Ninja Multi-Config ------------------ Generates multiple ``build-<Config>.ninja`` files. This generator is very much like the :generator:`Ninja` generator, but with some key differences. Only these differences will be discussed in this document. Unlike the :generator:`Ninja` generator, ``Ninja Multi-Config`` generates multiple configurations at once with :variable:`CMAKE_CONFIGURATION_TYPES` instead of only one configuration with :variable:`CMAKE_BUILD_TYPE`. One ``build-<Config>.ninja`` file will be generated for each of these configurations (with ``<Config>`` being the configuration name.) These files are intended to be run with ``ninja -f build-<Config>.ninja``. A ``build.ninja`` file is also generated, using the configuration from either :variable:`CMAKE_DEFAULT_BUILD_TYPE` or the first item from :variable:`CMAKE_CONFIGURATION_TYPES`. ``cmake --build . --config <Config>`` will always use ``build-<Config>.ninja`` to build. If no ``--config`` argument is specified, ``cmake --build .`` will default to ``build-Debug.ninja``, unless a ``build.ninja`` is generated (see below), in which case that will be used instead. Each ``build-<Config>.ninja`` file contains ``<target>`` targets as well as ``<target>:<Config>`` targets, where ``<Config>`` is the same as the configuration specified in ``build-<Config>.ninja`` Additionally, if cross-config mode is enabled, ``build-<Config>.ninja`` may contain ``<target>:<OtherConfig>`` targets, where ``<OtherConfig>`` is a cross-config, as well as ``<target>:all``, which builds the target in all cross-configs. See below for how to enable cross-config mode. The ``Ninja Multi-Config`` generator recognizes the following variables: :variable:`CMAKE_CONFIGURATION_TYPES` Specifies the total set of configurations to build. :variable:`CMAKE_CROSS_CONFIGS` Specifies a :ref:`semicolon-separated list <CMake Language Lists>` of configurations available from all ``build-<Config>.ninja`` files. :variable:`CMAKE_DEFAULT_BUILD_TYPE` Specifies the configuration to use by default in a ``build.ninja`` file. :variable:`CMAKE_DEFAULT_CONFIGS` Specifies a :ref:`semicolon-separated list <CMake Language Lists>` of configurations to build for a target in ``build.ninja`` if no ``:<Config>`` suffix is specified. Consider the following example: .. code-block:: cmake cmake_minimum_required(VERSION 3.16) project(MultiConfigNinja C) add_executable(generator generator.c) add_custom_command(OUTPUT generated.c COMMAND generator generated.c) add_library(generated ${CMAKE_BINARY_DIR}/generated.c) Now assume you configure the project with ``Ninja Multi-Config`` and run one of the following commands: .. code-block:: shell ninja -f build-Debug.ninja generated # OR cmake --build . --config Debug --target generated This would build the ``Debug`` configuration of ``generator``, which would be used to generate ``generated.c``, which would be used to build the ``Debug`` configuration of ``generated``. But if :variable:`CMAKE_CROSS_CONFIGS` is set to ``all``, and you run the following instead: .. code-block:: shell ninja -f build-Release.ninja generated:Debug # OR cmake --build . --config Release --target generated:Debug This would build the ``Release`` configuration of ``generator``, which would be used to generate ``generated.c``, which would be used to build the ``Debug`` configuration of ``generated``. This is useful for running a release-optimized version of a generator utility while still building the debug version of the targets built with the generated code.