Partially revert libc++ commit aa7f377c965c, restoring stdint.h

This partially reverts upstream libc++ commit aa7f377c965c:

  [libc++] Remove libc++'s own stdint.h and locale.h (#107436)

  These headers are not doing anything beyond the system or compiler
  provided equivalent headers, so there's no real reason to keep them
  around. Reducing the number of C headers we provide in libc++ simplifies
  our header layering and reduces the potential for confusion when headers
  are layered incorrectly.

The problem is that libc++'s own `stdint.h` _does_ do something: it
defines `__STDC_LIMIT_MACROS` and `__STDC_CONSTANT_MACROS` before
including the system `stdint.h`, causing the latter to expose macros
like `SIZE_MAX`, `UINT64_C`, and others.

If the `__STDC_LIMIT_MACROS` and `__STDC_CONSTANT_MACROS` macros are not
exposed, C++ programs compiled for standards before C++11 can fail with
errors due to those macros not being available.

PR:		292067
MFC after:	1 month

ObsoleteFiles.inc

@@ -492,7 +492,6 @@ OLD_FILES+=usr/include/c++/v1/__type_traits/is_unsigned_integer.h
 OLD_FILES+=usr/include/c++/v1/__type_traits/noexcept_move_assign_container.h
 OLD_FILES+=usr/include/c++/v1/experimental/__config
 OLD_FILES+=usr/include/c++/v1/locale.h
-OLD_FILES+=usr/include/c++/v1/stdint.h
 
 # 20260420: remove perfmon
 OLD_FILES+=boot/kernel/perfmon.ko

contrib/llvm-project/libcxx/include/cstdint

@@ -149,6 +149,14 @@ Types:
 #    include <stdint.h>
 #  endif
 
+#  ifndef _LIBCPP_STDINT_H
+#   error <cstdint> tried including <stdint.h> but didn't find libc++'s <stdint.h> header. \
+          This usually means that your header search paths are not configured properly. \
+          The header search paths should contain the C++ Standard Library headers before \
+          any C Standard Library, and you are probably using compiler flags that make that \
+          not be the case.
+#  endif
+
 #  if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #    pragma GCC system_header
 #  endif

contrib/llvm-project/libcxx/include/stdint.h

@@ -0,0 +1,127 @@
+// -*- C++ -*-
+//===----------------------------------------------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef _LIBCPP_STDINT_H
+// AIX system headers need stdint.h to be re-enterable while _STD_TYPES_T
+// is defined until an inclusion of it without _STD_TYPES_T occurs, in which
+// case the header guard macro is defined.
+#if !defined(_AIX) || !defined(_STD_TYPES_T)
+#  define _LIBCPP_STDINT_H
+#endif // _STD_TYPES_T
+
+/*
+    stdint.h synopsis
+
+Macros:
+
+    INT8_MIN
+    INT16_MIN
+    INT32_MIN
+    INT64_MIN
+
+    INT8_MAX
+    INT16_MAX
+    INT32_MAX
+    INT64_MAX
+
+    UINT8_MAX
+    UINT16_MAX
+    UINT32_MAX
+    UINT64_MAX
+
+    INT_LEAST8_MIN
+    INT_LEAST16_MIN
+    INT_LEAST32_MIN
+    INT_LEAST64_MIN
+
+    INT_LEAST8_MAX
+    INT_LEAST16_MAX
+    INT_LEAST32_MAX
+    INT_LEAST64_MAX
+
+    UINT_LEAST8_MAX
+    UINT_LEAST16_MAX
+    UINT_LEAST32_MAX
+    UINT_LEAST64_MAX
+
+    INT_FAST8_MIN
+    INT_FAST16_MIN
+    INT_FAST32_MIN
+    INT_FAST64_MIN
+
+    INT_FAST8_MAX
+    INT_FAST16_MAX
+    INT_FAST32_MAX
+    INT_FAST64_MAX
+
+    UINT_FAST8_MAX
+    UINT_FAST16_MAX
+    UINT_FAST32_MAX
+    UINT_FAST64_MAX
+
+    INTPTR_MIN
+    INTPTR_MAX
+    UINTPTR_MAX
+
+    INTMAX_MIN
+    INTMAX_MAX
+
+    UINTMAX_MAX
+
+    PTRDIFF_MIN
+    PTRDIFF_MAX
+
+    SIG_ATOMIC_MIN
+    SIG_ATOMIC_MAX
+
+    SIZE_MAX
+
+    WCHAR_MIN
+    WCHAR_MAX
+
+    WINT_MIN
+    WINT_MAX
+
+    INT8_C(value)
+    INT16_C(value)
+    INT32_C(value)
+    INT64_C(value)
+
+    UINT8_C(value)
+    UINT16_C(value)
+    UINT32_C(value)
+    UINT64_C(value)
+
+    INTMAX_C(value)
+    UINTMAX_C(value)
+
+*/
+
+#include <__config>
+
+#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
+#  pragma GCC system_header
+#endif
+
+/* C99 stdlib (e.g. glibc < 2.18) does not provide macros needed
+   for C++11 unless __STDC_LIMIT_MACROS and __STDC_CONSTANT_MACROS
+   are defined
+*/
+#if defined(__cplusplus) && !defined(__STDC_LIMIT_MACROS)
+#  define __STDC_LIMIT_MACROS
+#endif
+#if defined(__cplusplus) && !defined(__STDC_CONSTANT_MACROS)
+#  define __STDC_CONSTANT_MACROS
+#endif
+
+#if __has_include_next(<stdint.h>)
+#  include_next <stdint.h>
+#endif
+
+#endif // _LIBCPP_STDINT_H

lib/libc++/Makefile

@@ -232,6 +232,7 @@ STD_HEADERS+=	stdatomic.h
 STD_HEADERS+=	stdbool.h
 STD_HEADERS+=	stddef.h
 STD_HEADERS+=	stdexcept
+STD_HEADERS+=	stdint.h
 STD_HEADERS+=	stdio.h
 STD_HEADERS+=	stdlib.h
 STD_HEADERS+=	stop_token

lib/libc++/module.modulemap

@@ -2433,6 +2433,10 @@ module std_stddef_h [system] {
   // <stddef.h> supports being included multiple times with different pre-defined macros
   textual header "stddef.h"
 }
+module std_stdint_h [system] {
+  // <stdint.h> supports being included multiple times with different pre-defined macros
+  textual header "stdint.h"
+}
 module std_stdio_h [system] {
   // <stdio.h> supports being included multiple times with different pre-defined macros
   textual header "stdio.h"