target_link_libraries

Contents

• target_link_libraries

  • Overview

  • Libraries for a Target and/or its Dependents

  • Libraries for both a Target and its Dependents

  • Libraries for a Target and/or its Dependents (Legacy)

  • Libraries for Dependents Only (Legacy)

  • Cyclic Dependencies of Static Libraries

  • Creating Relocatable Packages

Specify libraries or flags to use when linking a given target and/or its dependents. Usage requirements from linked library targets will be propagated. Usage requirements of a target’s dependencies affect compilation of its own sources.

Overview

This command has several signatures as detailed in subsections below. All of them have the general form:

target_link_libraries(<target> ... <item>... ...)

The named <target> must have been created in the current directory by a command such as add_executable() or add_library(). Repeated calls for the same <target> append items in the order called. Each <item> may be:

• A library target name: The generated link line will have the full path to the linkable library file associated with the target. The buildsystem will have a dependency to re-link <target> if the library file changes.

  The named target must be created by add_library() within the project or as an IMPORTED library. If it is created within the project an ordering dependency will automatically be added in the build system to make sure the named library target is up-to-date before the <target> links.

  If an imported library has the IMPORTED_NO_SONAME target property set, CMake may ask the linker to search for the library instead of using the full path (e.g. /usr/lib/libfoo.so becomes -lfoo).

• A full path to a library file: The generated link line will normally preserve the full path to the file. The buildsystem will have a dependency to re-link <target> if the library file changes.

  There are some cases where CMake may ask the linker to search for the library (e.g. /usr/lib/libfoo.so becomes -lfoo), such as when a shared library is detected to have no SONAME field. See policy CMP0060 for discussion of another case.

  If the library file is in a Mac OSX framework, the Headers directory of the framework will also be processed as a usage requirement. This has the same effect as passing the framework directory as an include directory.

• A plain library name: The generated link line will ask the linker to search for the library (e.g. foo becomes -lfoo or foo.lib).

• A link flag: Item names starting with -, but not -l or -framework, are treated as linker flags. Note that such flags will be treated like any other library link item for purposes of transitive dependencies, so they are generally safe to specify only as private link items that will not propagate to dependents.

  Link flags specified here are inserted into the link command in the same place as the link libraries. This might not be correct, depending on the linker. Use the LINK_FLAGS target property to add link flags explicitly. The flags will then be placed at the toolchain-defined flag position in the link command.

• A debug, optimized, or general keyword immediately followed by another <item>. The item following such a keyword will be used only for the corresponding build configuration. The debug keyword corresponds to the Debug configuration (or to configurations named in the DEBUG_CONFIGURATIONS global property if it is set). The optimized keyword corresponds to all other configurations. The general keyword corresponds to all configurations, and is purely optional. Higher granularity may be achieved for per-configuration rules by creating and linking to IMPORTED library targets.

Items containing ::, such as Foo::Bar, are assumed to be IMPORTED or ALIAS library target names and will cause an error if no such target exists. See policy CMP0028.

Arguments to target_link_libraries may use “generator expressions” with the syntax $<...>. Note however, that generator expressions will not be used in OLD handling of CMP0003 or CMP0004. See the cmake-generator-expressions(7) manual for available expressions. See the cmake-buildsystem(7) manual for more on defining buildsystem properties.

Libraries for a Target and/or its Dependents

target_link_libraries(<target>
                      <PRIVATE|PUBLIC|INTERFACE> <item>...
                     [<PRIVATE|PUBLIC|INTERFACE> <item>...]...)

The PUBLIC, PRIVATE and INTERFACE keywords can be used to specify both the link dependencies and the link interface in one command. Libraries and targets following PUBLIC are linked to, and are made part of the link interface. Libraries and targets following PRIVATE are linked to, but are not made part of the link interface. Libraries following INTERFACE are appended to the link interface and are not used for linking <target>.

Libraries for both a Target and its Dependents

target_link_libraries(<target> <item>...)

Library dependencies are transitive by default with this signature. When this target is linked into another target then the libraries linked to this target will appear on the link line for the other target too. This transitive “link interface” is stored in the INTERFACE_LINK_LIBRARIES target property and may be overridden by setting the property directly. When CMP0022 is not set to NEW, transitive linking is built in but may be overridden by the LINK_INTERFACE_LIBRARIES property. Calls to other signatures of this command may set the property making any libraries linked exclusively by this signature private.

Libraries for a Target and/or its Dependents (Legacy)

target_link_libraries(<target>
                      <LINK_PRIVATE|LINK_PUBLIC> <lib>...
                     [<LINK_PRIVATE|LINK_PUBLIC> <lib>...]...)

The LINK_PUBLIC and LINK_PRIVATE modes can be used to specify both the link dependencies and the link interface in one command.

This signature is for compatibility only. Prefer the PUBLIC or PRIVATE keywords instead.

Libraries and targets following LINK_PUBLIC are linked to, and are made part of the INTERFACE_LINK_LIBRARIES. If policy CMP0022 is not NEW, they are also made part of the LINK_INTERFACE_LIBRARIES. Libraries and targets following LINK_PRIVATE are linked to, but are not made part of the INTERFACE_LINK_LIBRARIES (or LINK_INTERFACE_LIBRARIES).

Libraries for Dependents Only (Legacy)

target_link_libraries(<target> LINK_INTERFACE_LIBRARIES <item>...)

The LINK_INTERFACE_LIBRARIES mode appends the libraries to the INTERFACE_LINK_LIBRARIES target property instead of using them for linking. If policy CMP0022 is not NEW, then this mode also appends libraries to the LINK_INTERFACE_LIBRARIES and its per-configuration equivalent.

This signature is for compatibility only. Prefer the INTERFACE mode instead.

Libraries specified as debug are wrapped in a generator expression to correspond to debug builds. If policy CMP0022 is not NEW, the libraries are also appended to the LINK_INTERFACE_LIBRARIES_DEBUG property (or to the properties corresponding to configurations listed in the DEBUG_CONFIGURATIONS global property if it is set). Libraries specified as optimized are appended to the INTERFACE_LINK_LIBRARIES property. If policy CMP0022 is not NEW, they are also appended to the LINK_INTERFACE_LIBRARIES property. Libraries specified as general (or without any keyword) are treated as if specified for both debug and optimized.

Cyclic Dependencies of Static Libraries

The library dependency graph is normally acyclic (a DAG), but in the case of mutually-dependent STATIC libraries CMake allows the graph to contain cycles (strongly connected components). When another target links to one of the libraries, CMake repeats the entire connected component. For example, the code

add_library(A STATIC a.c)
add_library(B STATIC b.c)
target_link_libraries(A B)
target_link_libraries(B A)
add_executable(main main.c)
target_link_libraries(main A)

links main to A B A B. While one repetition is usually sufficient, pathological object file and symbol arrangements can require more. One may handle such cases by using the LINK_INTERFACE_MULTIPLICITY target property or by manually repeating the component in the last target_link_libraries call. However, if two archives are really so interdependent they should probably be combined into a single archive, perhaps by using Object Libraries.

Creating Relocatable Packages

Note that it is not advisable to populate the INTERFACE_LINK_LIBRARIES of a target with absolute paths to dependencies. That would hard-code into installed packages the library file paths for dependencies as found on the machine the package was made on.

See the Creating Relocatable Packages section of the cmake-packages(7) manual for discussion of additional care that must be taken when specifying usage requirements while creating packages for redistribution.