987f3fa4e0
Re-organize the "Binary Targets" section of the manual to have a dedicated subsection for each kind of binary target. Initialize each subsection by documenting the object file and link semantics of the corresponding target type.
306 lines
12 KiB
ReStructuredText
306 lines
12 KiB
ReStructuredText
add_library
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-----------
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.. only:: html
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.. contents::
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Add a library to the project using the specified source files.
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Normal Libraries
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^^^^^^^^^^^^^^^^
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.. signature::
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add_library(<name> [<type>] [EXCLUDE_FROM_ALL] <sources>...)
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:target: normal
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Add a library target called ``<name>`` to be built from the source files
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listed in the command invocation.
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The optional ``<type>`` specifies the type of library to be created:
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``STATIC``
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A :ref:`Static Library <Static Libraries>`:
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an archive of object files for use when linking other targets.
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``SHARED``
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A :ref:`Shared Library <Shared Libraries>`:
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a dynamic library that may be linked by other targets and loaded
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at runtime.
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``MODULE``
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A :ref:`Module Library <Module Libraries>`:
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a plugin that may not be linked by other targets, but may be
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dynamically loaded at runtime using dlopen-like functionality.
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If no ``<type>`` is given the default is ``STATIC`` or ``SHARED``
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based on the value of the :variable:`BUILD_SHARED_LIBS` variable.
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The options are:
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``EXCLUDE_FROM_ALL``
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Set the :prop_tgt:`EXCLUDE_FROM_ALL` target property automatically.
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See documentation of that target property for details.
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The ``<name>`` corresponds to the logical target name and must be globally
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unique within a project. The actual file name of the library built is
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constructed based on conventions of the native platform (such as
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``lib<name>.a`` or ``<name>.lib``).
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.. versionadded:: 3.1
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Source arguments to ``add_library`` may use "generator expressions" with
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the syntax ``$<...>``. See the :manual:`cmake-generator-expressions(7)`
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manual for available expressions.
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.. versionadded:: 3.11
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The source files can be omitted if they are added later using
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:command:`target_sources`.
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For ``SHARED`` and ``MODULE`` libraries the
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:prop_tgt:`POSITION_INDEPENDENT_CODE` target
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property is set to ``ON`` automatically.
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A ``SHARED`` library may be marked with the :prop_tgt:`FRAMEWORK`
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target property to create an macOS Framework.
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.. versionadded:: 3.8
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A ``STATIC`` library may be marked with the :prop_tgt:`FRAMEWORK`
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target property to create a static Framework.
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If a library does not export any symbols, it must not be declared as a
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``SHARED`` library. For example, a Windows resource DLL or a managed C++/CLI
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DLL that exports no unmanaged symbols would need to be a ``MODULE`` library.
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This is because CMake expects a ``SHARED`` library to always have an
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associated import library on Windows.
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By default the library file will be created in the build tree directory
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corresponding to the source tree directory in which the command was
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invoked. See documentation of the :prop_tgt:`ARCHIVE_OUTPUT_DIRECTORY`,
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:prop_tgt:`LIBRARY_OUTPUT_DIRECTORY`, and
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:prop_tgt:`RUNTIME_OUTPUT_DIRECTORY` target properties to change this
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location. See documentation of the :prop_tgt:`OUTPUT_NAME` target
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property to change the ``<name>`` part of the final file name.
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See the :manual:`cmake-buildsystem(7)` manual for more on defining
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buildsystem properties.
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See also :prop_sf:`HEADER_FILE_ONLY` on what to do if some sources are
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pre-processed, and you want to have the original sources reachable from
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within IDE.
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.. versionchanged:: 3.30
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On platforms that do not support shared libraries, ``add_library``
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now fails on calls creating ``SHARED`` libraries instead of
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automatically converting them to ``STATIC`` libraries as before.
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See policy :policy:`CMP0164`.
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Object Libraries
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^^^^^^^^^^^^^^^^
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.. signature::
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add_library(<name> OBJECT <sources>...)
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:target: OBJECT
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Add an :ref:`Object Library <Object Libraries>` to compile source files
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without archiving or linking their object files into a library.
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Other targets created by ``add_library`` or :command:`add_executable`
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may reference the objects using an expression of the
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form :genex:`$\<TARGET_OBJECTS:objlib\> <TARGET_OBJECTS>` as a source, where
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``objlib`` is the object library name. For example:
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.. code-block:: cmake
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add_library(... $<TARGET_OBJECTS:objlib> ...)
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add_executable(... $<TARGET_OBJECTS:objlib> ...)
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will include objlib's object files in a library and an executable
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along with those compiled from their own sources. Object libraries
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may contain only sources that compile, header files, and other files
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that would not affect linking of a normal library (e.g. ``.txt``).
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They may contain custom commands generating such sources, but not
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``PRE_BUILD``, ``PRE_LINK``, or ``POST_BUILD`` commands. Some native build
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systems (such as Xcode) may not like targets that have only object files, so
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consider adding at least one real source file to any target that references
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:genex:`$\<TARGET_OBJECTS:objlib\> <TARGET_OBJECTS>`.
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.. versionadded:: 3.12
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Object libraries can be linked to with :command:`target_link_libraries`.
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Interface Libraries
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^^^^^^^^^^^^^^^^^^^
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.. signature::
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add_library(<name> INTERFACE)
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:target: INTERFACE
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Add an :ref:`Interface Library <Interface Libraries>` target that may
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specify usage requirements for dependents but does not compile sources
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and does not produce a library artifact on disk.
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An interface library with no source files is not included as a target
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in the generated buildsystem. However, it may have
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properties set on it and it may be installed and exported.
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Typically, ``INTERFACE_*`` properties are populated on an interface
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target using the commands:
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* :command:`set_property`,
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* :command:`target_link_libraries(INTERFACE)`,
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* :command:`target_link_options(INTERFACE)`,
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* :command:`target_include_directories(INTERFACE)`,
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* :command:`target_compile_options(INTERFACE)`,
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* :command:`target_compile_definitions(INTERFACE)`, and
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* :command:`target_sources(INTERFACE)`,
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and then it is used as an argument to :command:`target_link_libraries`
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like any other target.
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.. versionadded:: 3.15
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An interface library can have :prop_tgt:`PUBLIC_HEADER` and
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:prop_tgt:`PRIVATE_HEADER` properties. The headers specified by those
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properties can be installed using the :command:`install(TARGETS)` command.
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.. signature::
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add_library(<name> INTERFACE [EXCLUDE_FROM_ALL] <sources>...)
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:target: INTERFACE-with-sources
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.. versionadded:: 3.19
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Add an :ref:`Interface Library <Interface Libraries>` target with
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source files (in addition to usage requirements and properties as
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documented by the :command:`above signature <add_library(INTERFACE)>`).
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Source files may be listed directly in the ``add_library`` call
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or added later by calls to :command:`target_sources` with the
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``PRIVATE`` or ``PUBLIC`` keywords.
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If an interface library has source files (i.e. the :prop_tgt:`SOURCES`
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target property is set), or header sets (i.e. the :prop_tgt:`HEADER_SETS`
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target property is set), it will appear in the generated buildsystem
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as a build target much like a target defined by the
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:command:`add_custom_target` command. It does not compile any sources,
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but does contain build rules for custom commands created by the
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:command:`add_custom_command` command.
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The options are:
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``EXCLUDE_FROM_ALL``
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Set the :prop_tgt:`EXCLUDE_FROM_ALL` target property automatically.
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See documentation of that target property for details.
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.. note::
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In most command signatures where the ``INTERFACE`` keyword appears,
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the items listed after it only become part of that target's usage
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requirements and are not part of the target's own settings. However,
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in this signature of ``add_library``, the ``INTERFACE`` keyword refers
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to the library type only. Sources listed after it in the ``add_library``
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call are ``PRIVATE`` to the interface library and do not appear in its
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:prop_tgt:`INTERFACE_SOURCES` target property.
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.. _`add_library imported libraries`:
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Imported Libraries
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^^^^^^^^^^^^^^^^^^
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.. signature::
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add_library(<name> <type> IMPORTED [GLOBAL])
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:target: IMPORTED
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Add an :ref:`IMPORTED library target <Imported Targets>` called ``<name>``.
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The target name may be referenced like any target built within the project,
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except that by default it is visible only in the directory in which it is
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created, and below.
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The ``<type>`` must be one of:
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``STATIC``, ``SHARED``, ``MODULE``, ``UNKNOWN``
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References a library file located outside the project. The
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:prop_tgt:`IMPORTED_LOCATION` target property (or its per-configuration
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variant :prop_tgt:`IMPORTED_LOCATION_<CONFIG>`) specifies the
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location of the main library file on disk:
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* For a ``SHARED`` library on most non-Windows platforms, the main library
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file is the ``.so`` or ``.dylib`` file used by both linkers and dynamic
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loaders. If the referenced library file has a ``SONAME`` (or on macOS,
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has a ``LC_ID_DYLIB`` starting in ``@rpath/``), the value of that field
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should be set in the :prop_tgt:`IMPORTED_SONAME` target property.
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If the referenced library file does not have a ``SONAME``, but the
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platform supports it, then the :prop_tgt:`IMPORTED_NO_SONAME` target
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property should be set.
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* For a ``SHARED`` library on Windows, the :prop_tgt:`IMPORTED_IMPLIB`
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target property (or its per-configuration variant
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:prop_tgt:`IMPORTED_IMPLIB_<CONFIG>`) specifies the location of the
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DLL import library file (``.lib`` or ``.dll.a``) on disk, and the
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``IMPORTED_LOCATION`` is the location of the ``.dll`` runtime
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library (and is optional, but needed by the :genex:`TARGET_RUNTIME_DLLS`
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generator expression).
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Additional usage requirements may be specified in ``INTERFACE_*``
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properties.
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An ``UNKNOWN`` library type is typically only used in the implementation
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of :ref:`Find Modules`. It allows the path to an imported library
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(often found using the :command:`find_library` command) to be used
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without having to know what type of library it is. This is especially
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useful on Windows where a static library and a DLL's import library
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both have the same file extension.
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``OBJECT``
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References a set of object files located outside the project.
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The :prop_tgt:`IMPORTED_OBJECTS` target property (or its per-configuration
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variant :prop_tgt:`IMPORTED_OBJECTS_<CONFIG>`) specifies the locations of
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object files on disk.
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Additional usage requirements may be specified in ``INTERFACE_*``
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properties.
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``INTERFACE``
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Does not reference any library or object files on disk, but may
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specify usage requirements in ``INTERFACE_*`` properties.
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The options are:
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``GLOBAL``
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Make the target name globally visible.
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No rules are generated to build imported targets, and the :prop_tgt:`IMPORTED`
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target property is ``True``. Imported libraries are useful for convenient
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reference from commands like :command:`target_link_libraries`.
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Details about the imported library are specified by setting properties whose
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names begin in ``IMPORTED_`` and ``INTERFACE_``. See documentation of
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such properties for more information.
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Alias Libraries
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^^^^^^^^^^^^^^^
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.. signature::
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add_library(<name> ALIAS <target>)
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:target: ALIAS
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Creates an :ref:`Alias Target <Alias Targets>`, such that ``<name>`` can be
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used to refer to ``<target>`` in subsequent commands. The ``<name>`` does
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not appear in the generated buildsystem as a make target. The ``<target>``
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may not be an ``ALIAS``.
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.. versionadded:: 3.11
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An ``ALIAS`` can target a ``GLOBAL`` :ref:`Imported Target <Imported Targets>`
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.. versionadded:: 3.18
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An ``ALIAS`` can target a non-``GLOBAL`` Imported Target. Such alias is
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scoped to the directory in which it is created and below.
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The :prop_tgt:`ALIAS_GLOBAL` target property can be used to check if the
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alias is global or not.
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``ALIAS`` targets can be used as linkable targets and as targets to
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read properties from. They can also be tested for existence with the
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regular :command:`if(TARGET)` subcommand. The ``<name>`` may not be used
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to modify properties of ``<target>``, that is, it may not be used as the
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operand of :command:`set_property`, :command:`set_target_properties`,
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:command:`target_link_libraries` etc. An ``ALIAS`` target may not be
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installed or exported.
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See Also
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^^^^^^^^
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* :command:`add_executable`
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