Follow the approach from commit 92320466dd (try_compile: Restore
platform-default link flags in pre-CMP0210 projects, 2026-08-22)
to make the CMP0181 policy setting available in `try_compile`
projects before the toolchain file is loaded.
Fixes: #28108
The CMP0210 compatibility shims in the Darwin, AIX, HP-UX and ARMClang
modules read the policy with cmake_policy(GET CMP0210 ...) during
enable_language(), which runs inside project(). cmCoreTryCompile emitted
cmake_policy(SET CMP0210 ...) after project() in the generated test
project, so those shims always observed NEW regardless of the calling
project's setting.
On affected platforms this dropped the platform default link flags from
every try_compile, and left a toolchain-file value of
CMAKE_<LANG>_LINK_FLAGS unclobbered so that it reached the OLD code path.
For projects that are also not using CMP0181 NEW, that path uses the
variable as is and does not expand the LINKER: prefix.
Move the emission into the existing pre-project() policy block alongside
CMP0126, CMP0128 and CMP0197, which exist for exactly this reason.
Fixes: #28102
Prior to commit 243462fafe (try_compile: Tolerate compile features from
non-enabled languages, 2026-05-18, v4.4.0-rc1~84^2) we accidentally
tolerated toolchain files setting `CMAKE_<LANG>_COMPILER_LOADED`.
Meson accidentally relied on this, so restore toleration of it.
Fixes: #27971
Tweak `cmMessenger` to also show the "warning is for project developers"
notice for all diagnostics that are descendants of the `CMD_AUTHOR`
category. When doing so, also show both command-line options which can
suppress the message.
Update expected test output to account for the new format of diagnostic
messages. These changes were applied entirely by `sed` using the
following commands:
- `/Use -Wno-dev to suppress/s/-Wno-dev/-Wno-author/g`
- `s/Warning [\\][(]dev[\\][)]/Warning \\(author\\)/g`
- `s/CMake Deprecation Warning/CMake Warning \\(deprecated\\)/g`
This is not a complete fix, but covers a significant fraction of the
needed changes, and this commit is strictly automated changes.
The OLD behaviors of all policies are deprecated, but only by
documentation. Add an explicit deprecation diagnostic for policies
introduced in CMake 3.21 and below to encourage projects to port
away from setting policies to OLD.
If a `CMakeLists.txt` or `CMAKE_TOOLCHAIN_FILE` sets a variable named
`C`, `CXX`, or `CUDA`, we were previously comparing each enabled
language name to the value of that variable, rather than the name
itself. Double-quote the string to take advantage of policy `CMP0054`,
but also add "x" prefixes to support projects that do not set the
policy.
Fixes: #22125
Any `include_directories()` calls in toolchain files are used during our
ABI detection step even though it does not include any system headers.
Since commit 5990ecb741 (Compute implicit include directories from
compiler output, 2018-12-07, v3.14.0-rc1~108^2), that check is also used
to detect implicit include directories. Any `include_directories()` in
a toolchain file are detected as implicit and later excluded from
explicit specification on compiler command lines, thus breaking the
purpose of the calls in the first place.
Fix the implicit include directory detection step to avoid using paths
from `include_directories()` calls in the toolchain file.
Fixes: #19079
Document these variables.
Change our convention for setting these variables from:
set(CMAKE_EXE_LINKER_FLAGS_INIT "...")
to
string(APPEND CMAKE_EXE_LINKER_FLAGS_INIT " ...")
so that any value previously set by a toolchain file will be used.
Document these variables.
Change our convention for setting these variables from:
set(CMAKE_C_FLAGS_INIT "...")
to
string(APPEND CMAKE_C_FLAGS_INIT " ...")
so that any value previously set by a toolchain file will be used.
Automate the conversion with:
sed -i 's/set *(\(CMAKE_\(C\|CXX\|Fortran\|RC\|ASM\|${[^}]\+}\)_FLAGS\(_[^_]\+\)\?_INIT \+"\)/string(APPEND \1 /' \
Modules/Compiler/*.cmake Modules/Platform/*.cmake
and follow up with some manual fixes (e.g. to cases that already
meant to append). Also revert the automated changes to contexts
that are not protected from running multiple times.
Calling `project()` or `enable_language()` from a toolchain file will
infinitely recurse since those commands load the toolchain file.
Diagnose and reject this case with an error message instead of crashing
when the stack eventually overflows.
Brad King
Mickaël Germain
Matthew Woehlke
AJIOB
Hanna Rusakovich
Martin Storsjö
Samir Benmendil