| .. cmake-manual-description: CMake Generator Expressions |
| |
| cmake-generator-expressions(7) |
| ****************************** |
| |
| .. only:: html |
| |
| .. contents:: |
| |
| Introduction |
| ============ |
| |
| Generator expressions are evaluated during build system generation to produce |
| information specific to each build configuration. |
| |
| Generator expressions are allowed in the context of many target properties, |
| such as :prop_tgt:`LINK_LIBRARIES`, :prop_tgt:`INCLUDE_DIRECTORIES`, |
| :prop_tgt:`COMPILE_DEFINITIONS` and others. They may also be used when using |
| commands to populate those properties, such as :command:`target_link_libraries`, |
| :command:`target_include_directories`, :command:`target_compile_definitions` |
| and others. |
| |
| They enable conditional linking, conditional definitions used when compiling, |
| conditional include directories, and more. The conditions may be based on |
| the build configuration, target properties, platform information or any other |
| queryable information. |
| |
| Generator expressions have the form ``$<...>``. To avoid confusion, this page |
| deviates from most of the CMake documentation in that it omits angular brackets |
| ``<...>`` around placeholders like ``condition``, ``string``, ``target``, |
| among others. |
| |
| Generator expressions can be nested, as shown in most of the examples below. |
| |
| .. _`Boolean Generator Expressions`: |
| |
| Boolean Generator Expressions |
| ============================= |
| |
| Boolean expressions evaluate to either ``0`` or ``1``. |
| They are typically used to construct the condition in a :ref:`conditional |
| generator expression<Conditional Generator Expressions>`. |
| |
| Available boolean expressions are: |
| |
| Logical Operators |
| ----------------- |
| |
| .. genex:: $<BOOL:string> |
| |
| Converts ``string`` to ``0`` or ``1``. Evaluates to ``0`` if any of the |
| following is true: |
| |
| * ``string`` is empty, |
| * ``string`` is a case-insensitive equal of |
| ``0``, ``FALSE``, ``OFF``, ``N``, ``NO``, ``IGNORE``, or ``NOTFOUND``, or |
| * ``string`` ends in the suffix ``-NOTFOUND`` (case-sensitive). |
| |
| Otherwise evaluates to ``1``. |
| |
| .. genex:: $<AND:conditions> |
| |
| where ``conditions`` is a comma-separated list of boolean expressions. |
| Evaluates to ``1`` if all conditions are ``1``. |
| Otherwise evaluates to ``0``. |
| |
| .. genex:: $<OR:conditions> |
| |
| where ``conditions`` is a comma-separated list of boolean expressions. |
| Evaluates to ``1`` if at least one of the conditions is ``1``. |
| Otherwise evaluates to ``0``. |
| |
| .. genex:: $<NOT:condition> |
| |
| ``0`` if ``condition`` is ``1``, else ``1``. |
| |
| String Comparisons |
| ------------------ |
| |
| .. genex:: $<STREQUAL:string1,string2> |
| |
| ``1`` if ``string1`` and ``string2`` are equal, else ``0``. |
| The comparison is case-sensitive. For a case-insensitive comparison, |
| combine with a :ref:`string transforming generator expression |
| <String Transforming Generator Expressions>`, |
| |
| .. code-block:: cmake |
| |
| $<STREQUAL:$<UPPER_CASE:${foo}>,"BAR"> # "1" if ${foo} is any of "BAR", "Bar", "bar", ... |
| |
| .. genex:: $<EQUAL:value1,value2> |
| |
| ``1`` if ``value1`` and ``value2`` are numerically equal, else ``0``. |
| |
| .. genex:: $<IN_LIST:string,list> |
| |
| .. versionadded:: 3.12 |
| |
| ``1`` if ``string`` is member of the semicolon-separated ``list``, else ``0``. |
| Uses case-sensitive comparisons. |
| |
| .. genex:: $<VERSION_LESS:v1,v2> |
| |
| ``1`` if ``v1`` is a version less than ``v2``, else ``0``. |
| |
| .. genex:: $<VERSION_GREATER:v1,v2> |
| |
| ``1`` if ``v1`` is a version greater than ``v2``, else ``0``. |
| |
| .. genex:: $<VERSION_EQUAL:v1,v2> |
| |
| ``1`` if ``v1`` is the same version as ``v2``, else ``0``. |
| |
| .. genex:: $<VERSION_LESS_EQUAL:v1,v2> |
| |
| .. versionadded:: 3.7 |
| |
| ``1`` if ``v1`` is a version less than or equal to ``v2``, else ``0``. |
| |
| .. genex:: $<VERSION_GREATER_EQUAL:v1,v2> |
| |
| .. versionadded:: 3.7 |
| |
| ``1`` if ``v1`` is a version greater than or equal to ``v2``, else ``0``. |
| |
| Variable Queries |
| ---------------- |
| |
| .. genex:: $<TARGET_EXISTS:target> |
| |
| .. versionadded:: 3.12 |
| |
| ``1`` if ``target`` exists, else ``0``. |
| |
| .. genex:: $<CONFIG:cfgs> |
| |
| ``1`` if config is any one of the entries in comma-separated list |
| ``cfgs``, else ``0``. This is a case-insensitive comparison. The mapping in |
| :prop_tgt:`MAP_IMPORTED_CONFIG_<CONFIG>` is also considered by this |
| expression when it is evaluated on a property on an :prop_tgt:`IMPORTED` |
| target. |
| |
| .. genex:: $<PLATFORM_ID:platform_ids> |
| |
| where ``platform_ids`` is a comma-separated list. |
| ``1`` if the CMake's platform id matches any one of the entries in |
| ``platform_ids``, otherwise ``0``. |
| See also the :variable:`CMAKE_SYSTEM_NAME` variable. |
| |
| .. genex:: $<C_COMPILER_ID:compiler_ids> |
| |
| where ``compiler_ids`` is a comma-separated list. |
| ``1`` if the CMake's compiler id of the C compiler matches any one |
| of the entries in ``compiler_ids``, otherwise ``0``. |
| See also the :variable:`CMAKE_<LANG>_COMPILER_ID` variable. |
| |
| .. genex:: $<CXX_COMPILER_ID:compiler_ids> |
| |
| where ``compiler_ids`` is a comma-separated list. |
| ``1`` if the CMake's compiler id of the CXX compiler matches any one |
| of the entries in ``compiler_ids``, otherwise ``0``. |
| See also the :variable:`CMAKE_<LANG>_COMPILER_ID` variable. |
| |
| .. genex:: $<CUDA_COMPILER_ID:compiler_ids> |
| |
| .. versionadded:: 3.15 |
| |
| where ``compiler_ids`` is a comma-separated list. |
| ``1`` if the CMake's compiler id of the CUDA compiler matches any one |
| of the entries in ``compiler_ids``, otherwise ``0``. |
| See also the :variable:`CMAKE_<LANG>_COMPILER_ID` variable. |
| |
| .. genex:: $<OBJC_COMPILER_ID:compiler_ids> |
| |
| .. versionadded:: 3.16 |
| |
| where ``compiler_ids`` is a comma-separated list. |
| ``1`` if the CMake's compiler id of the Objective-C compiler matches any one |
| of the entries in ``compiler_ids``, otherwise ``0``. |
| See also the :variable:`CMAKE_<LANG>_COMPILER_ID` variable. |
| |
| .. genex:: $<OBJCXX_COMPILER_ID:compiler_ids> |
| |
| .. versionadded:: 3.16 |
| |
| where ``compiler_ids`` is a comma-separated list. |
| ``1`` if the CMake's compiler id of the Objective-C++ compiler matches any one |
| of the entries in ``compiler_ids``, otherwise ``0``. |
| See also the :variable:`CMAKE_<LANG>_COMPILER_ID` variable. |
| |
| .. genex:: $<Fortran_COMPILER_ID:compiler_ids> |
| |
| where ``compiler_ids`` is a comma-separated list. |
| ``1`` if the CMake's compiler id of the Fortran compiler matches any one |
| of the entries in ``compiler_ids``, otherwise ``0``. |
| See also the :variable:`CMAKE_<LANG>_COMPILER_ID` variable. |
| |
| .. genex:: $<HIP_COMPILER_ID:compiler_ids> |
| |
| .. versionadded:: 3.21 |
| |
| where ``compiler_ids`` is a comma-separated list. |
| ``1`` if the CMake's compiler id of the HIP compiler matches any one |
| of the entries in ``compiler_ids``, otherwise ``0``. |
| See also the :variable:`CMAKE_<LANG>_COMPILER_ID` variable. |
| |
| .. genex:: $<ISPC_COMPILER_ID:compiler_ids> |
| |
| .. versionadded:: 3.19 |
| |
| where ``compiler_ids`` is a comma-separated list. |
| ``1`` if the CMake's compiler id of the ISPC compiler matches any one |
| of the entries in ``compiler_ids``, otherwise ``0``. |
| See also the :variable:`CMAKE_<LANG>_COMPILER_ID` variable. |
| |
| .. genex:: $<C_COMPILER_VERSION:version> |
| |
| ``1`` if the version of the C compiler matches ``version``, otherwise ``0``. |
| See also the :variable:`CMAKE_<LANG>_COMPILER_VERSION` variable. |
| |
| .. genex:: $<CXX_COMPILER_VERSION:version> |
| |
| ``1`` if the version of the CXX compiler matches ``version``, otherwise ``0``. |
| See also the :variable:`CMAKE_<LANG>_COMPILER_VERSION` variable. |
| |
| .. genex:: $<CUDA_COMPILER_VERSION:version> |
| |
| .. versionadded:: 3.15 |
| |
| ``1`` if the version of the CXX compiler matches ``version``, otherwise ``0``. |
| See also the :variable:`CMAKE_<LANG>_COMPILER_VERSION` variable. |
| |
| .. genex:: $<OBJC_COMPILER_VERSION:version> |
| |
| .. versionadded:: 3.16 |
| |
| ``1`` if the version of the OBJC compiler matches ``version``, otherwise ``0``. |
| See also the :variable:`CMAKE_<LANG>_COMPILER_VERSION` variable. |
| |
| .. genex:: $<OBJCXX_COMPILER_VERSION:version> |
| |
| .. versionadded:: 3.16 |
| |
| ``1`` if the version of the OBJCXX compiler matches ``version``, otherwise ``0``. |
| See also the :variable:`CMAKE_<LANG>_COMPILER_VERSION` variable. |
| |
| .. genex:: $<Fortran_COMPILER_VERSION:version> |
| |
| ``1`` if the version of the Fortran compiler matches ``version``, otherwise ``0``. |
| See also the :variable:`CMAKE_<LANG>_COMPILER_VERSION` variable. |
| |
| .. genex:: $<HIP_COMPILER_VERSION:version> |
| |
| .. versionadded:: 3.21 |
| |
| ``1`` if the version of the HIP compiler matches ``version``, otherwise ``0``. |
| See also the :variable:`CMAKE_<LANG>_COMPILER_VERSION` variable. |
| |
| .. genex:: $<ISPC_COMPILER_VERSION:version> |
| |
| .. versionadded:: 3.19 |
| |
| ``1`` if the version of the ISPC compiler matches ``version``, otherwise ``0``. |
| See also the :variable:`CMAKE_<LANG>_COMPILER_VERSION` variable. |
| |
| .. genex:: $<TARGET_POLICY:policy> |
| |
| ``1`` if the ``policy`` was NEW when the 'head' target was created, |
| else ``0``. If the ``policy`` was not set, the warning message for the policy |
| will be emitted. This generator expression only works for a subset of |
| policies. |
| |
| .. genex:: $<COMPILE_FEATURES:features> |
| |
| .. versionadded:: 3.1 |
| |
| where ``features`` is a comma-spearated list. |
| Evaluates to ``1`` if all of the ``features`` are available for the 'head' |
| target, and ``0`` otherwise. If this expression is used while evaluating |
| the link implementation of a target and if any dependency transitively |
| increases the required :prop_tgt:`C_STANDARD` or :prop_tgt:`CXX_STANDARD` |
| for the 'head' target, an error is reported. See the |
| :manual:`cmake-compile-features(7)` manual for information on |
| compile features and a list of supported compilers. |
| |
| .. _`Boolean COMPILE_LANGUAGE Generator Expression`: |
| |
| .. genex:: $<COMPILE_LANG_AND_ID:language,compiler_ids> |
| |
| .. versionadded:: 3.15 |
| |
| ``1`` when the language used for compilation unit matches ``language`` and |
| the CMake's compiler id of the language compiler matches any one of the |
| entries in ``compiler_ids``, otherwise ``0``. This expression is a short form |
| for the combination of ``$<COMPILE_LANGUAGE:language>`` and |
| ``$<LANG_COMPILER_ID:compiler_ids>``. This expression may be used to specify |
| compile options, compile definitions, and include directories for source files of a |
| particular language and compiler combination in a target. For example: |
| |
| .. code-block:: cmake |
| |
| add_executable(myapp main.cpp foo.c bar.cpp zot.cu) |
| target_compile_definitions(myapp |
| PRIVATE $<$<COMPILE_LANG_AND_ID:CXX,AppleClang,Clang>:COMPILING_CXX_WITH_CLANG> |
| $<$<COMPILE_LANG_AND_ID:CXX,Intel>:COMPILING_CXX_WITH_INTEL> |
| $<$<COMPILE_LANG_AND_ID:C,Clang>:COMPILING_C_WITH_CLANG> |
| ) |
| |
| This specifies the use of different compile definitions based on both |
| the compiler id and compilation language. This example will have a |
| ``COMPILING_CXX_WITH_CLANG`` compile definition when Clang is the CXX |
| compiler, and ``COMPILING_CXX_WITH_INTEL`` when Intel is the CXX compiler. |
| Likewise when the C compiler is Clang it will only see the ``COMPILING_C_WITH_CLANG`` |
| definition. |
| |
| Without the ``COMPILE_LANG_AND_ID`` generator expression the same logic |
| would be expressed as: |
| |
| .. code-block:: cmake |
| |
| target_compile_definitions(myapp |
| PRIVATE $<$<AND:$<COMPILE_LANGUAGE:CXX>,$<CXX_COMPILER_ID:AppleClang,Clang>>:COMPILING_CXX_WITH_CLANG> |
| $<$<AND:$<COMPILE_LANGUAGE:CXX>,$<CXX_COMPILER_ID:Intel>>:COMPILING_CXX_WITH_INTEL> |
| $<$<AND:$<COMPILE_LANGUAGE:C>,$<C_COMPILER_ID:Clang>>:COMPILING_C_WITH_CLANG> |
| ) |
| |
| .. genex:: $<COMPILE_LANGUAGE:languages> |
| |
| .. versionadded:: 3.3 |
| |
| ``1`` when the language used for compilation unit matches any of the entries |
| in ``languages``, otherwise ``0``. This expression may be used to specify |
| compile options, compile definitions, and include directories for source files of a |
| particular language in a target. For example: |
| |
| .. code-block:: cmake |
| |
| add_executable(myapp main.cpp foo.c bar.cpp zot.cu) |
| target_compile_options(myapp |
| PRIVATE $<$<COMPILE_LANGUAGE:CXX>:-fno-exceptions> |
| ) |
| target_compile_definitions(myapp |
| PRIVATE $<$<COMPILE_LANGUAGE:CXX>:COMPILING_CXX> |
| $<$<COMPILE_LANGUAGE:CUDA>:COMPILING_CUDA> |
| ) |
| target_include_directories(myapp |
| PRIVATE $<$<COMPILE_LANGUAGE:CXX,CUDA>:/opt/foo/headers> |
| ) |
| |
| This specifies the use of the ``-fno-exceptions`` compile option, |
| ``COMPILING_CXX`` compile definition, and ``cxx_headers`` include |
| directory for C++ only (compiler id checks elided). It also specifies |
| a ``COMPILING_CUDA`` compile definition for CUDA. |
| |
| Note that with :ref:`Visual Studio Generators` and :generator:`Xcode` there |
| is no way to represent target-wide compile definitions or include directories |
| separately for ``C`` and ``CXX`` languages. |
| Also, with :ref:`Visual Studio Generators` there is no way to represent |
| target-wide flags separately for ``C`` and ``CXX`` languages. Under these |
| generators, expressions for both C and C++ sources will be evaluated |
| using ``CXX`` if there are any C++ sources and otherwise using ``C``. |
| A workaround is to create separate libraries for each source file language |
| instead: |
| |
| .. code-block:: cmake |
| |
| add_library(myapp_c foo.c) |
| add_library(myapp_cxx bar.cpp) |
| target_compile_options(myapp_cxx PUBLIC -fno-exceptions) |
| add_executable(myapp main.cpp) |
| target_link_libraries(myapp myapp_c myapp_cxx) |
| |
| .. _`Boolean LINK_LANGUAGE Generator Expression`: |
| |
| .. genex:: $<LINK_LANG_AND_ID:language,compiler_ids> |
| |
| .. versionadded:: 3.18 |
| |
| ``1`` when the language used for link step matches ``language`` and the |
| CMake's compiler id of the language linker matches any one of the entries |
| in ``compiler_ids``, otherwise ``0``. This expression is a short form for the |
| combination of ``$<LINK_LANGUAGE:language>`` and |
| ``$<LANG_COMPILER_ID:compiler_ids>``. This expression may be used to specify |
| link libraries, link options, link directories and link dependencies of a |
| particular language and linker combination in a target. For example: |
| |
| .. code-block:: cmake |
| |
| add_library(libC_Clang ...) |
| add_library(libCXX_Clang ...) |
| add_library(libC_Intel ...) |
| add_library(libCXX_Intel ...) |
| |
| add_executable(myapp main.c) |
| if (CXX_CONFIG) |
| target_sources(myapp PRIVATE file.cxx) |
| endif() |
| target_link_libraries(myapp |
| PRIVATE $<$<LINK_LANG_AND_ID:CXX,Clang,AppleClang>:libCXX_Clang> |
| $<$<LINK_LANG_AND_ID:C,Clang,AppleClang>:libC_Clang> |
| $<$<LINK_LANG_AND_ID:CXX,Intel>:libCXX_Intel> |
| $<$<LINK_LANG_AND_ID:C,Intel>:libC_Intel>) |
| |
| This specifies the use of different link libraries based on both the |
| compiler id and link language. This example will have target ``libCXX_Clang`` |
| as link dependency when ``Clang`` or ``AppleClang`` is the ``CXX`` |
| linker, and ``libCXX_Intel`` when ``Intel`` is the ``CXX`` linker. |
| Likewise when the ``C`` linker is ``Clang`` or ``AppleClang``, target |
| ``libC_Clang`` will be added as link dependency and ``libC_Intel`` when |
| ``Intel`` is the ``C`` linker. |
| |
| See :ref:`the note related to |
| <Constraints LINK_LANGUAGE Generator Expression>` |
| ``$<LINK_LANGUAGE:language>`` for constraints about the usage of this |
| generator expression. |
| |
| .. genex:: $<LINK_LANGUAGE:languages> |
| |
| .. versionadded:: 3.18 |
| |
| ``1`` when the language used for link step matches any of the entries |
| in ``languages``, otherwise ``0``. This expression may be used to specify |
| link libraries, link options, link directories and link dependencies of a |
| particular language in a target. For example: |
| |
| .. code-block:: cmake |
| |
| add_library(api_C ...) |
| add_library(api_CXX ...) |
| add_library(api INTERFACE) |
| target_link_options(api INTERFACE $<$<LINK_LANGUAGE:C>:-opt_c> |
| $<$<LINK_LANGUAGE:CXX>:-opt_cxx>) |
| target_link_libraries(api INTERFACE $<$<LINK_LANGUAGE:C>:api_C> |
| $<$<LINK_LANGUAGE:CXX>:api_CXX>) |
| |
| add_executable(myapp1 main.c) |
| target_link_options(myapp1 PRIVATE api) |
| |
| add_executable(myapp2 main.cpp) |
| target_link_options(myapp2 PRIVATE api) |
| |
| This specifies to use the ``api`` target for linking targets ``myapp1`` and |
| ``myapp2``. In practice, ``myapp1`` will link with target ``api_C`` and |
| option ``-opt_c`` because it will use ``C`` as link language. And ``myapp2`` |
| will link with ``api_CXX`` and option ``-opt_cxx`` because ``CXX`` will be |
| the link language. |
| |
| .. _`Constraints LINK_LANGUAGE Generator Expression`: |
| |
| .. note:: |
| |
| To determine the link language of a target, it is required to collect, |
| transitively, all the targets which will be linked to it. So, for link |
| libraries properties, a double evaluation will be done. During the first |
| evaluation, ``$<LINK_LANGUAGE:..>`` expressions will always return ``0``. |
| The link language computed after this first pass will be used to do the |
| second pass. To avoid inconsistency, it is required that the second pass |
| do not change the link language. Moreover, to avoid unexpected |
| side-effects, it is required to specify complete entities as part of the |
| ``$<LINK_LANGUAGE:..>`` expression. For example: |
| |
| .. code-block:: cmake |
| |
| add_library(lib STATIC file.cxx) |
| add_library(libother STATIC file.c) |
| |
| # bad usage |
| add_executable(myapp1 main.c) |
| target_link_libraries(myapp1 PRIVATE lib$<$<LINK_LANGUAGE:C>:other>) |
| |
| # correct usage |
| add_executable(myapp2 main.c) |
| target_link_libraries(myapp2 PRIVATE $<$<LINK_LANGUAGE:C>:libother>) |
| |
| In this example, for ``myapp1``, the first pass will, unexpectedly, |
| determine that the link language is ``CXX`` because the evaluation of the |
| generator expression will be an empty string so ``myapp1`` will depends on |
| target ``lib`` which is ``C++``. On the contrary, for ``myapp2``, the first |
| evaluation will give ``C`` as link language, so the second pass will |
| correctly add target ``libother`` as link dependency. |
| |
| .. genex:: $<DEVICE_LINK:list> |
| |
| .. versionadded:: 3.18 |
| |
| Returns the list if it is the device link step, an empty list otherwise. |
| The device link step is controlled by :prop_tgt:`CUDA_SEPARABLE_COMPILATION` |
| and :prop_tgt:`CUDA_RESOLVE_DEVICE_SYMBOLS` properties and |
| policy :policy:`CMP0105`. This expression can only be used to specify link |
| options. |
| |
| .. genex:: $<HOST_LINK:list> |
| |
| .. versionadded:: 3.18 |
| |
| Returns the list if it is the normal link step, an empty list otherwise. |
| This expression is mainly useful when a device link step is also involved |
| (see ``$<DEVICE_LINK:list>`` generator expression). This expression can only |
| be used to specify link options. |
| |
| String-Valued Generator Expressions |
| =================================== |
| |
| These expressions expand to some string. |
| For example, |
| |
| .. code-block:: cmake |
| |
| include_directories(/usr/include/$<CXX_COMPILER_ID>/) |
| |
| expands to ``/usr/include/GNU/`` or ``/usr/include/Clang/`` etc, depending on |
| the compiler identifier. |
| |
| String-valued expressions may also be combined with other expressions. |
| Here an example for a string-valued expression within a boolean expressions |
| within a conditional expression: |
| |
| .. code-block:: cmake |
| |
| $<$<VERSION_LESS:$<CXX_COMPILER_VERSION>,4.2.0>:OLD_COMPILER> |
| |
| expands to ``OLD_COMPILER`` if the |
| :variable:`CMAKE_CXX_COMPILER_VERSION <CMAKE_<LANG>_COMPILER_VERSION>` is less |
| than 4.2.0. |
| |
| And here two nested string-valued expressions: |
| |
| .. code-block:: cmake |
| |
| -I$<JOIN:$<TARGET_PROPERTY:INCLUDE_DIRECTORIES>, -I> |
| |
| generates a string of the entries in the :prop_tgt:`INCLUDE_DIRECTORIES` target |
| property with each entry preceded by ``-I``. |
| |
| Expanding on the previous example, if one first wants to check if the |
| ``INCLUDE_DIRECTORIES`` property is non-empty, then it is advisable to |
| introduce a helper variable to keep the code readable: |
| |
| .. code-block:: cmake |
| |
| set(prop "$<TARGET_PROPERTY:INCLUDE_DIRECTORIES>") # helper variable |
| $<$<BOOL:${prop}>:-I$<JOIN:${prop}, -I>> |
| |
| The following string-valued generator expressions are available: |
| |
| Escaped Characters |
| ------------------ |
| |
| String literals to escape the special meaning a character would otherwise have: |
| |
| .. genex:: $<ANGLE-R> |
| |
| A literal ``>``. Used for example to compare strings that contain a ``>``. |
| |
| .. genex:: $<COMMA> |
| |
| A literal ``,``. Used for example to compare strings which contain a ``,``. |
| |
| .. genex:: $<SEMICOLON> |
| |
| A literal ``;``. Used to prevent list expansion on an argument with ``;``. |
| |
| .. _`Conditional Generator Expressions`: |
| |
| Conditional Expressions |
| ----------------------- |
| |
| Conditional generator expressions depend on a boolean condition |
| that must be ``0`` or ``1``. |
| |
| .. genex:: $<condition:true_string> |
| |
| Evaluates to ``true_string`` if ``condition`` is ``1``. |
| Otherwise evaluates to the empty string. |
| |
| .. genex:: $<IF:condition,true_string,false_string> |
| |
| .. versionadded:: 3.8 |
| |
| Evaluates to ``true_string`` if ``condition`` is ``1``. |
| Otherwise evaluates to ``false_string``. |
| |
| Typically, the ``condition`` is a :ref:`boolean generator expression |
| <Boolean Generator Expressions>`. For instance, |
| |
| .. code-block:: cmake |
| |
| $<$<CONFIG:Debug>:DEBUG_MODE> |
| |
| expands to ``DEBUG_MODE`` when the ``Debug`` configuration is used, and |
| otherwise expands to the empty string. |
| |
| .. _`String Transforming Generator Expressions`: |
| |
| String Transformations |
| ---------------------- |
| |
| .. genex:: $<JOIN:list,string> |
| |
| Joins the list with the content of ``string``. |
| |
| .. genex:: $<REMOVE_DUPLICATES:list> |
| |
| .. versionadded:: 3.15 |
| |
| Removes duplicated items in the given ``list``. The relative order of items |
| is preserved, but if duplicates are encountered, only the first instance is |
| preserved. |
| |
| .. genex:: $<FILTER:list,INCLUDE|EXCLUDE,regex> |
| |
| .. versionadded:: 3.15 |
| |
| Includes or removes items from ``list`` that match the regular expression ``regex``. |
| |
| .. genex:: $<LOWER_CASE:string> |
| |
| Content of ``string`` converted to lower case. |
| |
| .. genex:: $<UPPER_CASE:string> |
| |
| Content of ``string`` converted to upper case. |
| |
| .. genex:: $<GENEX_EVAL:expr> |
| |
| .. versionadded:: 3.12 |
| |
| Content of ``expr`` evaluated as a generator expression in the current |
| context. This enables consumption of generator expressions whose |
| evaluation results itself in generator expressions. |
| |
| .. genex:: $<TARGET_GENEX_EVAL:tgt,expr> |
| |
| .. versionadded:: 3.12 |
| |
| Content of ``expr`` evaluated as a generator expression in the context of |
| ``tgt`` target. This enables consumption of custom target properties that |
| themselves contain generator expressions. |
| |
| Having the capability to evaluate generator expressions is very useful when |
| you want to manage custom properties supporting generator expressions. |
| For example: |
| |
| .. code-block:: cmake |
| |
| add_library(foo ...) |
| |
| set_property(TARGET foo PROPERTY |
| CUSTOM_KEYS $<$<CONFIG:DEBUG>:FOO_EXTRA_THINGS> |
| ) |
| |
| add_custom_target(printFooKeys |
| COMMAND ${CMAKE_COMMAND} -E echo $<TARGET_PROPERTY:foo,CUSTOM_KEYS> |
| ) |
| |
| This naive implementation of the ``printFooKeys`` custom command is wrong |
| because ``CUSTOM_KEYS`` target property is not evaluated and the content |
| is passed as is (i.e. ``$<$<CONFIG:DEBUG>:FOO_EXTRA_THINGS>``). |
| |
| To have the expected result (i.e. ``FOO_EXTRA_THINGS`` if config is |
| ``Debug``), it is required to evaluate the output of |
| ``$<TARGET_PROPERTY:foo,CUSTOM_KEYS>``: |
| |
| .. code-block:: cmake |
| |
| add_custom_target(printFooKeys |
| COMMAND ${CMAKE_COMMAND} -E |
| echo $<TARGET_GENEX_EVAL:foo,$<TARGET_PROPERTY:foo,CUSTOM_KEYS>> |
| ) |
| |
| Variable Queries |
| ---------------- |
| |
| .. genex:: $<CONFIG> |
| |
| Configuration name. |
| |
| .. genex:: $<CONFIGURATION> |
| |
| Configuration name. Deprecated since CMake 3.0. Use ``CONFIG`` instead. |
| |
| .. genex:: $<PLATFORM_ID> |
| |
| The current system's CMake platform id. |
| See also the :variable:`CMAKE_SYSTEM_NAME` variable. |
| |
| .. genex:: $<C_COMPILER_ID> |
| |
| The CMake's compiler id of the C compiler used. |
| See also the :variable:`CMAKE_<LANG>_COMPILER_ID` variable. |
| |
| .. genex:: $<CXX_COMPILER_ID> |
| |
| The CMake's compiler id of the CXX compiler used. |
| See also the :variable:`CMAKE_<LANG>_COMPILER_ID` variable. |
| |
| .. genex:: $<CUDA_COMPILER_ID> |
| |
| The CMake's compiler id of the CUDA compiler used. |
| See also the :variable:`CMAKE_<LANG>_COMPILER_ID` variable. |
| |
| .. genex:: $<OBJC_COMPILER_ID> |
| |
| .. versionadded:: 3.16 |
| |
| The CMake's compiler id of the OBJC compiler used. |
| See also the :variable:`CMAKE_<LANG>_COMPILER_ID` variable. |
| |
| .. genex:: $<OBJCXX_COMPILER_ID> |
| |
| .. versionadded:: 3.16 |
| |
| The CMake's compiler id of the OBJCXX compiler used. |
| See also the :variable:`CMAKE_<LANG>_COMPILER_ID` variable. |
| |
| .. genex:: $<Fortran_COMPILER_ID> |
| |
| The CMake's compiler id of the Fortran compiler used. |
| See also the :variable:`CMAKE_<LANG>_COMPILER_ID` variable. |
| |
| .. genex:: $<HIP_COMPILER_ID> |
| |
| .. versionadded:: 3.21 |
| |
| The CMake's compiler id of the HIP compiler used. |
| See also the :variable:`CMAKE_<LANG>_COMPILER_ID` variable. |
| |
| .. genex:: $<ISPC_COMPILER_ID> |
| |
| .. versionadded:: 3.19 |
| |
| The CMake's compiler id of the ISPC compiler used. |
| See also the :variable:`CMAKE_<LANG>_COMPILER_ID` variable. |
| |
| .. genex:: $<C_COMPILER_VERSION> |
| |
| The version of the C compiler used. |
| See also the :variable:`CMAKE_<LANG>_COMPILER_VERSION` variable. |
| |
| .. genex:: $<CXX_COMPILER_VERSION> |
| |
| The version of the CXX compiler used. |
| See also the :variable:`CMAKE_<LANG>_COMPILER_VERSION` variable. |
| |
| .. genex:: $<CUDA_COMPILER_VERSION> |
| |
| The version of the CUDA compiler used. |
| See also the :variable:`CMAKE_<LANG>_COMPILER_VERSION` variable. |
| |
| .. genex:: $<OBJC_COMPILER_VERSION> |
| |
| .. versionadded:: 3.16 |
| |
| The version of the OBJC compiler used. |
| See also the :variable:`CMAKE_<LANG>_COMPILER_VERSION` variable. |
| |
| .. genex:: $<OBJCXX_COMPILER_VERSION> |
| |
| .. versionadded:: 3.16 |
| |
| The version of the OBJCXX compiler used. |
| See also the :variable:`CMAKE_<LANG>_COMPILER_VERSION` variable. |
| |
| .. genex:: $<Fortran_COMPILER_VERSION> |
| |
| The version of the Fortran compiler used. |
| See also the :variable:`CMAKE_<LANG>_COMPILER_VERSION` variable. |
| |
| .. genex:: $<HIP_COMPILER_VERSION> |
| |
| .. versionadded:: 3.21 |
| |
| The version of the HIP compiler used. |
| See also the :variable:`CMAKE_<LANG>_COMPILER_VERSION` variable. |
| |
| .. genex:: $<ISPC_COMPILER_VERSION> |
| |
| .. versionadded:: 3.19 |
| |
| The version of the ISPC compiler used. |
| See also the :variable:`CMAKE_<LANG>_COMPILER_VERSION` variable. |
| |
| .. genex:: $<COMPILE_LANGUAGE> |
| |
| .. versionadded:: 3.3 |
| |
| The compile language of source files when evaluating compile options. |
| See :ref:`the related boolean expression |
| <Boolean COMPILE_LANGUAGE Generator Expression>` |
| ``$<COMPILE_LANGUAGE:language>`` |
| for notes about the portability of this generator expression. |
| |
| .. genex:: $<LINK_LANGUAGE> |
| |
| .. versionadded:: 3.18 |
| |
| The link language of target when evaluating link options. |
| See :ref:`the related boolean expression |
| <Boolean LINK_LANGUAGE Generator Expression>` ``$<LINK_LANGUAGE:language>`` |
| for notes about the portability of this generator expression. |
| |
| .. note:: |
| |
| This generator expression is not supported by the link libraries |
| properties to avoid side-effects due to the double evaluation of |
| these properties. |
| |
| .. _`Target-Dependent Queries`: |
| |
| Target-Dependent Queries |
| ------------------------ |
| |
| These queries refer to a target ``tgt``. This can be any runtime artifact, |
| namely: |
| |
| * an executable target created by :command:`add_executable` |
| * a shared library target (``.so``, ``.dll`` but not their ``.lib`` import library) |
| created by :command:`add_library` |
| * a static library target created by :command:`add_library` |
| |
| In the following, "the ``tgt`` filename" means the name of the ``tgt`` |
| binary file. This has to be distinguished from "the target name", |
| which is just the string ``tgt``. |
| |
| .. genex:: $<TARGET_NAME_IF_EXISTS:tgt> |
| |
| .. versionadded:: 3.12 |
| |
| The target name ``tgt`` if the target exists, an empty string otherwise. |
| |
| Note that ``tgt`` is not added as a dependency of the target this |
| expression is evaluated on. |
| |
| .. genex:: $<TARGET_FILE:tgt> |
| |
| Full path to the ``tgt`` binary file. |
| |
| .. genex:: $<TARGET_FILE_BASE_NAME:tgt> |
| |
| .. versionadded:: 3.15 |
| |
| Base name of ``tgt``, i.e. ``$<TARGET_FILE_NAME:tgt>`` without prefix and |
| suffix. |
| For example, if the ``tgt`` filename is ``libbase.so``, the base name is ``base``. |
| |
| See also the :prop_tgt:`OUTPUT_NAME`, :prop_tgt:`ARCHIVE_OUTPUT_NAME`, |
| :prop_tgt:`LIBRARY_OUTPUT_NAME` and :prop_tgt:`RUNTIME_OUTPUT_NAME` |
| target properties and their configuration specific variants |
| :prop_tgt:`OUTPUT_NAME_<CONFIG>`, :prop_tgt:`ARCHIVE_OUTPUT_NAME_<CONFIG>`, |
| :prop_tgt:`LIBRARY_OUTPUT_NAME_<CONFIG>` and |
| :prop_tgt:`RUNTIME_OUTPUT_NAME_<CONFIG>`. |
| |
| The :prop_tgt:`<CONFIG>_POSTFIX` and :prop_tgt:`DEBUG_POSTFIX` target |
| properties can also be considered. |
| |
| Note that ``tgt`` is not added as a dependency of the target this |
| expression is evaluated on. |
| |
| .. genex:: $<TARGET_FILE_PREFIX:tgt> |
| |
| .. versionadded:: 3.15 |
| |
| Prefix of the ``tgt`` filename (such as ``lib``). |
| |
| See also the :prop_tgt:`PREFIX` target property. |
| |
| Note that ``tgt`` is not added as a dependency of the target this |
| expression is evaluated on. |
| |
| .. genex:: $<TARGET_FILE_SUFFIX:tgt> |
| |
| .. versionadded:: 3.15 |
| |
| Suffix of the ``tgt`` filename (extension such as ``.so`` or ``.exe``). |
| |
| See also the :prop_tgt:`SUFFIX` target property. |
| |
| Note that ``tgt`` is not added as a dependency of the target this |
| expression is evaluated on. |
| |
| .. genex:: $<TARGET_FILE_NAME:tgt> |
| |
| The ``tgt`` filename. |
| |
| Note that ``tgt`` is not added as a dependency of the target this |
| expression is evaluated on (see policy :policy:`CMP0112`). |
| |
| .. genex:: $<TARGET_FILE_DIR:tgt> |
| |
| Directory of the ``tgt`` binary file. |
| |
| Note that ``tgt`` is not added as a dependency of the target this |
| expression is evaluated on (see policy :policy:`CMP0112`). |
| |
| .. genex:: $<TARGET_LINKER_FILE:tgt> |
| |
| File used when linking to the ``tgt`` target. This will usually |
| be the library that ``tgt`` represents (``.a``, ``.lib``, ``.so``), |
| but for a shared library on DLL platforms, it would be the ``.lib`` |
| import library associated with the DLL. |
| |
| .. genex:: $<TARGET_LINKER_FILE_BASE_NAME:tgt> |
| |
| .. versionadded:: 3.15 |
| |
| Base name of file used to link the target ``tgt``, i.e. |
| ``$<TARGET_LINKER_FILE_NAME:tgt>`` without prefix and suffix. For example, |
| if target file name is ``libbase.a``, the base name is ``base``. |
| |
| See also the :prop_tgt:`OUTPUT_NAME`, :prop_tgt:`ARCHIVE_OUTPUT_NAME`, |
| and :prop_tgt:`LIBRARY_OUTPUT_NAME` target properties and their configuration |
| specific variants :prop_tgt:`OUTPUT_NAME_<CONFIG>`, |
| :prop_tgt:`ARCHIVE_OUTPUT_NAME_<CONFIG>` and |
| :prop_tgt:`LIBRARY_OUTPUT_NAME_<CONFIG>`. |
| |
| The :prop_tgt:`<CONFIG>_POSTFIX` and :prop_tgt:`DEBUG_POSTFIX` target |
| properties can also be considered. |
| |
| Note that ``tgt`` is not added as a dependency of the target this |
| expression is evaluated on. |
| |
| .. genex:: $<TARGET_LINKER_FILE_PREFIX:tgt> |
| |
| .. versionadded:: 3.15 |
| |
| Prefix of file used to link target ``tgt``. |
| |
| See also the :prop_tgt:`PREFIX` and :prop_tgt:`IMPORT_PREFIX` target |
| properties. |
| |
| Note that ``tgt`` is not added as a dependency of the target this |
| expression is evaluated on. |
| |
| .. genex:: $<TARGET_LINKER_FILE_SUFFIX:tgt> |
| |
| .. versionadded:: 3.15 |
| |
| Suffix of file used to link where ``tgt`` is the name of a target. |
| |
| The suffix corresponds to the file extension (such as ".so" or ".lib"). |
| |
| See also the :prop_tgt:`SUFFIX` and :prop_tgt:`IMPORT_SUFFIX` target |
| properties. |
| |
| Note that ``tgt`` is not added as a dependency of the target this |
| expression is evaluated on. |
| |
| .. genex:: $<TARGET_LINKER_FILE_NAME:tgt> |
| |
| Name of file used to link target ``tgt``. |
| |
| Note that ``tgt`` is not added as a dependency of the target this |
| expression is evaluated on (see policy :policy:`CMP0112`). |
| |
| .. genex:: $<TARGET_LINKER_FILE_DIR:tgt> |
| |
| Directory of file used to link target ``tgt``. |
| |
| Note that ``tgt`` is not added as a dependency of the target this |
| expression is evaluated on (see policy :policy:`CMP0112`). |
| |
| .. genex:: $<TARGET_SONAME_FILE:tgt> |
| |
| File with soname (``.so.3``) where ``tgt`` is the name of a target. |
| .. genex:: $<TARGET_SONAME_FILE_NAME:tgt> |
| |
| Name of file with soname (``.so.3``). |
| |
| Note that ``tgt`` is not added as a dependency of the target this |
| expression is evaluated on (see policy :policy:`CMP0112`). |
| |
| .. genex:: $<TARGET_SONAME_FILE_DIR:tgt> |
| |
| Directory of with soname (``.so.3``). |
| |
| Note that ``tgt`` is not added as a dependency of the target this |
| expression is evaluated on (see policy :policy:`CMP0112`). |
| |
| .. genex:: $<TARGET_PDB_FILE:tgt> |
| |
| .. versionadded:: 3.1 |
| |
| Full path to the linker generated program database file (.pdb) |
| where ``tgt`` is the name of a target. |
| |
| See also the :prop_tgt:`PDB_NAME` and :prop_tgt:`PDB_OUTPUT_DIRECTORY` |
| target properties and their configuration specific variants |
| :prop_tgt:`PDB_NAME_<CONFIG>` and :prop_tgt:`PDB_OUTPUT_DIRECTORY_<CONFIG>`. |
| |
| .. genex:: $<TARGET_PDB_FILE_BASE_NAME:tgt> |
| |
| .. versionadded:: 3.15 |
| |
| Base name of the linker generated program database file (.pdb) |
| where ``tgt`` is the name of a target. |
| |
| The base name corresponds to the target PDB file name (see |
| ``$<TARGET_PDB_FILE_NAME:tgt>``) without prefix and suffix. For example, |
| if target file name is ``base.pdb``, the base name is ``base``. |
| |
| See also the :prop_tgt:`PDB_NAME` target property and its configuration |
| specific variant :prop_tgt:`PDB_NAME_<CONFIG>`. |
| |
| The :prop_tgt:`<CONFIG>_POSTFIX` and :prop_tgt:`DEBUG_POSTFIX` target |
| properties can also be considered. |
| |
| Note that ``tgt`` is not added as a dependency of the target this |
| expression is evaluated on. |
| |
| .. genex:: $<TARGET_PDB_FILE_NAME:tgt> |
| |
| .. versionadded:: 3.1 |
| |
| Name of the linker generated program database file (.pdb). |
| |
| Note that ``tgt`` is not added as a dependency of the target this |
| expression is evaluated on (see policy :policy:`CMP0112`). |
| |
| .. genex:: $<TARGET_PDB_FILE_DIR:tgt> |
| |
| .. versionadded:: 3.1 |
| |
| Directory of the linker generated program database file (.pdb). |
| |
| Note that ``tgt`` is not added as a dependency of the target this |
| expression is evaluated on (see policy :policy:`CMP0112`). |
| |
| .. genex:: $<TARGET_BUNDLE_DIR:tgt> |
| |
| .. versionadded:: 3.9 |
| |
| Full path to the bundle directory (``/path/to/my.app``, |
| ``/path/to/my.framework``, or ``/path/to/my.bundle``), |
| where ``tgt`` is the name of a target. |
| |
| Note that ``tgt`` is not added as a dependency of the target this |
| expression is evaluated on (see policy :policy:`CMP0112`). |
| |
| .. genex:: $<TARGET_BUNDLE_DIR_NAME:tgt> |
| |
| .. versionadded:: 3.24 |
| |
| Name of the bundle directory (``my.app``, ``my.framework``, or |
| ``my.bundle``), where ``tgt`` is the name of a target. |
| |
| Note that ``tgt`` is not added as a dependency of the target this |
| expression is evaluated on (see policy :policy:`CMP0112`). |
| |
| .. genex:: $<TARGET_BUNDLE_CONTENT_DIR:tgt> |
| |
| .. versionadded:: 3.9 |
| |
| Full path to the bundle content directory where ``tgt`` is the name of a |
| target. For the macOS SDK it leads to ``/path/to/my.app/Contents``, |
| ``/path/to/my.framework``, or ``/path/to/my.bundle/Contents``. |
| For all other SDKs (e.g. iOS) it leads to ``/path/to/my.app``, |
| ``/path/to/my.framework``, or ``/path/to/my.bundle`` due to the flat |
| bundle structure. |
| |
| Note that ``tgt`` is not added as a dependency of the target this |
| expression is evaluated on (see policy :policy:`CMP0112`). |
| |
| .. genex:: $<TARGET_PROPERTY:tgt,prop> |
| |
| Value of the property ``prop`` on the target ``tgt``. |
| |
| Note that ``tgt`` is not added as a dependency of the target this |
| expression is evaluated on. |
| |
| .. genex:: $<TARGET_PROPERTY:prop> |
| |
| Value of the property ``prop`` on the target for which the expression |
| is being evaluated. Note that for generator expressions in |
| :ref:`Target Usage Requirements` this is the consuming target rather |
| than the target specifying the requirement. |
| |
| .. genex:: $<TARGET_RUNTIME_DLLS:tgt> |
| |
| .. versionadded:: 3.21 |
| |
| List of DLLs that the target depends on at runtime. This is determined by |
| the locations of all the ``SHARED`` targets in the target's transitive |
| dependencies. Using this generator expression on targets other than |
| executables, ``SHARED`` libraries, and ``MODULE`` libraries is an error. On |
| non-DLL platforms, it evaluates to an empty string. |
| |
| This generator expression can be used to copy all of the DLLs that a target |
| depends on into its output directory in a ``POST_BUILD`` custom command. For |
| example: |
| |
| .. code-block:: cmake |
| |
| find_package(foo CONFIG REQUIRED) # package generated by install(EXPORT) |
| |
| add_executable(exe main.c) |
| target_link_libraries(exe PRIVATE foo::foo foo::bar) |
| add_custom_command(TARGET exe POST_BUILD |
| COMMAND ${CMAKE_COMMAND} -E copy $<TARGET_RUNTIME_DLLS:exe> $<TARGET_FILE_DIR:exe> |
| COMMAND_EXPAND_LISTS |
| ) |
| |
| .. note:: |
| |
| :ref:`Imported Targets` are supported only if they know the location |
| of their ``.dll`` files. An imported ``SHARED`` library must have |
| :prop_tgt:`IMPORTED_LOCATION` set to its ``.dll`` file. See the |
| :ref:`add_library imported libraries <add_library imported libraries>` |
| section for details. Many :ref:`Find Modules` produce imported targets |
| with the ``UNKNOWN`` type and therefore will be ignored. |
| |
| .. genex:: $<INSTALL_PREFIX> |
| |
| Content of the install prefix when the target is exported via |
| :command:`install(EXPORT)`, or when evaluated in the |
| :prop_tgt:`INSTALL_NAME_DIR` property or the ``INSTALL_NAME_DIR`` argument of |
| :command:`install(RUNTIME_DEPENDENCY_SET)`, and empty otherwise. |
| |
| Output-Related Expressions |
| -------------------------- |
| |
| .. genex:: $<TARGET_NAME:...> |
| |
| Marks ``...`` as being the name of a target. This is required if exporting |
| targets to multiple dependent export sets. The ``...`` must be a literal |
| name of a target- it may not contain generator expressions. |
| |
| .. genex:: $<LINK_ONLY:...> |
| |
| .. versionadded:: 3.1 |
| |
| Content of ``...``, except while collecting :ref:`Target Usage Requirements`, |
| in which case it is the empty string. This is intended for use in an |
| :prop_tgt:`INTERFACE_LINK_LIBRARIES` target property, typically populated |
| via the :command:`target_link_libraries` command, to specify private link |
| dependencies without other usage requirements. |
| |
| .. versionadded:: 3.24 |
| ``LINK_ONLY`` may also be used in a :prop_tgt:`LINK_LIBRARIES` target |
| property. See policy :policy:`CMP0131`. |
| |
| .. genex:: $<LINK_LIBRARY:feature,library-list> |
| |
| .. versionadded:: 3.24 |
| |
| Manage how libraries are specified during the link step. |
| This expression may be used to specify how to link libraries in a target. |
| For example: |
| |
| .. code-block:: cmake |
| |
| add_library(lib1 STATIC ...) |
| add_library(lib2 ...) |
| target_link_libraries(lib2 PRIVATE "$<LINK_LIBRARY:load_archive,lib1>") |
| |
| This specify to use the ``lib1`` target with feature ``load_archive`` for |
| linking target ``lib2``. The feature must have be defined by |
| :variable:`CMAKE_<LANG>_LINK_LIBRARY_USING_<FEATURE>` variable or, if |
| :variable:`CMAKE_<LANG>_LINK_LIBRARY_USING_<FEATURE>_SUPPORTED` is false, |
| by :variable:`CMAKE_LINK_LIBRARY_USING_<FEATURE>` variable. |
| |
| .. note:: |
| |
| The evaluation of this generator expression will use, for the following |
| variables, the values defined at the level of the creation of the target: |
| |
| * :variable:`CMAKE_<LANG>_LINK_LIBRARY_USING_<FEATURE>_SUPPORTED` |
| * :variable:`CMAKE_<LANG>_LINK_LIBRARY_USING_<FEATURE>` |
| * :variable:`CMAKE_LINK_LIBRARY_USING_<FEATURE>_SUPPORTED` |
| * :variable:`CMAKE_LINK_LIBRARY_USING_<FEATURE>` |
| |
| This expression can only be used to specify link libraries (i.e. part of |
| :command:`link_libraries` or :command:`target_link_libraries` commands and |
| :prop_tgt:`LINK_LIBRARIES` or :prop_tgt:`INTERFACE_LINK_LIBRARIES` target |
| properties). |
| |
| .. note:: |
| |
| If this expression appears in the :prop_tgt:`INTERFACE_LINK_LIBRARIES` |
| property of a target, it will be included in the imported target generated |
| by :command:`install(EXPORT)` command. It is the responsibility of the |
| environment consuming this import to define the link feature used by this |
| expression. |
| |
| The ``library-list`` argument can hold CMake targets or external libraries. |
| Any CMake target of type :ref:`OBJECT <Object Libraries>` or |
| :ref:`INTERFACE <Interface Libraries>` will be ignored by this expression and |
| will be handled in the standard way. |
| |
| Each target or external library involved in the link step must have only one |
| kind of feature (the absence of feature is also incompatible with any |
| feature). For example: |
| |
| .. code-block:: cmake |
| |
| add_library(lib1 ...) |
| |
| add_library(lib2 ...) |
| target_link_libraries(lib2 PUBLIC "$<LINK_LIBRARY:feature1,lib1>") |
| |
| add_library(lib3 ...) |
| target_link_libraries(lib3 PRIVATE lib1 lib2) |
| # an error will be raised here because lib1 has two different features |
| |
| To resolve such incompatibilities, the :prop_tgt:`LINK_LIBRARY_OVERRIDE` |
| and :prop_tgt:`LINK_LIBRARY_OVERRIDE_<LIBRARY>` target properties can be |
| used. |
| |
| .. note:: |
| |
| This expression does not guarantee that the list of specified libraries |
| will be kept grouped. So, to manage constructs like ``start-group`` and |
| ``end-group``, as supported by ``GNU ld``, the :genex:`LINK_GROUP` |
| generator expression can be used. |
| |
| CMake pre-defines some features of general interest: |
| |
| .. include:: ../variable/LINK_LIBRARY_PREDEFINED_FEATURES.txt |
| |
| .. genex:: $<LINK_GROUP:feature,library-list> |
| |
| .. versionadded:: 3.24 |
| |
| Manage the grouping of libraries during the link step. |
| This expression may be used to specify how to kept groups of libraries during |
| the link of a target. |
| For example: |
| |
| .. code-block:: cmake |
| |
| add_library(lib1 STATIC ...) |
| add_library(lib2 ...) |
| target_link_libraries(lib2 PRIVATE "$<LINK_GROUP:cross_refs,lib1,external>") |
| |
| This specify to use the ``lib1`` target and ``external`` library with the |
| group feature ``cross_refs`` for linking target ``lib2``. The feature must |
| have be defined by :variable:`CMAKE_<LANG>_LINK_GROUP_USING_<FEATURE>` |
| variable or, if :variable:`CMAKE_<LANG>_LINK_GROUP_USING_<FEATURE>_SUPPORTED` |
| is false, by :variable:`CMAKE_LINK_GROUP_USING_<FEATURE>` variable. |
| |
| .. note:: |
| |
| The evaluation of this generator expression will use, for the following |
| variables, the values defined at the level of the creation of the target: |
| |
| * :variable:`CMAKE_<LANG>_LINK_GROUP_USING_<FEATURE>_SUPPORTED` |
| * :variable:`CMAKE_<LANG>_LINK_GROUP_USING_<FEATURE>` |
| * :variable:`CMAKE_LINK_GROUP_USING_<FEATURE>_SUPPORTED` |
| * :variable:`CMAKE_LINK_GROUP_USING_<FEATURE>` |
| |
| This expression can only be used to specify link libraries (i.e. part of |
| :command:`link_libraries` or :command:`target_link_libraries` commands and |
| :prop_tgt:`LINK_LIBRARIES` or :prop_tgt:`INTERFACE_LINK_LIBRARIES` target |
| properties). |
| |
| .. note:: |
| |
| If this expression appears in the :prop_tgt:`INTERFACE_LINK_LIBRARIES` |
| property of a target, it will be included in the imported target generated |
| by :command:`install(EXPORT)` command. It is the responsibility of the |
| environment consuming this import to define the link feature used by this |
| expression. |
| |
| The ``library-list`` argument can hold CMake targets or external libraries. |
| Any CMake target of type :ref:`OBJECT <Object Libraries>` or |
| :ref:`INTERFACE <Interface Libraries>` will be ignored by this expression and |
| will be handled in the standard way. |
| |
| .. note:: |
| |
| This expression is compatible with the :genex:`LINK_LIBRARY` generator |
| expression. The libraries involved in a group can be specified using the |
| :genex:`LINK_LIBRARY` generator expression. |
| |
| Each target or external library involved in the link step can be part of |
| different groups as far as these groups use the same feature, so mixing |
| different group features for the same target or library is forbidden. The |
| different groups will be part of the link step. |
| |
| .. code-block:: cmake |
| |
| add_library(lib1 ...) |
| add_library(lib2 ...) |
| |
| add_library(lib3 ...) |
| target_link_libraries(lib3 PUBLIC "$<LINK_GROUP:feature1,lib1,lib2>") |
| |
| add_library(lib4 ...) |
| target_link_libraries(lib4 PRIVATE "$<LINK_GROUP:feature1,lib1,lib3>") |
| # lib4 will be linked with the groups {lib1,lib2} and {lib1,lib3} |
| |
| add_library(lib5 ...) |
| target_link_libraries(lib5 PRIVATE "$<LINK_GROUP:feature2,lib1,lib3>") |
| # an error will be raised here because lib1 is part of two groups with |
| # different features |
| |
| When a target or an external library is involved in the link step as part of |
| a group and also as standalone, any occurrence of the standalone link item |
| will be replaced by the group or groups it belong to. |
| |
| .. code-block:: cmake |
| |
| add_library(lib1 ...) |
| add_library(lib2 ...) |
| |
| add_library(lib3 ...) |
| target_link_libraries(lib3 PUBLIC lib1) |
| |
| add_library(lib4 ...) |
| target_link_libraries(lib4 PRIVATE lib3 "$<LINK_GROUP:feature1,lib1,lib2>") |
| # lib4 will only be linked with lib3 and the group {lib1,lib2} |
| |
| This example will be "re-written" by CMake in the following form: |
| |
| .. code-block:: cmake |
| |
| add_library(lib1 ...) |
| add_library(lib2 ...) |
| |
| add_library(lib3 ...) |
| target_link_libraries(lib3 PUBLIC "$<LINK_GROUP:feature1,lib1,lib2>") |
| |
| add_library(lib4 ...) |
| target_link_libraries(lib4 PRIVATE lib3 "$<LINK_GROUP:feature1,lib1,lib2>") |
| # lib4 will only be linked with lib3 and the group {lib1,lib2} |
| |
| Be aware that the precedence of the group over the standalone link item can |
| result in some circular dependency between groups, which will raise an |
| error because circular dependencies are not allowed for groups. |
| |
| .. code-block:: cmake |
| |
| add_library(lib1A ...) |
| add_library(lib1B ...) |
| |
| add_library(lib2A ...) |
| add_library(lib2B ...) |
| |
| target_link_libraries(lib1A PUBLIC lib2A) |
| target_link_libraries(lib2B PUBLIC lib1B) |
| |
| add_library(lib ...) |
| target_link_libraries(lib3 PRIVATE "$<LINK_GROUP:feat,lib1A,lib1B>" |
| "$<LINK_GROUP:feat,lib2A,lib2B>") |
| |
| This example will be "re-written" by CMake in the following form: |
| |
| .. code-block:: cmake |
| |
| add_library(lib1A ...) |
| add_library(lib1B ...) |
| |
| add_library(lib2A ...) |
| add_library(lib2B ...) |
| |
| target_link_libraries(lib1A PUBLIC "$<LINK_GROUP:feat,lib2A,lib2B>") |
| target_link_libraries(lib2B PUBLIC "$<LINK_GROUP:feat,lib1A,lib1B>") |
| |
| add_library(lib ...) |
| target_link_libraries(lib3 PRIVATE "$<LINK_GROUP:feat,lib1A,lib1B>" |
| "$<LINK_GROUP:feat,lib2A,lib2B>") |
| |
| So, we have a circular dependency between groups ``{lib1A,lib1B}`` and |
| ``{lib2A,lib2B}``. |
| |
| CMake pre-defines some features of general interest: |
| |
| .. include:: ../variable/LINK_GROUP_PREDEFINED_FEATURES.txt |
| |
| .. genex:: $<INSTALL_INTERFACE:...> |
| |
| Content of ``...`` when the property is exported using :command:`install(EXPORT)`, |
| and empty otherwise. |
| |
| .. genex:: $<BUILD_INTERFACE:...> |
| |
| Content of ``...`` when the property is exported using :command:`export`, or |
| when the target is used by another target in the same buildsystem. Expands to |
| the empty string otherwise. |
| |
| .. genex:: $<MAKE_C_IDENTIFIER:...> |
| |
| Content of ``...`` converted to a C identifier. The conversion follows the |
| same behavior as :command:`string(MAKE_C_IDENTIFIER)`. |
| |
| .. genex:: $<TARGET_OBJECTS:objLib> |
| |
| .. versionadded:: 3.1 |
| |
| List of objects resulting from build of ``objLib``. |
| |
| .. genex:: $<SHELL_PATH:...> |
| |
| .. versionadded:: 3.4 |
| |
| Content of ``...`` converted to shell path style. For example, slashes are |
| converted to backslashes in Windows shells and drive letters are converted |
| to posix paths in MSYS shells. The ``...`` must be an absolute path. |
| |
| .. versionadded:: 3.14 |
| The ``...`` may be a :ref:`semicolon-separated list <CMake Language Lists>` |
| of paths, in which case each path is converted individually and a result |
| list is generated using the shell path separator (``:`` on POSIX and |
| ``;`` on Windows). Be sure to enclose the argument containing this genex |
| in double quotes in CMake source code so that ``;`` does not split arguments. |
| |
| .. genex:: $<OUTPUT_CONFIG:...> |
| |
| .. versionadded:: 3.20 |
| |
| Only valid in :command:`add_custom_command` and :command:`add_custom_target` |
| as the outer-most generator expression in an argument. |
| With the :generator:`Ninja Multi-Config` generator, generator expressions |
| in ``...`` are evaluated using the custom command's "output config". |
| With other generators, the content of ``...`` is evaluated normally. |
| |
| .. genex:: $<COMMAND_CONFIG:...> |
| |
| .. versionadded:: 3.20 |
| |
| Only valid in :command:`add_custom_command` and :command:`add_custom_target` |
| as the outer-most generator expression in an argument. |
| With the :generator:`Ninja Multi-Config` generator, generator expressions |
| in ``...`` are evaluated using the custom command's "command config". |
| With other generators, the content of ``...`` is evaluated normally. |
| |
| Debugging |
| ========= |
| |
| Since generator expressions are evaluated during generation of the buildsystem, |
| and not during processing of ``CMakeLists.txt`` files, it is not possible to |
| inspect their result with the :command:`message()` command. |
| |
| One possible way to generate debug messages is to add a custom target, |
| |
| .. code-block:: cmake |
| |
| add_custom_target(genexdebug COMMAND ${CMAKE_COMMAND} -E echo "$<...>") |
| |
| The shell command ``make genexdebug`` (invoked after execution of ``cmake``) |
| would then print the result of ``$<...>``. |
| |
| Another way is to write debug messages to a file: |
| |
| .. code-block:: cmake |
| |
| file(GENERATE OUTPUT filename CONTENT "$<...>") |