Ninja Multi-Config ------------------ .. versionadded:: 3.17 Generates multiple ``build-.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-.ninja`` file will be generated for each of these configurations (with ```` being the configuration name.) These files are intended to be run with ``ninja -f build-.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 `` will always use ``build-.ninja`` to build. If no ``--config`` argument is specified, ``cmake --build .`` will use ``build.ninja``. Each ``build-.ninja`` file contains ```` targets as well as ``:`` targets, where ```` is the same as the configuration specified in ``build-.ninja`` Additionally, if cross-config mode is enabled, ``build-.ninja`` may contain ``:`` targets, where ```` is a cross-config, as well as ``: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. Unlike with other multi-config generators, this variable has a value of ``Debug;Release;RelWithDebInfo`` by default. :variable:`CMAKE_CROSS_CONFIGS` Specifies a :ref:`semicolon-separated list ` of configurations available from all ``build-.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 ` of configurations to build for a target in ``build.ninja`` if no ``:`` 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 ${CMAKE_BINARY_DIR}/generated.c) Now assume you configure the project with ``Ninja Multi-Config`` and run one of the following commands: .. code-block:: shell ninja -f build-Debug.ninja generated # OR cmake --build . --config Debug --target generated This would build the ``Debug`` configuration of ``generator``, which would be used to generate ``generated.c``, which would be used to build the ``Debug`` configuration of ``generated``. But if :variable:`CMAKE_CROSS_CONFIGS` is set to ``all``, and you run the following instead: .. code-block:: shell ninja -f build-Release.ninja generated:Debug # OR cmake --build . --config Release --target generated:Debug This would build the ``Release`` configuration of ``generator``, which would be used to generate ``generated.c``, which would be used to build the ``Debug`` configuration of ``generated``. This is useful for running a release-optimized version of a generator utility while still building the debug version of the targets built with the generated code. Custom Commands ^^^^^^^^^^^^^^^ .. versionadded:: 3.20 The ``Ninja Multi-Config`` generator adds extra capabilities to :command:`add_custom_command` and :command:`add_custom_target` through its cross-config mode. The ``COMMAND``, ``DEPENDS``, and ``WORKING_DIRECTORY`` arguments can be evaluated in the context of either the "command config" (the "native" configuration of the ``build-.ninja`` file in use) or the "output config" (the configuration used to evaluate the ``OUTPUT`` and ``BYPRODUCTS``). If either ``OUTPUT`` or ``BYPRODUCTS`` names a path that is common to more than one configuration (e.g. it does not use any generator expressions), all arguments are evaluated in the command config by default. If all ``OUTPUT`` and ``BYPRODUCTS`` paths are unique to each configuration (e.g. by using the ``$`` generator expression), the first argument of ``COMMAND`` is still evaluated in the command config by default, while all subsequent arguments, as well as the arguments to ``DEPENDS`` and ``WORKING_DIRECTORY``, are evaluated in the output config. These defaults can be overridden with the ``$`` and ``$`` generator-expressions. Note that if a target is specified by its name in ``DEPENDS``, or as the first argument of ``COMMAND``, it is always evaluated in the command config, even if it is wrapped in ``$`` (because its plain name is not a generator expression). As an example, consider the following: .. code-block:: cmake add_custom_command( OUTPUT "$.txt" COMMAND generator "$.txt" "$>" "$>" DEPENDS tgt1 "$" "$>" "$>" ) Assume that ``generator``, ``tgt1``, ``tgt2``, ``tgt3``, and ``tgt4`` are all executable targets, and assume that ``$.txt`` is built in the ``Debug`` output config using the ``Release`` command config. The ``Release`` build of the ``generator`` target is called with ``Debug.txt Debug Release`` as arguments. The command depends on the ``Release`` builds of ``tgt1`` and ``tgt4``, and the ``Debug`` builds of ``tgt2`` and ``tgt3``. ``PRE_BUILD``, ``PRE_LINK``, and ``POST_BUILD`` custom commands for targets only get run in their "native" configuration (the ``Release`` configuration in the ``build-Release.ninja`` file) unless they have no ``BYPRODUCTS`` or their ``BYPRODUCTS`` are unique per config. Consider the following example: .. code-block:: cmake add_executable(exe main.c) add_custom_command( TARGET exe POST_BUILD COMMAND ${CMAKE_COMMAND} -E echo "Running no-byproduct command" ) add_custom_command( TARGET exe POST_BUILD COMMAND ${CMAKE_COMMAND} -E echo "Running separate-byproduct command for $" BYPRODUCTS $.txt ) add_custom_command( TARGET exe POST_BUILD COMMAND ${CMAKE_COMMAND} -E echo "Running common-byproduct command for $" BYPRODUCTS exe.txt ) In this example, if you build ``exe:Debug`` in ``build-Release.ninja``, the first and second custom commands get run, since their byproducts are unique per-config, but the last custom command does not. However, if you build ``exe:Release`` in ``build-Release.ninja``, all three custom commands get run.