This header was introduced in a recent STL release. Modularise the
header properly, adding a shim for compatibility with older releases.
Partially based on a change from @egorzhdan.
`__msvc_bit_utils.hpp` was added in a recent version of MSVC, and it is causing build errors for SwiftCompilerSources:
```
C:\Program Files\Microsoft Visual Studio\2022\Community\VC\Tools\MSVC\14.39.33519\include\numeric:598:12: error: function '_Select_countr_zero_impl<unsigned long long, (lambda at C:\Program Files\Microsoft Visual Studio\2022\Community\VC\Tools\MSVC\14.39.33519\include\numeric:598:55)>' with deduced return type cannot be used before it is defined
return _Select_countr_zero_impl<_Common_unsigned>([=](auto _Countr_zero_impl) {
```
This change references the `__msvc_bit_utils.hpp` header from the modulemap. Since we still need to support older versions of Visual Studio that do not provide `__msvc_bit_utils.hpp`, this also teaches ClangImporter to inject an empty header file named `__msvc_bit_utils.hpp` into the system include directory, unless it already exists.
rdar://137066642
The new headers for LWG-3268 in the new VC release broke the
modularisation of `std.atomic`. Add the dependent private module to
ensure that we correctly modularise the dependency and allow
`std.atomic` to be built again.
`<xstddef>` was removed since MSVC 14.37. It isn't meant to be used by most users, but the reference will break all clients of `vcruntime`, including Swift standard library itself.
This makes the `stdint` module implicit which repairs the ability to
build some components. In order to accomplish this, we need to
potentially break the fragile Swift build system. Due to the incorrect
handling of compilers we need some workarounds to support
cross-compilation. This removes the injected system header paths when
building on Windows to ensure that the clang resource headers are not
following the system headers which breaks the modules as the clang
resources are dependent on the system headers when running in hosted
mode.
Add the missing `std._Private.xstddef`, `std._Private.yvals`, and
`std._Private.yvals_core` modules. This repairs the use of `std.map` as
a private member variable of a type with an explicit ctor.
Specify the C++ standard required for these submodules. Although this
has no practical implications, it is useful for isolating the features
with different C++ standards.
Add some of the x* headers to the c++ module. These are included
multiply and so we create private modules for them rather than
associate them with a different module which could cause issues
in practice due to intra-module dependencies.
Restructure the `visualc` module into `vcruntime` in order to help
expose the various components (SAL, vcruntime, ucrt, corecrt, STL) for C++
modularization. Include the `stdint.h` textually to deal with
redefinition of types in clang resources and MSVC.
