[cmake-developers] [Patch] Adding Windows 10 support

[Brad King]

On 09/01/2015 05:19 PM, Gilles Khouzam wrote:
> For VS_DEFAULT_TARGET_PLATFORM_VERSION, what I'm trying to
> achieve is almost an internal property that is used for the
> try_compile phase. Since the generator is not used in that
> scenario, the project is using the template from
> Modules/CompilerId/VS-10.vcxproj.in. In that case, we need to set
> the tag for the WindowsTargetPlatformVersion. During the
> generation, I query for the latest SDK version in the
> GlobalGenerator and set the VS_DEFAULT_TARGET_PLATFORM_VERSION
> property that is then used in CMakeDetermineCompilerId.cmake to
> set the variable that the template uses in the Windows 10 case.

The generator *is* used for try_compile calls.  The template
in Modules/CompilerId/VS-10.vcxproj.in is used *only* for the
compiler identification step which occurs before we have enough
information to do a full try_compile.  The compiler id step does
need special handling to set this value, but it should be based
on however the value is determined for the generator normally.

As discussed in http://www.cmake.org/Bug/view.php?id=15670
the SDK for the latest Windows version may not be the proper
default choice.  Perhaps it should be the SDK for the host
machine's version of Windows to make sure we don't use APIs
that cannot run on the current machine.  IIRC this is the
default on OS X with CMAKE_OSX_SYSROOT.

Unlike CMAKE_OSX_SYSROOT, which is used by all generators on
OS X, the WindowsTargetPlatformVersion value is something only
for the VS IDE generators.  In any command-line build we expect
the INCLUDE/LIB environment variables to already be set to the
proper location.  Therefore we need to define a way to set the
WindowsTargetPlatformVersion only for VS IDE generators since
they generate the environment in which to run the toolchain.

CMAKE_GENERATOR_TOOLSET and CMAKE_GENERATOR_PLATFORM are
existing options with generator-specific behavior.  For VS
they set <PlatformToolset> and <Platform>, respectively.
There is quite a bit of C++-side infrastructure to propagate
these values to all the right places (and honor cmake -T
and -A options on the command line).  I'd rather not have
something quite so heavyweight for WindowsTargetPlatformVersion
because it is a pretty narrow case that should not need a
dedicated command-line option and won't be meaningful to
other generators.

We could simply define a

 CMAKE_VS_TARGET_PLATFORM_VERSION

variable that is used to initialize VS_TARGET_PLATFORM_VERSION
target properties (see SetPropertyDefault calls in the source).
Then the generator can look just at the target property.  If
not set it should choose a default based on the current host
version of Windows as discussed above.  Then we just need to
teach cmCoreTryCompile to propagate this setting.

The above-linked issue also mentions that TargetFrameworkVersion
may need similar infrastructure.

-Brad