A common idiom in CMake-based build systems is to have custom commands
that generate files not listed explicitly as outputs so that these
files do not have to be newer than the inputs. The file modification
times of such "byproducts" are updated only when their content changes.
Then other build rules can depend on the byproducts explicitly so that
their dependents rebuild when the content of the original byproducts
really does change.
This "undeclared byproduct" approach is necessary for Makefile, VS, and
Xcode build tools because if a byproduct were listed as an output of a
rule then the rule would always rerun when the input is newer than the
byproduct but the byproduct may never be updated.
Ninja solves this problem by offering a 'restat' feature to check
whether an output was really modified after running a rule and tracking
the fact that it is up to date separately from its timestamp. However,
Ninja also stats all dependencies up front and will only restat files
that are listed as outputs of rules with the 'restat' option enabled.
Therefore an undeclared byproduct that does not exist at the start of
the build will be considered missing and the build will fail even if
other dependencies would cause the byproduct to be available before its
dependents build.
CMake works around this limitation by adding 'phony' build rules for
custom command dependencies in the build tree that do not have any
explicit specification of what produces them. This is not optimal
because it prevents Ninja from reporting an error when an input to a
rule really is missing. A better approach is to allow projects to
explicitly specify the byproducts of their custom commands so that no
phony rules are needed for them. In order to work with the non-Ninja
generators, the byproducts must be known separately from the outputs.
Add a new "BYPRODUCTS" option to the add_custom_command and
add_custom_target commands to specify byproducts explicitly. Teach the
Ninja generator to specify byproducts as outputs of the custom commands.
In the case of POST_BUILD, PRE_LINK, and PRE_BUILD events on targets
that link, the byproducts must be specified as outputs of the link rule
that runs the commands. Activate 'restat' for such rules so that Ninja
knows it needs to check the byproducts, but not for link rules that have
no byproducts.
Use the clang RemoveCStrCalls tool to automatically migrate the
code. This was only run on linux, so does not have any positive or
negative effect on other platforms.
Replace the boolean value that indicates whether an argument is unquoted
or quoted with a generalized enumeration of possible argument types.
For now "Quoted" and "Unquoted" remain the only types.
This converts the CMake license to a pure 3-clause OSI-approved BSD
License. We drop the previous license clause requiring modified
versions to be plainly marked. We also update the CMake copyright to
cover the full development time range.
Long ago the native build system generators needed HEADER_FILE_ONLY to
be set on header files to stop them from building. The modern
generators correctly handle headers without the help of this property.
This removes automatic setting of the property so that it can be used
reliably as an indicator of project author intention. It fixes VS IDE
project files to show header files normally instead of excluded (broken
by the fix for issue #7845).
CMake-SourceFile2-bp and CMake-SourceFile2-b-mp1 to trunk. This
commit is surrounded by tags CMake-SourceFile2-b-mp1-pre and
CMake-SourceFile2-b-mp1-post on the trunk.
The changes re-implement cmSourceFile and the use of it to allow
instances to be created much earlier. The use of cmSourceFileLocation
allows locating a source file referenced by a user to be much simpler
and more robust. The two SetName methods are no longer needed so some
duplicate code has been removed. The strange "SourceName" stuff is
gone. Code that created cmSourceFile instances on the stack and then
sent them to cmMakefile::AddSource has been simplified and converted
to getting cmSourceFile instances from cmMakefile. The CPluginAPI has
preserved the old API through a compatibility interface.
Source lists are gone. Targets now get real instances of cmSourceFile
right away instead of storing a list of strings until the final pass.
TraceVSDependencies has been re-written to avoid the use of
SourceName. It is now called TraceDependencies since it is not just
for VS. It is now implemented with a helper object which makes the
code simpler.
