add_custom_command.rst 11.4 KB
Newer Older
1
2
3
4
5
add_custom_command
------------------

Add a custom build rule to the generated build system.

6
There are two main signatures for ``add_custom_command``.
7

8
9
10
Generating Files
^^^^^^^^^^^^^^^^

11
12
13
The first signature is for adding a custom command to produce an output:

.. code-block:: cmake
14
15
16
17
18
19

  add_custom_command(OUTPUT output1 [output2 ...]
                     COMMAND command1 [ARGS] [args1...]
                     [COMMAND command2 [ARGS] [args2...] ...]
                     [MAIN_DEPENDENCY depend]
                     [DEPENDS [depends...]]
20
                     [BYPRODUCTS [files...]]
21
22
23
                     [IMPLICIT_DEPENDS <lang1> depend1
                                      [<lang2> depend2] ...]
                     [WORKING_DIRECTORY dir]
24
                     [COMMENT comment]
25
                     [DEPFILE depfile]
26
                     [JOB_POOL job_pool]
27
28
                     [VERBATIM] [APPEND] [USES_TERMINAL]
                     [COMMAND_EXPAND_LISTS])
29

30
31
32
33
34
35
36
37
38
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::
39
40
41
42

  OUTPUT: MAIN_DEPENDENCY DEPENDS
          COMMAND

43
44
45
46
47
48
49
50
51
52
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.

53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
``BYPRODUCTS``
  Specify the files the command is expected to produce but whose
  modification time may or may not be newer than the dependencies.
  If a byproduct name is a relative path it will be interpreted
  relative to the build tree directory corresponding to the
  current source directory.
  Each byproduct file will be marked with the :prop_sf:`GENERATED`
  source file property automatically.

  Explicit specification of byproducts is supported by the
  :generator:`Ninja` generator to tell the ``ninja`` build tool
  how to regenerate byproducts when they are missing.  It is
  also useful when other build rules (e.g. custom commands)
  depend on the byproducts.  Ninja requires a build rule for any
  generated file on which another rule depends even if there are
  order-only dependencies to ensure the byproducts will be
  available before their dependents build.

71
72
``COMMAND``
  Specify the command-line(s) to execute at build time.
73
74
  If more than one ``COMMAND`` is specified they will be executed in order,
  but *not* necessarily composed into a stateful shell or batch script.
75
76
77
  (To run a full script, use the :command:`configure_file` command or the
  :command:`file(GENERATE)` command to create it, and then specify
  a ``COMMAND`` to launch it.)
78
79
80
  The optional ``ARGS`` argument is for backward compatibility and
  will be ignored.

81
  If ``COMMAND`` specifies an executable target name (created by the
82
83
84
85
86
87
88
89
90
91
92
93
94
  :command:`add_executable` command), it will automatically be replaced
  by the location of the executable created at build time if either of
  the following is true:

  * The target is not being cross-compiled (i.e. the
    :variable:`CMAKE_CROSSCOMPILING` variable is not set to true).
  * The target is being cross-compiled and an emulator is provided (i.e.
    its :prop_tgt:`CROSSCOMPILING_EMULATOR` target property is set).
    In this case, the contents of :prop_tgt:`CROSSCOMPILING_EMULATOR` will be
    prepended to the command before the location of the target executable.

  If neither of the above conditions are met, it is assumed that the
  command name is a program to be found on the ``PATH`` at build time.
95
96
97

  Arguments to ``COMMAND`` may use
  :manual:`generator expressions <cmake-generator-expressions(7)>`.
98
99
100
101
102
103
104
105
106
107
108
  Use the ``TARGET_FILE`` generator expression to refer to the location of
  a target later in the command line (i.e. as a command argument rather
  than as the command to execute).

  Whenever a target is used as a command to execute or is mentioned in a
  generator expression as a command argument, a target-level dependency
  will be added automatically so that the mentioned 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.  List target names with
  the ``DEPENDS`` option to add such file-level dependencies.
109
110
111
112
113
114
115
116
117
118

``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.
119
120
121
  A target-level dependency is added if any dependency is listed as
  ``BYPRODUCTS`` of a target or any of its build events in the same
  directory to ensure the byproducts will be available.
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
  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)>`.

137
138
139
140
141
142
143
144
``COMMAND_EXPAND_LISTS``
  Lists in ``COMMAND`` arguments will be expanded, including those
  created with
  :manual:`generator expressions <cmake-generator-expressions(7)>`,
  allowing ``COMMAND`` arguments such as
  ``${CC} "-I$<JOIN:$<TARGET_PROPERTY:foo,INCLUDE_DIRECTORIES>,;-I>" foo.cc``
  to be properly expanded.

145
146
147
148
149
150
151
152
153
154
155
``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.

156
157
158
159
160
161
162
``JOB_POOL``
  Specify a :prop_gbl:`pool <JOB_POOLS>` for the :generator:`Ninja`
  generator. Incompatible with ``USES_TERMINAL``, which implies
  the ``console`` pool.
  Using a pool that is not defined by :prop_gbl:`JOB_POOLS` causes
  an error by ninja at build time.

163
164
165
166
``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
167
168
169
170
  the custom command. Each source file may have at most one command
  specifying it as its main dependency. A compile command (i.e. for a
  library or an executable) counts as an implicit main dependency which
  gets silently overwritten by a custom command specification.
171
172
173
174
175
176

``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.
177
178
  Each output file will be marked with the :prop_sf:`GENERATED`
  source file property automatically.
179
180
181
182
  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.

183
184
185
``USES_TERMINAL``
  The command will be given direct access to the terminal if possible.
  With the :generator:`Ninja` generator, this places the command in
Stephen Kelly's avatar
Stephen Kelly committed
186
  the ``console`` :prop_gbl:`pool <JOB_POOLS>`.
187

188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
``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.

203
204
205
  Arguments to ``WORKING_DIRECTORY`` may use
  :manual:`generator expressions <cmake-generator-expressions(7)>`.

206
207
208
209
210
211
``DEPFILE``
  Specify a ``.d`` depfile for the :generator:`Ninja` generator.
  A ``.d`` file holds dependencies usually emitted by the custom
  command itself.
  Using ``DEPFILE`` with other generators than Ninja is an error.

212
213
Build Events
^^^^^^^^^^^^
214
215
216
217
218
219
220

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.

221
.. code-block:: cmake
222

223
  add_custom_command(TARGET <target>
224
225
226
                     PRE_BUILD | PRE_LINK | POST_BUILD
                     COMMAND command1 [ARGS] [args1...]
                     [COMMAND command2 [ARGS] [args2...] ...]
227
                     [BYPRODUCTS [files...]]
228
                     [WORKING_DIRECTORY dir]
229
                     [COMMENT comment]
230
231
                     [VERBATIM] [USES_TERMINAL]
                     [COMMAND_EXPAND_LISTS])
232
233

This defines a new command that will be associated with building the
234
235
236
237
specified ``<target>``.  The ``<target>`` must be defined in the current
directory; targets defined in other directories may not be specified.

When the command will happen is determined by which
238
239
of the following is specified:

240
``PRE_BUILD``
241
242
243
  On :ref:`Visual Studio Generators`, run before any other rules are
  executed within the target.
  On other generators, run just before ``PRE_LINK`` commands.
244
245
246
``PRE_LINK``
  Run after sources have been compiled but before linking the binary
  or running the librarian or archiver tool of a static library.
247
248
  This is not defined for targets created by the
  :command:`add_custom_target` command.
249
250
``POST_BUILD``
  Run after all other rules within the target have been executed.
251
252
253
254
255
256
257
258
259
260

.. note::
  Because generator expressions can be used in custom commands,
  it is possible to define ``COMMAND`` lines or whole custom commands
  which evaluate to empty strings for certain configurations.
  For **Visual Studio 2010 (and newer)** generators these command
  lines or custom commands will be omitted for the specific
  configuration and no "empty-string-command" will be added.

  This allows to add individual build events for every configuration.