Fix ABI compatibility of `<stdexcept>` with VCRuntime.

Summary:
Currently, libc++'s `<stdexcept>` doesn't play nice with `vcruntime`. Specifically:

* `logic_error` and `runtime_error` have a different layout.
* libc++'s `logic_error` and `runtime_error` override `what()` but `vcruntime` does not.
*  `vcruntime` uses weak vtables for `<stdexcept>` types.
* libc++'s `<stdexcept>` constructors and assignment operators may have different manglings than `vcruntimes`.

This patch makes libc++'s declarations in `<stdexcept>` match those provided by MSVC's STL as closely as possible.
If MSVC doesn't declare a special member, then neither do we. This ensures that the implicit definitions have the same linkage, visibility, triviality, and noexcept-ness.







Reviewers: thomasanderson, ldionne, smeenai

Reviewed By: thomasanderson

Subscribers: jdoerfert, libcxx-commits

Differential Revision: https://reviews.llvm.org/D58945

llvm-svn: 355546

2 files changed, 81 insertions, 0 deletions

diff --git a/libcxx/src/support/runtime/stdexcept_default.ipp b/libcxx/src/support/runtime/stdexcept_default.ipp
new file mode 100644
index 00000000000..91dd54b28cf
--- /dev/null
+++ b/libcxx/src/support/runtime/stdexcept_default.ipp
@@ -0,0 +1,65 @@
+//===--------------------- stdexcept_default.ipp --------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "../../include/refstring.h"
+
+/* For _LIBCPPABI_VERSION */
+#if !defined(_LIBCPP_BUILDING_HAS_NO_ABI_LIBRARY) &&                           \
+    (defined(LIBCXX_BUILDING_LIBCXXABI) || defined(__APPLE__) ||               \
+     defined(LIBCXXRT))
+#include <cxxabi.h>
+#endif
+
+static_assert(sizeof(std::__libcpp_refstring) == sizeof(const char*), "");
+
+namespace std // purposefully not using versioning namespace
+{
+
+logic_error::logic_error(const string& msg) : __imp_(msg.c_str()) {}
+
+logic_error::logic_error(const char* msg) : __imp_(msg) {}
+
+logic_error::logic_error(const logic_error& le) _NOEXCEPT : __imp_(le.__imp_) {}
+
+logic_error& logic_error::operator=(const logic_error& le) _NOEXCEPT {
+  __imp_ = le.__imp_;
+  return *this;
+}
+
+runtime_error::runtime_error(const string& msg) : __imp_(msg.c_str()) {}
+
+runtime_error::runtime_error(const char* msg) : __imp_(msg) {}
+
+runtime_error::runtime_error(const runtime_error& re) _NOEXCEPT
+    : __imp_(re.__imp_) {}
+
+runtime_error& runtime_error::operator=(const runtime_error& re) _NOEXCEPT {
+  __imp_ = re.__imp_;
+  return *this;
+}
+
+#if !defined(_LIBCPPABI_VERSION) && !defined(LIBSTDCXX)
+
+const char* logic_error::what() const _NOEXCEPT { return __imp_.c_str(); }
+
+const char* runtime_error::what() const _NOEXCEPT { return __imp_.c_str(); }
+
+logic_error::~logic_error() _NOEXCEPT {}
+domain_error::~domain_error() _NOEXCEPT {}
+invalid_argument::~invalid_argument() _NOEXCEPT {}
+length_error::~length_error() _NOEXCEPT {}
+out_of_range::~out_of_range() _NOEXCEPT {}
+
+runtime_error::~runtime_error() _NOEXCEPT {}
+range_error::~range_error() _NOEXCEPT {}
+overflow_error::~overflow_error() _NOEXCEPT {}
+underflow_error::~underflow_error() _NOEXCEPT {}
+
+#endif
+
+} // namespace std
diff --git a/libcxx/src/support/runtime/stdexcept_vcruntime.ipp b/libcxx/src/support/runtime/stdexcept_vcruntime.ipp
new file mode 100644
index 00000000000..94eed465ae9
--- /dev/null
+++ b/libcxx/src/support/runtime/stdexcept_vcruntime.ipp
@@ -0,0 +1,16 @@
+//===------------------- stdexcept_vcruntime.ipp --------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef _LIBCPP_ABI_VCRUNTIME
+#error This file may only be used when defering to vcruntime
+#endif
+
+namespace std {
+logic_error::logic_error(std::string const& s) : exception(s.c_str()) {}
+runtime_error::runtime_error(std::string const& s) : exception(s.c_str()) {}
+} // namespace std