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# CMake module
This module provides helper tools for generating cmake package files.
It also supports the usage of CMake based subprojects, similar to
the normal [meson subprojects](Subprojects.md).
## Usage
To use this module, just do: **`cmake = import('cmake')`**. The
following functions will then be available as methods on the object
with the name `cmake`. You can, of course, replace the name `cmake`
with anything else.
## CMake subprojects
Using CMake subprojects is similar to using the "normal" meson
subprojects. They also have to be located in the `subprojects`
directory.
Example:
```cmake
add_library(cm_lib SHARED ${SOURCES})
```
```meson
cmake = import('cmake')
# Configure the CMake project
sub_proj = cmake.subproject('libsimple_cmake')
# Fetch the dependency object
cm_lib = sub_proj.dependency('cm_lib')
executable(exe1, ['sources'], dependencies: [cm_lib])
```
The `subproject` method is almost identical to the normal meson
`subproject` function. The only difference is that a CMake project
instead of a meson project is configured.
Also, project specific CMake options can be added with the `cmake_options` key.
The returned `sub_proj` supports the same options as a "normal" subproject.
Meson automatically detects CMake build targets, which can be accessed with
the methods listed [below](#subproject-object).
It is usually enough to just use the dependency object returned by the
`dependency()` method in the build targets. This is almost identical to
using `declare_dependency()` object from a normal meson subproject.
It is also possible to use executables defined in the CMake project as code
generators with the `target()` method:
```cmake
add_executable(cm_exe ${EXE_SRC})
```
```meson
cmake = import('cmake')
# Subproject with the "code generator"
sub_pro = cmake.subproject('cmCodeGen')
# Fetch the code generator exe
sub_exe = sub_pro.target('cm_exe')
# Use the code generator
generated = custom_target(
'cmake-generated',
input: [],
output: ['test.cpp'],
command: [sub_exe, '@OUTPUT@']
)
```
It should be noted that not all projects are guaranteed to work. The
safest approach would still be to create a `meson.build` for the
subprojects in question.
### `subproject` object
This object is returned by the `subproject` function described above
and supports the following methods:
- `dependency(target)` returns a dependency object for any CMake target.
- `include_directories(target)` returns a meson `include_directories()`
object for the specified target. Using this function is not neccessary
if the dependency object is used.
- `target(target)` returns the raw build target.
- `target_type(target)` returns the type of the target as a string
- `target_list()` returns a list of all target *names*.
- `get_variable(name)` fetches the specified variable from inside
the subproject. Usually `dependency()` or `target()` should be
prefered to extract build targets.
## CMake configuration files
### cmake.write_basic_package_version_file()
This function is the equivalent of the corresponding [CMake function](https://cmake.org/cmake/help/v3.11/module/CMakePackageConfigHelpers.html#generating-a-package-version-file),
it generates a `name` package version file.
* `name`: the name of the package.
* `version`: the version of the generated package file.
* `compatibility`: a string indicating the kind of compatibility, the accepted values are
`AnyNewerVersion`, `SameMajorVersion`, `SameMinorVersion` or `ExactVersion`.
It defaults to `AnyNewerVersion`. Depending on your cmake installation some kind of
compatibility may not be available.
* `install_dir`: optional installation directory, it defaults to `$(libdir)/cmake/$(name)`
Example:
```meson
cmake = import('cmake')
cmake.write_basic_package_version_file(name: 'myProject', version: '1.0.0')
```
### cmake.configure_package_config_file()
This function is the equivalent of the corresponding [CMake function](https://cmake.org/cmake/help/v3.11/module/CMakePackageConfigHelpers.html#generating-a-package-configuration-file),
it generates a `name` package configuration file from the `input` template file. Just like the cmake function
in this file the `@PACKAGE_INIT@` statement will be replaced by the appropriate piece of cmake code.
The equivalent `PATH_VARS` argument is given through the `configuration` parameter.
* `name`: the name of the package.
* `input`: the template file where that will be treated for variable substitutions contained in `configuration`.
* `install_dir`: optional installation directory, it defaults to `$(libdir)/cmake/$(name)`.
* `configuration`: a `configuration_data` object that will be used for variable substitution in the template file.
Example:
meson.build:
```meson
cmake = import('cmake')
conf = configuration_data()
conf.set_quoted('VAR', 'variable value')
cmake.configure_package_config_file(
name: 'myProject',
input: 'myProject.cmake.in',
configuration: conf
)
```
myProject.cmake.in:
```text
@PACKAGE_INIT@
set(MYVAR VAR)
```