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.
Teach the add_custom_command and add_custom_target commands a new
USES_TERMINAL option. Use it to tell the generator to give the command
direct access to the terminal if possible.
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.
Teach add_custom_target to check the policy too. Extend the policy to
disallow reserved target names that we use for builtin targets like
"all".
Extend the RunCMake.CMP0037 test to cover these cases.
Drop all behavior activated by setting CMAKE_BACKWARDS_COMPATIBILITY to
a value lower than 2.4, and generate an error when projects or the user
attempt to do so. In the error suggest using a CMake 2.8.x release.
Teach cmake_minimum_required to warn about projects that do not require
at least CMake 2.4. They are not supported by CMake >= 3.0.
Replace the documentation of CMAKE_BACKWARDS_COMPATIBILITY with a
reference to policy CMP0001.
All commands accepting file paths should normalize the slashes so that
the string-represented names can be compared reliably. The commands
add_library and add_executable have done this for years. We taught
add_custom_command to normalize its OUTPUT names in commit a75a0a14
(Normalize add_custom_command OUTPUT names, 2010-12-15). We handled a
special case of the DEPENDS option in commit 7befc007 (Handle trailing
slashes on add_custom_command DEPENDS, 2011-01-26).
Teach both add_custom_command and add_custom_target to normalize slashes
of DEPENDS files up front. This approach subsumes the above-mentioned
special case so remove the one line added for it but keep its test.
Extend the CustomCommand test to check that slash count mismatches
between custom command OUTPUT and DEPENDS can still be linked correctly.
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.
This adds a SOURCES option to ADD_CUSTOM_TARGET, enabling users to
specify extra sources for inclusion in the target. Such sources may not
build, but will show up in the IDE project files for convenient editing.
See issue #5848.
- Remove CMP_0001 (no slash in target name) and restore
old CMAKE_BACKWARDS_COMPATIBILITY check for it
- Replace all checks of CMAKE_BACKWARDS_COMPATIBILITY
with cmLocalGenerator::NeedBackwardsCompatibility calls
- Create new CMP_0001 to determine whether or not
CMAKE_BACKWARDS_COMPATIBILITY is used.
(old = use, new = ignore)
- Show CMAKE_BACKWARDS_COMPATIBILITY in cache only when
CMP_0001 is set to OLD or WARN
- Update documentation of cmake_policy and cmake_minimum_required
to indicate their relationship and the 2.4 version boundary
- When no cmake policy version is set in top level makefile
implicitly call cmake_policy(VERSION 2.4) which restores
CMAKE_BACKWARDS_COMPATIBILITY and other 2.4 compatibility
- Fix tests MakeClean and Preprocess to call
cmake_policy(VERSION 2.6) because they depend on new policies
- Add cmMakefile methods IssueError and IssueWarning
- Maintain an explicit call stack in cmMakefile
- Include context/call-stack info in messages
- Nested errors now unwind the call stack
- Use new mechanism for policy warnings and errors
- Improve policy error message
- Include cmExecutionStatus pointer in call stack
so that errors deeper in the C++ stack under
a command invocation will become errors for the
command
- Error if imported target is involved in conflict
- Error for non-imported target conflict unless
CMAKE_BACKWARDS_COMPATIBILITY <= 2.4
- Include OUTPUT_NAME property in error message
- Update add_executable and add_library command documentation
Brad King
Peter Collingbourne
Nils Gladitz
Stephen Kelly
Bill Hoffman
Ken Martin
Andy Cedilnik
Will Schroeder