cja

A CMake-compatible build system that generates Ninja build files.

Build a project with a CMakeLists.txt using:

cja
ninja

This is equivalent to the following with CMake:

cmake -Bbuild -GNinja -DCMAKE_BUILD_TYPE=Debug \
  -DCMAKE_COLOR_DIAGNOSTICS=1 -DCMAKE_EXPORT_COMPILE_COMMANDS=1
ninja -Cbuild

Install

pip install cja

Or, if you're in a managed Python environment:

pipx install cja

Comparison to CMake

• The build.ninja file is generated in your project root, not in the build directory. To allow multiple build configurations in parallel, the file name is <builddir>.ninja.
• Paths are relative to the project root, while CMake uses absolute paths. This is faster, reduces output, and also reduces binary size as paths (e.g. for debug symbols) are shorter. When reading output from a Docker container, this lets you click paths and open the correct files in your local editor.
• Instead of a separate tool like CTest, cja generates a phony test target that runs all tests as part of the Ninja build graph, so tests can start as soon as the first test binary is ready.
• Colors for compiler diagnostics are enabled by default.
• _builddir_/compile_commands.json is always generated.
• More colorful, simplified output. For example, when downloading dependencies, cja shows progress bars using Rich, while CMake shows no output (or simple multi-line output when -DFETCHCONTENT_QUIET=0 is specified).

Limitations to keep cja simple:

• Only generates Ninja build files.
• Out-of-tree builds aren't allowed.
• Only supports Linux, macOS, and Windows.
• Only supports clang with a GNU-like command line on Windows.

Build Subcommand

cja supports a build subcommand, which runs ninja automatically afterward.

cja build --release

Equivalent to calling:

cja -Bbuild-release -DCMAKE_BUILD_TYPE=Release
ninja -f build-release.ninja

Run Subcommand

cja also generates a run phony target that executes the first executable (or the one set via VS_STARTUP_PROJECT) in your CMakeLists.txt.