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Diffstat (limited to 'Help/manual/cmake-generator-expressions.7.rst')
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1 files changed, 151 insertions, 31 deletions
diff --git a/Help/manual/cmake-generator-expressions.7.rst b/Help/manual/cmake-generator-expressions.7.rst index 691481b..72de4ac 100644 --- a/Help/manual/cmake-generator-expressions.7.rst +++ b/Help/manual/cmake-generator-expressions.7.rst @@ -259,6 +259,109 @@ Variable Queries add_executable(myapp main.cpp) target_link_libraries(myapp myapp_c myapp_cxx) +.. _`Boolean LINK_LANGUAGE Generator Expression`: + +``$<LINK_LANG_AND_ID:language,compiler_ids>`` + ``1`` when the language used for link step matches ``language`` and the + CMake's compiler id of the language linker matches any one of the entries + in ``compiler_ids``, otherwise ``0``. This expression is a short form for the + combination of ``$<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>` + ``$<LINK_LANGUAGE:language>`` for constraints about the usage of this + generator expression. + +``$<LINK_LANGUAGE:languages>`` + ``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. + String-Valued Generator Expressions =================================== @@ -450,22 +553,41 @@ Variable Queries <Boolean COMPILE_LANGUAGE Generator Expression>` ``$<COMPILE_LANGUAGE:language>`` for notes about the portability of this generator expression. +``$<LINK_LANGUAGE>`` + The link language of target when evaluating link options. + See :ref:`the related boolean expression + <Boolean LINK_LANGUAGE Generator Expression>` ``$<LINK_LANGUAGE:language>`` + for notes about the portability of this generator expression. + + .. note:: + + This generator expression is not supported by the link libraries + properties to avoid side-effects due to the double evaluation of + these properties. Target-Dependent Queries ------------------------ +These queries refer to a target ``tgt``. This can be any runtime artifact, +namely: + +* an executable target created by :command:`add_executable` +* a shared library target (``.so``, ``.dll`` but not their ``.lib`` import library) + created by :command:`add_library` +* a static library target created by :command:`add_library` + +In the following, "the ``tgt`` filename" means the name of the ``tgt`` +binary file. This has to be distinguished from "the target name", +which is just the string ``tgt``. + ``$<TARGET_NAME_IF_EXISTS:tgt>`` - Expands to the ``tgt`` if the given target exists, an empty string - otherwise. + The target name ``tgt`` if the target exists, an empty string otherwise. ``$<TARGET_FILE:tgt>`` - Full path to main file (.exe, .so.1.2, .a) where ``tgt`` is the name of a - target. + Full path to the ``tgt`` binary file. ``$<TARGET_FILE_BASE_NAME:tgt>`` - Base name of main file where ``tgt`` is the name of a target. - - The base name corresponds to the target file name (see - ``$<TARGET_FILE_NAME:tgt>``) without prefix and suffix. For example, if - target file name is ``libbase.so``, the base name is ``base``. + Base name of ``tgt``, i.e. ``$<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` @@ -480,32 +602,31 @@ Target-Dependent Queries Note that ``tgt`` is not added as a dependency of the target this expression is evaluated on. ``$<TARGET_FILE_PREFIX:tgt>`` - Prefix of main file where ``tgt`` is the name of a target. + Prefix of the ``tgt`` filename (such as ``lib``). See also the :prop_tgt:`PREFIX` target property. Note that ``tgt`` is not added as a dependency of the target this expression is evaluated on. ``$<TARGET_FILE_SUFFIX:tgt>`` - Suffix of main file where ``tgt`` is the name of a target. - - The suffix corresponds to the file extension (such as ".so" or ".exe"). + 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. ``$<TARGET_FILE_NAME:tgt>`` - Name of main file (.exe, .so.1.2, .a). + The ``tgt`` filename. ``$<TARGET_FILE_DIR:tgt>`` - Directory of main file (.exe, .so.1.2, .a). + Directory of the ``tgt`` binary file. ``$<TARGET_LINKER_FILE:tgt>`` - File used to link (.a, .lib, .so) where ``tgt`` is the name of a target. + File used when linking to the ``tgt`` target. This will usually + be the library that ``tgt`` represents (``.a``, ``.lib``, ``.so``), + but for a shared library on DLL platforms, it would be the ``.lib`` + import library associated with the DLL. ``$<TARGET_LINKER_FILE_BASE_NAME:tgt>`` - Base name of file used to link where ``tgt`` is the name of a target. - - The base name corresponds to the target linker file name (see - ``$<TARGET_LINKER_FILE_NAME:tgt>``) without prefix and suffix. For example, + Base name of file used to link the target ``tgt``, i.e. + ``$<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`, @@ -520,7 +641,7 @@ Target-Dependent Queries Note that ``tgt`` is not added as a dependency of the target this expression is evaluated on. ``$<TARGET_LINKER_FILE_PREFIX:tgt>`` - Prefix of file used to link where ``tgt`` is the name of a target. + Prefix of file used to link target ``tgt``. See also the :prop_tgt:`PREFIX` and :prop_tgt:`IMPORT_PREFIX` target properties. @@ -538,15 +659,15 @@ Target-Dependent Queries Note that ``tgt`` is not added as a dependency of the target this expression is evaluated on. ``$<TARGET_LINKER_FILE_NAME:tgt>`` - Name of file used to link (.a, .lib, .so). + Name of file used to link target ``tgt``. ``$<TARGET_LINKER_FILE_DIR:tgt>`` - Directory of file used to link (.a, .lib, .so). + Directory of file used to link target ``tgt``. ``$<TARGET_SONAME_FILE:tgt>`` - File with soname (.so.3) where ``tgt`` is the name of a target. + File with soname (``.so.3``) where ``tgt`` is the name of a target. ``$<TARGET_SONAME_FILE_NAME:tgt>`` - Name of file with soname (.so.3). + Name of file with soname (``.so.3``). ``$<TARGET_SONAME_FILE_DIR:tgt>`` - Directory of with soname (.so.3). + Directory of with soname (``.so.3``). ``$<TARGET_PDB_FILE:tgt>`` Full path to the linker generated program database file (.pdb) where ``tgt`` is the name of a target. @@ -589,11 +710,10 @@ Target-Dependent Queries Note that ``tgt`` is not added as a dependency of the target this expression is evaluated on. ``$<TARGET_PROPERTY:prop>`` - Value of the property ``prop`` on the target on which the generator - expression is evaluated. Note that for generator expressions in - :ref:`Target Usage Requirements` this is the value of the property - on the consuming target rather than the target specifying the - requirement. + 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. ``$<INSTALL_PREFIX>`` Content of the install prefix when the target is exported via :command:`install(EXPORT)`, or when evaluated in |