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CMAKE-GENERATOR-EXPRESSIONS(7) |
CMake |
CMAKE-GENERATOR-EXPRESSIONS(7) |
cmake-generator-expressions - CMake Generator Expressions
Generator expressions are evaluated during build system generation
to produce information specific to each build configuration. They have the
form $<...>. For example:
target_include_directories(tgt PRIVATE /opt/include/$<CXX_COMPILER_ID>)
This would expand to /opt/include/GNU,
/opt/include/Clang, etc. depending on the C++ compiler used.
Generator expressions are allowed in the context of many target
properties, 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(), target_include_directories(),
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 can be nested:
target_compile_definitions(tgt PRIVATE
$<$<VERSION_LESS:$<CXX_COMPILER_VERSION>,4.2.0>:OLD_COMPILER>
)
The above would expand to OLD_COMPILER if the
CMAKE_CXX_COMPILER_VERSION is less than 4.2.0.
Generator expressions are typically parsed after command
arguments. If a generator expression contains spaces, new lines, semicolons
or other characters that may be interpreted as command argument separators,
the whole expression should be surrounded by quotes when passed to a
command. Failure to do so may result in the expression being split and it
may no longer be recognized as a generator expression.
When using add_custom_command() or
add_custom_target(), use the VERBATIM and
COMMAND_EXPAND_LISTS options to obtain robust argument splitting and
quoting.
# WRONG: Embedded space will be treated as an argument separator.
# This ends up not being seen as a generator expression at all.
add_custom_target(run_some_tool
COMMAND some_tool -I$<JOIN:$<TARGET_PROPERTY:tgt,INCLUDE_DIRECTORIES>, -I>
VERBATIM
)
# Better, but still not robust. Quotes prevent the space from splitting the
# expression. However, the tool will receive the expanded value as a single
# argument.
add_custom_target(run_some_tool
COMMAND some_tool "-I$<JOIN:$<TARGET_PROPERTY:tgt,INCLUDE_DIRECTORIES>, -I>"
VERBATIM
)
# Nearly correct. Using a semicolon to separate arguments and adding the
# COMMAND_EXPAND_LISTS option means that paths with spaces will be handled
# correctly. Quoting the whole expression ensures it is seen as a generator
# expression. But if the target property is empty, we will get a bare -I
# with nothing after it.
add_custom_target(run_some_tool
COMMAND some_tool "-I$<JOIN:$<TARGET_PROPERTY:tgt,INCLUDE_DIRECTORIES>,;-I>"
COMMAND_EXPAND_LISTS
VERBATIM
)
Using variables to build up a more complex generator expression is
also a good way to reduce errors and improve readability. The above example
can be improved further like so:
# The $<BOOL:...> check prevents adding anything if the property is empty,
# assuming the property value cannot be one of CMake's false constants.
set(prop "$<TARGET_PROPERTY:tgt,INCLUDE_DIRECTORIES>")
add_custom_target(run_some_tool
COMMAND some_tool "$<$<BOOL:${prop}>:-I$<JOIN:${prop},;-I>>"
COMMAND_EXPAND_LISTS
VERBATIM
)
Finally, the above example can be expressed in a more simple and
robust way using an alternate generator expression:
add_custom_target(run_some_tool
COMMAND some_tool "$<LIST:TRANSFORM,$<TARGET_PROPERTY:tgt,INCLUDE_DIRECTORIES>,PREPEND,-I>"
COMMAND_EXPAND_LISTS
VERBATIM
)
A common mistake is to try to split a generator expression across
multiple lines with indenting:
# WRONG: New lines and spaces all treated as argument separators, so the
# generator expression is split and not recognized correctly.
target_compile_definitions(tgt PRIVATE
$<$<AND:
$<CXX_COMPILER_ID:GNU>,
$<VERSION_GREATER_EQUAL:$<CXX_COMPILER_VERSION>,5>
>:HAVE_5_OR_LATER>
)
Again, use helper variables with well-chosen names to build up a
readable expression instead:
set(is_gnu "$<CXX_COMPILER_ID:GNU>")
set(v5_or_later "$<VERSION_GREATER_EQUAL:$<CXX_COMPILER_VERSION>,5>")
set(meet_requirements "$<AND:${is_gnu},${v5_or_later}>")
target_compile_definitions(tgt PRIVATE
"$<${meet_requirements}:HAVE_5_OR_LATER>"
)
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 message() command. One
possible way to generate debug messages is to add a custom target:
add_custom_target(genexdebug COMMAND ${CMAKE_COMMAND} -E echo "$<...>")
After running cmake, you can then build the
genexdebug target to print the result of the $<...>
expression (i.e. run the command cmake --build ... --target
genexdebug).
Another way is to write debug messages to a file with
file(GENERATE):
file(GENERATE OUTPUT filename CONTENT "$<...>")
NOTE:
This reference deviates from most of the CMake
documentation in that it omits angular brackets <...> around
placeholders like condition, string, target, etc. This is
to prevent an opportunity for those placeholders to be misinterpreted as
generator expressions.
A fundamental category of generator expressions relates to
conditional logic. Two forms of conditional generator expressions are
supported:
- $<condition:true_string>
- Evaluates to true_string if condition is 1, or an
empty string if condition evaluates to 0. Any other value
for condition results in an error.
- $<IF:condition,true_string,false_string>
- New in version 3.8.
Evaluates to true_string if condition is
1, or false_string if condition is 0. Any
other value for condition results in an error.
New in version 3.28: This generator expression short-circuits
such that generator expressions in false_string will not evaluate
when condition is 1, and generator expressions in
true_string will not evaluate when condition is 0.
Typically, the condition is itself a generator expression.
For instance, the following expression expands to DEBUG_MODE when the
Debug configuration is used, and the empty string for all other
configurations:
$<$<CONFIG:Debug>:DEBUG_MODE>
Boolean-like condition values other than 1 or
0 can be handled by wrapping them with the $<BOOL:...>
generator expression:
- $<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.
The $<BOOL:...> generator expression is often used
when a condition is provided by a CMake variable:
$<$<BOOL:${HAVE_SOME_FEATURE}>:-DENABLE_SOME_FEATURE>
The common boolean logic operators are supported:
- $<AND:conditions>
- where conditions is a comma-separated list of boolean expressions,
all of which must evaluate to either 1 or 0. The whole
expression evaluates to 1 if all conditions are 1. If any
condition is 0, the whole expression evaluates to 0.
- $<OR:conditions>
- where conditions is a comma-separated list of boolean expressions.
all of which must evaluate to either 1 or 0. The whole
expression evaluates to 1 if at least one of the conditions
is 1. If all conditions evaluate to 0, the whole
expression evaluates to 0.
- $<NOT:condition>
- condition must be 0 or 1. The result of the
expression is 0 if condition is 1, else
1.
New in version 3.28: Logical operators short-circuit such that
generator expressions in the arguments list will not be evaluated once a
return value can be determined.
CMake supports a variety of generator expressions that compare
things. This section covers the primary and most widely used comparison
types. Other more specific comparison types are documented in their own
separate sections further below.
- $<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 string transforming generator expression. For
example, the following evaluates to 1 if ${foo} is any of
BAR, Bar, bar, etc.
$<STREQUAL:$<UPPER_CASE:${foo}>,BAR>
- $<EQUAL:value1,value2>
- 1 if value1 and value2 are numerically equal, else
0.
- $<VERSION_LESS:v1,v2>
- 1 if v1 is a version less than v2, else
0.
- $<VERSION_GREATER:v1,v2>
- 1 if v1 is a version greater than v2, else
0.
- $<VERSION_EQUAL:v1,v2>
- 1 if v1 is the same version as v2, else
0.
- $<VERSION_LESS_EQUAL:v1,v2>
- New in version 3.7.
1 if v1 is a version less than or equal to
v2, else 0.
- $<VERSION_GREATER_EQUAL:v1,v2>
- New in version 3.7.
1 if v1 is a version greater than or equal to
v2, else 0.
- $<LOWER_CASE:string>
- Content of string converted to lower case.
- $<UPPER_CASE:string>
- Content of string converted to upper case.
- $<MAKE_C_IDENTIFIER:...>
- Content of ... converted to a C identifier. The conversion follows
the same behavior as string(MAKE_C_IDENTIFIER).
Most of the expressions in this section are closely associated
with the list() command, providing the same capabilities, but in the
form of a generator expression.
In each of the following list-related generator expressions, the
list must not contain any commas if that generator expression expects
something to be provided after the list. For example, the expression
$<LIST:FIND,list,value> requires a value after the
list. Since a comma is used to separate the list and the
value, the list cannot itself contain a comma. This
restriction does not apply to the list() command, it is specific to
the list-handling generator expressions only.
- $<IN_LIST:string,list>
- New in version 3.12.
1 if string is an item in the
semicolon-separated list, else 0. It uses case-sensitive
comparisons.
- $<LIST:LENGTH,list>
- New in version 3.27.
The number of items in the list.
- $<LIST:GET,list,index,...>
- New in version 3.27.
Expands to the list of items specified by indices from the
list.
- $<LIST:SUBLIST,list,begin,length>
- New in version 3.27.
A sublist of the given list. If length is 0, an
empty list will be returned. If length is -1 or the list is
smaller than begin + length, the remaining items of the list
starting at begin will be returned.
- $<LIST:FIND,list,value>
- New in version 3.27.
The index of the first item in list with the specified
value, or -1 if value is not in the list.
- $<LIST:JOIN,list,glue>
- New in version 3.27.
Converts list to a single string with the content of
the glue string inserted between each item. This is conceptually
the same operation as $<JOIN:list,glue>, but the two have
different behavior with regard to empty items.
$<LIST:JOIN,list,glue> preserves all empty items, whereas
$<JOIN:list,glue> drops all empty items from the list.
- $<LIST:APPEND,list,item,...>
- New in version 3.27.
The list with each item appended. Multiple items
should be separated by commas.
- $<LIST:PREPEND,list,item,...>
- New in version 3.27.
The list with each item inserted at the
beginning. If there are multiple items, they should be separated by
commas, and the order of the prepended items will be preserved.
- $<LIST:INSERT,list,index,item,...>
- New in version 3.27.
The list with the item (or multiple items)
inserted at the specified index. Multiple items should be
separated by commas.
It is an error to specify an out-of-range index. Valid
indexes are 0 to N, where N is the length of the list, inclusive. An
empty list has length 0.
- $<LIST:POP_BACK,list>
- New in version 3.27.
The list with the last item removed.
- $<LIST:POP_FRONT,list>
- New in version 3.27.
The list with the first item removed.
- $<LIST:REMOVE_ITEM,list,value,...>
- New in version 3.27.
The list with all instances of the given value
(or values) removed. If multiple values are given, they should be
separated by commas.
- $<LIST:REMOVE_AT,list,index,...>
- New in version 3.27.
The list with the item at each given index
removed.
- $<LIST:REMOVE_DUPLICATES,list>
- New in version 3.27.
The list with all duplicated items removed. The
relative order of items is preserved, but if duplicates are encountered,
only the first instance is preserved. The result is the same as
$<REMOVE_DUPLICATES:list>.
- $<LIST:FILTER,list,INCLUDE|EXCLUDE,regex>
- New in version 3.27.
A list of items from the list which match
(INCLUDE) or do not match (EXCLUDE) the regular expression
regex. The result is the same as
$<FILTER:list,INCLUDE|EXCLUDE,regex>.
- $<LIST:TRANSFORM,list,ACTION[,SELECTOR]>
- New in version 3.27.
The list transformed by applying an ACTION to
all or, by specifying a SELECTOR, to the selected list items.
NOTE:
The TRANSFORM sub-command does not change the
number of items in the list. If a SELECTOR is specified, only some
items will be changed, the other ones will remain the same as before the
transformation.
ACTION specifies the action to apply to the items of the
list. The actions have exactly the same semantics as for the
list(TRANSFORM) command. ACTION must be one of the
following:
- APPEND,
PREPEND
- Append, prepend specified value to each item of the list.
$<LIST:TRANSFORM,list,(APPEND|PREPEND),value[,SELECTOR]>
- TOLOWER,
TOUPPER
- Convert each item of the list to lower, upper characters.
$<LIST:TRANSFORM,list,(TOLOWER|TOUPPER)[,SELECTOR]>
- STRIP
- Remove leading and trailing spaces from each item of the list.
$<LIST:TRANSFORM,list,STRIP[,SELECTOR]>
- REPLACE:
- Match the regular expression as many times as possible and substitute the
replacement expression for the match for each item of the list.
$<LIST:TRANSFORM,list,REPLACE,regular_expression,replace_expression[,SELECTOR]>
SELECTOR determines which items of the list will be
transformed. Only one type of selector can be specified at a time. When
given, SELECTOR must be one of the following:
- AT
- Specify a list of indexes.
$<LIST:TRANSFORM,list,ACTION,AT,index[,index...]>
- FOR
- Specify a range with, optionally, an increment used to iterate over the
range.
$<LIST:TRANSFORM,list,ACTION,FOR,start,stop[,step]>
- REGEX
- Specify a regular expression. Only items matching the regular expression
will be transformed.
$<LIST:TRANSFORM,list,ACTION,REGEX,regular_expression>
- $<JOIN:list,glue>
- Joins the list with the content of the glue string inserted
between each item. This is conceptually the same operation as
$<LIST:JOIN,list,glue>, but the two have different behavior
with regard to empty items. $<LIST:JOIN,list,glue> preserves
all empty items, whereas $<JOIN,list,glue> drops all empty
items from the list.
- $<REMOVE_DUPLICATES:list>
- New in version 3.15.
Removes duplicated items in the given list. The
relative order of items is preserved, and if duplicates are encountered,
only the first instance is retained. The result is the same as
$<LIST:REMOVE_DUPLICATES,list>.
- $<FILTER:list,INCLUDE|EXCLUDE,regex>
- New in version 3.15.
Includes or removes items from list that match the
regular expression regex. The result is the same as
$<LIST:FILTER,list,INCLUDE|EXCLUDE,regex>.
- $<LIST:REVERSE,list>
- New in version 3.27.
The list with the items in reverse order.
- $<LIST:SORT,list[,(COMPARE:option|CASE:option|ORDER:option)]...>
- New in version 3.27.
The list sorted according to the specified options.
Use one of the COMPARE options to select the comparison
method for sorting:
- STRING
- Sorts a list of strings alphabetically. This is the default behavior if
the COMPARE option is not given.
- FILE_BASENAME
- Sorts a list of file paths by their basenames.
- NATURAL
- Sorts a list of strings using natural order (see the man page for
strverscmp(3)), such that contiguous digits are compared as whole
numbers. For example, the following list 10.0 1.1 2.1 8.0 2.0 3.1
will be sorted as 1.1 2.0 2.1 3.1 8.0 10.0 if the NATURAL
comparison is selected, whereas it will be sorted as 1.1 10.0 2.0 2.1
3.1 8.0 with the STRING comparison.
Use one of the CASE options to select a case-sensitive or
case-insensitive sort mode:
- SENSITIVE
- List items are sorted in a case-sensitive manner. This is the default
behavior if the CASE option is not given.
- INSENSITIVE
- List items are sorted in a case-insensitive manner. The order of items
which differ only by upper/lowercase is not specified.
To control the sort order, one of the ORDER options can be
given:
- ASCENDING
- Sorts the list in ascending order. This is the default behavior when the
ORDER option is not given.
- DESCENDING
- Sorts the list in descending order.
Options can be specified in any order, but it is an error to
specify the same option multiple times.
$<LIST:SORT,list,CASE:SENSITIVE,COMPARE:STRING,ORDER:DESCENDING>
Most of the expressions in this section are closely associated
with the cmake_path() command, providing the same capabilities, but
in the form of a generator expression.
For all generator expressions in this section, paths are expected
to be in cmake-style format. The $<PATH:CMAKE_PATH> generator
expression can be used to convert a native path to a cmake-style one.
- $<PATH_EQUAL:path1,path2>
- New in version 3.24.
Compares the lexical representations of two paths. No
normalization is performed on either path. Returns 1 if the paths
are equal, 0 otherwise.
See cmake_path(COMPARE) for more details.
These expressions provide the generation-time capabilities
equivalent to the Query options of the cmake_path() command.
All paths are expected to be in cmake-style format.
- $<PATH:HAS_*,path>
- New in version 3.24.
The following operations return 1 if the particular
path component is present, 0 otherwise. See Path Structure And
Terminology for the meaning of each path component.
$<PATH:HAS_ROOT_NAME,path>
$<PATH:HAS_ROOT_DIRECTORY,path>
$<PATH:HAS_ROOT_PATH,path>
$<PATH:HAS_FILENAME,path>
$<PATH:HAS_EXTENSION,path>
$<PATH:HAS_STEM,path>
$<PATH:HAS_RELATIVE_PART,path>
$<PATH:HAS_PARENT_PATH,path>
Note the following special cases:
- For HAS_ROOT_PATH, a true result will only be returned if at least
one of root-name or root-directory is non-empty.
- For HAS_PARENT_PATH, the root directory is also considered to have
a parent, which will be itself. The result is true except if the path
consists of just a filename.
- $<PATH:IS_ABSOLUTE,path>
- New in version 3.24.
Returns 1 if the path is absolute, 0
otherwise.
- $<PATH:IS_RELATIVE,path>
- New in version 3.24.
This will return the opposite of IS_ABSOLUTE.
- $<PATH:IS_PREFIX[,NORMALIZE],path,input>
- New in version 3.24.
Returns 1 if path is the prefix of input,
0 otherwise.
When the NORMALIZE option is specified, path and
input are normalized before the check.
These expressions provide the generation-time capabilities
equivalent to the Decomposition options of the cmake_path()
command. All paths are expected to be in cmake-style format.
- $<PATH:GET_*,...>
- New in version 3.24.
The following operations retrieve a different component or
group of components from a path. See Path Structure And
Terminology for the meaning of each path component.
Changed in version 3.27: All operations now accept a list of
paths as argument. When a list of paths is specified, the operation will
be applied to each path.
$<PATH:GET_ROOT_NAME,path...>
$<PATH:GET_ROOT_DIRECTORY,path...>
$<PATH:GET_ROOT_PATH,path...>
$<PATH:GET_FILENAME,path...>
$<PATH:GET_EXTENSION[,LAST_ONLY],path...>
$<PATH:GET_STEM[,LAST_ONLY],path...>
$<PATH:GET_RELATIVE_PART,path...>
$<PATH:GET_PARENT_PATH,path...>
If a requested component is not present in the path, an empty
string is returned.
These expressions provide the generation-time capabilities
equivalent to the Modification and Generation options of the
cmake_path() command. All paths are expected to be in cmake-style
format.
Changed in version 3.27: All operations now accept a list of paths
as argument. When a list of paths is specified, the operation will be
applied to each path.
- $<PATH:CMAKE_PATH[,NORMALIZE],path...>
- New in version 3.24.
Returns path. If path is a native path, it is
converted into a cmake-style path with forward-slashes (/). On
Windows, the long filename marker is taken into account.
When the NORMALIZE option is specified, the path is
normalized after the conversion.
- $<PATH:APPEND,path...,input,...>
- New in version 3.24.
Returns all the input arguments appended to path
using / as the directory-separator. Depending on the
input, the value of path may be discarded.
See cmake_path(APPEND) for more details.
- $<PATH:REMOVE_FILENAME,path...>
- New in version 3.24.
Returns path with filename component (as returned by
$<PATH:GET_FILENAME>) removed. After removal, any trailing
directory-separator is left alone, if present.
See cmake_path(REMOVE_FILENAME) for more details.
- $<PATH:REPLACE_FILENAME,path...,input>
- New in version 3.24.
Returns path with the filename component replaced by
input. If path has no filename component (i.e.
$<PATH:HAS_FILENAME> returns 0), path is
unchanged.
See cmake_path(REPLACE_FILENAME) for more details.
- $<PATH:REMOVE_EXTENSION[,LAST_ONLY],path...>
- New in version 3.24.
Returns path with the extension removed, if
any.
See cmake_path(REMOVE_EXTENSION) for more details.
- $<PATH:REPLACE_EXTENSION[,LAST_ONLY],path...,input>
- New in version 3.24.
Returns path with the extension replaced by
input, if any.
See cmake_path(REPLACE_EXTENSION) for more details.
- $<PATH:NORMAL_PATH,path...>
- New in version 3.24.
Returns path normalized according to the steps
described in Normalization.
- $<PATH:RELATIVE_PATH,path...,base_directory>
- New in version 3.24.
Returns path, modified to make it relative to the
base_directory argument.
See cmake_path(RELATIVE_PATH) for more details.
- $<PATH:ABSOLUTE_PATH[,NORMALIZE],path...,base_directory>
- New in version 3.24.
Returns path as absolute. If path is a relative
path ($<PATH:IS_RELATIVE> returns 1), it is
evaluated relative to the given base directory specified by
base_directory argument.
When the NORMALIZE option is specified, the path is
normalized after the path computation.
See cmake_path(ABSOLUTE_PATH) for more details.
- $<SHELL_PATH:...>
- New in version 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.
New in version 3.14: The ... may be a
semicolon-separated list 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.
- $<CONFIG>
- Configuration name. Use this instead of the deprecated
CONFIGURATION generator expression.
- $<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 MAP_IMPORTED_CONFIG_<CONFIG> is also considered by
this expression when it is evaluated on a property of an IMPORTED
target.
Changed in version 3.19: Multiple configurations can be
specified for cfgs. CMake 3.18 and earlier only accepted a single
configuration.
- $<OUTPUT_CONFIG:...>
- New in version 3.20.
Only valid in add_custom_command() and
add_custom_target() as the outer-most generator expression in an
argument. With the 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.
- $<COMMAND_CONFIG:...>
- New in version 3.20.
Only valid in add_custom_command() and
add_custom_target() as the outer-most generator expression in an
argument. With the 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.
- $<PLATFORM_ID>
- The current system's CMake platform id. See also the
CMAKE_SYSTEM_NAME variable.
- $<PLATFORM_ID:platform_ids>
- 1 if CMake's platform id matches any one of the entries in
comma-separated list platform_ids, otherwise 0. See also the
CMAKE_SYSTEM_NAME variable.
See also the CMAKE_<LANG>_COMPILER_VERSION variable,
which is closely related to the expressions in this sub-section.
- $<C_COMPILER_VERSION>
- The version of the C compiler used.
- $<C_COMPILER_VERSION:version>
- 1 if the version of the C compiler matches version,
otherwise 0.
- $<CXX_COMPILER_VERSION>
- The version of the CXX compiler used.
- $<CXX_COMPILER_VERSION:version>
- 1 if the version of the C++ compiler matches version,
otherwise 0.
- $<CUDA_COMPILER_VERSION>
- New in version 3.15.
The version of the CUDA compiler used.
- $<CUDA_COMPILER_VERSION:version>
- New in version 3.15.
1 if the version of the C++ compiler matches
version, otherwise 0.
- $<OBJC_COMPILER_VERSION>
- New in version 3.16.
The version of the Objective-C compiler used.
- $<OBJC_COMPILER_VERSION:version>
- New in version 3.16.
1 if the version of the Objective-C compiler matches
version, otherwise 0.
- $<OBJCXX_COMPILER_VERSION>
- New in version 3.16.
The version of the Objective-C++ compiler used.
- $<OBJCXX_COMPILER_VERSION:version>
- New in version 3.16.
1 if the version of the Objective-C++ compiler matches
version, otherwise 0.
- $<Fortran_COMPILER_VERSION>
- The version of the Fortran compiler used.
- $<Fortran_COMPILER_VERSION:version>
- 1 if the version of the Fortran compiler matches version,
otherwise 0.
- $<HIP_COMPILER_VERSION>
- New in version 3.21.
The version of the HIP compiler used.
- $<HIP_COMPILER_VERSION:version>
- New in version 3.21.
1 if the version of the HIP compiler matches
version, otherwise 0.
- $<ISPC_COMPILER_VERSION>
- New in version 3.19.
The version of the ISPC compiler used.
- $<ISPC_COMPILER_VERSION:version>
- New in version 3.19.
1 if the version of the ISPC compiler matches
version, otherwise 0.
See also the CMAKE_<LANG>_COMPILER_ID and
CMAKE_<LANG>_COMPILER_FRONTEND_VARIANT variables, which are
closely related to most of the expressions in this sub-section.
- $<C_COMPILER_ID>
- CMake's compiler id of the C compiler used.
- $<C_COMPILER_ID:compiler_ids>
- where compiler_ids is a comma-separated list. 1 if CMake's
compiler id of the C compiler matches any one of the entries in
compiler_ids, otherwise 0.
Changed in version 3.15: Multiple compiler_ids can be
specified. CMake 3.14 and earlier only accepted a single compiler
ID.
- $<CXX_COMPILER_ID>
- CMake's compiler id of the C++ compiler used.
- $<CXX_COMPILER_ID:compiler_ids>
- where compiler_ids is a comma-separated list. 1 if CMake's
compiler id of the C++ compiler matches any one of the entries in
compiler_ids, otherwise 0.
Changed in version 3.15: Multiple compiler_ids can be
specified. CMake 3.14 and earlier only accepted a single compiler
ID.
- $<CUDA_COMPILER_ID>
- New in version 3.15.
CMake's compiler id of the CUDA compiler used.
- $<CUDA_COMPILER_ID:compiler_ids>
- New in version 3.15.
where compiler_ids is a comma-separated list. 1
if CMake's compiler id of the CUDA compiler matches any one of the
entries in compiler_ids, otherwise 0.
- $<OBJC_COMPILER_ID>
- New in version 3.16.
CMake's compiler id of the Objective-C compiler used.
- $<OBJC_COMPILER_ID:compiler_ids>
- New in version 3.16.
where compiler_ids is a comma-separated list. 1
if CMake's compiler id of the Objective-C compiler matches any one of
the entries in compiler_ids, otherwise 0.
- $<OBJCXX_COMPILER_ID>
- New in version 3.16.
CMake's compiler id of the Objective-C++ compiler used.
- $<OBJCXX_COMPILER_ID:compiler_ids>
- New in version 3.16.
where compiler_ids is a comma-separated list. 1
if CMake's compiler id of the Objective-C++ compiler matches any one of
the entries in compiler_ids, otherwise 0.
- $<Fortran_COMPILER_ID>
- CMake's compiler id of the Fortran compiler used.
- $<Fortran_COMPILER_ID:compiler_ids>
- where compiler_ids is a comma-separated list. 1 if CMake's
compiler id of the Fortran compiler matches any one of the entries in
compiler_ids, otherwise 0.
Changed in version 3.15: Multiple compiler_ids can be
specified. CMake 3.14 and earlier only accepted a single compiler
ID.
- $<HIP_COMPILER_ID>
- New in version 3.21.
CMake's compiler id of the HIP compiler used.
- $<HIP_COMPILER_ID:compiler_ids>
- New in version 3.21.
where compiler_ids is a comma-separated list. 1
if CMake's compiler id of the HIP compiler matches any one of the
entries in compiler_ids, otherwise 0.
- $<ISPC_COMPILER_ID>
- New in version 3.19.
CMake's compiler id of the ISPC compiler used.
- $<ISPC_COMPILER_ID:compiler_ids>
- New in version 3.19.
where compiler_ids is a comma-separated list. 1
if CMake's compiler id of the ISPC compiler matches any one of the
entries in compiler_ids, otherwise 0.
- $<C_COMPILER_FRONTEND_VARIANT>
- New in version 3.30.
CMake's compiler frontend variant of the C compiler used.
- $<C_COMPILER_FRONTEND_VARIANT:compiler_ids>
- New in version 3.30.
where compiler_ids is a comma-separated list. 1
if CMake's compiler frontend variant of the C compiler matches any one
of the entries in compiler_ids, otherwise 0.
- $<CXX_COMPILER_FRONTEND_VARIANT>
- New in version 3.30.
CMake's compiler frontend variant of the C++ compiler
used.
- $<CXX_COMPILER_FRONTEND_VARIANT:compiler_ids>
- New in version 3.30.
where compiler_ids is a comma-separated list. 1
if CMake's compiler frontend variant of the C++ compiler matches any one
of the entries in compiler_ids, otherwise 0.
- $<CUDA_COMPILER_FRONTEND_VARIANT>
- New in version 3.30.
CMake's compiler id of the CUDA compiler used.
- $<CUDA_COMPILER_FRONTEND_VARIANT:compiler_ids>
- New in version 3.30.
where compiler_ids is a comma-separated list. 1
if CMake's compiler frontend variant of the CUDA compiler matches any
one of the entries in compiler_ids, otherwise 0.
- $<OBJC_COMPILER_FRONTEND_VARIANT>
- New in version 3.30.
CMake's compiler frontend variant of the Objective-C compiler
used.
- $<OBJC_COMPILER_FRONTEND_VARIANT:compiler_ids>
- New in version 3.30.
where compiler_ids is a comma-separated list. 1
if CMake's compiler frontend variant of the Objective-C compiler matches
any one of the entries in compiler_ids, otherwise 0.
- $<OBJCXX_COMPILER_FRONTEND_VARIANT>
- New in version 3.30.
CMake's compiler frontend variant of the Objective-C++
compiler used.
- $<OBJCXX_COMPILER_FRONTEND_VARIANT:compiler_ids>
- New in version 3.30.
where compiler_ids is a comma-separated list. 1
if CMake's compiler frontend variant of the Objective-C++ compiler
matches any one of the entries in compiler_ids, otherwise
0.
- $<Fortran_COMPILER_FRONTEND_VARIANT>
- New in version 3.30.
CMake's compiler id of the Fortran compiler used.
- $<Fortran_COMPILER_FRONTEND_VARIANT:compiler_ids>
- New in version 3.30.
where compiler_ids is a comma-separated list. 1
if CMake's compiler frontend variant of the Fortran compiler matches any
one of the entries in compiler_ids, otherwise 0.
- $<HIP_COMPILER_FRONTEND_VARIANT>
- New in version 3.30.
CMake's compiler id of the HIP compiler used.
- $<HIP_COMPILER_FRONTEND_VARIANT:compiler_ids>
- New in version 3.30.
where compiler_ids is a comma-separated list. 1
if CMake's compiler frontend variant of the HIP compiler matches any one
of the entries in compiler_ids, otherwise 0.
- $<ISPC_COMPILER_FRONTEND_VARIANT>
- New in version 3.30.
CMake's compiler id of the ISPC compiler used.
- $<ISPC_COMPILER_FRONTEND_VARIANT:compiler_ids>
- New in version 3.30.
where compiler_ids is a comma-separated list. 1
if CMake's compiler frontend variant of the ISPC compiler matches any
one of the entries in compiler_ids, otherwise 0.
- $<COMPILE_LANGUAGE>
- New in version 3.3.
The compile language of source files when evaluating compile
options. See the related boolean expression
$<COMPILE_LANGUAGE:language> for notes about the
portability of this generator expression.
- $<COMPILE_LANGUAGE:languages>
- New in version 3.3.
Changed in version 3.15: Multiple languages can be specified
for languages. CMake 3.14 and earlier only accepted a single
language.
1 when the language used for compilation unit matches
any of the comma-separated 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:
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 Visual Studio Generators and Xcode
there is no way to represent target-wide compile definitions or include
directories separately for C and CXX languages. Also, with
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:
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)
- $<COMPILE_LANG_AND_ID:language,compiler_ids>
- New in version 3.15.
1 when the language used for compilation unit matches
language and CMake's compiler id of the language compiler
matches any one of the comma-separated 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:
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:
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>
)
- $<COMPILE_FEATURES:features>
- New in version 3.1.
where features is a comma-separated 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 C_STANDARD or
CXX_STANDARD for the 'head' target, an error is reported. See the
cmake-compile-features(7) manual for information on compile
features and a list of supported compilers.
- $<COMPILE_ONLY:...>
- New in version 3.27.
Content of ..., when collecting transitive compile
properties, otherwise it is the empty string. This is intended for
use in an INTERFACE_LINK_LIBRARIES and LINK_LIBRARIES
target properties, typically populated via the
target_link_libraries() command. Provides compilation usage
requirements without any linking requirements.
Use cases include header-only usage where all usages are known
to not have linking requirements (e.g., all-inline or C++
template libraries).
Note that for proper evaluation of this expression requires
policy CMP0099 to be set to NEW.
- $<LINK_LANGUAGE>
- New in version 3.18.
The link language of the target when evaluating link options.
See the related boolean expression
$<LINK_LANGUAGE:languages> 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.
- $<LINK_LANGUAGE:languages>
- New in version 3.18.
1 when the language used for link step matches any of
the comma-separated 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:
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.
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
$<LINK_LANGUAGE:..> expression. For example:
add_library(lib STATIC file.cxx)
add_library(libother STATIC file.c)
# bad usage
add_executable(myapp1 main.c)
target_link_libraries(myapp1 PRIVATE lib$<$<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.
- $<LINK_LANG_AND_ID:language,compiler_ids>
- New in version 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 comma-separated 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:
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 the note related to
$<LINK_LANGUAGE:language> for constraints about the usage of
this generator expression.
- $<LINK_LIBRARY:feature,library-list>
- New in version 3.24.
Specify a set of libraries to link to a target, along with a
feature which provides details about how they should be
linked. For example:
add_library(lib1 STATIC ...)
add_library(lib2 ...)
target_link_libraries(lib2 PRIVATE "$<LINK_LIBRARY:WHOLE_ARCHIVE,lib1>")
This specifies that lib2 should link to lib1 and use
the WHOLE_ARCHIVE feature when doing so.
Feature names are case-sensitive and may only contain letters,
numbers and underscores. Feature names defined in all uppercase are reserved
for CMake's own built-in features. The pre-defined built-in library features
are:
- DEFAULT
- This feature corresponds to standard linking, essentially equivalent to
using no feature at all. It is typically only used with the
LINK_LIBRARY_OVERRIDE and
LINK_LIBRARY_OVERRIDE_<LIBRARY> target properties.
- WHOLE_ARCHIVE
- Force inclusion of all members of a static library. This feature is only
supported for the following platforms, with limitations as noted:
- Linux.
- All BSD variants.
- SunOS.
- All Apple variants. The library must be specified as a CMake target name,
a library file name (such as libfoo.a), or a library file path
(such as /path/to/libfoo.a). Due to a limitation of the Apple
linker, it cannot be specified as a plain library name like foo,
where foo is not a CMake target.
- Windows. When using a MSVC or MSVC-like toolchain, the MSVC version must
be greater than 1900.
- Cygwin.
- MSYS.
- FRAMEWORK
- This option tells the linker to search for the specified framework using
the -framework linker option. It can only be used on Apple
platforms, and only with a linker that understands the option used (i.e.
the linker provided with Xcode, or one compatible with it).
The framework can be specified as a CMake framework target, a
bare framework name, or a file path. If a target is given, that target
must have the FRAMEWORK target property set to true. For a file
path, if it contains a directory part, that directory will be added as a
framework search path.
add_library(lib SHARED ...)
target_link_libraries(lib PRIVATE "$<LINK_LIBRARY:FRAMEWORK,/path/to/my_framework>")
# The constructed linker command line will contain:
# -F/path/to -framework my_framework
File paths must conform to one of the following patterns (*
is a wildcard, and optional parts are shown as [...]):
- [/path/to/]FwName[.framework]
- [/path/to/]FwName.framework/FwName[suffix]
- [/path/to/]FwName.framework/Versions/*/FwName[suffix]
Note that CMake recognizes and automatically handles framework
targets, even without using the $<LINK_LIBRARY:FRAMEWORK,...>
expression. The generator expression can still be used with a CMake target
if the project wants to be explicit about it, but it is not required to do
so. The linker command line may have some differences between using the
generator expression or not, but the final result should be the same. On the
other hand, if a file path is given, CMake will recognize some paths
automatically, but not all cases. The project may want to use
$<LINK_LIBRARY:FRAMEWORK,...> for file paths so that the
expected behavior is clear.
New in version 3.25: The
FRAMEWORK_MULTI_CONFIG_POSTFIX_<CONFIG> target property as well
as the suffix of the framework library name are now supported by the
FRAMEWORK features.
- NEEDED_FRAMEWORK
- This is similar to the FRAMEWORK feature, except it forces the
linker to link with the framework even if no symbols are used from it. It
uses the -needed_framework option and has the same linker
constraints as FRAMEWORK.
- REEXPORT_FRAMEWORK
- This is similar to the FRAMEWORK feature, except it tells the
linker that the framework should be available to clients linking to the
library being created. It uses the -reexport_framework option and
has the same linker constraints as FRAMEWORK.
- WEAK_FRAMEWORK
- This is similar to the FRAMEWORK feature, except it forces the
linker to mark the framework and all references to it as weak imports. It
uses the -weak_framework option and has the same linker constraints
as FRAMEWORK.
- NEEDED_LIBRARY
- This is similar to the NEEDED_FRAMEWORK feature, except it is for
use with non-framework targets or libraries (Apple platforms only). It
uses the -needed_library or -needed-l option as appropriate,
and has the same linker constraints as NEEDED_FRAMEWORK.
- REEXPORT_LIBRARY
- This is similar to the REEXPORT_FRAMEWORK feature, except it is for
use with non-framework targets or libraries (Apple platforms only). It
uses the -reexport_library or -reexport-l option as
appropriate, and has the same linker constraints as
REEXPORT_FRAMEWORK.
- WEAK_LIBRARY
- This is similar to the WEAK_FRAMEWORK feature, except it is for use
with non-framework targets or libraries (Apple platforms only). It uses
the -weak_library or -weak-l option as appropriate, and has
the same linker constraints as WEAK_FRAMEWORK.
Built-in and custom library features are defined in terms of the
following variables:
- CMAKE_<LANG>_LINK_LIBRARY_USING_<FEATURE>_SUPPORTED
- CMAKE_<LANG>_LINK_LIBRARY_USING_<FEATURE>
- CMAKE_LINK_LIBRARY_USING_<FEATURE>_SUPPORTED
- CMAKE_LINK_LIBRARY_USING_<FEATURE>
The value used for each of these variables is the value as set at
the end of the directory scope in which the target was created. The usage is
as follows:
- 1.
- If the language-specific
CMAKE_<LANG>_LINK_LIBRARY_USING_<FEATURE>_SUPPORTED
variable is true, the feature must be defined by the corresponding
CMAKE_<LANG>_LINK_LIBRARY_USING_<FEATURE>
variable.
- 2.
- If no language-specific feature is supported, then the
CMAKE_LINK_LIBRARY_USING_<FEATURE>_SUPPORTED variable must be
true and the feature must be defined by the corresponding
CMAKE_LINK_LIBRARY_USING_<FEATURE> variable.
The following limitations should be noted:
- The library-list can specify CMake targets or libraries. Any CMake
target of type OBJECT or INTERFACE will ignore the feature
aspect of the expression and instead be linked in the standard way.
- The $<LINK_LIBRARY:...> generator expression can only be used
to specify link libraries. In practice, this means it can appear in the
LINK_LIBRARIES, INTERFACE_LINK_LIBRARIES, and
INTERFACE_LINK_LIBRARIES_DIRECT target properties, and be specified
in target_link_libraries() and link_libraries()
commands.
- If a $<LINK_LIBRARY:...> generator expression appears in the
INTERFACE_LINK_LIBRARIES property of a target, it will be included
in the imported target generated by a install(EXPORT) command. It
is the responsibility of the environment consuming this import to define
the link feature used by this expression.
- Each target or library involved in the link step must have at most only
one kind of library feature. The absence of a feature is also incompatible
with all other features. For example:
add_library(lib1 ...)
add_library(lib2 ...)
add_library(lib3 ...)
# lib1 will be associated with feature1
target_link_libraries(lib2 PUBLIC "$<LINK_LIBRARY:feature1,lib1>")
# lib1 is being linked with no feature here. This conflicts with the
# use of feature1 in the line above and would result in an error.
target_link_libraries(lib3 PRIVATE lib1 lib2)
Where it isn't possible to use the same feature throughout a build
for a given target or library, the LINK_LIBRARY_OVERRIDE and
LINK_LIBRARY_OVERRIDE_<LIBRARY> target properties can be used
to resolve such incompatibilities.
- •
- The $<LINK_LIBRARY:...> generator expression does not
guarantee that the list of specified targets and libraries will be kept
grouped together. To manage constructs like --start-group and
--end-group, as supported by the GNU ld linker, use the
LINK_GROUP generator expression instead.
- $<LINK_GROUP:feature,library-list>
- New in version 3.24.
Specify a group of libraries to link to a target, along with a
feature which defines how that group should be linked. For
example:
add_library(lib1 STATIC ...)
add_library(lib2 ...)
target_link_libraries(lib2 PRIVATE "$<LINK_GROUP:RESCAN,lib1,external>")
This specifies that lib2 should link to lib1 and
external, and that both of those two libraries should be included on
the linker command line according to the definition of the RESCAN
feature.
Feature names are case-sensitive and may only contain letters,
numbers and underscores. Feature names defined in all uppercase are reserved
for CMake's own built-in features. Currently, there is only one pre-defined
built-in group feature:
- RESCAN
- Some linkers are single-pass only. For such linkers, circular references
between libraries typically result in unresolved symbols. This feature
instructs the linker to search the specified static libraries repeatedly
until no new undefined references are created.
Normally, a static library is searched only once in the order
that it is specified on the command line. If a symbol in that library is
needed to resolve an undefined symbol referred to by an object in a
library that appears later on the command line, the linker would not be
able to resolve that reference. By grouping the static libraries with
the RESCAN feature, they will all be searched repeatedly until
all possible references are resolved. This will use linker options like
--start-group and --end-group, or on SunOS, -z
rescan-start and -z rescan-end.
Using this feature has a significant performance cost. It is
best to use it only when there are unavoidable circular references
between two or more static libraries.
This feature is available when using toolchains that target
Linux, BSD, and SunOS. It can also be used when targeting Windows
platforms if the GNU toolchain is used.
Built-in and custom group features are defined in terms of the
following variables:
- CMAKE_<LANG>_LINK_GROUP_USING_<FEATURE>_SUPPORTED
- CMAKE_<LANG>_LINK_GROUP_USING_<FEATURE>
- CMAKE_LINK_GROUP_USING_<FEATURE>_SUPPORTED
- CMAKE_LINK_GROUP_USING_<FEATURE>
The value used for each of these variables is the value as set at
the end of the directory scope in which the target was created. The usage is
as follows:
- 1.
- If the language-specific
CMAKE_<LANG>_LINK_GROUP_USING_<FEATURE>_SUPPORTED
variable is true, the feature must be defined by the corresponding
CMAKE_<LANG>_LINK_GROUP_USING_<FEATURE> variable.
- 2.
- If no language-specific feature is supported, then the
CMAKE_LINK_GROUP_USING_<FEATURE>_SUPPORTED variable must be
true and the feature must be defined by the corresponding
CMAKE_LINK_GROUP_USING_<FEATURE> variable.
The LINK_GROUP generator expression is compatible with the
LINK_LIBRARY generator expression. The libraries involved in a group
can be specified using the LINK_LIBRARY generator expression.
Each target or external library involved in the link step is
allowed to be part of multiple groups, but only if all the groups involved
specify the same feature. Such groups will not be merged on the
linker command line, the individual groups will still be preserved. Mixing
different group features for the same target or library is forbidden.
add_library(lib1 ...)
add_library(lib2 ...)
add_library(lib3 ...)
add_library(lib4 ...)
add_library(lib5 ...)
target_link_libraries(lib3 PUBLIC "$<LINK_GROUP:feature1,lib1,lib2>")
target_link_libraries(lib4 PRIVATE "$<LINK_GROUP:feature1,lib1,lib3>")
# lib4 will be linked with the groups {lib1,lib2} and {lib1,lib3}.
# Both groups specify the same feature, so this is fine.
target_link_libraries(lib5 PRIVATE "$<LINK_GROUP:feature2,lib1,lib3>")
# An error will be raised here because both lib1 and lib3 are part of two
# groups with different features.
When a target or an external library is involved in the link step
as part of a group and also as not part of any group, any occurrence of the
non-group link item will be replaced by the groups it belongs to.
add_library(lib1 ...)
add_library(lib2 ...)
add_library(lib3 ...)
add_library(lib4 ...)
target_link_libraries(lib3 PUBLIC lib1)
target_link_libraries(lib4 PRIVATE lib3 "$<LINK_GROUP:feature1,lib1,lib2>")
# lib4 will only be linked with lib3 and the group {lib1,lib2}
Because lib1 is part of the group defined for lib4,
that group then gets applied back to the use of lib1 for lib3.
The end result will be as though the linking relationship for lib3
had been specified as:
target_link_libraries(lib3 PUBLIC "$<LINK_GROUP:feature1,lib1,lib2>")
Be aware that the precedence of the group over the non-group link
item can result in circular dependencies between groups. If this occurs, a
fatal error is raised because circular dependencies are not allowed for
groups.
add_library(lib1A ...)
add_library(lib1B ...)
add_library(lib2A ...)
add_library(lib2B ...)
add_library(lib3 ...)
# Non-group linking relationships, these are non-circular so far
target_link_libraries(lib1A PUBLIC lib2A)
target_link_libraries(lib2B PUBLIC lib1B)
# The addition of these groups creates circular dependencies
target_link_libraries(lib3 PRIVATE
"$<LINK_GROUP:feat,lib1A,lib1B>"
"$<LINK_GROUP:feat,lib2A,lib2B>"
)
Because of the groups defined for lib3, the linking
relationships for lib1A and lib2B effectively get expanded to
the equivalent of:
target_link_libraries(lib1A PUBLIC "$<LINK_GROUP:feat,lib2A,lib2B>")
target_link_libraries(lib2B PUBLIC "$<LINK_GROUP:feat,lib1A,lib1B>")
This creates a circular dependency between groups: lib1A -->
lib2B --> lib1A.
The following limitations should also be noted:
- The library-list can specify CMake targets or libraries. Any CMake
target of type OBJECT or INTERFACE will ignore the feature
aspect of the expression and instead be linked in the standard way.
- The $<LINK_GROUP:...> generator expression can only be used
to specify link libraries. In practice, this means it can appear in the
LINK_LIBRARIES, INTERFACE_LINK_LIBRARIES,and
INTERFACE_LINK_LIBRARIES_DIRECT target properties, and be specified
in target_link_libraries() and link_libraries()
commands.
- If a $<LINK_GROUP:...> generator expression appears in the
INTERFACE_LINK_LIBRARIES property of a target, it will be included
in the imported target generated by a install(EXPORT) command. It
is the responsibility of the environment consuming this import to define
the link feature used by this expression.
- $<LINK_ONLY:...>
- New in version 3.1.
Content of ..., except while collecting usage
requirements from transitive compile properties, in which case it
is the empty string. This is intended for use in an
INTERFACE_LINK_LIBRARIES target property, typically populated via
the target_link_libraries() command, to specify private link
dependencies without other usage requirements such as include
directories or compile options.
New in version 3.24: LINK_ONLY may also be used in a
LINK_LIBRARIES target property. See policy CMP0131.
- $<DEVICE_LINK:list>
- New in version 3.18.
Returns the list if it is the device link step, an empty list
otherwise. The device link step is controlled by
CUDA_SEPARABLE_COMPILATION and CUDA_RESOLVE_DEVICE_SYMBOLS
properties and policy CMP0105. This expression can only be used
to specify link options.
- $<HOST_LINK:list>
- New in version 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.
Target-Dependent Expressions
These expressions look up information about a target.
- $<TARGET_EXISTS:tgt>
- New in version 3.12.
1 if tgt exists as a CMake target, else
0.
- $<TARGET_NAME_IF_EXISTS:tgt>
- New in version 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.
- $<TARGET_NAME:tgt>
- The target name tgt as written. This marks tgt as being the
name of a target inside a larger expression, which is required if
exporting targets to multiple dependent export sets. The tgt text
must be a literal name of a target; it may not contain generator
expressions. The target does not have to exist.
- $<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.
These expressions look up the values of target
properties.
- $<TARGET_PROPERTY:tgt,prop>
- Value of the property prop on the target tgt, or empty if
the property is not set.
Note that tgt is not added as a dependency of the
target this expression is evaluated on.
Changed in version 3.26: When encountered during evaluation of
Target Usage Requirements, typically in an INTERFACE_*
target property, lookup of the tgt name occurs in the directory
of the target specifying the requirement, rather than the directory of
the consuming target for which the expression is being evaluated.
- $<TARGET_PROPERTY:prop>
- Value of the property prop on the target for which the expression
is being evaluated, or empty if the property is not set. Note that for
generator expressions in Target Usage Requirements this is the
consuming target rather than the target specifying the requirement.
The expressions have special evaluation rules for some
properties:
- Target Build
Specification Properties
- These evaluate as a semicolon-separated list representing the union
of the value on the target itself with the values of the corresponding
Target Usage Requirements on targets named by the target's
LINK_LIBRARIES:
- For Target Compile Properties, evaluation of corresponding usage
requirements is transitive over the closure of the linked targets'
INTERFACE_LINK_LIBRARIES excluding entries guarded by the
LINK_ONLY generator expression.
- For Target Link Properties, evaluation of corresponding usage
requirements is transitive over the closure of the linked targets'
INTERFACE_LINK_LIBRARIES including entries guarded by the
LINK_ONLY generator expression. See policy CMP0166.
Evaluation of LINK_LIBRARIES itself is not transitive.
- Target Usage
Requirement Properties
- These evaluate as a semicolon-separated list representing the union
of the value on the target itself with the values of the same properties
on targets named by the target's INTERFACE_LINK_LIBRARIES:
- For Transitive Compile Properties, evaluation is transitive over
the closure of the target's INTERFACE_LINK_LIBRARIES
excluding entries guarded by the LINK_ONLY generator
expression.
- For Transitive Link Properties, evaluation is transitive over the
closure of the target's INTERFACE_LINK_LIBRARIES including
entries guarded by the LINK_ONLY generator expression. See policy
CMP0166.
Evaluation of INTERFACE_LINK_LIBRARIES itself is not
transitive.
- Custom Transitive
Properties
- New in version 3.30.
These are processed during evaluation as follows:
- •
- Evaluation of $<TARGET_PROPERTY:tgt,PROP> for some property
PROP, named without an INTERFACE_ prefix, checks the
TRANSITIVE_COMPILE_PROPERTIES and TRANSITIVE_LINK_PROPERTIES
properties on target tgt, on targets named by its
LINK_LIBRARIES, and on the transitive closure of targets named by
the linked targets' INTERFACE_LINK_LIBRARIES.
If PROP is listed by one of those properties, then it
evaluates as a semicolon-separated list representing the union of
the value on the target itself with the values of the corresponding
INTERFACE_PROP on targets named by the target's
LINK_LIBRARIES:
- If PROP is named by TRANSITIVE_COMPILE_PROPERTIES,
evaluation of the corresponding INTERFACE_PROP is transitive over
the closure of the linked targets' INTERFACE_LINK_LIBRARIES,
excluding entries guarded by the LINK_ONLY generator
expression.
- If PROP is named by TRANSITIVE_LINK_PROPERTIES, evaluation
of the corresponding INTERFACE_PROP is transitive over the closure
of the linked targets' INTERFACE_LINK_LIBRARIES, including entries
guarded by the LINK_ONLY generator expression.
- •
- Evaluation of $<TARGET_PROPERTY:tgt,INTERFACE_PROP> for some
property INTERFACE_PROP, named with an INTERFACE_ prefix,
checks the TRANSITIVE_COMPILE_PROPERTIES and
TRANSITIVE_LINK_PROPERTIES properties on target tgt, and on
the transitive closure of targets named by its
INTERFACE_LINK_LIBRARIES.
If the corresponding PROP is listed by one of those
properties, then INTERFACE_PROP evaluates as a
semicolon-separated list representing the union of the value on
the target itself with the value of the same property on targets named
by the target's INTERFACE_LINK_LIBRARIES:
- If PROP is named by TRANSITIVE_COMPILE_PROPERTIES,
evaluation of the corresponding INTERFACE_PROP is transitive over
the closure of the target's INTERFACE_LINK_LIBRARIES, excluding
entries guarded by the LINK_ONLY generator expression.
- If PROP is named by TRANSITIVE_LINK_PROPERTIES, evaluation
of the corresponding INTERFACE_PROP is transitive over the closure
of the target's INTERFACE_LINK_LIBRARIES, including entries guarded
by the LINK_ONLY generator expression.
If a PROP is named by both
TRANSITIVE_COMPILE_PROPERTIES and TRANSITIVE_LINK_PROPERTIES,
the latter takes precedence.
- Compatible
Interface Properties
- These evaluate as a single value combined from the target itself, from
targets named by the target's LINK_LIBRARIES, and from the
transitive closure of the linked targets' INTERFACE_LINK_LIBRARIES.
Values of a compatible interface property from multiple targets combine
based on the type of compatibility required by the
COMPATIBLE_INTERFACE_* property defining it.
These expressions look up information about artifacts associated
with a given target tgt. Unless otherwise stated, this can be any
runtime artifact, namely:
- An executable target created by add_executable().
- A shared library target (.so, .dll but not their .lib
import library) created by add_library().
- A static library target created by add_library().
In the following, the phrase "the tgt filename"
means the name of the tgt binary file. This has to be distinguished
from the phrase "the target name", which is just the string
tgt.
- $<TARGET_FILE:tgt>
- Full path to the tgt binary file.
Note that tgt is not added as a dependency of the
target this expression is evaluated on, unless the expression is being
used in add_custom_command() or add_custom_target().
- $<TARGET_FILE_BASE_NAME:tgt>
- New in version 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 OUTPUT_NAME, ARCHIVE_OUTPUT_NAME,
LIBRARY_OUTPUT_NAME and RUNTIME_OUTPUT_NAME target
properties and their configuration specific variants
OUTPUT_NAME_<CONFIG>,
ARCHIVE_OUTPUT_NAME_<CONFIG>,
LIBRARY_OUTPUT_NAME_<CONFIG> and
RUNTIME_OUTPUT_NAME_<CONFIG>.
The <CONFIG>_POSTFIX and 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.
- $<TARGET_FILE_PREFIX:tgt>
- New in version 3.15.
Prefix of the tgt filename (such as lib).
See also the PREFIX target property.
Note that tgt is not added as a dependency of the
target this expression is evaluated on.
- $<TARGET_FILE_SUFFIX:tgt>
- New in version 3.15.
Suffix of the tgt filename (extension such as
.so or .exe).
See also the SUFFIX target property.
Note that tgt is not added as a dependency of the
target this expression is evaluated on.
- $<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 CMP0112).
- $<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 CMP0112).
- $<TARGET_IMPORT_FILE:tgt>
- New in version 3.27.
Full path to the linker import file. On DLL platforms, it
would be the .lib file. For executables on AIX, and for shared
libraries on macOS, it could be, respectively, the .imp or
.tbd import file, depending on the value of the
ENABLE_EXPORTS property.
This expands to an empty string when there is no import file
associated with the target.
- $<TARGET_IMPORT_FILE_BASE_NAME:tgt>
- New in version 3.27.
Base name of the linker import file of the target tgt
without prefix or suffix. For example, if the target file name is
libbase.tbd, the base name is base.
See also the OUTPUT_NAME and ARCHIVE_OUTPUT_NAME
target properties and their configuration specific variants
OUTPUT_NAME_<CONFIG> and
ARCHIVE_OUTPUT_NAME_<CONFIG>.
The <CONFIG>_POSTFIX and 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.
- $<TARGET_IMPORT_FILE_PREFIX:tgt>
- New in version 3.27.
Prefix of the import file of the target tgt.
See also the IMPORT_PREFIX target property.
Note that tgt is not added as a dependency of the
target this expression is evaluated on.
- $<TARGET_IMPORT_FILE_SUFFIX:tgt>
- New in version 3.27.
Suffix of the import file of the target tgt.
The suffix corresponds to the file extension (such as
.lib or .tbd).
See also the IMPORT_SUFFIX target property.
Note that tgt is not added as a dependency of the
target this expression is evaluated on.
- $<TARGET_IMPORT_FILE_NAME:tgt>
- New in version 3.27.
Name of the import file of the target tgt.
Note that tgt is not added as a dependency of the
target this expression is evaluated on.
- $<TARGET_IMPORT_FILE_DIR:tgt>
- New in version 3.27.
Directory of the import file of the target tgt.
Note that tgt is not added as a dependency of the
target this expression is evaluated on.
- $<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.
New in version 3.27: On macOS, it could be the .tbd
import file associated with the shared library, depending on the value
of the ENABLE_EXPORTS property.
This generator expression is equivalent to
$<TARGET_LINKER_LIBRARY_FILE> or
$<TARGET_LINKER_IMPORT_FILE> generator expressions,
depending on the characteristics of the target and the platform.
- $<TARGET_LINKER_FILE_BASE_NAME:tgt>
- New in version 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 OUTPUT_NAME, ARCHIVE_OUTPUT_NAME,
and LIBRARY_OUTPUT_NAME target properties and their configuration
specific variants OUTPUT_NAME_<CONFIG>,
ARCHIVE_OUTPUT_NAME_<CONFIG> and
LIBRARY_OUTPUT_NAME_<CONFIG>.
The <CONFIG>_POSTFIX and 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.
- $<TARGET_LINKER_FILE_PREFIX:tgt>
- New in version 3.15.
Prefix of file used to link target tgt.
See also the PREFIX and IMPORT_PREFIX target
properties.
Note that tgt is not added as a dependency of the
target this expression is evaluated on.
- $<TARGET_LINKER_FILE_SUFFIX:tgt>
- New in version 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 SUFFIX and IMPORT_SUFFIX target
properties.
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 target tgt.
Note that tgt is not added as a dependency of the
target this expression is evaluated on (see policy CMP0112).
- $<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 CMP0112).
- $<TARGET_LINKER_LIBRARY_FILE:tgt>
- New in version 3.27.
File used when linking o the tgt target is done using
directly the library, and not an import file. This will usually be the
library that tgt represents (.a, .so,
.dylib). So, on DLL platforms, it will be an empty string.
- $<TARGET_LINKER_LIBRARY_FILE_BASE_NAME:tgt>
- New in version 3.27.
Base name of library file used to link the target tgt,
i.e. $<TARGET_LINKER_LIBRARY_FILE_NAME:tgt> without prefix
and suffix. For example, if target file name is libbase.a, the
base name is base.
See also the OUTPUT_NAME, ARCHIVE_OUTPUT_NAME,
and LIBRARY_OUTPUT_NAME target properties and their configuration
specific variants OUTPUT_NAME_<CONFIG>,
ARCHIVE_OUTPUT_NAME_<CONFIG> and
LIBRARY_OUTPUT_NAME_<CONFIG>.
The <CONFIG>_POSTFIX and 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.
- $<TARGET_LINKER_LIBRARY_FILE_PREFIX:tgt>
- New in version 3.27.
Prefix of the library file used to link target tgt.
See also the PREFIX target property.
Note that tgt is not added as a dependency of the
target this expression is evaluated on.
- $<TARGET_LINKER_LIBRARY_FILE_SUFFIX:tgt>
- New in version 3.27.
Suffix of the library file used to link target tgt.
The suffix corresponds to the file extension (such as
".a" or ".dylib").
See also the SUFFIX target property.
Note that tgt is not added as a dependency of the
target this expression is evaluated on.
- $<TARGET_LINKER_LIBRARY_FILE_NAME:tgt>
- New in version 3.27.
Name of the library file used to link target tgt.
Note that tgt is not added as a dependency of the
target this expression is evaluated on.
- $<TARGET_LINKER_LIBRARY_FILE_DIR:tgt>
- New in version 3.27.
Directory of the library file used to link target
tgt.
Note that tgt is not added as a dependency of the
target this expression is evaluated on.
- $<TARGET_LINKER_IMPORT_FILE:tgt>
- New in version 3.27.
File used when linking to the tgt target is done using
an import file. This will usually be the import file that tgt
represents (.lib, .tbd). So, when no import file is
involved in the link step, an empty string is returned.
- $<TARGET_LINKER_IMPORT_FILE_BASE_NAME:tgt>
- New in version 3.27.
Base name of the import file used to link the target
tgt, i.e. $<TARGET_LINKER_IMPORT_FILE_NAME:tgt>
without prefix and suffix. For example, if target file name is
libbase.tbd, the base name is base.
See also the OUTPUT_NAME and
ARCHIVE_OUTPUT_NAME, target properties and their configuration
specific variants OUTPUT_NAME_<CONFIG> and
ARCHIVE_OUTPUT_NAME_<CONFIG>.
The <CONFIG>_POSTFIX and 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.
- $<TARGET_LINKER_IMPORT_FILE_PREFIX:tgt>
- New in version 3.27.
Prefix of the import file used to link target tgt.
See also the IMPORT_PREFIX target property.
Note that tgt is not added as a dependency of the
target this expression is evaluated on.
- $<TARGET_LINKER_IMPORT_FILE_SUFFIX:tgt>
- New in version 3.27.
Suffix of the import file used to link target tgt.
The suffix corresponds to the file extension (such as
".lib" or ".tbd").
See also the IMPORT_SUFFIX target property.
Note that tgt is not added as a dependency of the
target this expression is evaluated on.
- $<TARGET_LINKER_IMPORT_FILE_NAME:tgt>
- New in version 3.27.
Name of the import file used to link target tgt.
Note that tgt is not added as a dependency of the
target this expression is evaluated on.
- $<TARGET_LINKER_IMPORT_FILE_DIR:tgt>
- New in version 3.27.
Directory of the import file used to link target
tgt.
Note that tgt is not added as a dependency of the
target this expression is evaluated on.
- $<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).
Note that tgt is not added as a dependency of the
target this expression is evaluated on (see policy CMP0112).
- $<TARGET_SONAME_FILE_DIR:tgt>
- Directory 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 CMP0112).
- $<TARGET_SONAME_IMPORT_FILE:tgt>
- New in version 3.27.
Import file with soname (.3.tbd) where tgt is
the name of a target.
- $<TARGET_SONAME_IMPORT_FILE_NAME:tgt>
- New in version 3.27.
Name of the import file with soname (.3.tbd).
Note that tgt is not added as a dependency of the
target this expression is evaluated on.
- $<TARGET_SONAME_IMPORT_FILE_DIR:tgt>
- New in version 3.27.
Directory of the import file with soname (.3.tbd).
Note that tgt is not added as a dependency of the
target this expression is evaluated on.
- $<TARGET_PDB_FILE:tgt>
- New in version 3.1.
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_BASE_NAME:tgt>
- New in version 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 PDB_NAME target property and its
configuration specific variant PDB_NAME_<CONFIG>.
The <CONFIG>_POSTFIX and 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.
- $<TARGET_PDB_FILE_NAME:tgt>
- New in version 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 CMP0112).
- $<TARGET_PDB_FILE_DIR:tgt>
- New in version 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 CMP0112).
- $<TARGET_BUNDLE_DIR:tgt>
- New in version 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 CMP0112).
- $<TARGET_BUNDLE_DIR_NAME:tgt>
- New in version 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 CMP0112).
- $<TARGET_BUNDLE_CONTENT_DIR:tgt>
- New in version 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 CMP0112).
- $<TARGET_OBJECTS:tgt>
- New in version 3.1.
List of objects resulting from building tgt. This would
typically be used on object library targets.
- $<TARGET_RUNTIME_DLLS:tgt>
- New in version 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. If only the directories of the DLLs
are needed, see the TARGET_RUNTIME_DLL_DIRS generator expression.
Using this generator expression on targets other than executables,
SHARED libraries, and MODULE libraries is an error. On
non-DLL platforms, this expression always 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 using the cmake -E copy -t
command. For example:
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 -t $<TARGET_FILE_DIR:exe> $<TARGET_RUNTIME_DLLS:exe>
COMMAND_EXPAND_LISTS
)
NOTE:
Imported Targets are supported only if they know
the location of their .dll files. An imported SHARED library
must have IMPORTED_LOCATION set to its .dll file. See the
add_library imported libraries section for details. Many Find
Modules produce imported targets with the UNKNOWN type and
therefore will be ignored.
On platforms that support runtime paths (RPATH), refer to
the INSTALL_RPATH target property. On Apple platforms, refer to the
INSTALL_NAME_DIR target property.
- $<TARGET_RUNTIME_DLL_DIRS:tgt>
- New in version 3.27.
List of the directories which contain the DLLs that the target
depends on at runtime (see TARGET_RUNTIME_DLLS). 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, this
expression always evaluates to an empty string.
This generator expression can e.g. be used to create a batch
file using file(GENERATE) which sets the PATH environment
variable accordingly.
- $<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 buildsystem.
Expands to the empty string otherwise.
- $<BUILD_LOCAL_INTERFACE:...>
- New in version 3.26.
Content of ... when the target is used by another
target in the same buildsystem. Expands to the empty string
otherwise.
- $<INSTALL_PREFIX>
- Content of the install prefix when the target is exported via
install(EXPORT), or when evaluated in the INSTALL_NAME_DIR
property or the INSTALL_NAME_DIR argument of
install(RUNTIME_DEPENDENCY_SET), and empty otherwise.
Changed in version 3.27: Evaluates to the content of the
install prefix in the code argument of install(CODE) or the file
argument of install(SCRIPT).
- $<GENEX_EVAL:expr>
- New in version 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.
- $<TARGET_GENEX_EVAL:tgt,expr>
- New in version 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:
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>:
add_custom_target(printFooKeys
COMMAND ${CMAKE_COMMAND} -E
echo $<TARGET_GENEX_EVAL:foo,$<TARGET_PROPERTY:foo,CUSTOM_KEYS>>
)
These expressions evaluate to specific string literals. Use them
in place of the actual string literal where you need to prevent them from
having their special meaning.
- $<ANGLE-R>
- A literal >. Used for example to compare strings that contain a
>.
- $<COMMA>
- A literal ,. Used for example to compare strings which contain a
,.
- $<SEMICOLON>
- A literal ;. Used to prevent list expansion on an argument with
;.
- $<QUOTE>
- New in version 3.30.
A literal ". Used to allow string literal quotes
inside a generator expression.
- $<CONFIGURATION>
- Configuration name. Deprecated since CMake 3.0. Use CONFIG
instead.
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