1 files changed, 69 insertions, 34 deletions

diff --git a/gl/stddef.in.h b/gl/stddef.in.h
index fa8998d9..e8c55ff1 100644
--- a/gl/stddef.in.h
+++ b/gl/stddef.in.h
@@ -1,6 +1,6 @@
 /* A substitute for POSIX 2008 <stddef.h>, for platforms that have issues.
 
-   Copyright (C) 2009-2024 Free Software Foundation, Inc.
+   Copyright (C) 2009-2025 Free Software Foundation, Inc.
 
    This file is free software: you can redistribute it and/or modify
    it under the terms of the GNU Lesser General Public License as
@@ -27,13 +27,21 @@
 #endif
 @PRAGMA_COLUMNS@
 
-#if defined __need_wchar_t || defined __need_size_t  \
-  || defined __need_ptrdiff_t || defined __need_NULL \
-  || defined __need_wint_t
+#if (defined __need_wchar_t || defined __need_size_t                \
+     || defined __need_ptrdiff_t || defined __need_NULL             \
+     || defined __need_wint_t)                                      \
+    /* Avoid warning triggered by "gcc -std=gnu23 -Wsystem-headers" \
+       in GCC 13.3 and 14.2                                         \
+       <https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114870>.  */   \
+    && !@STDDEF_NOT_IDEMPOTENT@
 /* Special invocation convention inside gcc header files.  In
-   particular, gcc provides a version of <stddef.h> that blindly
-   redefines NULL even when __need_wint_t was defined, even though
-   wint_t is not normally provided by <stddef.h>.  Hence, we must
+   particular, <stddef.h> in some ancient versions of GCC blindly
+   redefined NULL when __need_wint_t was defined, even though wint_t
+   is not normally provided by <stddef.h>.
+   (FIXME: It's not clear what GCC versions those were - perhaps so
+   ancient that we can stop worrying about this?)
+   Although glibc 2.26 (2017) and later do not use __need_wint_t,
+   for portability to macOS, Cygwin, Haiku, and older Glibc + GCC,
    remember if special invocation has ever been used to obtain wint_t,
    in which case we need to clean up NULL yet again.  */
 
@@ -52,6 +60,13 @@
 # endif
 
 #else
+/* For @STDDEF_NOT_IDEMPOTENT@.  */
+# undef __need_wchar_t
+# undef __need_size_t
+# undef __need_ptrdiff_t
+# undef __need_NULL
+# undef __need_wint_t
+
 /* Normal invocation convention.  */
 
 # ifndef _@GUARD_PREFIX@_STDDEF_H
@@ -74,6 +89,12 @@ typedef long max_align_t;
 #   endif
 #  endif
 
+#  if !defined _GCC_NULLPTR_T && !@NULLPTR_T_NEEDS_STDDEF@
+    /* Suppress unwanted nullptr_t typedef.  See
+       <https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114869>.  */
+#   define _GCC_NULLPTR_T
+#  endif
+
 /* The include_next requires a split double-inclusion guard.  */
 
 #  @INCLUDE_NEXT@ @NEXT_STDDEF_H@
@@ -110,7 +131,7 @@ typedef long max_align_t;
  */
 #ifndef _GL_ATTRIBUTE_NOTHROW
 # if defined __cplusplus
-#  if (__GNUC__ + (__GNUC_MINOR__ >= 8) > 2) || __clang_major >= 4
+#  if (__GNUC__ + (__GNUC_MINOR__ >= 8) > 2) || __clang_major__ >= 4
 #   if __cplusplus >= 201103L
 #    define _GL_ATTRIBUTE_NOTHROW noexcept (true)
 #   else
@@ -128,11 +149,6 @@ typedef long max_align_t;
 # endif
 #endif
 
-/* Some platforms lack wchar_t.  */
-#if !@HAVE_WCHAR_T@
-# define wchar_t int
-#endif
-
 /* Some platforms lack max_align_t.  The check for _GCC_MAX_ALIGN_T is
    a hack in case the configure-time test was done with g++ even though
    we are currently compiling with gcc.
@@ -172,38 +188,57 @@ typedef union
 #endif
 
 /* ISO C 23 § 7.21.1 The unreachable macro  */
-#ifndef unreachable
+/* This macro is only usable in C, not in C++.
+   There is no way to define it as a macro in C++, because that would break code
+   that does
+       #include <utility>
+       ... std::unreachable() ...
+   Similarly, there is no way to define it as an inline function in C++, because
+   that would break code that does
+       #include <utility>
+       using std::unreachable;
+   As a workaround, we define a macro gl_unreachable, that is like unreachable,
+   but is usable in both C and C++.  */
 
 /* Code borrowed from verify.h.  */
-# ifndef _GL_HAS_BUILTIN_UNREACHABLE
-#  if defined __clang_major__ && __clang_major__ < 5
-#   define _GL_HAS_BUILTIN_UNREACHABLE 0
-#  elif 4 < __GNUC__ + (5 <= __GNUC_MINOR__)
-#   define _GL_HAS_BUILTIN_UNREACHABLE 1
-#  elif defined __has_builtin
-#   define _GL_HAS_BUILTIN_UNREACHABLE __has_builtin (__builtin_unreachable)
-#  else
-#   define _GL_HAS_BUILTIN_UNREACHABLE 0
-#  endif
+#ifndef _GL_HAS_BUILTIN_UNREACHABLE
+# if defined __clang_major__ && __clang_major__ < 5
+#  define _GL_HAS_BUILTIN_UNREACHABLE 0
+# elif 4 < __GNUC__ + (5 <= __GNUC_MINOR__) && !defined __clang__
+#  define _GL_HAS_BUILTIN_UNREACHABLE 1
+# elif defined __has_builtin
+#  define _GL_HAS_BUILTIN_UNREACHABLE __has_builtin (__builtin_unreachable)
+# else
+#  define _GL_HAS_BUILTIN_UNREACHABLE 0
 # endif
+#endif
 
-# if _GL_HAS_BUILTIN_UNREACHABLE
-#  define unreachable() __builtin_unreachable ()
-# elif 1200 <= _MSC_VER
-#  define unreachable() __assume (0)
-# else
+#if _GL_HAS_BUILTIN_UNREACHABLE
+# define gl_unreachable() __builtin_unreachable ()
+#elif 1200 <= _MSC_VER
+# define gl_unreachable() __assume (0)
+#elif !defined __cplusplus && @HAVE_C_UNREACHABLE@
+# define gl_unreachable() unreachable ()
+#else
 /* Declare abort(), without including <stdlib.h>.  */
 extern
-#  if defined __cplusplus
+# if defined __cplusplus
 "C"
-#  endif
+# endif
 _Noreturn
 void abort (void)
-#  if defined __cplusplus && (__GLIBC__ >= 2)
+# if defined __cplusplus && (__GLIBC__ >= 2)
 _GL_ATTRIBUTE_NOTHROW
-#  endif
+# endif
 ;
-#  define unreachable() abort ()
+# define gl_unreachable() abort ()
+#endif
+
+#if !defined __cplusplus && !@HAVE_C_UNREACHABLE@
+/* In C, define unreachable as a macro.  */
+
+# ifndef unreachable
+#  define unreachable() gl_unreachable ()
 # endif
 
 #endif