Merge topic 'codegen'

197cb419d1 add_custom_command: Add CODEGEN support

Acked-by: Kitware Robot <kwrobot@kitware.com>
Tested-by: buildbot <buildbot@kitware.com>
Merge-request: !9581

Help/command/add_custom_command.rst

@@ -26,6 +26,7 @@ The first signature is for adding a custom command to produce an output:
                      [JOB_POOL job_pool]
                      [JOB_SERVER_AWARE <bool>]
                      [VERBATIM] [APPEND] [USES_TERMINAL]
+                     [CODEGEN]
                      [COMMAND_EXPAND_LISTS]
                      [DEPENDS_EXPLICIT_ONLY])
 
@@ -203,6 +204,18 @@ The options are:
   ``${CC} "-I$<JOIN:$<TARGET_PROPERTY:foo,INCLUDE_DIRECTORIES>,;-I>" foo.cc``
   to be properly expanded.
 
+``CODEGEN``
+  .. versionadded:: 3.31
+
+  Adds the custom command to a global ``codegen`` target that can be
+  used to execute the custom command while avoiding the majority of the
+  build graph.
+
+  This option is supported only by :ref:`Ninja Generators` and
+  :ref:`Makefile Generators`, and is ignored by other generators.
+  Furthermore, this option is allowed only if policy :policy:`CMP0171`
+  is set to ``NEW``.
+
 ``IMPLICIT_DEPENDS``
   Request scanning of implicit dependencies of an input file.
   The language given specifies the programming language whose
@@ -454,6 +467,25 @@ will re-run whenever ``in.txt`` changes.
   where ``<config>`` is the build configuration, and then compile the generated
   source as part of a library.
 
+.. versionadded:: 3.31
+  Use the ``CODEGEN`` option to add a custom command's outputs to the builtin
+  ``codegen`` target.  This is useful to make generated code available for
+   static analysis without building the entire project.  For example:
+
+  .. code-block:: cmake
+
+    add_executable(someTool someTool.c)
+
+    add_custom_command(
+      OUTPUT out.c
+      COMMAND someTool -o out.c
+      CODEGEN)
+
+    add_library(myLib out.c)
+
+  A user may build the ``codegen`` target to generate ``out.c``.
+  ``someTool`` is built as dependency, but ``myLib`` is not built at all.
+
 Example: Generating Files for Multiple Targets
 """"""""""""""""""""""""""""""""""""""""""""""
 

Help/manual/cmake-policies.7.rst

@@ -51,6 +51,14 @@ The :variable:`CMAKE_MINIMUM_REQUIRED_VERSION` variable may also be used
 to determine whether to report an error on use of deprecated macros or
 functions.
 
+Policies Introduced by CMake 3.31
+=================================
+
+.. toctree::
+   :maxdepth: 1
+
+   CMP0171: 'codegen' is a reserved target name. </policy/CMP0171>
+
 Policies Introduced by CMake 3.30
 =================================
 

Help/policy/CMP0171.rst

@@ -0,0 +1,26 @@
+CMP0171
+-------
+
+.. versionadded:: 3.31
+
+``codegen`` is a reserved target name.
+
+CMake 3.30 and earlier did not reserve ``codegen`` as a builtin target name,
+leaving projects free to create their own target with that name.
+CMake 3.31 and later prefer to reserve ``codegen`` as a builtin target name
+to drive custom commands created with the ``CODEGEN`` option to
+:command:`add_custom_command`.  In order to support building the ``codegen``
+target in scripted environments, e.g., ``cmake --build . --target codegen``,
+the ``codegen`` target needs to be generated even if no custom commands
+use the ``CODEGEN`` option.  This policy provides compatibility for projects
+that have not been updated to avoid creating a target named ``codegen``.
+
+The ``OLD`` behavior of this policy allows projects to create a target
+with the name ``codegen``.  The ``NEW`` behavior halts with a fatal error
+if a target with the name ``codegen`` is created.
+
+.. |INTRODUCED_IN_CMAKE_VERSION| replace:: 3.31
+.. |WARNS_OR_DOES_NOT_WARN| replace:: warns
+.. include:: STANDARD_ADVICE.txt
+
+.. include:: DEPRECATED.txt

Help/release/dev/codegen.rst

@@ -0,0 +1,10 @@
+codegen
+-------
+
+* The :ref:`Ninja Generators` and :ref:`Makefile Generators` now produce
+  a ``codegen`` build target.  See policy :policy:`CMP0171`.  It drives a
+  subset of the build graph sufficient to run custom commands created with
+  :command:`add_custom_command`'s new ``CODEGEN`` option.
+
+* The :command:`add_custom_command` command gained a ``CODEGEN`` option
+  to mark a custom commands outputs as dependencies of a ``codegen`` target.