In libc++'s `wchar.h`, before we forward to the system `wchar.h`, we set `__CORRECT_ISO_CPP_WCHAR_H_PROTO` to ensure it defines the correct signature (e.g. `extern "C++" const wchar_t *wmemchr` and not `extern wchar_t *wmemchr`). After D148542, there are cases where we include the system `wchar.h` from within `__mbstate_t.h` without setting that, and so we get a function type mismatch if we transitively include `wchar.h` through multiple headers in a modules-enabled build. Consistently setting it here resolves those build errors.
Alternative 1: we could put this in `__config` instead. I chose to put it here for a more limited scope.
Alternative 2: we could patch `wchar.h` itself to work correctly and remove references `__CORRECT_ISO_CPP_WCHAR_H_PROTO` from libc++ entirely. It does already set it, but with an additional condition that it is being built by GCC >= 4.4. Clang does pretend to be GCC via `__GNUC__` etc. which can be controlled via `-fgnuc-version` command line flags, but that might have other consequences.
Reviewed By: ldionne, #libc, MaskRay
Differential Revision: https://reviews.llvm.org/D150015
// This does not define std::mbstate_t -- this only brings in the declaration
// in the global namespace.
+// We define this here to support older versions of glibc <wchar.h> that do
+// not define this for clang. This is also set in libc++'s <wchar.h> header,
+// and we need to do so here too to avoid a different function signature given
+// a different include order.
+#ifdef __cplusplus
+# define __CORRECT_ISO_CPP_WCHAR_H_PROTO
+#endif
+
#if __has_include(<bits/types/mbstate_t.h>)
# include <bits/types/mbstate_t.h> // works on most Unixes
#elif __has_include(<sys/_types/_mbstate_t.h>)
# pragma GCC system_header
#endif
+// We define this here to support older versions of glibc <wchar.h> that do
+// not define this for clang.
#ifdef __cplusplus
#define __CORRECT_ISO_CPP_WCHAR_H_PROTO
#endif
--- /dev/null
+//===----------------------------------------------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+// <cwchar>
+
+// XFAIL: no-wide-characters
+
+// Tests that include ordering does not affect the definition of wcsstr.
+// See: https://llvm.org/PR62638
+
+// clang-format off
+#include <cwchar>
+#include <iosfwd>
+// clang-format on
+
+void func() {
+ wchar_t* v1;
+ const wchar_t* cv2 = L"/";
+ v1 = wcsstr(cv2, L"/"); // expected-error {{assigning to 'wchar_t *' from 'const wchar_t *' discards qualifiers}}
+}
--- /dev/null
+//===----------------------------------------------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+// <cwchar>
+
+// XFAIL: no-wide-characters
+
+// Tests that include ordering does not affect the definition of wcsstr.
+// See: https://llvm.org/PR62638
+
+// clang-format off
+#include <iosfwd>
+#include <cwchar>
+// clang-format on
+
+void func() {
+ wchar_t* v1;
+ const wchar_t* cv2 = L"/";
+ v1 = wcsstr(cv2, L"/"); // expected-error {{assigning to 'wchar_t *' from 'const wchar_t *' discards qualifiers}}
+}