[PATCH] D124026: [Headers][MSVC] Define wchar_t in stddef.h like MSVC if not using the builtin type

Stephen Long via Phabricator via cfe-commits cfe-commits at lists.llvm.org
Tue Apr 19 11:11:02 PDT 2022

steplong created this revision.
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MSVC expects wchar_t to be defined in stddef.h if /Zc:wchar_t- is specified

  rG LLVM Github Monorepo



Index: clang/test/Headers/ms-no-wchar.cpp
--- /dev/null
+++ clang/test/Headers/ms-no-wchar.cpp
@@ -0,0 +1,6 @@
+// RUN: %clang_cc1 -fsyntax-only -triple x86_64-pc-windows-msvc -fms-compatibility-version=17.00 -fno-wchar %s
+// MSVC defines wchar_t instead of using the builtin if /Zc:wchar_t- is passed
+#include <stddef.h>
+wchar_t c;
Index: clang/lib/Headers/stddef.h
--- clang/lib/Headers/stddef.h
+++ clang/lib/Headers/stddef.h
@@ -62,7 +62,7 @@
 #endif /* defined(__need_STDDEF_H_misc) */
 #if defined(__need_wchar_t)
-#ifndef __cplusplus
+#if !defined(__cplusplus) || (defined(_MSC_VER) && !_NATIVE_WCHAR_T_DEFINED)
 /* Always define wchar_t when modules are available. */
 #if !defined(_WCHAR_T) || __has_feature(modules)
 #if !__has_feature(modules)

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