Make logic choosing between Windows 10 SDKs and the Windows 8.1 SDK
easier to follow by consolidating it in the VS 14 generator. The only
information we need from VS 15+ generators is whether the 8.1 SDK is
installed.
VS 17.6 now implements `ScanSourceforModuleDependencies` using the same
`cl /scanDependencies` scanner that our Ninja generator uses. It can
distinguish module internal partitions from module interface units based
on their content. Switch from `CompileAsCppModule` to `CompileAsCpp`
for `CXX_MODULES` sources so that MSBuild can scan and classify them.
VS 2017 and above come with a Visual Studio Installer tool that tracks
four-component Visual Studio version numbers. We already detect the VS
version number because it is needed to make some generation decisions.
Provide the number to projects in a `CMAKE_VS_VERSION_BUILD_NUMBER`
variable so they can use it similarly.
Fixes: #24230
CMake accepts the toolset version that is default in the current VS
version by matching the name later VS versions will use for the SxS
props files. It predicts the future name based on the first two
components of the current VS version's default toolset. However, this
heuristic breaks naming the VS 16.8 toolset version 14.28 under VS 16.9
because the latter's default toolset version is 14.28.29910, which did
not increment the second version component (unprecedented in VS).
Fix this by always using the requested version's SxS props file when it
exists, even if it matches the first two components of the current VS
version's default toolset. Also add a special case for the name VS
16.10 will use for VS 16.9's default toolset, so that it can be used
with VS 16.9 too.
Fixes: #21922
The `CMAKE_VS_WINDOWS_TARGET_PLATFORM_VERSION_MAXIMUM` variable added in
CMake 3.19 by commit ba497111f6 (VS: Add option for custom Win10 SDK
version maximum, 2020-08-20, v3.19.0-rc1~262^2) was documented as if it
worked for all generators but implemented only to override CMake's
builtin default for the VS 2015 max SDK version. Generalize the
variable to set a custom max SDK version for later VS versions too.
Fixes: #21720
#pragma once is a widely supported compiler pragma, even though it is
not part of the C++ standard. Many of the issues keeping #pragma once
from being standardized (distributed filesystems, build farms, hard
links, etc.) do not apply to CMake - it is easy to build CMake on a
single machine. CMake also does not install any header files which can
be consumed by other projects (though cmCPluginAPI.h has been
deliberately omitted from this conversion in case anyone is still using
it.) Finally, #pragma once has been required to build CMake since at
least August 2017 (7f29bbe6 enabled server mode unconditionally, which
had been using #pragma once since September 2016 (b13d3e0d)). The fact
that we now require C++11 filters out old compilers, and it is unlikely
that there is a compiler which supports C++11 but does not support
#pragma once.
Since commit 83ddc4d289 (VS: Do not select a Windows SDK too high for
current VS version, 2017-08-07, v3.13.0-rc1~72^2~2) we enforce a maximum
SDK version for the VS 2015 generator. The blog post linked in the
original commit is no longer available, but it can be seen here:
* https://web.archive.org/web/20190108032520/https://blogs.msdn.microsoft.com/chuckw/2018/10/02/windows-10-october-2018-update/
In particular, it states:
> VS 2015 Users: The Windows 10 SDK (15063, 16299, 17134, 17763)
> is officially only supported for VS 2017.
However, in some circumstances a higher version can be used.
Add a `CMAKE_VS_WINDOWS_TARGET_PLATFORM_VERSION_MAXIMUM` to override the
generator's default maximum SDK version.
Fixes: #20633
VS 16.6 added a `StdOutEncoding` setting for custom commands to tell
MSBuild that the output is encoded as UTF-8. In commit bc877a7e94 (Add
support to indicate UTF-8 custom command pipe output encoding,
2020-04-08) CMake learned to add the setting in anticipation of the VS
16.6 release. However, when 16.6 was released it had a bug in the
implementation of custom tasks with StdOutEncoding enabled that was
exposed by our test suite. In commit 5058fb5401 (VS: Drop
StdOutEncoding with VS 16.6 pending investigation, 2020-05-29) we
disabled the setting pending investigation.
The problem is fixed in VS 16.7 Preview 3, so restore use of the
setting when a VS instance of at least that version is detected.
Fixes: #20769
Add this generator *without* support for specifying the target
architecture in the generator name. cmake-gui will be taught
to provide a field for this, and command-line builds can use -A.
Also, teach this generator to select a default target architecture
based on the host architecture.
Fixes: #18689
Inspired-by: Egor Pugin <egor.pugin@gmail.com>
