[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

llvm-svn: 302393

1 files changed, 54 insertions, 3 deletions

diff --git a/libcxx/include/exception b/libcxx/include/exception
index 9999ca096c0..ca2eaf5c6a0 100644
--- a/libcxx/include/exception
+++ b/libcxx/include/exception
@@ -134,23 +134,26 @@ class _LIBCPP_TYPE_VIS exception_ptr;
 _LIBCPP_FUNC_VIS exception_ptr current_exception() _NOEXCEPT;
 _LIBCPP_NORETURN _LIBCPP_FUNC_VIS void rethrow_exception(exception_ptr);
 
+#ifndef _LIBCPP_ABI_MICROSOFT
+
 class _LIBCPP_TYPE_VIS exception_ptr
 {
     void* __ptr_;
 public:
     _LIBCPP_INLINE_VISIBILITY exception_ptr() _NOEXCEPT : __ptr_() {}
     _LIBCPP_INLINE_VISIBILITY exception_ptr(nullptr_t) _NOEXCEPT : __ptr_() {}
+
     exception_ptr(const exception_ptr&) _NOEXCEPT;
     exception_ptr& operator=(const exception_ptr&) _NOEXCEPT;
     ~exception_ptr() _NOEXCEPT;
 
-    _LIBCPP_INLINE_VISIBILITY
-    _LIBCPP_EXPLICIT
-        operator bool() const _NOEXCEPT {return __ptr_ != nullptr;}
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_EXPLICIT operator bool() const _NOEXCEPT
+    {return __ptr_ != nullptr;}
 
     friend _LIBCPP_INLINE_VISIBILITY
     bool operator==(const exception_ptr& __x, const exception_ptr& __y) _NOEXCEPT
         {return __x.__ptr_ == __y.__ptr_;}
+
     friend _LIBCPP_INLINE_VISIBILITY
     bool operator!=(const exception_ptr& __x, const exception_ptr& __y) _NOEXCEPT
         {return !(__x == __y);}
@@ -178,6 +181,54 @@ make_exception_ptr(_Ep __e) _NOEXCEPT
 #endif
 }
 
+#else // _LIBCPP_ABI_MICROSOFT
+
+class _LIBCPP_TYPE_VIS exception_ptr
+{
+#if defined(__clang__)
+#pragma clang diagnostic push
+#pragma clang diagnostic ignored "-Wunused-private-field"
+#endif
+    void* __ptr1_;
+    void* __ptr2_;
+#if defined(__clang__)
+#pragma clang diagnostic pop
+#endif
+public:
+    exception_ptr() _NOEXCEPT;
+    exception_ptr(nullptr_t) _NOEXCEPT;
+    exception_ptr(const exception_ptr& __other) _NOEXCEPT;
+    exception_ptr& operator=(const exception_ptr& __other) _NOEXCEPT;
+    exception_ptr& operator=(nullptr_t) _NOEXCEPT;
+    ~exception_ptr() _NOEXCEPT;
+    _LIBCPP_EXPLICIT operator bool() const _NOEXCEPT;
+};
+
+_LIBCPP_FUNC_VIS
+bool operator==(const exception_ptr& __x, const exception_ptr& __y) _NOEXCEPT;
+
+inline _LIBCPP_INLINE_VISIBILITY
+bool operator!=(const exception_ptr& __x, const exception_ptr& __y) _NOEXCEPT
+    {return !(__x == __y);}
+
+_LIBCPP_FUNC_VIS void swap(exception_ptr&, exception_ptr&) _NOEXCEPT;
+
+_LIBCPP_FUNC_VIS exception_ptr __copy_exception_ptr(void *__except, const void* __ptr);
+_LIBCPP_FUNC_VIS exception_ptr current_exception() _NOEXCEPT;
+_LIBCPP_NORETURN _LIBCPP_FUNC_VIS void rethrow_exception(exception_ptr p);
+
+// This is a built-in template function which automagically extracts the required
+// information.
+template <class _E> void *__GetExceptionInfo(_E);
+
+template<class _Ep>
+exception_ptr
+make_exception_ptr(_Ep __e) _NOEXCEPT
+{
+  return __copy_exception_ptr(_VSTD::addressof(__e), __GetExceptionInfo(__e));
+}
+
+#endif // _LIBCPP_ABI_MICROSOFT
 // nested_exception
 
 class _LIBCPP_EXCEPTION_ABI nested_exception