`Microsoft.Cl.Common.props` changes some default settings based on
`UseDebugLibraries`. CMake models its own controls for these settings,
so if the project does not set them, explicitly suppress them to avoid
letting `UseDebugLibraries` affect them.
LLVMFlang 18.0 adds MSVC runtime library selection flags and associated
Fortran runtime library variants. Resolve the corresponding FIXME left
by commit 26bf32cdc6 (LLVMFlang: Add support for targeting MSVC ABI on
Windows, 2023-09-28, v3.28.0-rc1~10^2).
Issue: #24840
The compiler does not yet support everything needed to integrate well
with the MSVC ABI, in particular for runtime library selection and debug
format selection. Document them in FIXME comments and leave this
support undocumented by CMake for now.
Fixes: #24840
Inspired-by: Pierrick Bouvier <pierrick.bouvier@linaro.org>
In commit fb3370b6a1 (MSVC: Add abstraction for runtime library
selection, 2019-04-10, v3.15.0-rc1~229^2) we overlooked updating flags
for Flang on Windows. Add them now and update the MSVCRuntimeLibrary
Fortran test to work with Flang. Base the flags on those we already
use for the GNU-like Clang targeting the MSVC ABI.
Fixes: #19583
In commit fb3370b6a1 (MSVC: Add abstraction for runtime library
selection, 2019-04-10, v3.15.0-rc1~229^2) we overlooked updating flags
for CUDA on Windows, where nvcc uses MSVC as the host compiler. Add
them now and update the MSVCRuntimeLibrary test to cover CUDA.
Fixes: #19428
Extend tests added by commit fb3370b6a1 (MSVC: Add abstraction for
runtime library selection, 2019-04-10) to cover an empty value for
the property. It should result in no specific setting.
Issue: #19108
Replace our hard-coded defaults for `/MD` and `/MDd` with a first-class
abstraction to select the runtime library from an enumeration of logical
names. We've long hesitated to do this because the idea of "runtime
library selection" touches on related concepts on several platforms.
Avoid that scope creep by simply defining an abstraction that applies
only when targeting the MSVC ABI on Windows.
Removing the old default flags requires a policy because existing
projects may rely on string processing to edit them and choose a runtime
library under the old behavior. Add policy CMP0091 to provide
compatibility.
Fixes: #19108
