This allows for a more graceful transition for projects using C++20
without scanner support (e.g., Clang 15 or GCC 13). While newer
compilers will (needlessly) scan, it allows C++20-using projects to use
older compilers without having to set `CMAKE_CXX_SCAN_FOR_MODULES` to
support newer CMake minimum versions.
Fixes: #25357
With CMP0155 NEW behavior, we scan C++ sources in targets using C++ 20,
i.e., in which the `cxx_std_20` feature is available. However, our
check for C++ feature availability may incorrectly succeed in two cases:
* MSVC versions from VS 2013 do not model C++ standard levels,
so we assume all features are available as a heuristic to let
projects at least try compiling with them.
* During ABI detection the `CMAKE_CXX20_COMPILE_FEATURES` variable is not
populated so we assume all features are available, knowing that our
ABI detection project does not need them.
For purposes of detecting targets using C++ 20, we do not want to assume
`cxx_std_20` is available, so verify that we really know it is.
Now that scanning support is no longer experimental, the logic for
whether or not to scan C++ 20 sources is now important because all
projects are now exposted to the logic. Make the scanning rules explicit
in the documentation and rework the queries to localize all of the
associated logic.
A policy to handle the ultimate fallback logic will be implemented in a
following commit.
42654cc818 Tests/CXXModules: add tests for modules with include requirements
7217cb78cf Tests/CXXModules: relax line number matching in stderr
b3d1bbbbcc cmExportFileGenerator: relocate include directories for C++ modules
349ff8b080 cmGeneratorTarget: remove not-INTERFACE assertion
681a763425 cmGeneratorTarget: use a character literal
Acked-by: Kitware Robot <kwrobot@kitware.com>
Acked-by: buildbot <buildbot@kitware.com>
Merge-request: !8838
IMPORTED INTERFACE targets which provide C++ modules may have include
directories that need checked for whether they are system directories or
not. These directories are intended for the module compilation
themselves (which may include headers that module consumers do not need).
* fortran-object-libraries-release:
cmComputeLinkInformation: compute link info for module-using targets
cmGeneratorTarget: support config-independent Fortran source queries
571b5e1f2c cxxmodules: improve error messages for C++ module setup
8b4d32c18b cmStandardLevelResolver: add query for the effective standard level
17ddc4ac76 cmStandardLevelResolver: compare with static string literals
6f1dae2b01 cmStandardLevelResolver: use `cmStrCat` where possible
0d45d40e13 cmStandardLevelResolver: use character literals where possible
Acked-by: Kitware Robot <kwrobot@kitware.com>
Tested-by: buildbot <buildbot@kitware.com>
Merge-request: !8755
We need to be able to construct BMIs that will be usable from the client
modules for the target importing the module, so create BMI-only
compilation rules for `IMPORTED` targets to create these BMIs.
After b665966933 (cmComputeLinkInformation: track `OBJECT` library
dependencies, 2023-07-22), introduced in !8645 as a fix for #25112,
`OBJECT` libraries were tracked in a separate member to reduce the risk
of further regressions. This commit prepares consumers to handle
`OBJECT` libraries once they start appearing as link items.
`include-what-you-use` diagnostics, in practice, are specific to
the environment's compiler and standard library. Update includes
to satisfy IWYU for our CI job under Debian 12.
This generator expression is the inverse of `LINK_ONLY` and only coveys
usage requirements for the purposes of compilation. Its intended use is
to avoid needing to export targets that do not have link usage
requirements (e.g., header-only libraries) when used by another target.
See: #15415
375e6fdbbe Link step: use linker dependency linker file
24a3e5cda0 cmLocalGenerator::MayBeRelativeToWorkDir: take care of all cases
Acked-by: Kitware Robot <kwrobot@kitware.com>
Merge-request: !8443
7bf4e30090 Autogen: Default AUTOGEN_USE_SYSTEM_INCLUDE to ON if it is not set
033dc7ee2f Autogen: Add AUTOGEN_USE_SYSTEM_INCLUDE target property
8ba16db163 Tests/RunCMake: Add option for dynamic expected output
Acked-by: Kitware Robot <kwrobot@kitware.com>
Acked-by: buildbot <buildbot@kitware.com>
Merge-request: !8400
`AUTOGEN_USE_SYSTEM_INCLUDE` was added. `AUTOGEN_USE_SYSTEM_INCLUDE`
is a boolean property that can be set on a target to indicate that the
autogen target include directory should be added as a system include
directory or normal include directory to the target.
