CMAKE-GENERATOR-EXPRESSIONS(7) CMake CMAKE-GENERATOR-EXPRESSIONS(7)NAMEcmake-generator-expressions - CMake Generator Expressions
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 proper‐
ties, such as LINK_LIBRARIES, INCLUDE_DIRECTORIES, COMPILE_DEFINITIONS
and others. They may also be used when using commands to populate
those properties, such as target_link_libraries(), tar‐
get_include_directories(), target_compile_definitions() and others.
This means that they enable conditional linking, conditional defini‐
tions used when compiling, and conditional include directories and
more. The conditions may be based on the build configuration, target
properties, platform information or any other queryable information.
LOGICAL EXPRESSIONS
Logical expressions are used to create conditional output. The basic
expressions are the 0 and 1 expressions. Because other logical expres‐
sions evaluate to either 0 or 1, they can be composed to create condi‐
tional output:
$<$<CONFIG:Debug>:DEBUG_MODE>
expands to DEBUG_MODE when the Debug configuration is used, and other‐
wise expands to nothing.
Available logical expressions are:
$<BOOL:...>
1 if the ... is true, else 0
$<AND:?[,?]...>
1 if all ? are 1, else 0
The ? must always be either 0 or 1 in boolean expressions.
$<OR:?[,?]...>
0 if all ? are 0, else 1
$<NOT:?>
0 if ? is 1, else 1
$<STREQUAL:a,b>
1 if a is STREQUAL b, else 0
$<EQUAL:a,b>
1 if a is EQUAL b in a numeric comparison, else 0
$<CONFIG:cfg>
1 if config is cfg, else 0. This is a case-insensitive compari‐
son. The mapping in MAP_IMPORTED_CONFIG_<CONFIG> is also con‐
sidered by this expression when it is evaluated on a property on
an IMPORTED target.
$<PLATFORM_ID:comp>
1 if the CMake-id of the platform matches comp, otherwise 0.
$<C_COMPILER_ID:comp>
1 if the CMake-id of the C compiler matches comp, otherwise 0.
$<CXX_COMPILER_ID:comp>
1 if the CMake-id of the CXX compiler matches comp, otherwise 0.
$<VERSION_GREATER:v1,v2>
1 if v1 is a version greater than v2, else 0.
$<VERSION_LESS:v1,v2>
1 if v1 is a version less than v2, else 0.
$<VERSION_EQUAL:v1,v2>
1 if v1 is the same version as v2, else 0.
$<C_COMPILER_VERSION:ver>
1 if the version of the C compiler matches ver, otherwise 0.
$<CXX_COMPILER_VERSION:ver>
1 if the version of the CXX compiler matches ver, otherwise 0.
$<TARGET_POLICY:pol>
1 if the policy pol 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.
$<COMPILE_FEATURES:feature[,feature]...>
1 if all of the feature features are available for the 'head'
target, and 0 otherwise. If this expression is used while evalu‐
ating the link implementation of a target and if any dependency
transitively increases the required C_STANDARD or CXX_STANDARD
for the 'head' target, an error is reported. See the cmake-com‐
pile-features(7) manual for information on compile features and
a list of supported compilers.
$<COMPILE_LANGUAGE:lang>
1 when the language used for compilation unit matches lang, oth‐
erwise 0. This expression used to specify compile options for
source files of a particular language in a target. For example,
to specify the use of the -fno-exceptions compile option (com‐
piler id checks elided):
add_executable(myapp main.cpp foo.c bar.cpp)
target_compile_options(myapp
PRIVATE $<$<COMPILE_LANGUAGE:CXX>:-fno-exceptions>
)
This generator expression has limited use because it is not pos‐
sible to use it with the Visual Studio generators. Portable
buildsystems would not use this expression, and would create
separate libraries for each source file language instead:
add_library(myapp_c foo.c)
add_library(myapp_cxx foo.c)
target_compile_options(myapp_cxx PUBLIC -fno-exceptions)
add_executable(myapp main.cpp)
target_link_libraries(myapp myapp_c myapp_cxx)
The Makefile and Ninja based generators can also use this
expression to specify compile-language specific compile defini‐
tions and include directories:
add_executable(myapp main.cpp foo.c bar.cpp)
target_compile_definitions(myapp
PRIVATE $<$<COMPILE_LANGUAGE:CXX>:COMPILING_CXX>
)
target_include_directories(myapp
PRIVATE $<$<COMPILE_LANGUAGE:CXX>:/opt/foo/cxx_headers>
)
INFORMATIONAL EXPRESSIONS
These expressions expand to some information. The information may be
used directly, eg:
include_directories(/usr/include/$<CXX_COMPILER_ID>/)
expands to /usr/include/GNU/ or /usr/include/Clang/ etc, depending on
the Id of the compiler.
These expressions may also may be combined with logical expressions:
$<$<VERSION_LESS:$<CXX_COMPILER_VERSION>,4.2.0>:OLD_COMPILER>
expands to OLD_COMPILER if the CMAKE_CXX_COMPILER_VERSION is less than
4.2.0.
Available informational expressions are:
$<CONFIGURATION>
Configuration name. Deprecated. Use CONFIG instead.
$<CONFIG>
Configuration name
$<PLATFORM_ID>
The CMake-id of the platform. See also the CMAKE_SYSTEM_NAME
variable.
$<C_COMPILER_ID>
The CMake-id of the C compiler used. See also the
CMAKE_<LANG>_COMPILER_ID variable.
$<CXX_COMPILER_ID>
The CMake-id of the CXX compiler used. See also the
CMAKE_<LANG>_COMPILER_ID variable.
$<C_COMPILER_VERSION>
The version of the C compiler used. See also the
CMAKE_<LANG>_COMPILER_VERSION variable.
$<CXX_COMPILER_VERSION>
The version of the CXX compiler used. See also the
CMAKE_<LANG>_COMPILER_VERSION variable.
$<TARGET_FILE:tgt>
Full path to main file (.exe, .so.1.2, .a) where tgt is the name
of a target.
$<TARGET_FILE_NAME:tgt>
Name of main file (.exe, .so.1.2, .a).
$<TARGET_FILE_DIR:tgt>
Directory of main file (.exe, .so.1.2, .a).
$<TARGET_LINKER_FILE:tgt>
File used to link (.a, .lib, .so) where tgt is the name of a
target.
$<TARGET_LINKER_FILE_NAME:tgt>
Name of file used to link (.a, .lib, .so).
$<TARGET_LINKER_FILE_DIR:tgt>
Directory of file used to link (.a, .lib, .so).
$<TARGET_SONAME_FILE:tgt>
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).
$<TARGET_SONAME_FILE_DIR:tgt>
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.
See also the PDB_NAME and PDB_OUTPUT_DIRECTORY target properties
and their configuration specific variants PDB_NAME_<CONFIG> and
PDB_OUTPUT_DIRECTORY_<CONFIG>.
$<TARGET_PDB_FILE_NAME:tgt>
Name of the linker generated program database file (.pdb).
$<TARGET_PDB_FILE_DIR:tgt>
Directory of the linker generated program database file (.pdb).
$<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.
$<TARGET_PROPERTY:prop>
Value of the property prop on the target on which the generator
expression is evaluated.
$<INSTALL_PREFIX>
Content of the install prefix when the target is exported via
install(EXPORT) and empty otherwise.
$<COMPILE_LANGUAGE>
The compile language of source files when evaluating compile
options. See the unary version for notes about portability of
this generator expression.
OUTPUT EXPRESSIONS
These expressions generate output, in some cases depending on an input.
These expressions may be combined with other expressions for informa‐
tion or logical comparison:
-I$<JOIN:$<TARGET_PROPERTY:INCLUDE_DIRECTORIES>, -I>
generates a string of the entries in the INCLUDE_DIRECTORIES target
property with each entry preceeded by -I. Note that a more-complete use
in this situation would require first checking if the INCLUDE_DIRECTO‐
RIES property is non-empty:
$<$<BOOL:${prop}>:-I$<JOIN:${prop}, -I>>
where ${prop} refers to a helper variable:
set(prop "$<TARGET_PROPERTY:INCLUDE_DIRECTORIES>")
Available output expressions are:
$<0:...>
Empty string (ignores ...)
$<1:...>
Content of ...
$<JOIN:list,...>
Joins the list with the content of ...
$<ANGLE-R>
A literal >. Used to compare strings which contain a > for exam‐
ple.
$<COMMA>
A literal ,. Used to compare strings which contain a , for exam‐
ple.
$<SEMICOLON>
A literal ;. Used to prevent list expansion on an argument with
;.
$<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.
$<LINK_ONLY:...>
Content of ... except when evaluated in a link interface while
propagating Target Usage Requirements, in which case it is the
empty string. Intended for use only in an INTER‐
FACE_LINK_LIBRARIES target property, perhaps via the tar‐
get_link_libraries() command, to specify private link dependen‐
cies without other usage requirements.
$<INSTALL_INTERFACE:...>
Content of ... when the property is exported using
install(EXPORT), and empty otherwise.
$<BUILD_INTERFACE:...>
Content of ... when the property is exported using export(), or
when the target is used by another target in the same buildsys‐
tem. Expands to the empty string otherwise.
$<LOWER_CASE:...>
Content of ... converted to lower case.
$<UPPER_CASE:...>
Content of ... converted to upper case.
$<MAKE_C_IDENTIFIER:...>
Content of ... converted to a C identifier.
$<TARGET_OBJECTS:objLib>
List of objects resulting from build of objLib. objLib must be
an object of type OBJECT_LIBRARY. This expression may only be
used in the sources of add_library() and add_executable() com‐
mands.
$<SHELL_PATH:...>
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.
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3.4.2 February 17, 2016CMAKE-GENERATOR-EXPRESSIONS(7)