[libc++] Implement exception_ptr on Windows
Summary:
This patch implements exception_ptr on Windows using the `__ExceptionPtrFoo` functions provided by MSVC.
The `__ExceptionPtrFoo` functions are defined inside the C++ standard library, `msvcprt`, which is unfortunate because it requires libc++ to link to the MSVC STL. However this doesn't seem to cause any immediate problems. However to be safe I kept all usages within the libc++ dylib so that user programs wouldn't have to link to MSVCPRT as well.
Note there are still 2 outstanding exception_ptr/nested_exception test failures.
* `current_exception.pass.cpp` needs to be rewritten for the Windows exception_ptr semantics which copy the exception every time.
* `rethrow_if_nested.pass.cpp` need investigation. It hits a stack overflow, likely from recursion.
This patch also gets most of the `<future>` tests passing as well.
Reviewers: mclow.lists, compnerd, bcraig, rmaprath, majnemer, BillyONeal, STL_MSFT
Subscribers: mgorny, cfe-commits
Differential Revision: https://reviews.llvm.org/D32927
git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@302393 91177308-0d34-0410-b5e6-96231b3b80d8
16 files changed