locale: update ctype access for MSVC CRT 14+

Visual C++ 14 and newer split msvcrt into msvcrt and ucrt with flavours
of the ucrt for different environments.  This changed the access to the
ctype table by introducing the `__pctype_func` and `__pwctype_func`
accessors.  Use this rather than directly accessing `_ctype` which
allows us to be safer in threaded situations by going through the libc
locking.

llvm-svn: 290823

libcxx/include/support/win32/locale_win32.h

@@ -11,8 +11,12 @@
 #ifndef _LIBCPP_SUPPORT_WIN32_LOCALE_WIN32_H
 #define _LIBCPP_SUPPORT_WIN32_LOCALE_WIN32_H
 
+#include <crtversion.h>
+
+#if _VC_CRT_MAJOR_VERSION < 14
 // ctype mask table defined in msvcrt.dll
-extern "C" unsigned short  __declspec(dllimport) _ctype[];
+extern "C" unsigned short __declspec(dllimport) _ctype[];
+#endif
 
 #include "support/win32/support.h"
 #include "support/win32/locale_mgmt_win32.h"

libcxx/src/locale.cpp

@@ -24,6 +24,9 @@
 #endif
 #include "clocale"
 #include "cstring"
+#if defined(_LIBCPP_MSVCRT)
+#define _CTYPE_DISABLE_MACROS
+#endif
 #include "cwctype"
 #include "__sso_allocator"
 #if defined(_LIBCPP_MSVCRT) || defined(__MINGW32__)
@@ -1108,9 +1111,13 @@ ctype<char>::classic_table()  _NOEXCEPT
 #elif __sun__
     return __ctype_mask;
 #elif defined(_LIBCPP_MSVCRT) || defined(__MINGW32__)
+#if _VC_CRT_MAJOR_VERSION < 14
+    // This is assumed to be safe, which is a nonsense assumption because we're
+    // going to end up dereferencing it later...
     return _ctype+1; // internal ctype mask table defined in msvcrt.dll
-// This is assumed to be safe, which is a nonsense assumption because we're
-// going to end up dereferencing it later...
+#else
+    return __pctype_func();
+#endif
 #elif defined(__EMSCRIPTEN__)
     return *__ctype_b_loc();
 #elif defined(_NEWLIB_VERSION)