659896d3ed
Organize the documentation into subsections to separate the signatures. Refactor the discussion of allowed link items into bullet points and expand into more detail on each.
199 lines
8.7 KiB
ReStructuredText
199 lines
8.7 KiB
ReStructuredText
target_link_libraries
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---------------------
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.. only:: html
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.. contents::
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Specify libraries or flags to use when linking a given target and/or
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its dependents. :ref:`Usage requirements <Target Usage Requirements>`
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from linked library targets will be propagated. Usage requirements
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of a target's dependencies affect compilation of its own sources.
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Overview
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^^^^^^^^
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This command has several signatures as detailed in subsections below.
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All of them have the general form::
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target_link_libraries(<target> ... <item>... ...)
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The named ``<target>`` must have been created in the current directory by
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a command such as :command:`add_executable` or :command:`add_library`.
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Repeated calls for the same ``<target>`` append items in the order called.
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Each ``<item>`` may be:
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* **A library target name**: The generated link line will have the
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full path to the linkable library file associated with the target.
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The buildsystem will have a dependency to re-link ``<target>`` if
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the library file changes.
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The named target must be created by :command:`add_library` within
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the project or as an :ref:`IMPORTED library <Imported Targets>`.
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If it is created within the project an ordering dependency will
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automatically be added in the build system to make sure the named
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library target is up-to-date before the ``<target>`` links.
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* **A full path to a library file**: The generated link line will
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normally preserve the full path to the file. However, there are
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some cases where CMake must ask the linker to search for the library
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(e.g. ``/usr/lib/libfoo.so`` becomes ``-lfoo``), such as when it
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appears in a system library directory that the compiler front-end
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may replace with an alternative. Either way, the buildsystem will
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have a dependency to re-link ``<target>`` if the library file changes.
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If the library file is in a Mac OSX framework, the ``Headers`` directory
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of the framework will also be processed as a
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:ref:`usage requirement <Target Usage Requirements>`. This has the same
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effect as passing the framework directory as an include directory.
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* **A plain library name**: The generated link line will ask the linker
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to search for the library (e.g. ``foo`` becomes ``-lfoo`` or ``foo.lib``).
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* **A link flag**: Item names starting with ``-``, but not ``-l`` or
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``-framework``, are treated as linker flags. Note that such flags will
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be treated like any other library link item for purposes of transitive
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dependencies, so they are generally safe to specify only as private link
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items that will not propagate to dependents.
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* A ``debug``, ``optimized``, or ``general`` keyword immediately followed
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by another ``<item>``. The item following such a keyword will be used
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only for the corresponding build configuration. The ``debug`` keyword
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corresponds to the ``Debug`` configuration (or to configurations named
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in the :prop_gbl:`DEBUG_CONFIGURATIONS` global property if it is set).
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The ``optimized`` keyword corresponds to all other configurations. The
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``general`` keyword corresponds to all configurations, and is purely
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optional. Higher granularity may be achieved for per-configuration
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rules by creating and linking to
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:ref:`IMPORTED library targets <Imported Targets>`.
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Items containing ``::``, such as ``Foo::Bar``, are assumed to be
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:ref:`IMPORTED <Imported Targets>` or :ref:`ALIAS <Alias Targets>` library
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target names and will cause an error if no such target exists.
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See policy :policy:`CMP0028`.
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Arguments to ``target_link_libraries`` may use "generator expressions"
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with the syntax ``$<...>``. Note however, that generator expressions
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will not be used in OLD handling of :policy:`CMP0003` or :policy:`CMP0004`.
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See the :manual:`cmake-generator-expressions(7)` manual for available
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expressions. See the :manual:`cmake-buildsystem(7)` manual for more on
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defining buildsystem properties.
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Libraries for a Target and/or its Dependents
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^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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::
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target_link_libraries(<target>
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<PRIVATE|PUBLIC|INTERFACE> <item>...
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[<PRIVATE|PUBLIC|INTERFACE> <item>...]...)
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The ``PUBLIC``, ``PRIVATE`` and ``INTERFACE`` keywords can be used to
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specify both the link dependencies and the link interface in one command.
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Libraries and targets following ``PUBLIC`` are linked to, and are made
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part of the link interface. Libraries and targets following ``PRIVATE``
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are linked to, but are not made part of the link interface. Libraries
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following ``INTERFACE`` are appended to the link interface and are not
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used for linking ``<target>``.
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Libraries for both a Target and its Dependents
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^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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::
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target_link_libraries(<target> <item>...)
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Library dependencies are transitive by default with this signature.
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When this target is linked into another target then the libraries
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linked to this target will appear on the link line for the other
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target too. This transitive "link interface" is stored in the
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:prop_tgt:`INTERFACE_LINK_LIBRARIES` target property and may be overridden
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by setting the property directly. When :policy:`CMP0022` is not set to
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``NEW``, transitive linking is built in but may be overridden by the
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:prop_tgt:`LINK_INTERFACE_LIBRARIES` property. Calls to other signatures
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of this command may set the property making any libraries linked
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exclusively by this signature private.
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Libraries for a Target and/or its Dependents (Legacy)
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^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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::
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target_link_libraries(<target>
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<LINK_PRIVATE|LINK_PUBLIC> <lib>...
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[<LINK_PRIVATE|LINK_PUBLIC> <lib>...]...)
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The ``LINK_PUBLIC`` and ``LINK_PRIVATE`` modes can be used to specify both
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the link dependencies and the link interface in one command.
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This signature is for compatibility only. Prefer the ``PUBLIC`` or
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``PRIVATE`` keywords instead.
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Libraries and targets following ``LINK_PUBLIC`` are linked to, and are
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made part of the :prop_tgt:`INTERFACE_LINK_LIBRARIES`. If policy
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:policy:`CMP0022` is not ``NEW``, they are also made part of the
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:prop_tgt:`LINK_INTERFACE_LIBRARIES`. Libraries and targets following
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``LINK_PRIVATE`` are linked to, but are not made part of the
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:prop_tgt:`INTERFACE_LINK_LIBRARIES` (or :prop_tgt:`LINK_INTERFACE_LIBRARIES`).
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Libraries for Dependents Only (Legacy)
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^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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::
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target_link_libraries(<target> LINK_INTERFACE_LIBRARIES <item>...)
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The ``LINK_INTERFACE_LIBRARIES`` mode appends the libraries to the
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:prop_tgt:`INTERFACE_LINK_LIBRARIES` target property instead of using them
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for linking. If policy :policy:`CMP0022` is not ``NEW``, then this mode
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also appends libraries to the :prop_tgt:`LINK_INTERFACE_LIBRARIES` and its
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per-configuration equivalent.
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This signature is for compatibility only. Prefer the ``INTERFACE`` mode
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instead.
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Libraries specified as ``debug`` are wrapped in a generator expression to
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correspond to debug builds. If policy :policy:`CMP0022` is
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not ``NEW``, the libraries are also appended to the
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:prop_tgt:`LINK_INTERFACE_LIBRARIES_DEBUG <LINK_INTERFACE_LIBRARIES_<CONFIG>>`
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property (or to the properties corresponding to configurations listed in
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the :prop_gbl:`DEBUG_CONFIGURATIONS` global property if it is set).
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Libraries specified as ``optimized`` are appended to the
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:prop_tgt:`INTERFACE_LINK_LIBRARIES` property. If policy :policy:`CMP0022`
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is not ``NEW``, they are also appended to the
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:prop_tgt:`LINK_INTERFACE_LIBRARIES` property. Libraries specified as
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``general`` (or without any keyword) are treated as if specified for both
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``debug`` and ``optimized``.
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Cyclic Dependencies of Static Libraries
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^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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The library dependency graph is normally acyclic (a DAG), but in the case
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of mutually-dependent ``STATIC`` libraries CMake allows the graph to
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contain cycles (strongly connected components). When another target links
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to one of the libraries, CMake repeats the entire connected component.
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For example, the code
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.. code-block:: cmake
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add_library(A STATIC a.c)
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add_library(B STATIC b.c)
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target_link_libraries(A B)
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target_link_libraries(B A)
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add_executable(main main.c)
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target_link_libraries(main A)
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links ``main`` to ``A B A B``. While one repetition is usually
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sufficient, pathological object file and symbol arrangements can require
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more. One may handle such cases by using the
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:prop_tgt:`LINK_INTERFACE_MULTIPLICITY` target property or by manually
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repeating the component in the last ``target_link_libraries`` call.
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However, if two archives are really so interdependent they should probably
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be combined into a single archive, perhaps by using :ref:`Object Libraries`.
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Creating Relocatable Packages
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^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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.. |INTERFACE_PROPERTY_LINK| replace:: :prop_tgt:`INTERFACE_LINK_LIBRARIES`
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.. include:: /include/INTERFACE_LINK_LIBRARIES_WARNING.txt
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