Commit 2a58c872 authored by Brad King's avatar Brad King 💬
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Help: Revise and format 'add_custom_command' docs

Format the reStructuredText markup manually.  Organize the command
options into a definition list.  Use inline markup to cross-reference
related documents.
parent cb88742d
......@@ -3,10 +3,12 @@ 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.
There are two main signatures for ``add_custom_command``.
::
Generating Files
^^^^^^^^^^^^^^^^
The first signature is for adding a custom command to produce an output::
add_custom_command(OUTPUT output1 [output2 ...]
COMMAND command1 [ARGS] [args1...]
......@@ -18,28 +20,117 @@ signature is for adding a custom command to produce an output.
[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:
::
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 the :command:`add_custom_target` command to drive the
command and make the other targets depend on that one).
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 options are:
``APPEND``
Append the ``COMMAND`` and ``DEPENDS`` option values 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``, ``MAIN_DEPENDENCY``, and ``WORKING_DIRECTORY``
options are currently ignored when APPEND is given, but may be
used in the future.
``COMMAND``
Specify the command-line(s) to execute at build time.
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.
If ``COMMAND`` specifies an executable target (created by the
:command:`add_executable` command) 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
:manual:`generator expressions <cmake-generator-expressions(7)>`.
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-level dependencies.
``COMMENT``
Display the given message before the commands are executed at
build time.
``DEPENDS``
Specify 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 the
:command:`add_custom_target`, :command:`add_executable`, or
:command:`add_library` 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.
Arguments to ``DEPENDS`` may use
:manual:`generator expressions <cmake-generator-expressions(7)>`.
``IMPLICIT_DEPENDS``
Request 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.
``MAIN_DEPENDENCY``
Specify the primary input source file to the command. This is
treated just like any value given to the ``DEPENDS`` option
but also suggests to Visual Studio generators where to hang
the custom command.
``OUTPUT``
Specify the output files the command is expected to produce.
If an output name is a relative path it will be interpreted
relative to the build tree directory corresponding to the
current source directory.
If the output of the custom command is not actually created
as a file on disk it should be marked with the :prop_sf:`SYMBOLIC`
source file property.
``VERBATIM``
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.
``WORKING_DIRECTORY``
Execute the command with the given current working directory.
If it is a relative path it will be interpreted relative to the
build tree directory corresponding to the current source directory.
Build Events
^^^^^^^^^^^^
The second signature adds a custom command to a target such as a
library or executable. This is useful for performing an operation
......@@ -60,79 +151,13 @@ 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
``$<...>``. See the :manual:`cmake-generator-expressions(7)` manual for
available expressions.
References to target names in generator expressions imply target-level
dependencies, but NOT file-level dependencies. List target names with
the DEPENDS option to add file dependencies.
The DEPENDS option specifies files on which the command depends. If
any dependency is an OUTPUT of another custom command in the same
directory (CMakeLists.txt file) CMake automatically brings the other
custom command into the target in which this command is built. If
DEPENDS is not specified the command will run whenever the OUTPUT is
missing; if the command does not actually create the OUTPUT then the
rule will always run. If DEPENDS specifies any target (created by an
ADD_* command) a target-level dependency is created to make sure the
target is built before any target using this custom command.
Additionally, if the target is an executable or library a file-level
dependency is created to cause the custom command to re-run whenever
the target is recompiled.
Arguments to ``DEPENDS`` may use "generator expressions" with the syntax
``$<...>``. See the :manual:`cmake-generator-expressions(7)` manual for
available expressions.
``PRE_BUILD``
Run before any other rules are executed within the target.
This is supported only on Visual Studio 7 or later.
For all other generators ``PRE_BUILD`` will be treated as
``PRE_LINK``.
``PRE_LINK``
Run after sources have been compiled but before linking the binary
or running the librarian or archiver tool of a static library.
``POST_BUILD``
Run after all other rules within the target have been executed.
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