P cmkr.cmake

What this does:

•Downloads the cmkr executable to build/_deps/cmkr-src/
•Creates a minimal cmake.toml file if it doesn't exist
•Generates CMakeLists.txt from your cmake.toml

2. Configure Your Project in cmake.toml

toml

[project]
name = "myproject"
version = "1.0.0"
description = "My awesome C++ project"
languages = ["CXX"]

[target.myapp]
type = "executable"
sources = ["src/main.cpp"]

3. Build Your Project

bash

# Configure (cmkr auto-regenerates CMakeLists.txt if cmake.toml changed)
cmake -B build

# Build
cmake --build build

# Run
./build/myapp

No extra steps! After modifying cmake.toml, just run cmake --build build and cmkr automatically regenerates CMakeLists.txt.

Understanding cmkr Architecture

How It Works

code

cmake.toml → [cmkr parses] → CMakeLists.txt → [CMake processes] → Build files

•You edit cmake.toml (clean, readable TOML syntax)
•cmkr generates modern, idiomatic CMakeLists.txt
•CMake processes the generated file normally
•Your build system (Make, Ninja, Visual Studio) compiles

File Commit Guide

Commit these to version control:

•✅ cmake.toml - Your project configuration
•✅ cmkr.cmake - Bootstrap script (enables CI builds)
•✅ CMakeLists.txt - Generated (regenerates automatically)

cmake.toml Reference

Project Section [project]

toml

[project]
name = "myproject"                    # Required: project name
version = "1.0.0"                     # Optional: project version
description = "Description here"      # Optional: project description
languages = ["CXX", "C"]              # Optional: enabled languages
cmake-before = """                   # Optional: CMake code before project()
message(STATUS "Before project")
"""
cmake-after = """                    # Optional: CMake code after project()
message(STATUS "After project")
"""

Supported languages: C, CXX (C++), CSharp, CUDA, OBJC, OBJCXX, Fortran, HIP, ISPC, Swift, ASM, ASM_MASM (MASM), ASM_NASM, ASM_MARMASM, ASM-ATT

Target Section [target.<name>]

toml

[target.mylib]
type = "static"                       # Required: executable, library, shared, static, interface, object, custom
sources = ["src/*.cpp"]               # Source files (supports globbing)
headers = ["include/*.hpp"]           # Header files (for documentation)
include-directories = ["include"]     # Public include paths
compile-definitions = ["MYLIB_EXPORT"] # Preprocessor defines
compile-features = ["cxx_std_20"]     # C++ standard version
compile-options = ["-Wall", "-Wextra"] # Compiler flags
link-libraries = ["otherlib"]         # Link dependencies
link-options = []                     # Linker flags
precompile-headers = ["pch.hpp"]      # Precompiled headers

[target.mylib.properties]
CXX_STANDARD = 17
CXX_STANDARD_REQUIRED = true

Target Types:

Type	Purpose	Visibility Default
`executable`	Program you run (.exe)	PRIVATE
`static`	Static library (.lib, .a)	PUBLIC
`shared`	Dynamic library (.dll, .so, .dylib)	PUBLIC
`library`	Let CMake decide static/shared	PUBLIC
`interface`	Header-only library	INTERFACE
`object`	Object files collection	PUBLIC

Visibility Controls:

•Public properties: include-directories, compile-definitions, link-libraries
•Private properties: Prefix with private- (e.g., private-compile-options)
•Interface-only: Use on interface targets

Conditions [conditions]

toml

[conditions]
# Predefined (override if needed):
windows = "WIN32"
macos = "CMAKE_SYSTEM_NAME MATCHES \"Darwin\""
linux = "CMAKE_SYSTEM_NAME MATCHES \"Linux\""
unix = "UNIX"
msvc = "MSVC"
clang = "CMAKE_CXX_COMPILER_ID MATCHES \"Clang\""
gcc = "CMAKE_CXX_COMPILER_ID STREQUAL \"GNU\""
x64 = "CMAKE_SIZEOF_VOID_P EQUAL 8"
root = "CMKR_ROOT_PROJECT"

# Custom conditions:
build-tests = "MYPROJECT_BUILD_TESTS"
ptr64 = "CMAKE_SIZEOF_VOID_P EQUAL 8"

Using conditions:

toml

[target.myapp]
type = "executable"
sources = ["src/main.cpp"]
windows.sources = ["src/win32_specific.cpp"]
linux.compile-options = ["-fPIC"]

Options [options]

toml

[options]
MYPROJECT_BUILD_TESTS = false
MYPROJECT_BUILD_EXAMPLES = { value = true, help = "Build example programs" }
MYPROJECT_ENABLE_FEATURE = "root"     # Only true if this is root project

Usage:

bash

cmake -B build -DMYPROJECT_BUILD_TESTS=ON

Each option creates a condition with the same name (lowercase, dashes).

Variables [variables]

toml

[variables]
MY_CUSTOM_VAR = "value"
MY_BOOL_VAR = true

Emits: set(MY_CUSTOM_VAR "value")

Dependencies

vcpkg [vcpkg]

toml

[vcpkg]
version = "2024.11.16"                # vcpkg version (auto-generates URL)
packages = ["fmt", "zlib", "boost"]   # Packages to install

# Package with features:
# packages = ["imgui[docking-experimental,freetype,sdl2-binding]"]

# Disable default features:
# packages = ["cpp-httplib[core,openssl]"]

overlay-ports = ["my-ports"]          # Custom ports directory
overlay-triplets = ["my-triplets"]    # Custom triplets directory
overlay = "vcpkg-overlay"             # Both in one directory

FetchContent [fetch-content.<name>]

toml

[fetch-content.fmt]
git = "https://github.com/fmtlib/fmt"
tag = "10.2.1"
shallow = true                        # --depth 1

[fetch-content.somelib]
url = "https://example.com/lib.zip"
sha256 = "abc123..."

Find Package [find-package.<name>]

toml

[find-package.Boost]
required = true
version = "1.82"
components = ["filesystem", "system"]

[find-package.OpenSSL]
required = false
config = true

Subdirectories [subdir.<name>]

toml

[subdir.thirdparty]
condition = "root"                    # Only add if this is root project

Templates [template.<name>]

toml

[template.example]
condition = "build-examples"
type = "executable"
link-libraries = ["mylib::mylib"]
add-function = ""                     # Custom add function (e.g., pybind11_add_module)
add-arguments = []                    # Arguments to add-function
pass-sources = false                  # Pass sources to add-function

[target.example1]
type = "example"
sources = ["examples/example1.cpp"]

Common Project Examples

Simple Executable

toml

[project]
name = "hello"
version = "1.0.0"

[target.hello]
type = "executable"
sources = ["src/main.cpp"]

Library with Examples

toml

[project]
name = "mylib"
version = "2.0.0"

[options]
MYLIB_BUILD_EXAMPLES = { value = true, help = "Build examples" }

[target.mylib]
type = "static"
sources = ["src/mylib.cpp"]
headers = ["include/mylib.hpp"]
include-directories = ["include"]

[template.example]
condition = "mylib-build-examples"
type = "executable"
link-libraries = ["mylib"]

[target.example_basic]
type = "example"
sources = ["examples/basic.cpp"]

Using vcpkg Dependencies

toml

[project]
name = "app-with-deps"

[vcpkg]
packages = ["fmt", "spdlog", "nlohmann-json"]

[target.app]
type = "executable"
sources = ["src/main.cpp"]
link-libraries = ["fmt::fmt", "spdlog::spdlog", "nlohmann_json::nlohmann_json"]

Platform-Specific Code

toml

[project]
name = "cross-platform"

[target.app]
type = "executable"
sources = ["src/main.cpp", "src/common.cpp"]

# Windows-specific
windows.sources = ["src/win32.cpp"]
windows.link-libraries = ["kernel32"]

# Linux-specific
linux.sources = ["src/linux.cpp"]
linux.compile-options = ["-fPIC"]
linux.link-libraries = ["pthread"]

# macOS-specific
macos.sources = ["src/macos.cpp"]
macos.compile-options = ["-mmacosx-version-min=10.14"]

Header-Only Library

toml

[project]
name = "header-lib"

[target.header-lib]
type = "interface"
headers = ["include/header-lib/*.hpp"]
include-directories = ["include"]

Multiple Targets

toml

[project]
name = "multi-target"

[target.lib1]
type = "static"
sources = ["lib1/*.cpp"]
include-directories = ["lib1/include"]

[target.lib2]
type = "static"
sources = ["lib2/*.cpp"]
include-directories = ["lib2/include"]
link-libraries = ["lib1"]

[target.app]
type = "executable"
sources = ["app/main.cpp"]
link-libraries = ["lib2"]

CLI Commands

If you install cmkr to your PATH:

bash

cmkr init [type]          # Create new project (executable|library|shared|static|interface)
cmkr gen                  # Regenerate CMakeLists.txt manually
cmkr build [args]         # Configure and build
cmkr install              # Run cmake --install
cmkr clean                # Clean build directory
cmkr help                 # Show help
cmkr version              # Show version

Without cmkr in PATH (using CMake only):

bash

# Regenerate (if cmake.toml changed)
cmake -B build

# Force regeneration
cmake -B build --fresh

CMake Integration

In CI/CD

yaml

# GitHub Actions example
steps:
  - uses: actions/checkout@v4
  - name: Configure
    run: cmake -B build
  - name: Build
    run: cmake --build build
  - name: Test
    run: ctest --test-dir build

No special setup needed! The cmkr.cmake bootstrap handles everything. In CI, cmkr downloads itself automatically on first configure.

With IDEs

VS Code:

•Install CMake Tools extension
•cmkr automatically regenerates CMakeLists.txt when you save cmake.toml
•Works seamlessly with IntelliSense and debugging

CLion:

•Open project with CMakeLists.txt
•Edit cmake.toml, save
•CLion auto-detects changes and reloads

Visual Studio:

•Open folder with CMakeLists.txt
•cmkr manages regeneration automatically

Build Types

bash

# Debug (default)
cmake -B build -DCMAKE_BUILD_TYPE=Debug
cmake --build build

# Release
cmake -B build -DCMAKE_BUILD_TYPE=Release
cmake --build build

# RelWithDebInfo (optimized with debug symbols)
cmake -B build -DCMAKE_BUILD_TYPE=RelWithDebInfo

# MinSizeRel (minimum size)
cmake -B build -DCMAKE_BUILD_TYPE=MinSizeRel

Troubleshooting

Issue: CMakeLists.txt not regenerating

Solution:

bash

# Force regeneration
cmake -B build --fresh

# Or manually trigger
cmake -B build

Issue: vcpkg packages not found

Solution:

bash

# Delete build directory to reset vcpkg
cmake -E rm -rf build
cmake -B build

Issue: Link errors with libraries

Solution:

•Ensure link-libraries uses target names (e.g., fmt::fmt not just fmt)
•Check visibility: Public for libraries, Private for executables
•Verify Find Package or Fetch Content is configured

Issue: cmkr bootstrap fails

Solution:

bash

# Manual download
curl -L https://github.com/build-cpp/cmkr/releases/latest/download/cmkr -o cmkr
chmod +x cmkr
./cmkr gen

Best Practices

•Start simple: Begin with minimal cmake.toml, add complexity incrementally
•Use templates: For repeated target patterns (examples, tests)
•Leverage conditions: Keep platform-specific code organized
•Commit bootstrap: Include cmkr.cmake in version control for CI
•Prefer vcpkg: For dependencies, use vcpkg when available
•Check before commit: cmake.toml and CMakeLists.txt should both be committed

Migration from CMakeLists.txt

•Create cmake.toml with equivalent structure
•Run cmake -P cmkr.cmake to generate
•Compare generated CMakeLists.txt with original
•Adjust cmake.toml until output matches desired CMake
•Remove manual CMakeLists.txt edits (they get overwritten)

Resources

•Documentation: https://cmkr.build/
•GitHub: https://github.com/build-cpp/cmkr
•Examples: https://cmkr.build/examples/
•Template: https://github.com/build-cpp/cmkr_for_beginners