add_library

• Normal Libraries
• Object Libraries
• Interface Libraries
• Imported Libraries
• Alias Libraries

Add a library to the project using the specified source files.

Normal Libraries

add_library(<name> [STATIC | SHARED | MODULE]
            [EXCLUDE_FROM_ALL]
            [<source>...])

Adds a library target called <name> to be built from the source files listed in the command invocation. (The source files can be omitted here if they are added later using target_sources().) The <name> corresponds to the logical target name and must be globally unique within a project. The actual file name of the library built is constructed based on conventions of the native platform (such as lib<name>.a or <name>.lib).

STATIC, SHARED, or MODULE may be given to specify the type of library to be created. STATIC libraries are archives of object files for use when linking other targets. SHARED libraries are linked dynamically and loaded at runtime. MODULE libraries are plugins that are not linked into other targets but may be loaded dynamically at runtime using dlopen-like functionality. If no type is given explicitly the type is STATIC or SHARED based on whether the current value of the variable BUILD_SHARED_LIBS is ON. For SHARED and MODULE libraries the POSITION_INDEPENDENT_CODE target property is set to ON automatically. A SHARED or STATIC library may be marked with the FRAMEWORK target property to create an macOS Framework.

If a library does not export any symbols, it must not be declared as a SHARED library. For example, a Windows resource DLL or a managed C++/CLI DLL that exports no unmanaged symbols would need to be a MODULE library. This is because CMake expects a SHARED library to always have an associated import library on Windows.

By default the library file will be created in the build tree directory corresponding to the source tree directory in which the command was invoked. See documentation of the ARCHIVE_OUTPUT_DIRECTORY, LIBRARY_OUTPUT_DIRECTORY, and RUNTIME_OUTPUT_DIRECTORY target properties to change this location. See documentation of the OUTPUT_NAME target property to change the <name> part of the final file name.

If EXCLUDE_FROM_ALL is given the corresponding property will be set on the created target. See documentation of the EXCLUDE_FROM_ALL target property for details.

Source arguments to add_library may use “generator expressions” with the syntax $<...>. See the cmake-generator-expressions(7) manual for available expressions. See the cmake-buildsystem(7) manual for more on defining buildsystem properties.

See also HEADER_FILE_ONLY on what to do if some sources are pre-processed, and you want to have the original sources reachable from within IDE.

Object Libraries

add_library(<name> OBJECT [<source>...])

Creates an Object Library. An object library compiles source files but does not archive or link their object files into a library. Instead other targets created by add_library() or add_executable() may reference the objects using an expression of the form $<TARGET_OBJECTS:objlib> as a source, where objlib is the object library name. For example:

add_library(... $<TARGET_OBJECTS:objlib> ...)
add_executable(... $<TARGET_OBJECTS:objlib> ...)

will include objlib’s object files in a library and an executable along with those compiled from their own sources. Object libraries may contain only sources that compile, header files, and other files that would not affect linking of a normal library (e.g. .txt). They may contain custom commands generating such sources, but not PRE_BUILD, PRE_LINK, or POST_BUILD commands. Some native build systems (such as Xcode) may not like targets that have only object files, so consider adding at least one real source file to any target that references $<TARGET_OBJECTS:objlib>.

Interface Libraries

add_library(<name> INTERFACE)

Creates an Interface Library. An INTERFACE library target does not compile sources and does not produce a library artifact on disk. However, it may have properties set on it and it may be installed and exported. Typically, INTERFACE_* properties are populated on an interface target using the commands:

• set_property(),
• target_link_libraries(INTERFACE),
• target_link_options(INTERFACE),
• target_include_directories(INTERFACE),
• target_compile_options(INTERFACE),
• target_compile_definitions(INTERFACE), and
• target_sources(INTERFACE),

and then it is used as an argument to target_link_libraries() like any other target.

An interface library created with the above signature has no source files itself and is not included as a target in the generated buildsystem.

Since CMake 3.19, an interface library target may be created with source files:

add_library(<name> INTERFACE [<source>...] [EXCLUDE_FROM_ALL])

Source files may be listed directly in the add_library call or added later by calls to target_sources() with the PRIVATE or PUBLIC keywords.

If an interface library has source files (i.e. the SOURCES target property is set), it will appear in the generated buildsystem as a build target much like a target defined by the add_custom_target() command. It does not compile any sources, but does contain build rules for custom commands created by the add_custom_command() command.

Imported Libraries

add_library(<name> <type> IMPORTED [GLOBAL])

Creates an IMPORTED library target called <name>. No rules are generated to build it, and the IMPORTED target property is True. The target name has scope in the directory in which it is created and below, but the GLOBAL option extends visibility. It may be referenced like any target built within the project. IMPORTED libraries are useful for convenient reference from commands like target_link_libraries(). Details about the imported library are specified by setting properties whose names begin in IMPORTED_ and INTERFACE_.

The <type> must be one of:

STATIC, SHARED, MODULE, UNKNOWN

References a library file located outside the project. The IMPORTED_LOCATION target property (or its per-configuration variant IMPORTED_LOCATION_<CONFIG>) specifies the location of the main library file on disk. In the case of a SHARED library on Windows, the IMPORTED_IMPLIB target property (or its per-configuration variant IMPORTED_IMPLIB_<CONFIG>) specifies the location of the DLL import library file (.lib or .dll.a) on disk, and the IMPORTED_LOCATION is the location of the .dll runtime library (and is optional). Additional usage requirements may be specified in INTERFACE_* properties.

An UNKNOWN library type is typically only used in the implementation of Find Modules. It allows the path to an imported library (often found using the find_library() command) to be used without having to know what type of library it is. This is especially useful on Windows where a static library and a DLL’s import library both have the same file extension.

OBJECT

References a set of object files located outside the project. The IMPORTED_OBJECTS target property (or its per-configuration variant IMPORTED_OBJECTS_<CONFIG>) specifies the locations of object files on disk. Additional usage requirements may be specified in INTERFACE_* properties.

INTERFACE

Does not reference any library or object files on disk, but may specify usage requirements in INTERFACE_* properties.

See documentation of the IMPORTED_* and INTERFACE_* properties for more information.

Alias Libraries

add_library(<name> ALIAS <target>)

Creates an Alias Target, such that <name> can be used to refer to <target> in subsequent commands. The <name> does not appear in the generated buildsystem as a make target. The <target> may not be an ALIAS.

An ALIAS to a non-GLOBAL Imported Target has scope in the directory in which the alias is created and below. The ALIAS_GLOBAL target property can be used to check if the alias is global or not.

ALIAS targets can be used as linkable targets and as targets to read properties from. They can also be tested for existence with the regular if(TARGET) subcommand. The <name> may not be used to modify properties of <target>, that is, it may not be used as the operand of set_property(), set_target_properties(), target_link_libraries() etc. An ALIAS target may not be installed or exported.