[libc++] Implement terminate(), unexpected() and uncaught_exceptions() on Windows

[EricWF]

Summary

This patch implements the following functions on Windows by forwarding to the MSVCRT:

• get_terminate()
• set_terminate()
• terminate()
• set_unexpected()
• get_unexpected()
• unexpected()
• uncaught_exception()

• uncaught_exceptions()

[smeenai]

Hooray for Microsoft for putting all these in msvcrt (their C runtime library) instead of msvcprt (their C++ runtime library), I guess :p

src/exception.cpp

53

MSDN says "unexpected is not used in the current C++ exception-handling implementation", which is maybe not the most desirable thing in the world, but I guess this is going away in C++17 anyway :D

139

Yay undocumented APIs (at least as far as I can see).

[EricWF]

In D28442#638862, @smeenai wrote:

Hooray for Microsoft for putting all these in msvcrt (their C runtime library) instead of msvcprt (their C++ runtime library), I guess :p

Although Boo to eh.h for being in the same directory as the MSVC STL headers. If possible I would like to be able to compile libc++ without
adding that directory to the include paths.

src/exception.cpp

53

Actually unexpected() has gone away in C++17 since C++17 removes "dynamic exception specifications" (ie void foo() throw(int, ...)). Therefore I suspect the doc is referring to that.

However I suspect are still used when clang-cl targets C++14 or newer.

139

Undocumented API for sure. Unfortunately libc++ is going to have to rely on a number of undocumented API's because Microsoft doesn't provide documentation for porting an STL to Windows.

src/exception.cpp

 //===------------------------ exception.cpp -------------------------------===//
 //
 //                     The LLVM Compiler Infrastructure
 //
 // This file is dual licensed under the MIT and the University of Illinois Open
 // Source Licenses. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
 #include <stdlib.h>
 #include <stdio.h>
 
 #include "exception"
 #include "new"
 
-#if defined(__APPLE__) && !defined(LIBCXXRT) && \
+#if defined(_LIBCPP_ABI_MICROSOFT)
+#include <eh.h>
+#include <corecrt_terminate.h>
+#elif defined(__APPLE__) && !defined(LIBCXXRT) && \
     !defined(_LIBCPP_BUILDING_HAS_NO_ABI_LIBRARY)
   #include <cxxabi.h>
 
   using namespace __cxxabiv1;
   #define HAVE_DEPENDENT_EH_ABI 1
   #ifndef _LIBCPPABI_VERSION
     using namespace __cxxabiapple;
     // On Darwin, there are two STL shared libraries and a lower level ABI

 {
 
 #if !defined(LIBCXXRT) && !defined(_LIBCPPABI_VERSION) && !defined(__GLIBCXX__)
 
 // libcxxrt provides implementations of these functions itself.
 unexpected_handler
 set_unexpected(unexpected_handler func) _NOEXCEPT
 {
-    return __sync_lock_test_and_set(&__unexpected_handler, func);
+#if defined(_LIBCPP_ABI_MICROSOFT)
+  return ::set_unexpected(func);
+#else
+#endif
 }
 
 unexpected_handler
 get_unexpected() _NOEXCEPT
 {
-    return __sync_fetch_and_add(&__unexpected_handler, (unexpected_handler)0);
+#if defined(_LIBCPP_ABI_MICROSOFT)
+  return ::_get_unexpected();
+#else
+#endif
 }
 
 _LIBCPP_NORETURN
 void
 unexpected()
 {
     (*get_unexpected())();
     // unexpected handler should not return
     terminate();
 }
 
 terminate_handler
 set_terminate(terminate_handler func) _NOEXCEPT
 {
-    return __sync_lock_test_and_set(&__terminate_handler, func);
+#if defined(_LIBCPP_ABI_MICROSOFT)
+  return ::set_terminate(func);
+#else
+#endif
 }
 
 terminate_handler
 get_terminate() _NOEXCEPT
 {
-    return __sync_fetch_and_add(&__terminate_handler, (terminate_handler)0);
+#if defined(_LIBCPP_ABI_MICROSOFT)
+  return ::_get_terminate();
+#else
+#endif
 }
 
 #ifndef __EMSCRIPTEN__ // We provide this in JS
 _LIBCPP_NORETURN
 void
 terminate() _NOEXCEPT
 {
 #ifndef _LIBCPP_NO_EXCEPTIONS
catch (...)
         ::abort();
     }
 #endif  // _LIBCPP_NO_EXCEPTIONS
 }
 #endif // !__EMSCRIPTEN__
 #endif // !defined(LIBCXXRT) && !defined(_LIBCPPABI_VERSION)
 
 #if !defined(LIBCXXRT) && !defined(__GLIBCXX__) && !defined(__EMSCRIPTEN__)
+
 bool uncaught_exception() _NOEXCEPT { return uncaught_exceptions() > 0; }
 
 int uncaught_exceptions() _NOEXCEPT
 {
 #if !defined(_LIBCPP_BUILDING_HAS_NO_ABI_LIBRARY) && \
     (defined(__APPLE__) || defined(_LIBCPPABI_VERSION))
    // on Darwin, there is a helper function so __cxa_get_globals is private
 # if _LIBCPPABI_VERSION > 1101
     return __cxa_uncaught_exceptions();
 # else
     return __cxa_uncaught_exception() ? 1 : 0;
 # endif
-#else  // __APPLE__
+#elif defined(_LIBCPP_ABI_MICROSOFT)
+    return __uncaught_exceptions();
+#else
 #   if defined(_MSC_VER) && ! defined(__clang__)
         _LIBCPP_WARNING("uncaught_exceptions not yet implemented")
 #   else
 #       warning uncaught_exception not yet implemented
 #   endif
     fprintf(stderr, "uncaught_exceptions not yet implemented\n");
     ::abort();
 #endif  // __APPLE__