Help/command/add_custom_command.rst - third_party/cmake - Git at Google

 add_custom_command
 ------------------

 Add a custom build rule to the generated build system.

 There are two main signatures for add_custom_command The first
 signature is for adding a custom command to produce an output.

 ::

   add_custom_command(OUTPUT output1 [output2 ...]
                      COMMAND command1 [ARGS] [args1...]
                      [COMMAND command2 [ARGS] [args2...] ...]
                      [MAIN_DEPENDENCY depend]
                      [DEPENDS [depends...]]
                      [IMPLICIT_DEPENDS <lang1> depend1
                                       [<lang2> depend2] ...]
                      [WORKING_DIRECTORY dir]
                      [COMMENT comment] [VERBATIM] [APPEND])

 This defines a command to generate specified OUTPUT file(s).  A target
 created in the same directory (CMakeLists.txt file) that specifies any
 output of the custom command as a source file is given a rule to
 generate the file using the command at build time.  Do not list the
 output in more than one independent target that may build in parallel
 or the two instances of the rule may conflict (instead use
 add_custom_target to drive the command and make the other targets
 depend on that one).  If an output name is a relative path it will be
 interpreted relative to the build tree directory corresponding to the
 current source directory.  Note that MAIN_DEPENDENCY is completely
 optional and is used as a suggestion to visual studio about where to
 hang the custom command.  In makefile terms this creates a new target
 in the following form:

 ::

   OUTPUT: MAIN_DEPENDENCY DEPENDS
           COMMAND

 If more than one command is specified they will be executed in order.
 The optional ARGS argument is for backward compatibility and will be
 ignored.

 The second signature adds a custom command to a target such as a
 library or executable.  This is useful for performing an operation
 before or after building the target.  The command becomes part of the
 target and will only execute when the target itself is built.  If the
 target is already built, the command will not execute.

 ::

   add_custom_command(TARGET target
                      PRE_BUILD | PRE_LINK | POST_BUILD
                      COMMAND command1 [ARGS] [args1...]
                      [COMMAND command2 [ARGS] [args2...] ...]
                      [WORKING_DIRECTORY dir]
                      [COMMENT comment] [VERBATIM])

 This defines a new command that will be associated with building the
 specified target.  When the command will happen is determined by which
 of the following is specified:

 ::

   PRE_BUILD - run before all other dependencies
   PRE_LINK - run after other dependencies
   POST_BUILD - run after the target has been built

 Note that the PRE_BUILD option is only supported on Visual Studio 7 or
 later.  For all other generators PRE_BUILD will be treated as
 PRE_LINK.

 If WORKING_DIRECTORY is specified the command will be executed in the
 directory given.  If it is a relative path it will be interpreted
 relative to the build tree directory corresponding to the current
 source directory.  If COMMENT is set, the value will be displayed as a
 message before the commands are executed at build time.  If APPEND is
 specified the COMMAND and DEPENDS option values are appended to the
 custom command for the first output specified.  There must have
 already been a previous call to this command with the same output.
 The COMMENT, WORKING_DIRECTORY, and MAIN_DEPENDENCY options are
 currently ignored when APPEND is given, but may be used in the future.

 If VERBATIM is given then all arguments to the commands will be
 escaped properly for the build tool so that the invoked command
 receives each argument unchanged.  Note that one level of escapes is
 still used by the CMake language processor before add_custom_command
 even sees the arguments.  Use of VERBATIM is recommended as it enables
 correct behavior.  When VERBATIM is not given the behavior is platform
 specific because there is no protection of tool-specific special
 characters.

 If the output of the custom command is not actually created as a file
 on disk it should be marked as SYMBOLIC with
 SET_SOURCE_FILES_PROPERTIES.

 The IMPLICIT_DEPENDS option requests scanning of implicit dependencies
 of an input file.  The language given specifies the programming
 language whose corresponding dependency scanner should be used.
 Currently only C and CXX language scanners are supported.  The
 language has to be specified for every file in the IMPLICIT_DEPENDS
 list.  Dependencies discovered from the scanning are added to those of
 the custom command at build time.  Note that the IMPLICIT_DEPENDS
 option is currently supported only for Makefile generators and will be
 ignored by other generators.

 If COMMAND specifies an executable target (created by ADD_EXECUTABLE)
 it will automatically be replaced by the location of the executable
 created at build time.  Additionally a target-level dependency will be
 added so that the executable target will be built before any target
 using this custom command.  However this does NOT add a file-level
 dependency that would cause the custom command to re-run whenever the
 executable is recompiled.

 Arguments to COMMAND may use "generator expressions" with the syntax
 ``$<...>``.  See the :manual:`cmake-generator-expressions(7)` manual for
 available expressions.

 Note that tgt is not added as a dependency of the target this
 expression is evaluated on.

 ::

   $<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.
   $<INSTALL_PREFIX>         = Content of the install prefix when the target is exported via INSTALL(EXPORT) and empty otherwise.

 Boolean expressions:

 ::

   $<AND:?[,?]...>           = '1' if all '?' are '1', else '0'
   $<OR:?[,?]...>            = '0' if all '?' are '0', else '1'
   $<NOT:?>                  = '0' if '?' is '1', else '1'

 where '?' is always either '0' or '1'.

 Expressions with an implicit 'this' target:

 ::

   $<TARGET_PROPERTY:prop>   = The value of the property prop on the target on which the generator expression is evaluated.

 References to target names in generator expressions imply target-level
 dependencies, but NOT file-level dependencies.  List target names with
 the DEPENDS option to add file dependencies.

 The DEPENDS option specifies files on which the command depends.  If
 any dependency is an OUTPUT of another custom command in the same
 directory (CMakeLists.txt file) CMake automatically brings the other
 custom command into the target in which this command is built.  If
 DEPENDS is not specified the command will run whenever the OUTPUT is
 missing; if the command does not actually create the OUTPUT then the
 rule will always run.  If DEPENDS specifies any target (created by an
 ADD_* command) a target-level dependency is created to make sure the
 target is built before any target using this custom command.
 Additionally, if the target is an executable or library a file-level
 dependency is created to cause the custom command to re-run whenever
 the target is recompiled.
	add_custom_command
	------------------

	Add a custom build rule to the generated build system.

	There are two main signatures for add_custom_command The first
	signature is for adding a custom command to produce an output.

	::

	add_custom_command(OUTPUT output1 [output2 ...]
	COMMAND command1 [ARGS] [args1...]
	[COMMAND command2 [ARGS] [args2...] ...]
	[MAIN_DEPENDENCY depend]
	[DEPENDS [depends...]]
	[IMPLICIT_DEPENDS <lang1> depend1
	[<lang2> depend2] ...]
	[WORKING_DIRECTORY dir]
	[COMMENT comment] [VERBATIM] [APPEND])

	This defines a command to generate specified OUTPUT file(s). A target
	created in the same directory (CMakeLists.txt file) that specifies any
	output of the custom command as a source file is given a rule to
	generate the file using the command at build time. Do not list the
	output in more than one independent target that may build in parallel
	or the two instances of the rule may conflict (instead use
	add_custom_target to drive the command and make the other targets
	depend on that one). If an output name is a relative path it will be
	interpreted relative to the build tree directory corresponding to the
	current source directory. Note that MAIN_DEPENDENCY is completely
	optional and is used as a suggestion to visual studio about where to
	hang the custom command. In makefile terms this creates a new target
	in the following form:

	::

	OUTPUT: MAIN_DEPENDENCY DEPENDS
	COMMAND

	If more than one command is specified they will be executed in order.
	The optional ARGS argument is for backward compatibility and will be
	ignored.

	The second signature adds a custom command to a target such as a
	library or executable. This is useful for performing an operation
	before or after building the target. The command becomes part of the
	target and will only execute when the target itself is built. If the
	target is already built, the command will not execute.

	::

	add_custom_command(TARGET target
	PRE_BUILD \| PRE_LINK \| POST_BUILD
	COMMAND command1 [ARGS] [args1...]
	[COMMAND command2 [ARGS] [args2...] ...]
	[WORKING_DIRECTORY dir]
	[COMMENT comment] [VERBATIM])

	This defines a new command that will be associated with building the
	specified target. When the command will happen is determined by which
	of the following is specified:

	::

	PRE_BUILD - run before all other dependencies
	PRE_LINK - run after other dependencies
	POST_BUILD - run after the target has been built

	Note that the PRE_BUILD option is only supported on Visual Studio 7 or
	later. For all other generators PRE_BUILD will be treated as
	PRE_LINK.

	If WORKING_DIRECTORY is specified the command will be executed in the
	directory given. If it is a relative path it will be interpreted
	relative to the build tree directory corresponding to the current
	source directory. If COMMENT is set, the value will be displayed as a
	message before the commands are executed at build time. If APPEND is
	specified the COMMAND and DEPENDS option values are appended to the
	custom command for the first output specified. There must have
	already been a previous call to this command with the same output.
	The COMMENT, WORKING_DIRECTORY, and MAIN_DEPENDENCY options are
	currently ignored when APPEND is given, but may be used in the future.

	If VERBATIM is given then all arguments to the commands will be
	escaped properly for the build tool so that the invoked command
	receives each argument unchanged. Note that one level of escapes is
	still used by the CMake language processor before add_custom_command
	even sees the arguments. Use of VERBATIM is recommended as it enables
	correct behavior. When VERBATIM is not given the behavior is platform
	specific because there is no protection of tool-specific special
	characters.

	If the output of the custom command is not actually created as a file
	on disk it should be marked as SYMBOLIC with
	SET_SOURCE_FILES_PROPERTIES.

	The IMPLICIT_DEPENDS option requests scanning of implicit dependencies
	of an input file. The language given specifies the programming
	language whose corresponding dependency scanner should be used.
	Currently only C and CXX language scanners are supported. The
	language has to be specified for every file in the IMPLICIT_DEPENDS
	list. Dependencies discovered from the scanning are added to those of
	the custom command at build time. Note that the IMPLICIT_DEPENDS
	option is currently supported only for Makefile generators and will be
	ignored by other generators.

	If COMMAND specifies an executable target (created by ADD_EXECUTABLE)
	it will automatically be replaced by the location of the executable
	created at build time. Additionally a target-level dependency will be
	added so that the executable target will be built before any target
	using this custom command. However this does NOT add a file-level
	dependency that would cause the custom command to re-run whenever the
	executable is recompiled.

	Arguments to COMMAND may use "generator expressions" with the syntax
	``$<...>``. See the :manual:`cmake-generator-expressions(7)` manual for
	available expressions.

	Note that tgt is not added as a dependency of the target this
	expression is evaluated on.

	::

	$<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.
	$<INSTALL_PREFIX> = Content of the install prefix when the target is exported via INSTALL(EXPORT) and empty otherwise.

	Boolean expressions:

	::

	$<AND:?[,?]...> = '1' if all '?' are '1', else '0'
	$<OR:?[,?]...> = '0' if all '?' are '0', else '1'
	$<NOT:?> = '0' if '?' is '1', else '1'

	where '?' is always either '0' or '1'.

	Expressions with an implicit 'this' target:

	::

	$<TARGET_PROPERTY:prop> = The value of the property prop on the target on which the generator expression is evaluated.

	References to target names in generator expressions imply target-level
	dependencies, but NOT file-level dependencies. List target names with
	the DEPENDS option to add file dependencies.

	The DEPENDS option specifies files on which the command depends. If
	any dependency is an OUTPUT of another custom command in the same
	directory (CMakeLists.txt file) CMake automatically brings the other
	custom command into the target in which this command is built. If
	DEPENDS is not specified the command will run whenever the OUTPUT is
	missing; if the command does not actually create the OUTPUT then the
	rule will always run. If DEPENDS specifies any target (created by an
	ADD_* command) a target-level dependency is created to make sure the
	target is built before any target using this custom command.
	Additionally, if the target is an executable or library a file-level
	dependency is created to cause the custom command to re-run whenever
	the target is recompiled.