Add a variable to indicate the latest standard known to be supported for
each language:
* `CMAKE_C_STANDARD_LATEST`
* `CMAKE_CXX_STANDARD_LATEST`
* `CMAKE_CUDA_STANDARD_LATEST`
* `CMAKE_HIP_STANDARD_LATEST`
* `CMAKE_OBJC_STANDARD_LATEST`
* `CMAKE_OBJCXX_STANDARD_LATEST`
These variables, more generally referred to as
`CMAKE_<LANG>_STANDARD_LATEST`, are assigned an integer value which
represents the minimum between the latest version of the associated
language standard supported by the current compiler and the latest
version supported by CMake.
Add documentation for these variables in a new page called
`CMAKE_<LANG>_STANDARD_LATEST` was added under the "Variables for
Languages" section of the `cmake-variables(7)` page.
Update each compiler-specific CMake script under
`${CMAKE_ROOT}\Modules\Compiler` to manually define the relevant
`CMAKE_<LANG>_STANDARD_LATEST` variable as necessary. This will
require updating and maintaining as newer compiler versions become
recognized by CMake.
Closes: #25717
The IntelLLVM compiler, for compatibility with MSVC on Windows, always
runs with support for at least C++14. The `-Qstd=c++11` flag just
causes a warning that it is unused.
Fixes: #24316
In commit a90d2a9eed (IntelLLVM: Add support for Intel LLVM-based
compilers, 2020-11-02, v3.20.0-rc1~89^2~20) we accidentally left out
activation of the C/C++ standard level selection logic when IntelLLVM is
targeting the MSVC ABI.
Fixes: #22388
Using a single ID 'IntelLLVM' for the suite of Intel compilers based on
the LLVM backend. The 'IntelLLVM' ID are used for C, C++, and Fortran.
Data Parallel C++ will be handled in a separate commit.
The C and C++ definitions are based on the Clang definitions. The Intel
LLVM-based C and C++ compilers are based on the Clang front end, so
existing Clang options are more likely to be a good match than options
for the older Intel compilers.
Fortran is based on the older Fortran front end with the LLVM backend.
It has a similar interface to the older versions, though many options
are shared with the C and C++ compilers.
Fixes: #21561
Signed-off-by: William R. Dieter <william.r.dieter@intel.com>
