12 files changed, 137 insertions, 27 deletions
diff --git a/CMakeLists.txt b/CMakeLists.txt
index 7f87711c7..f0c4d1efb 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -615,6 +615,7 @@ config_define_if(LIBCXX_HAS_PTHREAD_API _LIBCPP_HAS_THREAD_API_PTHREAD)
 config_define_if(LIBCXX_HAS_EXTERNAL_THREAD_API _LIBCPP_HAS_THREAD_API_EXTERNAL)
 config_define_if(LIBCXX_BUILD_EXTERNAL_THREAD_LIBRARY _LIBCPP_HAS_THREAD_LIBRARY_EXTERNAL)
 config_define_if(LIBCXX_HAS_MUSL_LIBC _LIBCPP_HAS_MUSL_LIBC)
+config_define_if(LIBCXX_NO_VCRUNTIME _LIBCPP_NO_VCRUNTIME)
 
 if (LIBCXX_ABI_DEFINES)
   set(abi_defines)
diff --git a/docs/UsingLibcxx.rst b/docs/UsingLibcxx.rst
index 183664655..f54234d6a 100644
--- a/docs/UsingLibcxx.rst
+++ b/docs/UsingLibcxx.rst
@@ -185,6 +185,26 @@ thread safety annotations.
     * Giving `set`, `map`, `multiset`, `multimap` a comparator which is not
       const callable.
 
+**_LIBCPP_NO_VCRUNTIME**:
+  Microsoft's C and C++ headers are fairly entangled, and some of their C++
+  headers are fairly hard to avoid. In particular, `vcruntime_new.h` gets pulled
+  in from a lot of other headers and provides definitions which clash with
+  libc++ headers, such as `nothrow_t` (note that `nothrow_t` is a struct, so
+  there's no way for libc++ to provide a compatible definition, since you can't
+  have multiple definitions).
+
+  By default, libc++ solves this problem by deferring to Microsoft's vcruntime
+  headers where needed. However, it may be undesirable to depend on vcruntime
+  headers, since they may not always be available in cross-compilation setups,
+  or they may clash with other headers. The `_LIBCPP_NO_VCRUNTIME` macro
+  prevents libc++ from depending on vcruntime headers. Consequently, it also
+  prevents libc++ headers from being interoperable with vcruntime headers (from
+  the aforementioned clashes), so users of this macro are promising to not
+  attempt to combine libc++ headers with the problematic vcruntime headers. This
+  macro also currently prevents certain `operator new`/`operator delete`
+  replacement scenarios from working, e.g. replacing `operator new` and
+  expecting a non-replaced `operator new[]` to call the replaced `operator new`.
+
 C++17 Specific Configuration Macros
 -----------------------------------
 **_LIBCPP_ENABLE_CXX17_REMOVED_FEATURES**:
diff --git a/include/__config_site.in b/include/__config_site.in
index b2c9d6307..86418a3e1 100644
--- a/include/__config_site.in
+++ b/include/__config_site.in
@@ -25,6 +25,7 @@
 #cmakedefine _LIBCPP_HAS_THREAD_API_EXTERNAL
 #cmakedefine _LIBCPP_HAS_THREAD_LIBRARY_EXTERNAL
 #cmakedefine _LIBCPP_DISABLE_VISIBILITY_ANNOTATIONS
+#cmakedefine _LIBCPP_NO_VCRUNTIME
 
 @_LIBCPP_ABI_DEFINES@
 
diff --git a/include/exception b/include/exception
index ca2eaf5c6..79bd6ac2a 100644
--- a/include/exception
+++ b/include/exception
@@ -82,7 +82,7 @@ template <class E> void rethrow_if_nested(const E& e);
 #include <cstdlib>
 #include <type_traits>
 
-#if defined(_LIBCPP_ABI_MICROSOFT)
+#if defined(_LIBCPP_ABI_MICROSOFT) && !defined(_LIBCPP_NO_VCRUNTIME)
 #include <vcruntime_exception.h>
 #endif
 
@@ -93,7 +93,7 @@ template <class E> void rethrow_if_nested(const E& e);
 namespace std  // purposefully not using versioning namespace
 {
 
-#if !defined(_LIBCPP_ABI_MICROSOFT)
+#if !defined(_LIBCPP_ABI_MICROSOFT) || defined(_LIBCPP_NO_VCRUNTIME)
 class _LIBCPP_EXCEPTION_ABI exception
 {
 public:
@@ -110,7 +110,7 @@ public:
     virtual ~bad_exception() _NOEXCEPT;
     virtual const char* what() const _NOEXCEPT;
 };
-#endif // !_LIBCPP_ABI_MICROSOFT
+#endif // !_LIBCPP_ABI_MICROSOFT || _LIBCPP_NO_VCRUNTIME
 
 #if _LIBCPP_STD_VER <= 14 \
     || defined(_LIBCPP_ENABLE_CXX17_REMOVED_UNEXPECTED_FUNCTIONS) \
diff --git a/include/new b/include/new
index 34df2efee..06cf4a3e1 100644
--- a/include/new
+++ b/include/new
@@ -92,7 +92,7 @@ void  operator delete[](void* ptr, void*) noexcept;
 #include <cstdlib>
 #endif
 
-#if defined(_LIBCPP_ABI_MICROSOFT)
+#if defined(_LIBCPP_ABI_MICROSOFT) && !defined(_LIBCPP_NO_VCRUNTIME)
 #include <new.h>
 #endif
 
@@ -114,7 +114,7 @@ void  operator delete[](void* ptr, void*) noexcept;
 namespace std  // purposefully not using versioning namespace
 {
 
-#if !defined(_LIBCPP_ABI_MICROSOFT)
+#if !defined(_LIBCPP_ABI_MICROSOFT) || defined(_LIBCPP_NO_VCRUNTIME)
 struct _LIBCPP_TYPE_VIS nothrow_t {};
 extern _LIBCPP_FUNC_VIS const nothrow_t nothrow;
 
@@ -140,7 +140,7 @@ typedef void (*new_handler)();
 _LIBCPP_FUNC_VIS new_handler set_new_handler(new_handler) _NOEXCEPT;
 _LIBCPP_FUNC_VIS new_handler get_new_handler() _NOEXCEPT;
 
-#endif // !_LIBCPP_ABI_MICROSOFT
+#endif // !_LIBCPP_ABI_MICROSOFT || _LIBCPP_NO_VCRUNTIME
 
 _LIBCPP_NORETURN _LIBCPP_FUNC_VIS void __throw_bad_alloc();  // not in C++ spec
 
@@ -174,7 +174,7 @@ enum align_val_t { __zero = 0, __max = (size_t)-1 };
 #define _THROW_BAD_ALLOC
 #endif
 
-#if !defined(_LIBCPP_ABI_MICROSOFT)
+#if !defined(_LIBCPP_ABI_MICROSOFT) || defined(_LIBCPP_NO_VCRUNTIME)
 
 _LIBCPP_OVERRIDABLE_FUNC_VIS void* operator new(std::size_t __sz) _THROW_BAD_ALLOC;
 _LIBCPP_OVERRIDABLE_FUNC_VIS void* operator new(std::size_t __sz, const std::nothrow_t&) _NOEXCEPT _NOALIAS;
@@ -215,7 +215,7 @@ inline _LIBCPP_INLINE_VISIBILITY void* operator new[](std::size_t, void* __p) _N
 inline _LIBCPP_INLINE_VISIBILITY void  operator delete  (void*, void*) _NOEXCEPT {}
 inline _LIBCPP_INLINE_VISIBILITY void  operator delete[](void*, void*) _NOEXCEPT {}
 
-#endif // !_LIBCPP_ABI_MICROSOFT
+#endif // !_LIBCPP_ABI_MICROSOFT || _LIBCPP_NO_VCRUNTIME
 
 _LIBCPP_BEGIN_NAMESPACE_STD
 
diff --git a/src/new.cpp b/src/new.cpp
index 01df25121..e228a0d83 100644
--- a/src/new.cpp
+++ b/src/new.cpp
@@ -15,7 +15,9 @@
 #include "include/atomic_support.h"
 
 #if defined(_LIBCPP_ABI_MICROSOFT)
-// nothing todo
+#if defined(_LIBCPP_NO_VCRUNTIME)
+#include "support/runtime/new_handler_fallback.ipp"
+#endif
 #elif defined(LIBCXX_BUILDING_LIBCXXABI)
 #include <cxxabi.h>
 #elif defined(LIBCXXRT)
@@ -54,7 +56,8 @@ __throw_bad_alloc()
 
 }  // std
 
-#if !defined(__GLIBCXX__) && !defined(_LIBCPP_ABI_MICROSOFT) && \
+#if !defined(__GLIBCXX__) &&                                                   \
+    (!defined(_LIBCPP_ABI_MICROSOFT) || defined(_LIBCPP_NO_VCRUNTIME)) &&      \
     !defined(_LIBCPP_DISABLE_NEW_DELETE_DEFINITIONS)
 
 // Implement all new and delete operators as weak definitions
@@ -300,4 +303,4 @@ operator delete[] (void* ptr, size_t, std::align_val_t alignment) _NOEXCEPT
 }
 
 #endif // !_LIBCPP_HAS_NO_ALIGNED_ALLOCATION
-#endif // !__GLIBCXX__ && !_LIBCPP_ABI_MICROSOFT && !_LIBCPP_DISABLE_NEW_DELETE_DEFINITIONS
+#endif // !__GLIBCXX__ && (!_LIBCPP_ABI_MICROSOFT || _LIBCPP_NO_VCRUNTIME) && !_LIBCPP_DISABLE_NEW_DELETE_DEFINITIONS
diff --git a/src/support/runtime/exception_msvc.ipp b/src/support/runtime/exception_msvc.ipp
index 443961ebf..d5bf5b726 100644
--- a/src/support/runtime/exception_msvc.ipp
+++ b/src/support/runtime/exception_msvc.ipp
@@ -14,12 +14,35 @@
 
 #include <stdio.h>
 #include <stdlib.h>
-#include <eh.h>
-#include <corecrt_terminate.h>
+
+#if !defined(_ACRTIMP)
+#define _ACRTIMP __declspec(dllimport)
+#endif
+
+#if !defined(_VCRTIMP)
+#define _VCRTIMP __declspec(dllimport)
+#endif
+
+#if !defined(__CRTDECL)
+#define __CRTDECL __cdecl
+#endif
+
+extern "C" {
+typedef void (__CRTDECL* terminate_handler)();
+_ACRTIMP terminate_handler __cdecl set_terminate(
+    terminate_handler _NewTerminateHandler) throw();
+_ACRTIMP terminate_handler __cdecl _get_terminate();
+
+typedef void (__CRTDECL* unexpected_handler)();
+_VCRTIMP unexpected_handler __cdecl set_unexpected(
+    unexpected_handler _NewUnexpectedHandler) throw();
+_VCRTIMP unexpected_handler __cdecl _get_unexpected();
+
+_VCRTIMP int __cdecl __uncaught_exceptions();
+}
 
 namespace std {
 
-// libcxxrt provides implementations of these functions itself.
 unexpected_handler
 set_unexpected(unexpected_handler func) _NOEXCEPT {
   return ::set_unexpected(func);
@@ -114,4 +137,54 @@ bad_typeid::what() const _NOEXCEPT
   return "std::bad_typeid";
 }
 
+#if defined(_LIBCPP_NO_VCRUNTIME)
+exception::~exception() _NOEXCEPT
+{
+}
+
+const char* exception::what() const _NOEXCEPT
+{
+  return "std::exception";
+}
+
+
+bad_exception::~bad_exception() _NOEXCEPT
+{
+}
+
+const char* bad_exception::what() const _NOEXCEPT
+{
+  return "std::bad_exception";
+}
+
+
+bad_alloc::bad_alloc() _NOEXCEPT
+{
+}
+
+bad_alloc::~bad_alloc() _NOEXCEPT
+{
+}
+
+const char*
+bad_alloc::what() const _NOEXCEPT
+{
+    return "std::bad_alloc";
+}
+
+bad_array_new_length::bad_array_new_length() _NOEXCEPT
+{
+}
+
+bad_array_new_length::~bad_array_new_length() _NOEXCEPT
+{
+}
+
+const char*
+bad_array_new_length::what() const _NOEXCEPT
+{
+    return "bad_array_new_length";
+}
+#endif // _LIBCPP_NO_VCRUNTIME
+
 } // namespace std
diff --git a/src/support/runtime/exception_pointer_msvc.ipp b/src/support/runtime/exception_pointer_msvc.ipp
index eab5d30a9..5ca7519a6 100644
--- a/src/support/runtime/exception_pointer_msvc.ipp
+++ b/src/support/runtime/exception_pointer_msvc.ipp
@@ -10,26 +10,32 @@
 
 #include <stdio.h>
 #include <stdlib.h>
-#include <yvals.h> // for _CRTIMP2_PURE
 
-_CRTIMP2_PURE void __CLRCALL_PURE_OR_CDECL __ExceptionPtrCreate(_Out_ void*);
-_CRTIMP2_PURE void __CLRCALL_PURE_OR_CDECL __ExceptionPtrDestroy(_Inout_ void*);
-_CRTIMP2_PURE void __CLRCALL_PURE_OR_CDECL __ExceptionPtrCopy(_Out_ void*,
-                                                              _In_ const void*);
+#if !defined(_CRTIMP2_PURE)
+#define _CRTIMP2_PURE __declspec(dllimport)
+#endif
+
+#if !defined(__CLRCALL_PURE_OR_CDECL)
+#define __CLRCALL_PURE_OR_CDECL __cdecl
+#endif
+
+_CRTIMP2_PURE void __CLRCALL_PURE_OR_CDECL __ExceptionPtrCreate(void*);
+_CRTIMP2_PURE void __CLRCALL_PURE_OR_CDECL __ExceptionPtrDestroy(void*);
+_CRTIMP2_PURE void __CLRCALL_PURE_OR_CDECL __ExceptionPtrCopy(void*,
+                                                              const void*);
 _CRTIMP2_PURE void __CLRCALL_PURE_OR_CDECL
-__ExceptionPtrAssign(_Inout_ void*, _In_ const void*);
+__ExceptionPtrAssign(void*, const void*);
 _CRTIMP2_PURE bool __CLRCALL_PURE_OR_CDECL
-__ExceptionPtrCompare(_In_ const void*, _In_ const void*);
+__ExceptionPtrCompare(const void*, const void*);
 _CRTIMP2_PURE bool __CLRCALL_PURE_OR_CDECL
-__ExceptionPtrToBool(_In_ const void*);
-_CRTIMP2_PURE void __CLRCALL_PURE_OR_CDECL __ExceptionPtrSwap(_Inout_ void*,
-                                                              _Inout_ void*);
+__ExceptionPtrToBool(const void*);
+_CRTIMP2_PURE void __CLRCALL_PURE_OR_CDECL __ExceptionPtrSwap(void*, void*);
 _CRTIMP2_PURE void __CLRCALL_PURE_OR_CDECL
-__ExceptionPtrCurrentException(_Out_ void*);
+__ExceptionPtrCurrentException(void*);
 [[noreturn]] _CRTIMP2_PURE void __CLRCALL_PURE_OR_CDECL
-__ExceptionPtrRethrow(_In_ const void*);
+__ExceptionPtrRethrow(const void*);
 _CRTIMP2_PURE void __CLRCALL_PURE_OR_CDECL
-__ExceptionPtrCopyException(_Inout_ void*, _In_ const void*, _In_ const void*);
+__ExceptionPtrCopyException(void*, const void*, const void*);
 
 namespace std {
 
diff --git a/test/std/language.support/support.dynamic/new.delete/new.delete.array/new_array_nothrow_replace.pass.cpp b/test/std/language.support/support.dynamic/new.delete/new.delete.array/new_array_nothrow_replace.pass.cpp
index 53e26c99f..ba3f930c5 100644
--- a/test/std/language.support/support.dynamic/new.delete/new.delete.array/new_array_nothrow_replace.pass.cpp
+++ b/test/std/language.support/support.dynamic/new.delete/new.delete.array/new_array_nothrow_replace.pass.cpp
@@ -10,6 +10,7 @@
 // test operator new [] nothrow by replacing only operator new
 
 // UNSUPPORTED: sanitizer-new-delete
+// XFAIL: libcpp-no-vcruntime
 
 #include <new>
 #include <cstddef>
diff --git a/test/std/language.support/support.dynamic/new.delete/new.delete.array/new_array_replace.pass.cpp b/test/std/language.support/support.dynamic/new.delete/new.delete.array/new_array_replace.pass.cpp
index b0820b14f..3f8122745 100644
--- a/test/std/language.support/support.dynamic/new.delete/new.delete.array/new_array_replace.pass.cpp
+++ b/test/std/language.support/support.dynamic/new.delete/new.delete.array/new_array_replace.pass.cpp
@@ -10,6 +10,7 @@
 // test operator new[] replacement by replacing only operator new
 
 // UNSUPPORTED: sanitizer-new-delete
+// XFAIL: libcpp-no-vcruntime
 
 
 #include <new>
diff --git a/test/std/language.support/support.dynamic/new.delete/new.delete.single/new_nothrow_replace.pass.cpp b/test/std/language.support/support.dynamic/new.delete/new.delete.single/new_nothrow_replace.pass.cpp
index dbc64bace..31e190151 100644
--- a/test/std/language.support/support.dynamic/new.delete/new.delete.single/new_nothrow_replace.pass.cpp
+++ b/test/std/language.support/support.dynamic/new.delete/new.delete.single/new_nothrow_replace.pass.cpp
@@ -10,6 +10,7 @@
 // test operator new nothrow by replacing only operator new
 
 // UNSUPPORTED: sanitizer-new-delete
+// XFAIL: libcpp-no-vcruntime
 
 #include <new>
 #include <cstddef>
diff --git a/utils/libcxx/test/config.py b/utils/libcxx/test/config.py
index 6f88a3540..67927c912 100644
--- a/utils/libcxx/test/config.py
+++ b/utils/libcxx/test/config.py
@@ -668,6 +668,9 @@ class Configuration(object):
                 self.config.available_features.add('libcpp-abi-version-v%s'
                     % feature_macros[m])
                 continue
+            if m == '_LIBCPP_NO_VCRUNTIME':
+                self.config.available_features.add('libcpp-no-vcruntime')
+                continue
             assert m.startswith('_LIBCPP_HAS_') or m.startswith('_LIBCPP_ABI_')
             m = m.lower()[1:].replace('_', '-')
             self.config.available_features.add(m)