The mapping for this flag was added by commit 43aa632f57 (VS: Populate
`-Qspectre-` flag table entry for v142, 2019-01-24, v3.14.0-rc1~74^2~7).
However, it did not do anything because the special logic added by
commit bb60ed6e72 (VS: Add flag table entry for -Qspectre, 2018-10-08,
v3.13.0-rc1~4^2) to move the `SpectreMitigation` element from
`ClCompile` to the top level only handled the presence of the setting
and not its value. Extend the special logic to carry the value too.
Fixes: #19535
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
Since commit v3.11.0-rc1~467^2 (VS,Xcode: Add CMakeLists.txt sources
without mutating targets, 2017-10-18) we do not add `CMakeLists.txt` to
target sources but instead generate references to them directly. This
accidentally dropped generation of the `.vcxproj.filters` entry for a
source group in which `CMakeLists.txt` is the only member.
Fixes: #18795
Create `CMAKE_VS_SDK_*_DIRECTORIES` variables to tell the VS generator
how to populate fields in `.vcxproj` files that specify SDK directories.
Fixes: #17908
Since commit v3.11.0-rc1~467^2 (VS,Xcode: Add CMakeLists.txt sources
without mutating targets, 2017-10-18) we do not add `CMakeLists.txt` to
target sources but instead generate references to them directly. This
broke projects that explicitly specify their `CMakeLists.txt` file as a
source file because the explicit entry is no longer consolidated with
the generated one.
Teach the relevant generators to avoid duplicating `CMakeLists.txt`
source references and add test cases.
Fixes: #17828
Add a `VS_USER_PROPS_CXX` target property to set the user props file of
the generated `.vcxproj` file to be something other than the default
`$(UserRootDir)\\Microsoft.Cpp.$(Platform).user.props`.
With VS generators for 2010 and above, passing a `.targets` file to
`target_link_libraries` is expected to generate content in the
`.vcxproj` file to import the targets file. Add a test to cover this.
Brad King