Ninja Multi-Config¶
Generates multiple build-<Config>.ninja files.
This generator is very much like the Ninja generator, but with
some key differences. Only these differences will be discussed in this
document.
Unlike the Ninja generator, Ninja Multi-Config generates
multiple configurations at once with CMAKE_CONFIGURATION_TYPES
instead of only one configuration with 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
CMAKE_DEFAULT_BUILD_TYPE or the first item from
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:
CMAKE_CONFIGURATION_TYPESSpecifies the total set of configurations to build. See the variable’s documentation for more information.
CMAKE_CROSS_CONFIGSSpecifies a semicolon-separated list of configurations available from all
build-<Config>.ninjafiles. This variable activates cross-config mode. Targets from each config specified in this variable can be built from anybuild-<Config>.ninjafile. Custom commands will use the configuration native tobuild-<Config>.ninja. If it is set toall, all configurations fromCMAKE_CONFIGURATION_TYPESare cross-configs. If it is not specified, or empty, eachbuild-<Config>.ninjafile will only contain build rules for its own configuration.The value of this variable must be a subset of
CMAKE_CONFIGURATION_TYPES.CMAKE_DEFAULT_BUILD_TYPESpecifies the configuration to use by default in a
build.ninjafile. If this variable is specified,build.ninjauses build rules frombuild-<Config>.ninjaby default. All custom commands are executed with this configuration. If the variable is not specified, the first item fromCMAKE_CONFIGURATION_TYPESis used instead.The value of this variable must be one of the items from
CMAKE_CONFIGURATION_TYPES.CMAKE_DEFAULT_CONFIGSSpecifies a semicolon-separated list of configurations to build for a target in
build.ninjaif no:<Config>suffix is specified. If it is set toall, all configurations fromCMAKE_CROSS_CONFIGSare used. If it is not specified, it defaults toCMAKE_DEFAULT_BUILD_TYPE.For example, if you set
CMAKE_DEFAULT_BUILD_TYPEtoRelease, but setCMAKE_DEFAULT_CONFIGStoDebugorall, all<target>aliases inbuild.ninjawill resolve to<target>:Debugor<target>:all, but custom commands will still use theReleaseconfiguration.The value of this variable must be a subset of
CMAKE_CROSS_CONFIGSor be the same asCMAKE_DEFAULT_BUILD_TYPE. It must not be specified ifCMAKE_DEFAULT_BUILD_TYPEorCMAKE_CROSS_CONFIGSis not used.
Consider the following example:
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:
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 CMAKE_CROSS_CONFIGS is set to all, and you run the
following instead:
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.