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239 lines
10 KiB
239 lines
10 KiB
add_custom_command
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------------------
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Add a custom build rule to the generated build system.
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There are two main signatures for ``add_custom_command``.
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Generating Files
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^^^^^^^^^^^^^^^^
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The first signature is for adding a custom command to produce an output::
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add_custom_command(OUTPUT output1 [output2 ...]
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COMMAND command1 [ARGS] [args1...]
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[COMMAND command2 [ARGS] [args2...] ...]
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[MAIN_DEPENDENCY depend]
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[DEPENDS [depends...]]
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[BYPRODUCTS [files...]]
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[IMPLICIT_DEPENDS <lang1> depend1
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[<lang2> depend2] ...]
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[WORKING_DIRECTORY dir]
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[COMMENT comment]
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[DEPFILE depfile]
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[VERBATIM] [APPEND] [USES_TERMINAL]
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[COMMAND_EXPAND_LISTS])
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This defines a command to generate specified ``OUTPUT`` file(s).
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A target created in the same directory (``CMakeLists.txt`` file)
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that specifies any output of the custom command as a source file
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is given a rule to generate the file using the command at build time.
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Do not list the output in more than one independent target that
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may build in parallel or the two instances of the rule may conflict
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(instead use the :command:`add_custom_target` command to drive the
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command and make the other targets depend on that one).
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In makefile terms this creates a new target in the following form::
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OUTPUT: MAIN_DEPENDENCY DEPENDS
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COMMAND
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The options are:
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``APPEND``
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Append the ``COMMAND`` and ``DEPENDS`` option values to the custom
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command for the first output specified. There must have already
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been a previous call to this command with the same output.
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The ``COMMENT``, ``MAIN_DEPENDENCY``, and ``WORKING_DIRECTORY``
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options are currently ignored when APPEND is given, but may be
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used in the future.
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``BYPRODUCTS``
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Specify the files the command is expected to produce but whose
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modification time may or may not be newer than the dependencies.
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If a byproduct name is a relative path it will be interpreted
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relative to the build tree directory corresponding to the
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current source directory.
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Each byproduct file will be marked with the :prop_sf:`GENERATED`
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source file property automatically.
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Explicit specification of byproducts is supported by the
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:generator:`Ninja` generator to tell the ``ninja`` build tool
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how to regenerate byproducts when they are missing. It is
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also useful when other build rules (e.g. custom commands)
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depend on the byproducts. Ninja requires a build rule for any
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generated file on which another rule depends even if there are
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order-only dependencies to ensure the byproducts will be
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available before their dependents build.
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The ``BYPRODUCTS`` option is ignored on non-Ninja generators
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except to mark byproducts ``GENERATED``.
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``COMMAND``
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Specify the command-line(s) to execute at build time.
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If more than one ``COMMAND`` is specified they will be executed in order,
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but *not* necessarily composed into a stateful shell or batch script.
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(To run a full script, use the :command:`configure_file` command or the
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:command:`file(GENERATE)` command to create it, and then specify
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a ``COMMAND`` to launch it.)
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The optional ``ARGS`` argument is for backward compatibility and
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will be ignored.
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If ``COMMAND`` specifies an executable target name (created by the
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:command:`add_executable` command) it will automatically be replaced
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by the location of the executable created at build time. If set, the
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:prop_tgt:`CROSSCOMPILING_EMULATOR` executable target property will
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also be prepended to the command to allow the executable to run on
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the host.
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(Use the ``TARGET_FILE``
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:manual:`generator expression <cmake-generator-expressions(7)>` to
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reference an executable later in the command line.)
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Additionally a target-level dependency will be added so that the
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executable target will be built before any target using this custom
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command. However this does NOT add a file-level dependency that
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would cause the custom command to re-run whenever the executable is
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recompiled.
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Arguments to ``COMMAND`` may use
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:manual:`generator expressions <cmake-generator-expressions(7)>`.
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References to target names in generator expressions imply target-level
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dependencies, but NOT file-level dependencies. List target names with
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the ``DEPENDS`` option to add file-level dependencies.
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``COMMENT``
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Display the given message before the commands are executed at
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build time.
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``DEPENDS``
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Specify files on which the command depends. If any dependency is
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an ``OUTPUT`` of another custom command in the same directory
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(``CMakeLists.txt`` file) CMake automatically brings the other
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custom command into the target in which this command is built.
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If ``DEPENDS`` is not specified the command will run whenever
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the ``OUTPUT`` is missing; if the command does not actually
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create the ``OUTPUT`` then the rule will always run.
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If ``DEPENDS`` specifies any target (created by the
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:command:`add_custom_target`, :command:`add_executable`, or
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:command:`add_library` command) a target-level dependency is
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created to make sure the target is built before any target
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using this custom command. Additionally, if the target is an
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executable or library a file-level dependency is created to
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cause the custom command to re-run whenever the target is
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recompiled.
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Arguments to ``DEPENDS`` may use
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:manual:`generator expressions <cmake-generator-expressions(7)>`.
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``COMMAND_EXPAND_LISTS``
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Lists in ``COMMAND`` arguments will be expanded, including those
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created with
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:manual:`generator expressions <cmake-generator-expressions(7)>`,
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allowing ``COMMAND`` arguments such as
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``${CC} "-I$<JOIN:$<TARGET_PROPERTY:foo,INCLUDE_DIRECTORIES>,;-I>" foo.cc``
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to be properly expanded.
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``IMPLICIT_DEPENDS``
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Request scanning of implicit dependencies of an input file.
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The language given specifies the programming language whose
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corresponding dependency scanner should be used.
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Currently only ``C`` and ``CXX`` language scanners are supported.
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The language has to be specified for every file in the
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``IMPLICIT_DEPENDS`` list. Dependencies discovered from the
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scanning are added to those of the custom command at build time.
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Note that the ``IMPLICIT_DEPENDS`` option is currently supported
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only for Makefile generators and will be ignored by other generators.
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``MAIN_DEPENDENCY``
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Specify the primary input source file to the command. This is
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treated just like any value given to the ``DEPENDS`` option
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but also suggests to Visual Studio generators where to hang
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the custom command. Each source file may have at most one command
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specifying it as its main dependency. A compile command (i.e. for a
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library or an executable) counts as an implicit main dependency which
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gets silently overwritten by a custom command specification.
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``OUTPUT``
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Specify the output files the command is expected to produce.
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If an output name is a relative path it will be interpreted
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relative to the build tree directory corresponding to the
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current source directory.
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Each output file will be marked with the :prop_sf:`GENERATED`
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source file property automatically.
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If the output of the custom command is not actually created
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as a file on disk it should be marked with the :prop_sf:`SYMBOLIC`
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source file property.
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``USES_TERMINAL``
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The command will be given direct access to the terminal if possible.
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With the :generator:`Ninja` generator, this places the command in
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the ``console`` :prop_gbl:`pool <JOB_POOLS>`.
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``VERBATIM``
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All arguments to the commands will be escaped properly for the
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build tool so that the invoked command receives each argument
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unchanged. Note that one level of escapes is still used by the
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CMake language processor before add_custom_command even sees the
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arguments. Use of ``VERBATIM`` is recommended as it enables
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correct behavior. When ``VERBATIM`` is not given the behavior
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is platform specific because there is no protection of
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tool-specific special characters.
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``WORKING_DIRECTORY``
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Execute the command with the given current working directory.
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If it is a relative path it will be interpreted relative to the
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build tree directory corresponding to the current source directory.
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``DEPFILE``
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Specify a ``.d`` depfile for the :generator:`Ninja` generator.
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A ``.d`` file holds dependencies usually emitted by the custom
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command itself.
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Using ``DEPFILE`` with other generators than Ninja is an error.
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Build Events
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^^^^^^^^^^^^
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The second signature adds a custom command to a target such as a
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library or executable. This is useful for performing an operation
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before or after building the target. The command becomes part of the
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target and will only execute when the target itself is built. If the
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target is already built, the command will not execute.
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::
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add_custom_command(TARGET <target>
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PRE_BUILD | PRE_LINK | POST_BUILD
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COMMAND command1 [ARGS] [args1...]
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[COMMAND command2 [ARGS] [args2...] ...]
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[BYPRODUCTS [files...]]
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[WORKING_DIRECTORY dir]
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[COMMENT comment]
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[VERBATIM] [USES_TERMINAL])
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This defines a new command that will be associated with building the
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specified ``<target>``. The ``<target>`` must be defined in the current
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directory; targets defined in other directories may not be specified.
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When the command will happen is determined by which
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of the following is specified:
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``PRE_BUILD``
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On :ref:`Visual Studio Generators`, run before any other rules are
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executed within the target.
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On other generators, run just before ``PRE_LINK`` commands.
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``PRE_LINK``
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Run after sources have been compiled but before linking the binary
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or running the librarian or archiver tool of a static library.
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This is not defined for targets created by the
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:command:`add_custom_target` command.
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``POST_BUILD``
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Run after all other rules within the target have been executed.
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.. note::
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Because generator expressions can be used in custom commands,
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it is possible to define ``COMMAND`` lines or whole custom commands
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which evaluate to empty strings for certain configurations.
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For **Visual Studio 2010 (and newer)** generators these command
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lines or custom commands will be omitted for the specific
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configuration and no "empty-string-command" will be added.
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This allows to add individual build events for every configuration.
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