The macro's implementation converts a normal variable into a cache
variable intentionally, so both are set. Explicitly set CMP0126 to NEW
to avoid a warning in trace mode. This won't affect the module behavior
because the code path does not activate if a normal variable is already
defined anyway.
Fixes: #22548
Explain the purpose of this variable and the conditions under which
it can be set. Point out that it should not be set explicitly without
also setting `CMAKE_CUDA_COMPILER` explicitly.
Issue: #20826
Fix the condition added by commit fada8cbfd6 (CheckLanguage: Report
CMAKE_CUDA_HOST_COMPILER if needed for compilation, 2019-05-31,
v3.15.0-rc1~12^2) to activate CUDA-specific logic. The old condition
had worked in our test suite only by accident because the loop variable
used in the test happened to be the name and value that the old
condition used! Update the test to use a different name.
Fixes: #19013
The check_language sets internal variables with a common name in the
caller's scope: `result`, `output` and `content`.
They are now prefixed with `_cl_`,
inspired by the CheckLibraryExists module.
Per-source copyright/license notice headers that spell out copyright holder
names and years are hard to maintain and often out-of-date or plain wrong.
Precise contributor information is already maintained automatically by the
version control tool. Ultimately it is the receiver of a file who is
responsible for determining its licensing status, and per-source notices are
merely a convenience. Therefore it is simpler and more accurate for
each source to have a generic notice of the license name and references to
more detailed information on copyright holders and full license terms.
Our `Copyright.txt` file now contains a list of Contributors whose names
appeared source-level copyright notices. It also references version control
history for more precise information. Therefore we no longer need to spell
out the list of Contributors in each source file notice.
Replace CMake per-source copyright/license notice headers with a short
description of the license and links to `Copyright.txt` and online information
available from "https://cmake.org/licensing". The online URL also handles
cases of modules being copied out of our source into other projects, so we
can drop our notices about replacing links with full license text.
Run the `Utilities/Scripts/filter-notices.bash` script to perform the majority
of the replacements mechanically. Manually fix up shebang lines and trailing
newlines in a few files. Manually update the notices in a few files that the
script does not handle.
Update cmake_minimum_required calls in CMakeLists.txt in Modules and in
CMakeLists.txt generated by other modules, so that they are always in
sync with current CMake version.
Define a "check_language(<lang>)" macro to test whether <lang> can be
enabled. Cache the result in CMAKE_<lang>_COMPILER. Add a test case
covering expected results.
