Merge topic 'doc-add_custom_command'
5bf1c5ccHelp: Document add_custom_command PRE_BUILD/PRE_LINK for exe/lib only (#15059)2a58c872Help: Revise and format 'add_custom_command' docscb88742dHelp: Remove stray content from 'add_custom_command' docs
This commit is contained in:
Brad King
CMake Topic Stage
commit
a16a344b4b
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@ -3,10 +3,12 @@ add_custom_command
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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 The first
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signature is for adding a custom command to produce an output.
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There are two main signatures for ``add_custom_command``.
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::
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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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@ -18,28 +20,117 @@ signature is for adding a custom command to produce an output.
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[WORKING_DIRECTORY dir]
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[COMMENT comment] [VERBATIM] [APPEND])
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This defines a command to generate specified OUTPUT file(s). A target
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created in the same directory (CMakeLists.txt file) that specifies any
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output of the custom command as a source file is given a rule to
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generate the file using the command at build time. Do not list the
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output in more than one independent target that may build in parallel
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or the two instances of the rule may conflict (instead use
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add_custom_target to drive the command and make the other targets
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depend on that one). If an output name is a relative path it will be
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interpreted relative to the build tree directory corresponding to the
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current source directory. Note that MAIN_DEPENDENCY is completely
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optional and is used as a suggestion to visual studio about where to
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hang the custom command. In makefile terms this creates a new target
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in the following form:
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::
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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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If more than one command is specified they will be executed in order.
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The optional ARGS argument is for backward compatibility and will be
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ignored.
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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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``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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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 (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.
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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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``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.
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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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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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``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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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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@ -60,103 +151,15 @@ This defines a new command that will be associated with building the
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specified target. When the command will happen is determined by which
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of the following is specified:
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::
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PRE_BUILD - run before all other dependencies
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PRE_LINK - run after other dependencies
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POST_BUILD - run after the target has been built
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Note that the PRE_BUILD option is only supported on Visual Studio 7 or
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later. For all other generators PRE_BUILD will be treated as
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PRE_LINK.
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If WORKING_DIRECTORY is specified the command will be executed in the
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directory given. If it is a relative path it will be interpreted
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relative to the build tree directory corresponding to the current
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source directory. If COMMENT is set, the value will be displayed as a
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message before the commands are executed at build time. If APPEND is
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specified the COMMAND and DEPENDS option values are appended to the
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custom command for the first output specified. There must have
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already been a previous call to this command with the same output.
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The COMMENT, WORKING_DIRECTORY, and MAIN_DEPENDENCY options are
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currently ignored when APPEND is given, but may be used in the future.
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If VERBATIM is given then all arguments to the commands will be
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escaped properly for the build tool so that the invoked command
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receives each argument unchanged. Note that one level of escapes is
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still used by the CMake language processor before add_custom_command
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even sees the arguments. Use of VERBATIM is recommended as it enables
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correct behavior. When VERBATIM is not given the behavior is platform
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specific because there is no protection of tool-specific special
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characters.
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If the output of the custom command is not actually created as a file
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on disk it should be marked as SYMBOLIC with
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SET_SOURCE_FILES_PROPERTIES.
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The IMPLICIT_DEPENDS option requests scanning of implicit dependencies
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of an input file. The language given specifies the programming
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language whose corresponding dependency scanner should be used.
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Currently only C and CXX language scanners are supported. The
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language has to be specified for every file in the IMPLICIT_DEPENDS
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list. Dependencies discovered from the scanning are added to those of
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the custom command at build time. Note that the IMPLICIT_DEPENDS
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option is currently supported only for Makefile generators and will be
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ignored by other generators.
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If COMMAND specifies an executable target (created by ADD_EXECUTABLE)
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it will automatically be replaced by the location of the executable
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created at build time. Additionally a target-level dependency will be
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added so that the executable target will be built before any target
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using this custom command. However this does NOT add a file-level
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dependency that would cause the custom command to re-run whenever the
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executable is recompiled.
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Arguments to COMMAND may use "generator expressions" with the syntax
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``$<...>``. See the :manual:`cmake-generator-expressions(7)` manual for
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available expressions.
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Note that tgt is not added as a dependency of the target this
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expression is evaluated on.
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::
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$<TARGET_POLICY:pol> = '1' if the policy was NEW when the 'head' target was created, else '0'. If the policy was not set, the warning message for the policy will be emitted. This generator expression only works for a subset of policies.
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$<INSTALL_PREFIX> = Content of the install prefix when the target is exported via INSTALL(EXPORT) and empty otherwise.
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Boolean expressions:
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::
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$<AND:?[,?]...> = '1' if all '?' are '1', else '0'
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$<OR:?[,?]...> = '0' if all '?' are '0', else '1'
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$<NOT:?> = '0' if '?' is '1', else '1'
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where '?' is always either '0' or '1'.
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Expressions with an implicit 'this' target:
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::
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$<TARGET_PROPERTY:prop> = The value of the property prop on the target on which the generator expression is evaluated.
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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 dependencies.
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The DEPENDS option specifies files on which the command depends. If
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any dependency is an OUTPUT of another custom command in the same
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directory (CMakeLists.txt file) CMake automatically brings the other
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custom command into the target in which this command is built. If
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DEPENDS is not specified the command will run whenever the OUTPUT is
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missing; if the command does not actually create the OUTPUT then the
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rule will always run. If DEPENDS specifies any target (created by an
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ADD_* command) a target-level dependency is created to make sure the
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target is built before any target using this custom command.
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Additionally, if the target is an executable or library a file-level
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dependency is created to cause the custom command to re-run whenever
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the target is recompiled.
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Arguments to ``DEPENDS`` may use "generator expressions" with the syntax
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``$<...>``. See the :manual:`cmake-generator-expressions(7)` manual for
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available expressions.
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``PRE_BUILD``
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Run before any other rules are executed within the target.
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This is supported only on Visual Studio 7 or later.
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For all other generators ``PRE_BUILD`` will be treated as
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``PRE_LINK``.
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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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