Ubuntu Manpage: cmake-generator-expressions - CMake Generator Expressions

Provided by: cmake-data_3.28.3-1build7_all

NAME

       cmake-generator-expressions - CMake Generator Expressions

INTRODUCTION

       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.

WHITESPACE AND QUOTING

       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>"
          )

DEBUGGING

       Since generator expressions are evaluated during generation of the buildsystem, and not during processing
       of  CMakeLists.txt  files,  it  is  not possible to inspect their result with the 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 "$<...>")

GENERATOR EXPRESSION REFERENCE

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.

Conditional 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>

Logical Operators
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.

Primary Comparison Expressions
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.

String Comparisons
$<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 Comparisons
$<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.

String Transformations
$<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).

List Expressions
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.

List Comparisons
$<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 Queries
$<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 Transformations
$<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 Ordering
$<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>

Path Expressions
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 Comparisons
$<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.

Path Queries
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.

Path Decomposition
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.

Path Transformations
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 Paths
$<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.

Configuration Expressions
$<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.

Toolchain And Language Expressions
Platform
$<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.

Compiler Version
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 CXX 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 CXX compiler matches version, otherwise 0.

$<OBJC_COMPILER_VERSION>
New in version 3.16.

The version of the OBJC compiler used.

$<OBJC_COMPILER_VERSION:version>
New in version 3.16.

1 if the version of the OBJC compiler matches version, otherwise 0.

$<OBJCXX_COMPILER_VERSION>
New in version 3.16.

The version of the OBJCXX compiler used.

$<OBJCXX_COMPILER_VERSION:version>
New in version 3.16.

1 if the version of the OBJCXX 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.

Compiler Language And ID
See also the CMAKE_<LANG>_COMPILER_ID variable, which is 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.

$<CXX_COMPILER_ID>
CMake's compiler id of the CXX compiler used.

$<CXX_COMPILER_ID:compiler_ids>
where compiler_ids is a comma-separated list. 1 if CMake's compiler id of the CXX compiler
matches any one of the entries in compiler_ids, otherwise 0.

$<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 OBJC 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 OBJCXX 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.

$<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.

$<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
$<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 Context
$<COMPILE_ONLY:...>
New in version 3.27.

Content of ..., when collecting Transitive Usage Requirements, 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.

Linker Language And ID
$<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 Features
$<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.

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 Context
$<LINK_ONLY:...>
New in version 3.1.

Content of ..., except while collecting Transitive Usage Requirements, 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 queries refer to a 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_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:...>
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.

$<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.

Changed in version 3.26: When encountered during evaluation of Transitive 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. Note that
for generator expressions in Transitive Usage Requirements this is the consuming target rather
than the target specifying the requirement.

$<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_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.

$<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).

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3.28.3                                           April 15, 2024                   CMAKE-GENERATOR-EXPRESSIONS(7)