Merge branch 'master' of git.savannah.gnu.org:/srv/git/emacs into feature/pgtk

52 files changed, 1591 insertions, 614 deletions

diff --git a/m4/close-stream.m4 b/m4/close-stream.m4
deleted file mode 100644
index feeb4eae5d3..00000000000
--- a/m4/close-stream.m4
+++ /dev/null
@@ -1,11 +0,0 @@
-#serial 4
-dnl Copyright (C) 2006-2007, 2009-2021 Free Software Foundation, Inc.
-dnl This file is free software; the Free Software Foundation
-dnl gives unlimited permission to copy and/or distribute it,
-dnl with or without modifications, as long as this notice is preserved.
-
-dnl Prerequisites of lib/close-stream.c.
-AC_DEFUN([gl_CLOSE_STREAM],
-[
-  :
-])
diff --git a/m4/dirent_h.m4 b/m4/dirent_h.m4
index 6d861425855..17e2a20c5d4 100644
--- a/m4/dirent_h.m4
+++ b/m4/dirent_h.m4
@@ -1,4 +1,4 @@
-# dirent_h.m4 serial 16
+# dirent_h.m4 serial 19
 dnl Copyright (C) 2008-2021 Free Software Foundation, Inc.
 dnl This file is free software; the Free Software Foundation
 dnl gives unlimited permission to copy and/or distribute it,
@@ -6,10 +6,10 @@ dnl with or without modifications, as long as this notice is preserved.
 
 dnl Written by Bruno Haible.
 
-AC_DEFUN([gl_DIRENT_H],
+AC_DEFUN_ONCE([gl_DIRENT_H],
 [
-  dnl Use AC_REQUIRE here, so that the default behavior below is expanded
-  dnl once only, before all statements that occur in other macros.
+  dnl Ensure to expand the default settings once only, before all statements
+  dnl that occur in other macros.
   AC_REQUIRE([gl_DIRENT_H_DEFAULTS])
 
   dnl <dirent.h> is always overridden, because of GNULIB_POSIXCHECK.
@@ -27,26 +27,41 @@ AC_DEFUN([gl_DIRENT_H],
     ]], [alphasort closedir dirfd fdopendir opendir readdir rewinddir scandir])
 ])
 
+# gl_DIRENT_MODULE_INDICATOR([modulename])
+# sets the shell variable that indicates the presence of the given module
+# to a C preprocessor expression that will evaluate to 1.
+# This macro invocation must not occur in macros that are AC_REQUIREd.
 AC_DEFUN([gl_DIRENT_MODULE_INDICATOR],
 [
-  dnl Use AC_REQUIRE here, so that the default settings are expanded once only.
-  AC_REQUIRE([gl_DIRENT_H_DEFAULTS])
+  dnl Ensure to expand the default settings once only.
+  gl_DIRENT_H_REQUIRE_DEFAULTS
   gl_MODULE_INDICATOR_SET_VARIABLE([$1])
   dnl Define it also as a C macro, for the benefit of the unit tests.
   gl_MODULE_INDICATOR_FOR_TESTS([$1])
 ])
 
+# Initializes the default values for AC_SUBSTed shell variables.
+# This macro must not be AC_REQUIREd.  It must only be invoked, and only
+# outside of macros or in macros that are not AC_REQUIREd.
+AC_DEFUN([gl_DIRENT_H_REQUIRE_DEFAULTS],
+[
+  m4_defun(GL_MODULE_INDICATOR_PREFIX[_DIRENT_H_MODULE_INDICATOR_DEFAULTS], [
+    gl_UNISTD_H_REQUIRE_DEFAULTS dnl for REPLACE_FCHDIR
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_OPENDIR])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_READDIR])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_REWINDDIR])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_CLOSEDIR])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_DIRFD])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_FDOPENDIR])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_SCANDIR])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_ALPHASORT])
+  ])
+  m4_require(GL_MODULE_INDICATOR_PREFIX[_DIRENT_H_MODULE_INDICATOR_DEFAULTS])
+  AC_REQUIRE([gl_DIRENT_H_DEFAULTS])
+])
+
 AC_DEFUN([gl_DIRENT_H_DEFAULTS],
 [
-  AC_REQUIRE([gl_UNISTD_H_DEFAULTS]) dnl for REPLACE_FCHDIR
-  GNULIB_OPENDIR=0;     AC_SUBST([GNULIB_OPENDIR])
-  GNULIB_READDIR=0;     AC_SUBST([GNULIB_READDIR])
-  GNULIB_REWINDDIR=0;   AC_SUBST([GNULIB_REWINDDIR])
-  GNULIB_CLOSEDIR=0;    AC_SUBST([GNULIB_CLOSEDIR])
-  GNULIB_DIRFD=0;       AC_SUBST([GNULIB_DIRFD])
-  GNULIB_FDOPENDIR=0;   AC_SUBST([GNULIB_FDOPENDIR])
-  GNULIB_SCANDIR=0;     AC_SUBST([GNULIB_SCANDIR])
-  GNULIB_ALPHASORT=0;   AC_SUBST([GNULIB_ALPHASORT])
   dnl Assume proper GNU behavior unless another module says otherwise.
   HAVE_OPENDIR=1;       AC_SUBST([HAVE_OPENDIR])
   HAVE_READDIR=1;       AC_SUBST([HAVE_READDIR])
diff --git a/m4/environ.m4 b/m4/environ.m4
index d971770860c..ae5329108e9 100644
--- a/m4/environ.m4
+++ b/m4/environ.m4
@@ -1,4 +1,4 @@
-# environ.m4 serial 7
+# environ.m4 serial 8
 dnl Copyright (C) 2001-2004, 2006-2021 Free Software Foundation, Inc.
 dnl This file is free software; the Free Software Foundation
 dnl gives unlimited permission to copy and/or distribute it,
@@ -33,7 +33,8 @@ AC_DEFUN([gt_CHECK_VAR_DECL],
     [AC_COMPILE_IFELSE(
        [AC_LANG_PROGRAM(
           [[$1
-            extern struct { int foo; } $2;]],
+            typedef struct { int foo; } foo_t;
+            extern foo_t $2;]],
           [[$2.foo = 1;]])],
        [gt_cv_var=no],
        [gt_cv_var=yes])])
diff --git a/m4/explicit_bzero.m4 b/m4/explicit_bzero.m4
index d77ec5a3a5e..8c86d69e054 100644
--- a/m4/explicit_bzero.m4
+++ b/m4/explicit_bzero.m4
@@ -5,7 +5,7 @@ dnl with or without modifications, as long as this notice is preserved.
 
 AC_DEFUN([gl_FUNC_EXPLICIT_BZERO],
 [
-  AC_REQUIRE([gl_HEADER_STRING_H_DEFAULTS])
+  AC_REQUIRE([gl_STRING_H_DEFAULTS])
 
   dnl Persuade glibc <string.h> to declare explicit_bzero.
   AC_REQUIRE([AC_USE_SYSTEM_EXTENSIONS])
diff --git a/m4/extern-inline.m4 b/m4/extern-inline.m4
index a2acf126c87..a4ac5ea532a 100644
--- a/m4/extern-inline.m4
+++ b/m4/extern-inline.m4
@@ -17,7 +17,8 @@ AC_DEFUN([gl_EXTERN_INLINE],
    mishandles inline functions that call each other.  E.g., for 'inline void f
    (void) { } inline void g (void) { f (); }', c99 incorrectly complains
    'reference to static identifier "f" in extern inline function'.
-   This bug was observed with Sun C 5.12 SunOS_i386 2011/11/16.
+   This bug was observed with Oracle Developer Studio 12.6
+   (Sun C 5.15 SunOS_sparc 2017/05/30).
 
    Suppress extern inline (with or without __attribute__ ((__gnu_inline__)))
    on configurations that mistakenly use 'static inline' to implement
@@ -83,8 +84,8 @@ AC_DEFUN([gl_EXTERN_INLINE],
 # define _GL_EXTERN_INLINE extern
 # define _GL_EXTERN_INLINE_IN_USE
 #else
-# define _GL_INLINE static _GL_UNUSED
-# define _GL_EXTERN_INLINE static _GL_UNUSED
+# define _GL_INLINE _GL_UNUSED static
+# define _GL_EXTERN_INLINE _GL_UNUSED static
 #endif
 
 /* In GCC 4.6 (inclusive) to 5.1 (exclusive),
diff --git a/m4/fcntl_h.m4 b/m4/fcntl_h.m4
index e63a82f10a2..aba44735d14 100644
--- a/m4/fcntl_h.m4
+++ b/m4/fcntl_h.m4
@@ -1,4 +1,4 @@
-# serial 17
+# serial 20
 # Configure fcntl.h.
 dnl Copyright (C) 2006-2007, 2009-2021 Free Software Foundation, Inc.
 dnl This file is free software; the Free Software Foundation
@@ -7,7 +7,7 @@ dnl with or without modifications, as long as this notice is preserved.
 
 dnl Written by Paul Eggert.
 
-AC_DEFUN([gl_FCNTL_H],
+AC_DEFUN_ONCE([gl_FCNTL_H],
 [
   AC_REQUIRE([gl_FCNTL_H_DEFAULTS])
   AC_REQUIRE([gl_FCNTL_O_FLAGS])
@@ -26,25 +26,40 @@ AC_DEFUN([gl_FCNTL_H],
     ]], [fcntl openat])
 ])
 
+# gl_FCNTL_MODULE_INDICATOR([modulename])
+# sets the shell variable that indicates the presence of the given module
+# to a C preprocessor expression that will evaluate to 1.
+# This macro invocation must not occur in macros that are AC_REQUIREd.
 AC_DEFUN([gl_FCNTL_MODULE_INDICATOR],
 [
-  dnl Use AC_REQUIRE here, so that the default settings are expanded once only.
-  AC_REQUIRE([gl_FCNTL_H_DEFAULTS])
+  dnl Ensure to expand the default settings once only.
+  gl_FCNTL_H_REQUIRE_DEFAULTS
   gl_MODULE_INDICATOR_SET_VARIABLE([$1])
   dnl Define it also as a C macro, for the benefit of the unit tests.
   gl_MODULE_INDICATOR_FOR_TESTS([$1])
 ])
 
+# Initializes the default values for AC_SUBSTed shell variables.
+# This macro must not be AC_REQUIREd.  It must only be invoked, and only
+# outside of macros or in macros that are not AC_REQUIREd.
+AC_DEFUN([gl_FCNTL_H_REQUIRE_DEFAULTS],
+[
+  m4_defun(GL_MODULE_INDICATOR_PREFIX[_FCNTL_H_MODULE_INDICATOR_DEFAULTS], [
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_CREAT])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_FCNTL])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_NONBLOCKING])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_OPEN])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_OPENAT])
+    dnl Support Microsoft deprecated alias function names by default.
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_MDA_CREAT], [1])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_MDA_OPEN], [1])
+  ])
+  m4_require(GL_MODULE_INDICATOR_PREFIX[_FCNTL_H_MODULE_INDICATOR_DEFAULTS])
+  AC_REQUIRE([gl_FCNTL_H_DEFAULTS])
+])
+
 AC_DEFUN([gl_FCNTL_H_DEFAULTS],
 [
-  GNULIB_CREAT=0;        AC_SUBST([GNULIB_CREAT])
-  GNULIB_FCNTL=0;        AC_SUBST([GNULIB_FCNTL])
-  GNULIB_NONBLOCKING=0;  AC_SUBST([GNULIB_NONBLOCKING])
-  GNULIB_OPEN=0;         AC_SUBST([GNULIB_OPEN])
-  GNULIB_OPENAT=0;       AC_SUBST([GNULIB_OPENAT])
-  dnl Support Microsoft deprecated alias function names by default.
-  GNULIB_MDA_CREAT=1;    AC_SUBST([GNULIB_MDA_CREAT])
-  GNULIB_MDA_OPEN=1;     AC_SUBST([GNULIB_MDA_OPEN])
   dnl Assume proper GNU behavior unless another module says otherwise.
   HAVE_FCNTL=1;          AC_SUBST([HAVE_FCNTL])
   HAVE_OPENAT=1;         AC_SUBST([HAVE_OPENAT])
diff --git a/m4/free.m4 b/m4/free.m4
index d671376b0bb..a7923b90590 100644
--- a/m4/free.m4
+++ b/m4/free.m4
@@ -1,4 +1,4 @@
-# free.m4 serial 5
+# free.m4 serial 6
 # Copyright (C) 2003-2005, 2009-2021 Free Software Foundation, Inc.
 # This file is free software; the Free Software Foundation
 # gives unlimited permission to copy and/or distribute it,
@@ -40,7 +40,10 @@ AC_DEFUN([gl_FUNC_FREE],
     ])
 
   case $gl_cv_func_free_preserves_errno in
-   *yes) ;;
+   *yes)
+    AC_DEFINE([HAVE_FREE_POSIX], [1],
+      [Define if the 'free' function is guaranteed to preserve errno.])
+    ;;
    *) REPLACE_FREE=1 ;;
   esac
 ])
diff --git a/m4/gettimeofday.m4 b/m4/gettimeofday.m4
index 3c200815740..37c54404bb5 100644
--- a/m4/gettimeofday.m4
+++ b/m4/gettimeofday.m4
@@ -1,4 +1,4 @@
-# serial 28
+# serial 29
 
 # Copyright (C) 2001-2003, 2005, 2007, 2009-2021 Free Software Foundation, Inc.
 # This file is free software; the Free Software Foundation
@@ -9,10 +9,10 @@ dnl From Jim Meyering.
 
 AC_DEFUN([gl_FUNC_GETTIMEOFDAY],
 [
-  AC_REQUIRE([gl_HEADER_SYS_TIME_H_DEFAULTS])
+  AC_REQUIRE([gl_SYS_TIME_H_DEFAULTS])
   AC_REQUIRE([AC_C_RESTRICT])
   AC_REQUIRE([AC_CANONICAL_HOST])
-  AC_REQUIRE([gl_HEADER_SYS_TIME_H])
+  AC_REQUIRE([gl_SYS_TIME_H])
   AC_CHECK_FUNCS_ONCE([gettimeofday])
 
   gl_gettimeofday_timezone=void
diff --git a/m4/glibc21.m4 b/m4/glibc21.m4
deleted file mode 100644
index 74a781aa1c9..00000000000
--- a/m4/glibc21.m4
+++ /dev/null
@@ -1,34 +0,0 @@
-# glibc21.m4 serial 5
-dnl Copyright (C) 2000-2002, 2004, 2008, 2010-2021 Free Software
-dnl Foundation, Inc.
-dnl This file is free software; the Free Software Foundation
-dnl gives unlimited permission to copy and/or distribute it,
-dnl with or without modifications, as long as this notice is preserved.
-
-# Test for the GNU C Library, version 2.1 or newer, or uClibc.
-# From Bruno Haible.
-
-AC_DEFUN([gl_GLIBC21],
-  [
-    AC_CACHE_CHECK([whether we are using the GNU C Library >= 2.1 or uClibc],
-      [ac_cv_gnu_library_2_1],
-      [AC_EGREP_CPP([Lucky],
-        [
-#include <features.h>
-#ifdef __GNU_LIBRARY__
- #if (__GLIBC__ == 2 && __GLIBC_MINOR__ >= 1) || (__GLIBC__ > 2)
-  Lucky GNU user
- #endif
-#endif
-#ifdef __UCLIBC__
- Lucky user
-#endif
-        ],
-        [ac_cv_gnu_library_2_1=yes],
-        [ac_cv_gnu_library_2_1=no])
-      ]
-    )
-    AC_SUBST([GLIBC21])
-    GLIBC21="$ac_cv_gnu_library_2_1"
-  ]
-)
diff --git a/m4/gnulib-common.m4 b/m4/gnulib-common.m4
index f2eff10de6d..12b19dbcb44 100644
--- a/m4/gnulib-common.m4
+++ b/m4/gnulib-common.m4
@@ -1,4 +1,4 @@
-# gnulib-common.m4 serial 63
+# gnulib-common.m4 serial 67
 dnl Copyright (C) 2007-2021 Free Software Foundation, Inc.
 dnl This file is free software; the Free Software Foundation
 dnl gives unlimited permission to copy and/or distribute it,
@@ -85,12 +85,12 @@ AC_DEFUN([gl_COMMON_BODY], [
 # define _GL_ATTR_fallthrough _GL_GNUC_PREREQ (7, 0)
 # define _GL_ATTR_format _GL_GNUC_PREREQ (2, 7)
 # define _GL_ATTR_leaf _GL_GNUC_PREREQ (4, 6)
+# define _GL_ATTR_malloc _GL_GNUC_PREREQ (3, 0)
 # ifdef _ICC
 #  define _GL_ATTR_may_alias 0
 # else
 #  define _GL_ATTR_may_alias _GL_GNUC_PREREQ (3, 3)
 # endif
-# define _GL_ATTR_malloc _GL_GNUC_PREREQ (3, 0)
 # define _GL_ATTR_noinline _GL_GNUC_PREREQ (3, 1)
 # define _GL_ATTR_nonnull _GL_GNUC_PREREQ (3, 3)
 # define _GL_ATTR_nonstring _GL_GNUC_PREREQ (8, 0)
@@ -103,26 +103,47 @@ AC_DEFUN([gl_COMMON_BODY], [
 # define _GL_ATTR_warn_unused_result _GL_GNUC_PREREQ (3, 4)
 #endif
 
+#ifdef __has_c_attribute
+# define _GL_HAS_C_ATTRIBUTE(attr) __has_c_attribute (__##attr##__)
+#else
+# define _GL_HAS_C_ATTRIBUTE(attr) 0
+#endif
+
 ]dnl There is no _GL_ATTRIBUTE_ALIGNED; use stdalign's _Alignas instead.
 [
+/* _GL_ATTRIBUTE_ALLOC_SIZE ((N)) declares that the Nth argument of the function
+   is the size of the returned memory block.
+   _GL_ATTRIBUTE_ALLOC_SIZE ((M, N)) declares that the Mth argument multiplied
+   by the Nth argument of the function is the size of the returned memory block.
+ */
+/* Applies to: function, pointer to function, function types.  */
 #if _GL_HAS_ATTRIBUTE (alloc_size)
 # define _GL_ATTRIBUTE_ALLOC_SIZE(args) __attribute__ ((__alloc_size__ args))
 #else
 # define _GL_ATTRIBUTE_ALLOC_SIZE(args)
 #endif
 
+/* _GL_ATTRIBUTE_ALWAYS_INLINE tells that the compiler should always inline the
+   function and report an error if it cannot do so.  */
+/* Applies to: function.  */
 #if _GL_HAS_ATTRIBUTE (always_inline)
 # define _GL_ATTRIBUTE_ALWAYS_INLINE __attribute__ ((__always_inline__))
 #else
 # define _GL_ATTRIBUTE_ALWAYS_INLINE
 #endif
 
+/* _GL_ATTRIBUTE_ARTIFICIAL declares that the function is not important to show
+    in stack traces when debugging.  The compiler should omit the function from
+    stack traces.  */
+/* Applies to: function.  */
 #if _GL_HAS_ATTRIBUTE (artificial)
 # define _GL_ATTRIBUTE_ARTIFICIAL __attribute__ ((__artificial__))
 #else
 # define _GL_ATTRIBUTE_ARTIFICIAL
 #endif
 
+/* _GL_ATTRIBUTE_COLD declares that the function is rarely executed.  */
+/* Applies to: functions.  */
 /* Avoid __attribute__ ((cold)) on MinGW; see thread starting at
    <https://lists.gnu.org/r/emacs-devel/2019-04/msg01152.html>.
    Also, Oracle Studio 12.6 requires 'cold' not '__cold__'.  */
@@ -136,13 +157,41 @@ AC_DEFUN([gl_COMMON_BODY], [
 # define _GL_ATTRIBUTE_COLD
 #endif
 
+/* _GL_ATTRIBUTE_CONST declares that it is OK for a compiler to omit duplicate
+   calls to the function with the same arguments.
+   This attribute is safe for a function that neither depends on nor affects
+   observable state, and always returns exactly once - e.g., does not loop
+   forever, and does not call longjmp.
+   (This attribute is stricter than _GL_ATTRIBUTE_PURE.)  */
+/* Applies to: functions.  */
 #if _GL_HAS_ATTRIBUTE (const)
 # define _GL_ATTRIBUTE_CONST __attribute__ ((__const__))
 #else
 # define _GL_ATTRIBUTE_CONST
 #endif
 
-#if 201710L < __STDC_VERSION__
+/* _GL_ATTRIBUTE_DEALLOC (F, I) declares that the function returns pointers
+   that can be freed by passing them as the Ith argument to the
+   function F.
+   _GL_ATTRIBUTE_DEALLOC_FREE declares that the function returns pointers that
+   can be freed via 'free'; it can be used only after declaring 'free'.  */
+/* Applies to: functions.  Cannot be used on inline functions.  */
+#if _GL_GNUC_PREREQ (11, 0)
+# define _GL_ATTRIBUTE_DEALLOC(f, i) __attribute__ ((__malloc__ (f, i)))
+#else
+# define _GL_ATTRIBUTE_DEALLOC(f, i)
+#endif
+#define _GL_ATTRIBUTE_DEALLOC_FREE _GL_ATTRIBUTE_DEALLOC (free, 1)
+
+/* _GL_ATTRIBUTE_DEPRECATED: Declares that an entity is deprecated.
+   The compiler may warn if the entity is used.  */
+/* Applies to:
+     - function, variable,
+     - struct, union, struct/union member,
+     - enumeration, enumeration item,
+     - typedef,
+   in C++ also: namespace, class, template specialization.  */
+#if _GL_HAS_C_ATTRIBUTE (deprecated)
 # define _GL_ATTRIBUTE_DEPRECATED [[__deprecated__]]
 #elif _GL_HAS_ATTRIBUTE (deprecated)
 # define _GL_ATTRIBUTE_DEPRECATED __attribute__ ((__deprecated__))
@@ -150,6 +199,11 @@ AC_DEFUN([gl_COMMON_BODY], [
 # define _GL_ATTRIBUTE_DEPRECATED
 #endif
 
+/* _GL_ATTRIBUTE_ERROR(msg) requests an error if a function is called and
+   the function call is not optimized away.
+   _GL_ATTRIBUTE_WARNING(msg) requests a warning if a function is called and
+   the function call is not optimized away.  */
+/* Applies to: functions.  */
 #if _GL_HAS_ATTRIBUTE (error)
 # define _GL_ATTRIBUTE_ERROR(msg) __attribute__ ((__error__ (msg)))
 # define _GL_ATTRIBUTE_WARNING(msg) __attribute__ ((__warning__ (msg)))
@@ -161,14 +215,21 @@ AC_DEFUN([gl_COMMON_BODY], [
 # define _GL_ATTRIBUTE_WARNING(msg)
 #endif
 
+/* _GL_ATTRIBUTE_EXTERNALLY_VISIBLE declares that the entity should remain
+   visible to debuggers etc., even with '-fwhole-program'.  */
+/* Applies to: functions, variables.  */
 #if _GL_HAS_ATTRIBUTE (externally_visible)
 # define _GL_ATTRIBUTE_EXTERNALLY_VISIBLE __attribute__ ((externally_visible))
 #else
 # define _GL_ATTRIBUTE_EXTERNALLY_VISIBLE
 #endif
 
-/* FALLTHROUGH is special, because it always expands to something.  */
-#if 201710L < __STDC_VERSION__
+/* _GL_ATTRIBUTE_FALLTHROUGH declares that it is not a programming mistake if
+   the control flow falls through to the immediately following 'case' or
+   'default' label.  The compiler should not warn in this case.  */
+/* Applies to: Empty statement (;), inside a 'switch' statement.  */
+/* Always expands to something.  */
+#if _GL_HAS_C_ATTRIBUTE (fallthrough)
 # define _GL_ATTRIBUTE_FALLTHROUGH [[__fallthrough__]]
 #elif _GL_HAS_ATTRIBUTE (fallthrough)
 # define _GL_ATTRIBUTE_FALLTHROUGH __attribute__ ((__fallthrough__))
@@ -176,18 +237,47 @@ AC_DEFUN([gl_COMMON_BODY], [
 # define _GL_ATTRIBUTE_FALLTHROUGH ((void) 0)
 #endif
 
+/* _GL_ATTRIBUTE_FORMAT ((ARCHETYPE, STRING-INDEX, FIRST-TO-CHECK))
+   declares that the STRING-INDEXth function argument is a format string of
+   style ARCHETYPE, which is one of:
+     printf, gnu_printf
+     scanf, gnu_scanf,
+     strftime, gnu_strftime,
+     strfmon,
+   or the same thing prefixed and suffixed with '__'.
+   If FIRST-TO-CHECK is not 0, arguments starting at FIRST-TO_CHECK
+   are suitable for the format string.  */
+/* Applies to: functions.  */
 #if _GL_HAS_ATTRIBUTE (format)
 # define _GL_ATTRIBUTE_FORMAT(spec) __attribute__ ((__format__ spec))
 #else
 # define _GL_ATTRIBUTE_FORMAT(spec)
 #endif
 
+/* _GL_ATTRIBUTE_LEAF declares that if the function is called from some other
+   compilation unit, it executes code from that unit only by return or by
+   exception handling.  This declaration lets the compiler optimize that unit
+   more aggressively.  */
+/* Applies to: functions.  */
 #if _GL_HAS_ATTRIBUTE (leaf)
 # define _GL_ATTRIBUTE_LEAF __attribute__ ((__leaf__))
 #else
 # define _GL_ATTRIBUTE_LEAF
 #endif
 
+/* _GL_ATTRIBUTE_MALLOC declares that the function returns a pointer to freshly
+   allocated memory.  */
+/* Applies to: functions.  */
+#if _GL_HAS_ATTRIBUTE (malloc)
+# define _GL_ATTRIBUTE_MALLOC __attribute__ ((__malloc__))
+#else
+# define _GL_ATTRIBUTE_MALLOC
+#endif
+
+/* _GL_ATTRIBUTE_MAY_ALIAS declares that pointers to the type may point to the
+   same storage as pointers to other types.  Thus this declaration disables
+   strict aliasing optimization.  */
+/* Applies to: types.  */
 /* Oracle Studio 12.6 mishandles may_alias despite __has_attribute OK.  */
 #if _GL_HAS_ATTRIBUTE (may_alias) && !defined __SUNPRO_C
 # define _GL_ATTRIBUTE_MAY_ALIAS __attribute__ ((__may_alias__))
@@ -195,24 +285,33 @@ AC_DEFUN([gl_COMMON_BODY], [
 # define _GL_ATTRIBUTE_MAY_ALIAS
 #endif
 
-#if 201710L < __STDC_VERSION__
+/* _GL_ATTRIBUTE_MAYBE_UNUSED declares that it is not a programming mistake if
+   the entity is not used.  The compiler should not warn if the entity is not
+   used.  */
+/* Applies to:
+     - function, variable,
+     - struct, union, struct/union member,
+     - enumeration, enumeration item,
+     - typedef,
+   in C++ also: class.  */
+/* In C++ and C2x, this is spelled [[__maybe_unused__]].
+   GCC's syntax is __attribute__ ((__unused__)).
+   clang supports both syntaxes.  */
+#if _GL_HAS_C_ATTRIBUTE (maybe_unused)
 # define _GL_ATTRIBUTE_MAYBE_UNUSED [[__maybe_unused__]]
-#elif _GL_HAS_ATTRIBUTE (unused)
-# define _GL_ATTRIBUTE_MAYBE_UNUSED __attribute__ ((__unused__))
 #else
-# define _GL_ATTRIBUTE_MAYBE_UNUSED
+# define _GL_ATTRIBUTE_MAYBE_UNUSED _GL_ATTRIBUTE_UNUSED
 #endif
-/* Earlier spellings of this macro.  */
+/* Alternative spelling of this macro, for convenience.  */
 #define _GL_UNUSED _GL_ATTRIBUTE_MAYBE_UNUSED
+/* Earlier spellings of this macro.  */
 #define _UNUSED_PARAMETER_ _GL_ATTRIBUTE_MAYBE_UNUSED
 
-#if _GL_HAS_ATTRIBUTE (malloc)
-# define _GL_ATTRIBUTE_MALLOC __attribute__ ((__malloc__))
-#else
-# define _GL_ATTRIBUTE_MALLOC
-#endif
-
-#if 201710L < __STDC_VERSION__
+/* _GL_ATTRIBUTE_NODISCARD declares that the caller of the function should not
+   discard the return value.  The compiler may warn if the caller does not use
+   the return value, unless the caller uses something like ignore_value.  */
+/* Applies to: function, enumeration, class.  */
+#if _GL_HAS_C_ATTRIBUTE (nodiscard)
 # define _GL_ATTRIBUTE_NODISCARD [[__nodiscard__]]
 #elif _GL_HAS_ATTRIBUTE (warn_unused_result)
 # define _GL_ATTRIBUTE_NODISCARD __attribute__ ((__warn_unused_result__))
@@ -220,18 +319,30 @@ AC_DEFUN([gl_COMMON_BODY], [
 # define _GL_ATTRIBUTE_NODISCARD
 #endif
 
+/* _GL_ATTRIBUTE_NOINLINE tells that the compiler should not inline the
+   function.  */
+/* Applies to: functions.  */
 #if _GL_HAS_ATTRIBUTE (noinline)
 # define _GL_ATTRIBUTE_NOINLINE __attribute__ ((__noinline__))
 #else
 # define _GL_ATTRIBUTE_NOINLINE
 #endif
 
+/* _GL_ATTRIBUTE_NONNULL ((N1, N2,...)) declares that the arguments N1, N2,...
+   must not be NULL.
+   _GL_ATTRIBUTE_NONNULL () declares that all pointer arguments must not be
+   null.  */
+/* Applies to: functions.  */
 #if _GL_HAS_ATTRIBUTE (nonnull)
 # define _GL_ATTRIBUTE_NONNULL(args) __attribute__ ((__nonnull__ args))
 #else
 # define _GL_ATTRIBUTE_NONNULL(args)
 #endif
 
+/* _GL_ATTRIBUTE_NONSTRING declares that the contents of a character array is
+   not meant to be NUL-terminated.  */
+/* Applies to: struct/union members and variables that are arrays of element
+   type '[[un]signed] char'.  */
 #if _GL_HAS_ATTRIBUTE (nonstring)
 # define _GL_ATTRIBUTE_NONSTRING __attribute__ ((__nonstring__))
 #else
@@ -240,41 +351,77 @@ AC_DEFUN([gl_COMMON_BODY], [
 
 /* There is no _GL_ATTRIBUTE_NORETURN; use _Noreturn instead.  */
 
+/* _GL_ATTRIBUTE_NOTHROW declares that the function does not throw exceptions.
+ */
+/* Applies to: functions.  */
 #if _GL_HAS_ATTRIBUTE (nothrow) && !defined __cplusplus
 # define _GL_ATTRIBUTE_NOTHROW __attribute__ ((__nothrow__))
 #else
 # define _GL_ATTRIBUTE_NOTHROW
 #endif
 
+/* _GL_ATTRIBUTE_PACKED declares:
+   For struct members: The member has the smallest possible alignment.
+   For struct, union, class: All members have the smallest possible alignment,
+   minimizing the memory required.  */
+/* Applies to: struct members, struct, union,
+   in C++ also: class.  */
 #if _GL_HAS_ATTRIBUTE (packed)
 # define _GL_ATTRIBUTE_PACKED __attribute__ ((__packed__))
 #else
 # define _GL_ATTRIBUTE_PACKED
 #endif
 
+/* _GL_ATTRIBUTE_PURE declares that It is OK for a compiler to omit duplicate
+   calls to the function with the same arguments if observable state is not
+   changed between calls.
+   This attribute is safe for a function that does not affect
+   observable state, and always returns exactly once.
+   (This attribute is looser than _GL_ATTRIBUTE_CONST.)  */
+/* Applies to: functions.  */
 #if _GL_HAS_ATTRIBUTE (pure)
 # define _GL_ATTRIBUTE_PURE __attribute__ ((__pure__))
 #else
 # define _GL_ATTRIBUTE_PURE
 #endif
 
+/* _GL_ATTRIBUTE_RETURNS_NONNULL declares that the function's return value is
+   a non-NULL pointer.  */
+/* Applies to: functions.  */
 #if _GL_HAS_ATTRIBUTE (returns_nonnull)
 # define _GL_ATTRIBUTE_RETURNS_NONNULL __attribute__ ((__returns_nonnull__))
 #else
 # define _GL_ATTRIBUTE_RETURNS_NONNULL
 #endif
 
+/* _GL_ATTRIBUTE_SENTINEL(pos) declares that the variadic function expects a
+   trailing NULL argument.
+   _GL_ATTRIBUTE_SENTINEL () - The last argument is NULL (requires C99).
+   _GL_ATTRIBUTE_SENTINEL ((N)) - The (N+1)st argument from the end is NULL.  */
+/* Applies to: functions.  */
 #if _GL_HAS_ATTRIBUTE (sentinel)
 # define _GL_ATTRIBUTE_SENTINEL(pos) __attribute__ ((__sentinel__ pos))
 #else
 # define _GL_ATTRIBUTE_SENTINEL(pos)
 #endif
 
+/* A helper macro.  Don't use it directly.  */
+#if _GL_HAS_ATTRIBUTE (unused)
+# define _GL_ATTRIBUTE_UNUSED __attribute__ ((__unused__))
+#else
+# define _GL_ATTRIBUTE_UNUSED
+#endif
+
 ]dnl There is no _GL_ATTRIBUTE_VISIBILITY; see m4/visibility.m4 instead.
 [
-/* To support C++ as well as C, use _GL_UNUSED_LABEL with trailing ';'.  */
-#if !defined __cplusplus || _GL_GNUC_PREREQ (4, 5)
-# define _GL_UNUSED_LABEL _GL_ATTRIBUTE_MAYBE_UNUSED
+/* _GL_UNUSED_LABEL; declares that it is not a programming mistake if the
+   immediately preceding label is not used.  The compiler should not warn
+   if the label is not used.  */
+/* Applies to: label (both in C and C++).  */
+/* Note that g++ < 4.5 does not support the '__attribute__ ((__unused__)) ;'
+   syntax.  But clang does.  */
+#if !(defined __cplusplus && !_GL_GNUC_PREREQ (4, 5)) || defined __clang__
+# define _GL_UNUSED_LABEL _GL_ATTRIBUTE_UNUSED
 #else
 # define _GL_UNUSED_LABEL
 #endif
@@ -357,6 +504,16 @@ AC_DEFUN([gl_COMMON_BODY], [
   export LIBC_FATAL_STDERR_
 ])
 
+# gl_MODULE_INDICATOR_INIT_VARIABLE([variablename])
+# gl_MODULE_INDICATOR_INIT_VARIABLE([variablename], [initialvalue])
+# initializes the shell variable that indicates the presence of the given module
+# as a C preprocessor expression.
+AC_DEFUN([gl_MODULE_INDICATOR_INIT_VARIABLE],
+[
+  GL_MODULE_INDICATOR_PREFIX[]_[$1]=m4_if([$2], , [0], [$2])
+  AC_SUBST(GL_MODULE_INDICATOR_PREFIX[]_[$1])
+])
+
 # gl_MODULE_INDICATOR_CONDITION
 # expands to a C preprocessor expression that evaluates to 1 or 0, depending
 # whether a gnulib module that has been requested shall be considered present
@@ -369,9 +526,9 @@ m4_define([gl_MODULE_INDICATOR_CONDITION], [1])
 AC_DEFUN([gl_MODULE_INDICATOR_SET_VARIABLE],
 [
   gl_MODULE_INDICATOR_SET_VARIABLE_AUX(
-    [GNULIB_[]m4_translit([[$1]],
-                          [abcdefghijklmnopqrstuvwxyz./-],
-                          [ABCDEFGHIJKLMNOPQRSTUVWXYZ___])],
+    [GL_MODULE_INDICATOR_PREFIX[]_GNULIB_[]m4_translit([[$1]],
+                                                       [abcdefghijklmnopqrstuvwxyz./-],
+                                                       [ABCDEFGHIJKLMNOPQRSTUVWXYZ___])],
     [gl_MODULE_INDICATOR_CONDITION])
 ])
 
@@ -656,6 +813,72 @@ AC_DEFUN([gl_CACHE_VAL_SILENT],
   ])
 ])
 
+# gl_CC_ALLOW_WARNINGS
+# sets and substitutes a variable GL_CFLAG_ALLOW_WARNINGS, to a $(CC) option
+# that reverts a preceding '-Werror' option, if available.
+# This is expected to be '-Wno-error' on gcc, clang (except clang/MSVC), xlclang
+# and empty otherwise.
+AC_DEFUN([gl_CC_ALLOW_WARNINGS],
+[
+  AC_REQUIRE([AC_PROG_CC])
+  AC_CACHE_CHECK([for C compiler option to allow warnings],
+    [gl_cv_cc_wallow],
+    [rm -f conftest*
+     echo 'int dummy;' > conftest.c
+     AC_TRY_COMMAND([${CC-cc} $CFLAGS $CPPFLAGS -c conftest.c 2>conftest1.err]) >/dev/null
+     AC_TRY_COMMAND([${CC-cc} $CFLAGS $CPPFLAGS -Wno-error -c conftest.c 2>conftest2.err]) >/dev/null
+     dnl Test the number of error output lines, because AIX xlc accepts the
+     dnl option '-Wno-error', just to produce a warning
+     dnl "Option -Wno-error was incorrectly specified. The option will be ignored."
+     dnl afterwards.
+     if test $? = 0 && test `wc -l < conftest1.err` = `wc -l < conftest2.err`; then
+       gl_cv_cc_wallow='-Wno-error'
+     else
+       gl_cv_cc_wallow=none
+     fi
+     rm -f conftest*
+    ])
+  case "$gl_cv_cc_wallow" in
+    none) GL_CFLAG_ALLOW_WARNINGS='' ;;
+    *)    GL_CFLAG_ALLOW_WARNINGS="$gl_cv_cc_wallow" ;;
+  esac
+  AC_SUBST([GL_CFLAG_ALLOW_WARNINGS])
+])
+
+# gl_CXX_ALLOW_WARNINGS
+# sets and substitutes a variable GL_CXXFLAG_ALLOW_WARNINGS, to a $(CC) option
+# that reverts a preceding '-Werror' option, if available.
+AC_DEFUN([gl_CXX_ALLOW_WARNINGS],
+[
+  dnl Requires AC_PROG_CXX or gl_PROG_ANSI_CXX.
+  if test -n "$CXX" && test "$CXX" != no; then
+    AC_CACHE_CHECK([for C++ compiler option to allow warnings],
+      [gl_cv_cxx_wallow],
+      [rm -f conftest*
+       echo 'int dummy;' > conftest.cc
+       AC_TRY_COMMAND([${CXX-c++} $CXXFLAGS $CPPFLAGS -c conftest.cc 2>conftest1.err]) >/dev/null
+       AC_TRY_COMMAND([${CXX-c++} $CXXFLAGS $CPPFLAGS -Wno-error -c conftest.cc 2>conftest2.err]) >/dev/null
+       dnl Test the number of error output lines, because AIX xlC accepts the
+       dnl option '-Wno-error', just to produce a warning
+       dnl "Option -Wno-error was incorrectly specified. The option will be ignored."
+       dnl afterwards.
+       if test $? = 0 && test `wc -l < conftest1.err` = `wc -l < conftest2.err`; then
+         gl_cv_cxx_wallow='-Wno-error'
+       else
+         gl_cv_cxx_wallow=none
+       fi
+       rm -f conftest*
+      ])
+    case "$gl_cv_cxx_wallow" in
+      none) GL_CXXFLAG_ALLOW_WARNINGS='' ;;
+      *)    GL_CXXFLAG_ALLOW_WARNINGS="$gl_cv_cxx_wallow" ;;
+    esac
+  else
+    GL_CXXFLAG_ALLOW_WARNINGS=''
+  fi
+  AC_SUBST([GL_CXXFLAG_ALLOW_WARNINGS])
+])
+
 dnl Expands to some code for use in .c programs that, on native Windows, defines
 dnl the Microsoft deprecated alias function names to the underscore-prefixed
 dnl actual function names. With this macro, these function names are available
diff --git a/m4/gnulib-comp.m4 b/m4/gnulib-comp.m4
index 05e7faa9937..e314edcfb53 100644
--- a/m4/gnulib-comp.m4
+++ b/m4/gnulib-comp.m4
@@ -63,6 +63,7 @@ AC_DEFUN([gl_EARLY],
   # Code from module count-leading-zeros:
   # Code from module count-one-bits:
   # Code from module count-trailing-zeros:
+  # Code from module crypto/md5:
   # Code from module crypto/md5-buffer:
   # Code from module crypto/sha1-buffer:
   # Code from module crypto/sha256-buffer:
@@ -121,11 +122,13 @@ AC_DEFUN([gl_EARLY],
   # Code from module inttypes-incomplete:
   # Code from module largefile:
   AC_REQUIRE([AC_SYS_LARGEFILE])
+  AC_REQUIRE([gl_YEAR2038_EARLY])
   # Code from module lchmod:
   # Code from module libc-config:
   # Code from module libgmp:
   # Code from module limits-h:
   # Code from module lstat:
+  # Code from module malloc-posix:
   # Code from module manywarnings:
   # Code from module memmem-simple:
   # Code from module mempcpy:
@@ -136,6 +139,7 @@ AC_DEFUN([gl_EARLY],
   # Code from module mktime-internal:
   # Code from module multiarch:
   # Code from module nocrash:
+  # Code from module nproc:
   # Code from module nstrftime:
   # Code from module open:
   # Code from module openat-h:
@@ -147,6 +151,8 @@ AC_DEFUN([gl_EARLY],
   # Code from module rawmemchr:
   # Code from module readlink:
   # Code from module readlinkat:
+  # Code from module realloc-gnu:
+  # Code from module realloc-posix:
   # Code from module regex:
   # Code from module root-uid:
   # Code from module scratch_buffer:
@@ -189,6 +195,7 @@ AC_DEFUN([gl_EARLY],
   # Code from module u64:
   # Code from module unistd:
   # Code from module unlocked-io:
+  # Code from module unlocked-io-internal:
   # Code from module update-copyright:
   # Code from module utimens:
   # Code from module utimensat:
@@ -213,6 +220,8 @@ AC_DEFUN([gl_INIT],
   m4_pushdef([AC_LIBSOURCES], m4_defn([gl_LIBSOURCES]))
   m4_pushdef([gl_LIBSOURCES_LIST], [])
   m4_pushdef([gl_LIBSOURCES_DIR], [])
+  m4_pushdef([GL_MACRO_PREFIX], [gl])
+  m4_pushdef([GL_MODULE_INDICATOR_PREFIX], [GL])
   gl_COMMON
   gl_source_base='lib'
   gl_FUNC_ACL
@@ -245,6 +254,7 @@ AC_DEFUN([gl_INIT],
   gl_SHA512
   gl_CHECK_TYPE_STRUCT_DIRENT_D_TYPE
   gl_DIRENT_H
+  gl_DIRENT_H_REQUIRE_DEFAULTS
   gl_DOUBLE_SLASH_ROOT
   gl_FUNC_DUP2
   if test $REPLACE_DUP2 = 1; then
@@ -282,6 +292,7 @@ AC_DEFUN([gl_INIT],
   fi
   gl_FCNTL_MODULE_INDICATOR([fcntl])
   gl_FCNTL_H
+  gl_FCNTL_H_REQUIRE_DEFAULTS
   gl_FUNC_FDOPENDIR
   if test $HAVE_FDOPENDIR = 0 || test $REPLACE_FDOPENDIR = 1; then
     AC_LIBOBJ([fdopendir])
@@ -337,10 +348,10 @@ AC_DEFUN([gl_INIT],
   if test $REPLACE_GETOPT = 1; then
     AC_LIBOBJ([getopt])
     AC_LIBOBJ([getopt1])
-    dnl Arrange for unistd.h to include getopt.h.
-    GNULIB_GL_UNISTD_H_GETOPT=1
+    dnl Define the substituted variable GNULIB_UNISTD_H_GETOPT to 1.
+    gl_UNISTD_H_REQUIRE_DEFAULTS
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_UNISTD_H_GETOPT], [1])
   fi
-  AC_SUBST([GNULIB_GL_UNISTD_H_GETOPT])
   gl_UNISTD_MODULE_INDICATOR([getopt-posix])
   AC_REQUIRE([AC_CANONICAL_HOST])
   gl_FUNC_GETRANDOM
@@ -357,6 +368,7 @@ AC_DEFUN([gl_INIT],
   gl_SYS_TIME_MODULE_INDICATOR([gettimeofday])
   gl_IEEE754_H
   gl_INTTYPES_INCOMPLETE
+  gl_INTTYPES_H_REQUIRE_DEFAULTS
   AC_REQUIRE([gl_LARGEFILE])
   gl___INLINE
   gl_LIBGMP
@@ -402,6 +414,7 @@ AC_DEFUN([gl_INIT],
   fi
   gl_TIME_MODULE_INDICATOR([mktime])
   gl_MULTIARCH
+  gl_NPROC
   gl_FUNC_GNU_STRFTIME
   gl_PATHMAX
   gl_FUNC_PIPE2
@@ -444,22 +457,50 @@ AC_DEFUN([gl_INIT],
   fi
   gl_STRING_MODULE_INDICATOR([sigdescr_np])
   gl_SIGNAL_H
+  gl_SIGNAL_H_REQUIRE_DEFAULTS
   gl_TYPE_SOCKLEN_T
   gt_TYPE_SSIZE_T
   gl_STAT_TIME
   gl_STAT_BIRTHTIME
   gl_STDALIGN_H
   gl_STDDEF_H
+  gl_STDDEF_H_REQUIRE_DEFAULTS
   gl_STDINT_H
   gl_STDIO_H
+  gl_STDIO_H_REQUIRE_DEFAULTS
+  dnl No need to create extra modules for these functions. Everyone who uses
+  dnl <stdio.h> likely needs them.
+  gl_STDIO_MODULE_INDICATOR([fscanf])
+  gl_MODULE_INDICATOR([fscanf])
+  gl_STDIO_MODULE_INDICATOR([scanf])
+  gl_MODULE_INDICATOR([scanf])
+  gl_STDIO_MODULE_INDICATOR([fgetc])
+  gl_STDIO_MODULE_INDICATOR([getc])
+  gl_STDIO_MODULE_INDICATOR([getchar])
+  gl_STDIO_MODULE_INDICATOR([fgets])
+  gl_STDIO_MODULE_INDICATOR([fread])
+  dnl No need to create extra modules for these functions. Everyone who uses
+  dnl <stdio.h> likely needs them.
+  gl_STDIO_MODULE_INDICATOR([fprintf])
+  gl_STDIO_MODULE_INDICATOR([printf])
+  gl_STDIO_MODULE_INDICATOR([vfprintf])
+  gl_STDIO_MODULE_INDICATOR([vprintf])
+  gl_STDIO_MODULE_INDICATOR([fputc])
+  gl_STDIO_MODULE_INDICATOR([putc])
+  gl_STDIO_MODULE_INDICATOR([putchar])
+  gl_STDIO_MODULE_INDICATOR([fputs])
+  gl_STDIO_MODULE_INDICATOR([puts])
+  gl_STDIO_MODULE_INDICATOR([fwrite])
   gl_STDLIB_H
+  gl_STDLIB_H_REQUIRE_DEFAULTS
   gl_FUNC_STPCPY
   if test $HAVE_STPCPY = 0; then
     AC_LIBOBJ([stpcpy])
     gl_PREREQ_STPCPY
   fi
   gl_STRING_MODULE_INDICATOR([stpcpy])
-  gl_HEADER_STRING_H
+  gl_STRING_H
+  gl_STRING_H_REQUIRE_DEFAULTS
   gl_FUNC_STRNLEN
   if test $HAVE_DECL_STRNLEN = 0 || test $REPLACE_STRNLEN = 1; then
     AC_LIBOBJ([strnlen])
@@ -477,19 +518,25 @@ AC_DEFUN([gl_INIT],
     AC_LIBOBJ([symlink])
   fi
   gl_UNISTD_MODULE_INDICATOR([symlink])
-  gl_HEADER_SYS_RANDOM
+  gl_SYS_RANDOM_H
+  gl_SYS_RANDOM_H_REQUIRE_DEFAULTS
   AC_PROG_MKDIR_P
-  AC_REQUIRE([gl_HEADER_SYS_SELECT])
+  gl_SYS_SELECT_H
+  gl_SYS_SELECT_H_REQUIRE_DEFAULTS
   AC_PROG_MKDIR_P
-  gl_HEADER_SYS_STAT_H
+  gl_SYS_STAT_H
+  gl_SYS_STAT_H_REQUIRE_DEFAULTS
   AC_PROG_MKDIR_P
-  gl_HEADER_SYS_TIME_H
+  gl_SYS_TIME_H
+  gl_SYS_TIME_H_REQUIRE_DEFAULTS
   AC_PROG_MKDIR_P
   gl_SYS_TYPES_H
+  gl_SYS_TYPES_H_REQUIRE_DEFAULTS
   AC_PROG_MKDIR_P
   gl_FUNC_GEN_TEMPNAME
   gl_MODULE_INDICATOR([tempname])
-  gl_HEADER_TIME_H
+  gl_TIME_H
+  gl_TIME_H_REQUIRE_DEFAULTS
   gl_TIME_R
   if test $HAVE_LOCALTIME_R = 0 || test $REPLACE_LOCALTIME_R = 1; then
     AC_LIBOBJ([time_r])
@@ -510,6 +557,17 @@ AC_DEFUN([gl_INIT],
   gl_TIMER_TIME
   gl_TIMESPEC
   gl_UNISTD_H
+  gl_UNISTD_H_REQUIRE_DEFAULTS
+  AC_DEFINE([GNULIB_STDIO_SINGLE_THREAD], [1],
+    [Define to 1 if you want the FILE stream functions getc, putc, etc.
+     to use unlocked I/O if available, throughout the package.
+     Unlocked I/O can improve performance, sometimes dramatically.
+     But unlocked I/O is safe only in single-threaded programs,
+     as well as in multithreaded programs for which you can guarantee that
+     every FILE stream, including stdin, stdout, stderr, is used only
+     in a single thread.])
+  AC_DEFINE([USE_UNLOCKED_IO], [GNULIB_STDIO_SINGLE_THREAD],
+    [An alias of GNULIB_STDIO_SINGLE_THREAD.])
   gl_FUNC_GLIBC_UNLOCKED_IO
   gl_FUNC_UTIMENSAT
   if test $HAVE_UTIMENSAT = 0 || test $REPLACE_UTIMENSAT = 1; then
@@ -527,12 +585,14 @@ AC_DEFUN([gl_INIT],
   gl_gnulib_enabled_getgroups=false
   gl_gnulib_enabled_be453cec5eecf5731a274f2de7f2db36=false
   gl_gnulib_enabled_a9786850e999ae65a836a6041e8e5ed1=false
-  gl_gnulib_enabled_idx=false
   gl_gnulib_enabled_lchmod=false
+  gl_gnulib_enabled_ef455225c00f5049c808c2eda3e76866=false
   gl_gnulib_enabled_5264294aa0a5557541b53c8c741f7f31=false
   gl_gnulib_enabled_open=false
   gl_gnulib_enabled_03e0aaad4cb89ca757653bd367a6ccb7=false
   gl_gnulib_enabled_rawmemchr=false
+  gl_gnulib_enabled_d3b2383720ee0e541357aa2aac598e2b=false
+  gl_gnulib_enabled_61bcaca76b3e6f9ae55d57a1c3193bc4=false
   gl_gnulib_enabled_6099e9737f757db36c47fa9d9f02e88c=false
   gl_gnulib_enabled_scratch_buffer=false
   gl_gnulib_enabled_strtoll=false
@@ -571,6 +631,7 @@ AC_DEFUN([gl_INIT],
   func_gl_gnulib_m4code_dynarray ()
   {
     if ! $gl_gnulib_enabled_dynarray; then
+      AC_PROG_MKDIR_P
       gl_gnulib_enabled_dynarray=true
     fi
   }
@@ -617,6 +678,9 @@ AC_DEFUN([gl_INIT],
       fi
       gl_UNISTD_MODULE_INDICATOR([getgroups])
       gl_gnulib_enabled_getgroups=true
+      if test $HAVE_GETGROUPS = 0 || test $REPLACE_GETGROUPS = 1; then
+        func_gl_gnulib_m4code_ef455225c00f5049c808c2eda3e76866
+      fi
     fi
   }
   func_gl_gnulib_m4code_be453cec5eecf5731a274f2de7f2db36 ()
@@ -641,16 +705,10 @@ AC_DEFUN([gl_INIT],
         func_gl_gnulib_m4code_getgroups
       fi
       if test $HAVE_GROUP_MEMBER = 0; then
-        func_gl_gnulib_m4code_682e609604ccaac6be382e4ee3a4eaec
+        func_gl_gnulib_m4code_d3b2383720ee0e541357aa2aac598e2b
       fi
     fi
   }
-  func_gl_gnulib_m4code_idx ()
-  {
-    if ! $gl_gnulib_enabled_idx; then
-      gl_gnulib_enabled_idx=true
-    fi
-  }
   func_gl_gnulib_m4code_lchmod ()
   {
     if ! $gl_gnulib_enabled_lchmod; then
@@ -663,6 +721,20 @@ AC_DEFUN([gl_INIT],
       gl_gnulib_enabled_lchmod=true
     fi
   }
+  func_gl_gnulib_m4code_ef455225c00f5049c808c2eda3e76866 ()
+  {
+    if ! $gl_gnulib_enabled_ef455225c00f5049c808c2eda3e76866; then
+      AC_REQUIRE([gl_FUNC_MALLOC_POSIX])
+      if test $REPLACE_MALLOC = 1; then
+        AC_LIBOBJ([malloc])
+      fi
+      gl_STDLIB_MODULE_INDICATOR([malloc-posix])
+      gl_gnulib_enabled_ef455225c00f5049c808c2eda3e76866=true
+      if test $REPLACE_MALLOC = 1; then
+        func_gl_gnulib_m4code_682e609604ccaac6be382e4ee3a4eaec
+      fi
+    fi
+  }
   func_gl_gnulib_m4code_5264294aa0a5557541b53c8c741f7f31 ()
   {
     if ! $gl_gnulib_enabled_5264294aa0a5557541b53c8c741f7f31; then
@@ -707,6 +779,34 @@ AC_DEFUN([gl_INIT],
       gl_gnulib_enabled_rawmemchr=true
     fi
   }
+  func_gl_gnulib_m4code_d3b2383720ee0e541357aa2aac598e2b ()
+  {
+    if ! $gl_gnulib_enabled_d3b2383720ee0e541357aa2aac598e2b; then
+      gl_FUNC_REALLOC_GNU
+      if test $REPLACE_REALLOC = 1; then
+        AC_LIBOBJ([realloc])
+      fi
+      gl_gnulib_enabled_d3b2383720ee0e541357aa2aac598e2b=true
+      func_gl_gnulib_m4code_61bcaca76b3e6f9ae55d57a1c3193bc4
+    fi
+  }
+  func_gl_gnulib_m4code_61bcaca76b3e6f9ae55d57a1c3193bc4 ()
+  {
+    if ! $gl_gnulib_enabled_61bcaca76b3e6f9ae55d57a1c3193bc4; then
+      gl_FUNC_REALLOC_POSIX
+      if test $REPLACE_REALLOC = 1; then
+        AC_LIBOBJ([realloc])
+      fi
+      gl_STDLIB_MODULE_INDICATOR([realloc-posix])
+      gl_gnulib_enabled_61bcaca76b3e6f9ae55d57a1c3193bc4=true
+      if test $REPLACE_REALLOC = 1; then
+        func_gl_gnulib_m4code_ef455225c00f5049c808c2eda3e76866
+      fi
+      if test $REPLACE_REALLOC = 1; then
+        func_gl_gnulib_m4code_682e609604ccaac6be382e4ee3a4eaec
+      fi
+    fi
+  }
   func_gl_gnulib_m4code_6099e9737f757db36c47fa9d9f02e88c ()
   {
     if ! $gl_gnulib_enabled_6099e9737f757db36c47fa9d9f02e88c; then
@@ -716,14 +816,17 @@ AC_DEFUN([gl_INIT],
   func_gl_gnulib_m4code_scratch_buffer ()
   {
     if ! $gl_gnulib_enabled_scratch_buffer; then
+      AC_PROG_MKDIR_P
       gl_gnulib_enabled_scratch_buffer=true
+      func_gl_gnulib_m4code_ef455225c00f5049c808c2eda3e76866
+      func_gl_gnulib_m4code_61bcaca76b3e6f9ae55d57a1c3193bc4
     fi
   }
   func_gl_gnulib_m4code_strtoll ()
   {
     if ! $gl_gnulib_enabled_strtoll; then
       gl_FUNC_STRTOLL
-      if test $HAVE_STRTOLL = 0; then
+      if test $HAVE_STRTOLL = 0 || test $REPLACE_STRTOLL = 1; then
         AC_LIBOBJ([strtoll])
         gl_PREREQ_STRTOLL
       fi
@@ -748,9 +851,6 @@ AC_DEFUN([gl_INIT],
     func_gl_gnulib_m4code_925677f0343de64b89a9f0c790b4104c
   fi
   if test $HAVE_CANONICALIZE_FILE_NAME = 0 || test $REPLACE_CANONICALIZE_FILE_NAME = 1; then
-    func_gl_gnulib_m4code_idx
-  fi
-  if test $HAVE_CANONICALIZE_FILE_NAME = 0 || test $REPLACE_CANONICALIZE_FILE_NAME = 1; then
     func_gl_gnulib_m4code_rawmemchr
   fi
   if test $HAVE_CANONICALIZE_FILE_NAME = 0 || test $REPLACE_CANONICALIZE_FILE_NAME = 1; then
@@ -813,9 +913,6 @@ AC_DEFUN([gl_INIT],
   if { test $HAVE_DECL_STRTOIMAX = 0 || test $REPLACE_STRTOIMAX = 1; } && test $ac_cv_type_long_long_int = yes; then
     func_gl_gnulib_m4code_strtoll
   fi
-  if test $HAVE_TIMEZONE_T = 0; then
-    func_gl_gnulib_m4code_idx
-  fi
   if test $HAVE_TIMEGM = 0 || test $REPLACE_TIMEGM = 1; then
     func_gl_gnulib_m4code_5264294aa0a5557541b53c8c741f7f31
   fi
@@ -839,12 +936,14 @@ AC_DEFUN([gl_INIT],
   AM_CONDITIONAL([gl_GNULIB_ENABLED_getgroups], [$gl_gnulib_enabled_getgroups])
   AM_CONDITIONAL([gl_GNULIB_ENABLED_be453cec5eecf5731a274f2de7f2db36], [$gl_gnulib_enabled_be453cec5eecf5731a274f2de7f2db36])
   AM_CONDITIONAL([gl_GNULIB_ENABLED_a9786850e999ae65a836a6041e8e5ed1], [$gl_gnulib_enabled_a9786850e999ae65a836a6041e8e5ed1])
-  AM_CONDITIONAL([gl_GNULIB_ENABLED_idx], [$gl_gnulib_enabled_idx])
   AM_CONDITIONAL([gl_GNULIB_ENABLED_lchmod], [$gl_gnulib_enabled_lchmod])
+  AM_CONDITIONAL([gl_GNULIB_ENABLED_ef455225c00f5049c808c2eda3e76866], [$gl_gnulib_enabled_ef455225c00f5049c808c2eda3e76866])
   AM_CONDITIONAL([gl_GNULIB_ENABLED_5264294aa0a5557541b53c8c741f7f31], [$gl_gnulib_enabled_5264294aa0a5557541b53c8c741f7f31])
   AM_CONDITIONAL([gl_GNULIB_ENABLED_open], [$gl_gnulib_enabled_open])
   AM_CONDITIONAL([gl_GNULIB_ENABLED_03e0aaad4cb89ca757653bd367a6ccb7], [$gl_gnulib_enabled_03e0aaad4cb89ca757653bd367a6ccb7])
   AM_CONDITIONAL([gl_GNULIB_ENABLED_rawmemchr], [$gl_gnulib_enabled_rawmemchr])
+  AM_CONDITIONAL([gl_GNULIB_ENABLED_d3b2383720ee0e541357aa2aac598e2b], [$gl_gnulib_enabled_d3b2383720ee0e541357aa2aac598e2b])
+  AM_CONDITIONAL([gl_GNULIB_ENABLED_61bcaca76b3e6f9ae55d57a1c3193bc4], [$gl_gnulib_enabled_61bcaca76b3e6f9ae55d57a1c3193bc4])
   AM_CONDITIONAL([gl_GNULIB_ENABLED_6099e9737f757db36c47fa9d9f02e88c], [$gl_gnulib_enabled_6099e9737f757db36c47fa9d9f02e88c])
   AM_CONDITIONAL([gl_GNULIB_ENABLED_scratch_buffer], [$gl_gnulib_enabled_scratch_buffer])
   AM_CONDITIONAL([gl_GNULIB_ENABLED_strtoll], [$gl_gnulib_enabled_strtoll])
@@ -862,6 +961,8 @@ AC_DEFUN([gl_INIT],
       m4_if(m4_sysval, [0], [],
         [AC_FATAL([expected source file, required through AC_LIBSOURCES, not found])])
   ])
+  m4_popdef([GL_MODULE_INDICATOR_PREFIX])
+  m4_popdef([GL_MACRO_PREFIX])
   m4_popdef([gl_LIBSOURCES_DIR])
   m4_popdef([gl_LIBSOURCES_LIST])
   m4_popdef([AC_LIBSOURCES])
@@ -888,6 +989,8 @@ AC_DEFUN([gl_INIT],
   m4_pushdef([AC_LIBSOURCES], m4_defn([gltests_LIBSOURCES]))
   m4_pushdef([gltests_LIBSOURCES_LIST], [])
   m4_pushdef([gltests_LIBSOURCES_DIR], [])
+  m4_pushdef([GL_MACRO_PREFIX], [gltests])
+  m4_pushdef([GL_MODULE_INDICATOR_PREFIX], [GL])
   gl_COMMON
   gl_source_base='tests'
 changequote(,)dnl
@@ -909,6 +1012,8 @@ changequote([, ])dnl
       m4_if(m4_sysval, [0], [],
         [AC_FATAL([expected source file, required through AC_LIBSOURCES, not found])])
   ])
+  m4_popdef([GL_MODULE_INDICATOR_PREFIX])
+  m4_popdef([GL_MACRO_PREFIX])
   m4_popdef([gltests_LIBSOURCES_DIR])
   m4_popdef([gltests_LIBSOURCES_LIST])
   m4_popdef([AC_LIBSOURCES])
@@ -1092,6 +1197,7 @@ AC_DEFUN([gl_FILE_LIST], [
   lib/libc-config.h
   lib/limits.in.h
   lib/lstat.c
+  lib/malloc.c
   lib/malloc/dynarray-skeleton.c
   lib/malloc/dynarray.h
   lib/malloc/dynarray_at_failure.c
@@ -1104,6 +1210,7 @@ AC_DEFUN([gl_FILE_LIST], [
   lib/malloc/scratch_buffer_grow.c
   lib/malloc/scratch_buffer_grow_preserve.c
   lib/malloc/scratch_buffer_set_array_size.c
+  lib/md5-stream.c
   lib/md5.c
   lib/md5.h
   lib/memmem.c
@@ -1116,6 +1223,8 @@ AC_DEFUN([gl_FILE_LIST], [
   lib/mkostemp.c
   lib/mktime-internal.h
   lib/mktime.c
+  lib/nproc.c
+  lib/nproc.h
   lib/nstrftime.c
   lib/open.c
   lib/openat-priv.h
@@ -1130,6 +1239,7 @@ AC_DEFUN([gl_FILE_LIST], [
   lib/rawmemchr.valgrind
   lib/readlink.c
   lib/readlinkat.c
+  lib/realloc.c
   lib/regcomp.c
   lib/regex.c
   lib/regex.h
@@ -1250,6 +1360,7 @@ AC_DEFUN([gl_FILE_LIST], [
   m4/libgmp.m4
   m4/limits-h.m4
   m4/lstat.m4
+  m4/malloc.m4
   m4/manywarnings-c++.m4
   m4/manywarnings.m4
   m4/mbstate_t.m4
@@ -1263,6 +1374,7 @@ AC_DEFUN([gl_FILE_LIST], [
   m4/mode_t.m4
   m4/multiarch.m4
   m4/nocrash.m4
+  m4/nproc.m4
   m4/nstrftime.m4
   m4/off_t.m4
   m4/open-cloexec.m4
@@ -1276,6 +1388,7 @@ AC_DEFUN([gl_FILE_LIST], [
   m4/rawmemchr.m4
   m4/readlink.m4
   m4/readlinkat.m4
+  m4/realloc.m4
   m4/regex.m4
   m4/sha1.m4
   m4/sha256.m4
@@ -1322,5 +1435,6 @@ AC_DEFUN([gl_FILE_LIST], [
   m4/warnings.m4
   m4/wchar_t.m4
   m4/wint_t.m4
+  m4/year2038.m4
   m4/zzgnulib.m4
 ])
diff --git a/m4/inttypes.m4 b/m4/inttypes.m4
index f56e94a8881..64b1de5c42a 100644
--- a/m4/inttypes.m4
+++ b/m4/inttypes.m4
@@ -1,4 +1,4 @@
-# inttypes.m4 serial 32
+# inttypes.m4 serial 35
 dnl Copyright (C) 2006-2021 Free Software Foundation, Inc.
 dnl This file is free software; the Free Software Foundation
 dnl gives unlimited permission to copy and/or distribute it,
@@ -7,7 +7,7 @@ dnl with or without modifications, as long as this notice is preserved.
 dnl From Derek Price, Bruno Haible.
 dnl Test whether <inttypes.h> is supported or must be substituted.
 
-AC_DEFUN([gl_INTTYPES_H],
+AC_DEFUN_ONCE([gl_INTTYPES_H],
 [
   AC_REQUIRE([gl_INTTYPES_INCOMPLETE])
   gl_INTTYPES_PRI_SCN
@@ -136,19 +136,34 @@ AC_DEFUN([gl_INTTYPES_CHECK_LONG_LONG_INT_CONDITION],
   AC_SUBST([$1])
 ])
 
+# gl_INTTYPES_MODULE_INDICATOR([modulename])
+# sets the shell variable that indicates the presence of the given module
+# to a C preprocessor expression that will evaluate to 1.
+# This macro invocation must not occur in macros that are AC_REQUIREd.
 AC_DEFUN([gl_INTTYPES_MODULE_INDICATOR],
 [
-  dnl Use AC_REQUIRE here, so that the default settings are expanded once only.
-  AC_REQUIRE([gl_INTTYPES_H_DEFAULTS])
+  dnl Ensure to expand the default settings once only.
+  gl_INTTYPES_H_REQUIRE_DEFAULTS
   gl_MODULE_INDICATOR_SET_VARIABLE([$1])
 ])
 
+# Initializes the default values for AC_SUBSTed shell variables.
+# This macro must not be AC_REQUIREd.  It must only be invoked, and only
+# outside of macros or in macros that are not AC_REQUIREd.
+AC_DEFUN([gl_INTTYPES_H_REQUIRE_DEFAULTS],
+[
+  m4_defun(GL_MODULE_INDICATOR_PREFIX[_INTTYPES_H_MODULE_INDICATOR_DEFAULTS], [
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_IMAXABS])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_IMAXDIV])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_STRTOIMAX])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_STRTOUMAX])
+  ])
+  m4_require(GL_MODULE_INDICATOR_PREFIX[_INTTYPES_H_MODULE_INDICATOR_DEFAULTS])
+  AC_REQUIRE([gl_INTTYPES_H_DEFAULTS])
+])
+
 AC_DEFUN([gl_INTTYPES_H_DEFAULTS],
 [
-  GNULIB_IMAXABS=0;      AC_SUBST([GNULIB_IMAXABS])
-  GNULIB_IMAXDIV=0;      AC_SUBST([GNULIB_IMAXDIV])
-  GNULIB_STRTOIMAX=0;    AC_SUBST([GNULIB_STRTOIMAX])
-  GNULIB_STRTOUMAX=0;    AC_SUBST([GNULIB_STRTOUMAX])
   dnl Assume proper GNU behavior unless another module says otherwise.
   HAVE_DECL_IMAXABS=1;   AC_SUBST([HAVE_DECL_IMAXABS])
   HAVE_DECL_IMAXDIV=1;   AC_SUBST([HAVE_DECL_IMAXDIV])
diff --git a/m4/largefile.m4 b/m4/largefile.m4
index cadb16dc972..fbde5e66471 100644
--- a/m4/largefile.m4
+++ b/m4/largefile.m4
@@ -22,7 +22,8 @@ AC_DEFUN([gl_SET_LARGEFILE_SOURCE],
   esac
 ])
 
-# The following implementation works around a problem in autoconf <= 2.69;
+# Work around a problem in Autoconf through at least 2.71 on glibc 2.34+
+# with _TIME_BITS.  Also, work around a problem in autoconf <= 2.69:
 # AC_SYS_LARGEFILE does not configure for large inodes on Mac OS X 10.5,
 # or configures them incorrectly in some cases.
 m4_version_prereq([2.70], [], [
@@ -40,6 +41,7 @@ m4_define([_AC_SYS_LARGEFILE_TEST_INCLUDES],
                        && LARGE_OFF_T % 2147483647 == 1)
                       ? 1 : -1]];[]dnl
 ])
+])# m4_version_prereq 2.70
 
 
 # _AC_SYS_LARGEFILE_MACRO_VALUE(C-MACRO, VALUE,
@@ -54,7 +56,8 @@ m4_define([_AC_SYS_LARGEFILE_MACRO_VALUE],
     [AC_LANG_PROGRAM([$5], [$6])],
     [$3=no; break])
   m4_ifval([$6], [AC_LINK_IFELSE], [AC_COMPILE_IFELSE])(
-    [AC_LANG_PROGRAM([#define $1 $2
+    [AC_LANG_PROGRAM([#undef $1
+#define $1 $2
 $5], [$6])],
     [$3=$2; break])
   $3=unknown
@@ -80,9 +83,8 @@ rm -rf conftest*[]dnl
 AC_DEFUN([AC_SYS_LARGEFILE],
 [AC_ARG_ENABLE(largefile,
                [  --disable-largefile     omit support for large files])
-if test "$enable_largefile" != no; then
-
-  AC_CACHE_CHECK([for special C compiler options needed for large files],
+AS_IF([test "$enable_largefile" != no],
+ [AC_CACHE_CHECK([for special C compiler options needed for large files],
     ac_cv_sys_largefile_CC,
     [ac_cv_sys_largefile_CC=no
      if test "$GCC" != yes; then
@@ -107,15 +109,15 @@ if test "$enable_largefile" != no; then
     ac_cv_sys_file_offset_bits,
     [Number of bits in a file offset, on hosts where this is settable.],
     [_AC_SYS_LARGEFILE_TEST_INCLUDES])
-  if test $ac_cv_sys_file_offset_bits = unknown; then
-    _AC_SYS_LARGEFILE_MACRO_VALUE(_LARGE_FILES, 1,
-      ac_cv_sys_large_files,
-      [Define for large files, on AIX-style hosts.],
-      [_AC_SYS_LARGEFILE_TEST_INCLUDES])
-  fi
-fi
+  AS_CASE([$ac_cv_sys_file_offset_bits],
+    [unknown],
+      [_AC_SYS_LARGEFILE_MACRO_VALUE([_LARGE_FILES], [1],
+         [ac_cv_sys_large_files],
+         [Define for large files, on AIX-style hosts.],
+         [_AC_SYS_LARGEFILE_TEST_INCLUDES])],
+    [64],
+      [gl_YEAR2038_BODY([])])])
 ])# AC_SYS_LARGEFILE
-])# m4_version_prereq 2.70
 
 # Enable large files on systems where this is implemented by Gnulib, not by the
 # system headers.
diff --git a/m4/limits-h.m4 b/m4/limits-h.m4
index 70dbb7dcfa0..00c9fe9e50a 100644
--- a/m4/limits-h.m4
+++ b/m4/limits-h.m4
@@ -11,7 +11,7 @@ AC_DEFUN_ONCE([gl_LIMITS_H],
 [
   gl_CHECK_NEXT_HEADERS([limits.h])
 
-  AC_CACHE_CHECK([whether limits.h has LLONG_MAX, WORD_BIT, ULLONG_WIDTH etc.],
+  AC_CACHE_CHECK([whether limits.h has WORD_BIT, BOOL_WIDTH etc.],
     [gl_cv_header_limits_width],
     [AC_COMPILE_IFELSE(
        [AC_LANG_PROGRAM(
@@ -22,6 +22,7 @@ AC_DEFUN_ONCE([gl_LIMITS_H],
             long long llm = LLONG_MAX;
             int wb = WORD_BIT;
             int ullw = ULLONG_WIDTH;
+            int bw = BOOL_WIDTH;
           ]])],
        [gl_cv_header_limits_width=yes],
        [gl_cv_header_limits_width=no])])
diff --git a/m4/malloc.m4 b/m4/malloc.m4
new file mode 100644
index 00000000000..972e808ab7e
--- /dev/null
+++ b/m4/malloc.m4
@@ -0,0 +1,174 @@
+# malloc.m4 serial 27
+dnl Copyright (C) 2007, 2009-2021 Free Software Foundation, Inc.
+dnl This file is free software; the Free Software Foundation
+dnl gives unlimited permission to copy and/or distribute it,
+dnl with or without modifications, as long as this notice is preserved.
+
+# This is adapted with modifications from upstream Autoconf here:
+# https://git.savannah.gnu.org/cgit/autoconf.git/tree/lib/autoconf/functions.m4?id=v2.70#n949
+AC_DEFUN([_AC_FUNC_MALLOC_IF],
+[
+  AC_REQUIRE([AC_CANONICAL_HOST])dnl for cross-compiles
+  AC_CACHE_CHECK([whether malloc (0) returns nonnull],
+    [ac_cv_func_malloc_0_nonnull],
+    [AC_RUN_IFELSE(
+       [AC_LANG_PROGRAM(
+          [[#include <stdlib.h>
+          ]],
+          [[void *p = malloc (0);
+            int result = !p;
+            free (p);
+            return result;]])
+       ],
+       [ac_cv_func_malloc_0_nonnull=yes],
+       [ac_cv_func_malloc_0_nonnull=no],
+       [case "$host_os" in
+          # Guess yes on platforms where we know the result.
+          *-gnu* | freebsd* | netbsd* | openbsd* | bitrig* \
+          | gnu* | *-musl* | midnightbsd* \
+          | hpux* | solaris* | cygwin* | mingw* | msys* )
+            ac_cv_func_malloc_0_nonnull="guessing yes" ;;
+          # If we don't know, obey --enable-cross-guesses.
+          *) ac_cv_func_malloc_0_nonnull="$gl_cross_guess_normal" ;;
+        esac
+       ])
+    ])
+  AS_CASE([$ac_cv_func_malloc_0_nonnull], [*yes], [$1], [$2])
+])# _AC_FUNC_MALLOC_IF
+
+# gl_FUNC_MALLOC_GNU
+# ------------------
+# Replace malloc if it is not compatible with GNU libc.
+AC_DEFUN([gl_FUNC_MALLOC_GNU],
+[
+  AC_REQUIRE([gl_STDLIB_H_DEFAULTS])
+  AC_REQUIRE([gl_FUNC_MALLOC_POSIX])
+  if test $REPLACE_MALLOC = 0; then
+    _AC_FUNC_MALLOC_IF([], [REPLACE_MALLOC=1])
+  fi
+])
+
+# gl_FUNC_MALLOC_PTRDIFF
+# ----------------------
+# Test whether malloc (N) reliably fails when N exceeds PTRDIFF_MAX,
+# and replace malloc otherwise.
+AC_DEFUN([gl_FUNC_MALLOC_PTRDIFF],
+[
+  AC_REQUIRE([gl_STDLIB_H_DEFAULTS])
+  AC_REQUIRE([gl_CHECK_MALLOC_PTRDIFF])
+  test "$gl_cv_malloc_ptrdiff" = yes || REPLACE_MALLOC=1
+])
+
+# Test whether malloc, realloc, calloc refuse to create objects
+# larger than what can be expressed in ptrdiff_t.
+# Set gl_cv_func_malloc_gnu to yes or no accordingly.
+AC_DEFUN([gl_CHECK_MALLOC_PTRDIFF],
+[
+  AC_CACHE_CHECK([whether malloc is ptrdiff_t safe],
+    [gl_cv_malloc_ptrdiff],
+    [AC_COMPILE_IFELSE(
+       [AC_LANG_PROGRAM(
+          [[#include <stdint.h>
+          ]],
+          [[/* 64-bit ptrdiff_t is so wide that no practical platform
+               can exceed it.  */
+            #define WIDE_PTRDIFF (PTRDIFF_MAX >> 31 >> 31 != 0)
+
+            /* On rare machines where size_t fits in ptrdiff_t there
+               is no problem.  */
+            #define NARROW_SIZE (SIZE_MAX <= PTRDIFF_MAX)
+
+            /* glibc 2.30 and later malloc refuses to exceed ptrdiff_t
+               bounds even on 32-bit platforms.  We don't know which
+               non-glibc systems are safe.  */
+            #define KNOWN_SAFE (2 < __GLIBC__ + (30 <= __GLIBC_MINOR__))
+
+            #if WIDE_PTRDIFF || NARROW_SIZE || KNOWN_SAFE
+              return 0;
+            #else
+              #error "malloc might not be ptrdiff_t safe"
+              syntax error
+            #endif
+          ]])],
+       [gl_cv_malloc_ptrdiff=yes],
+       [gl_cv_malloc_ptrdiff=no])
+    ])
+])
+
+# gl_FUNC_MALLOC_POSIX
+# --------------------
+# Test whether 'malloc' is POSIX compliant (sets errno to ENOMEM when it
+# fails, and doesn't mess up with ptrdiff_t overflow), and replace
+# malloc if it is not.
+AC_DEFUN([gl_FUNC_MALLOC_POSIX],
+[
+  AC_REQUIRE([gl_STDLIB_H_DEFAULTS])
+  AC_REQUIRE([gl_FUNC_MALLOC_PTRDIFF])
+  AC_REQUIRE([gl_CHECK_MALLOC_POSIX])
+  if test "$gl_cv_func_malloc_posix" = yes; then
+    AC_DEFINE([HAVE_MALLOC_POSIX], [1],
+      [Define if malloc, realloc, and calloc set errno on allocation failure.])
+  else
+    REPLACE_MALLOC=1
+  fi
+])
+
+# Test whether malloc, realloc, calloc set errno to ENOMEM on failure.
+# Set gl_cv_func_malloc_posix to yes or no accordingly.
+AC_DEFUN([gl_CHECK_MALLOC_POSIX],
+[
+  AC_REQUIRE([AC_CANONICAL_HOST])
+  AC_CACHE_CHECK([whether malloc, realloc, calloc set errno on failure],
+    [gl_cv_func_malloc_posix],
+    [
+      dnl It is too dangerous to try to allocate a large amount of memory:
+      dnl some systems go to their knees when you do that. So assume that
+      dnl all Unix implementations of the function set errno on failure,
+      dnl except on those platforms where we have seen 'test-malloc-gnu',
+      dnl 'test-realloc-gnu', 'test-calloc-gnu' fail.
+      case "$host_os" in
+        mingw*)
+          gl_cv_func_malloc_posix=no ;;
+        irix* | solaris*)
+          dnl On IRIX 6.5, the three functions return NULL with errno unset
+          dnl when the argument is larger than PTRDIFF_MAX.
+          dnl On Solaris 11.3, the three functions return NULL with errno set
+          dnl to EAGAIN, not ENOMEM, when the argument is larger than
+          dnl PTRDIFF_MAX.
+          dnl Here is a test program:
+m4_divert_push([KILL])
+#include <errno.h>
+#include <stdio.h>
+#include <stdlib.h>
+#define ptrdiff_t long
+#ifndef PTRDIFF_MAX
+# define PTRDIFF_MAX ((ptrdiff_t) ((1UL << (8 * sizeof (ptrdiff_t) - 1)) - 1))
+#endif
+
+int main ()
+{
+  void *p;
+
+  fprintf (stderr, "PTRDIFF_MAX = %lu\n", (unsigned long) PTRDIFF_MAX);
+
+  errno = 0;
+  p = malloc ((unsigned long) PTRDIFF_MAX + 1);
+  fprintf (stderr, "p=%p errno=%d\n", p, errno);
+
+  errno = 0;
+  p = calloc (PTRDIFF_MAX / 2 + 1, 2);
+  fprintf (stderr, "p=%p errno=%d\n", p, errno);
+
+  errno = 0;
+  p = realloc (NULL, (unsigned long) PTRDIFF_MAX + 1);
+  fprintf (stderr, "p=%p errno=%d\n", p, errno);
+
+  return 0;
+}
+m4_divert_pop([KILL])
+          gl_cv_func_malloc_posix=no ;;
+        *)
+          gl_cv_func_malloc_posix=yes ;;
+      esac
+    ])
+])
diff --git a/m4/malloca.m4 b/m4/malloca.m4
deleted file mode 100644
index 7ee33773d25..00000000000
--- a/m4/malloca.m4
+++ /dev/null
@@ -1,14 +0,0 @@
-# malloca.m4 serial 2
-dnl Copyright (C) 2003-2004, 2006-2007, 2009-2021 Free Software
-dnl Foundation, Inc.
-dnl This file is free software; the Free Software Foundation
-dnl gives unlimited permission to copy and/or distribute it,
-dnl with or without modifications, as long as this notice is preserved.
-
-AC_DEFUN([gl_MALLOCA],
-[
-  dnl Use the autoconf tests for alloca(), but not the AC_SUBSTed variables
-  dnl @ALLOCA@ and @LTALLOCA@.
-  dnl gl_FUNC_ALLOCA   dnl Already brought in by the module dependencies.
-  AC_REQUIRE([gl_EEMALLOC])
-])
diff --git a/m4/manywarnings.m4 b/m4/manywarnings.m4
index 53ab1534036..872ea58e62a 100644
--- a/m4/manywarnings.m4
+++ b/m4/manywarnings.m4
@@ -1,4 +1,4 @@
-# manywarnings.m4 serial 21
+# manywarnings.m4 serial 23
 dnl Copyright (C) 2008-2021 Free Software Foundation, Inc.
 dnl This file is free software; the Free Software Foundation
 dnl gives unlimited permission to copy and/or distribute it,
@@ -195,15 +195,9 @@ AC_DEFUN([gl_MANYWARN_ALL_GCC(C)],
     gl_AS_VAR_APPEND([$1], [' -Wno-uninitialized'])
   fi
 
-  # Some warnings have too many false alarms in GCC 10.1.
-  # https://gcc.gnu.org/bugzilla/show_bug.cgi?id=93695
-  gl_AS_VAR_APPEND([$1], [' -Wno-analyzer-double-free'])
-  # https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94458
+  # This warning have too many false alarms in GCC 11.2.1.
+  # https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101713
   gl_AS_VAR_APPEND([$1], [' -Wno-analyzer-malloc-leak'])
-  # https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94851
-  gl_AS_VAR_APPEND([$1], [' -Wno-analyzer-null-dereference'])
-  # https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95758
-  gl_AS_VAR_APPEND([$1], [' -Wno-analyzer-use-after-free'])
 
   AC_LANG_POP([C])
 ])
diff --git a/m4/memmem.m4 b/m4/memmem.m4
index e2a785f48d4..6dac7661283 100644
--- a/m4/memmem.m4
+++ b/m4/memmem.m4
@@ -1,4 +1,4 @@
-# memmem.m4 serial 27
+# memmem.m4 serial 29
 dnl Copyright (C) 2002-2004, 2007-2021 Free Software Foundation, Inc.
 dnl This file is free software; the Free Software Foundation
 dnl gives unlimited permission to copy and/or distribute it,
@@ -10,7 +10,7 @@ AC_DEFUN([gl_FUNC_MEMMEM_SIMPLE],
   dnl Persuade glibc <string.h> to declare memmem().
   AC_REQUIRE([AC_USE_SYSTEM_EXTENSIONS])
 
-  AC_REQUIRE([gl_HEADER_STRING_H_DEFAULTS])
+  AC_REQUIRE([gl_STRING_H_DEFAULTS])
   AC_CHECK_FUNCS([memmem])
   if test $ac_cv_func_memmem = yes; then
     HAVE_MEMMEM=1
@@ -50,6 +50,7 @@ AC_DEFUN([gl_FUNC_MEMMEM_SIMPLE],
          dnl Assume that it works on all other platforms (even if not linear).
          AC_EGREP_CPP([Lucky user],
            [
+#include <string.h> /* for __GNU_LIBRARY__ */
 #ifdef __GNU_LIBRARY__
  #include <features.h>
  #if ((__GLIBC__ == 2 && ((__GLIBC_MINOR > 0 && __GLIBC_MINOR__ < 9) \
diff --git a/m4/mempcpy.m4 b/m4/mempcpy.m4
index c5ee2af8ccd..f9d9ec8f308 100644
--- a/m4/mempcpy.m4
+++ b/m4/mempcpy.m4
@@ -1,4 +1,4 @@
-# mempcpy.m4 serial 11
+# mempcpy.m4 serial 12
 dnl Copyright (C) 2003-2004, 2006-2007, 2009-2021 Free Software Foundation,
 dnl Inc.
 dnl This file is free software; the Free Software Foundation
@@ -13,7 +13,7 @@ AC_DEFUN([gl_FUNC_MEMPCPY],
   dnl The mempcpy() declaration in lib/string.in.h uses 'restrict'.
   AC_REQUIRE([AC_C_RESTRICT])
 
-  AC_REQUIRE([gl_HEADER_STRING_H_DEFAULTS])
+  AC_REQUIRE([gl_STRING_H_DEFAULTS])
   AC_CHECK_FUNCS([mempcpy])
   if test $ac_cv_func_mempcpy = no; then
     HAVE_MEMPCPY=0
diff --git a/m4/memrchr.m4 b/m4/memrchr.m4
index d0c05896e54..40f61c5ac0a 100644
--- a/m4/memrchr.m4
+++ b/m4/memrchr.m4
@@ -1,4 +1,4 @@
-# memrchr.m4 serial 10
+# memrchr.m4 serial 11
 dnl Copyright (C) 2002-2003, 2005-2007, 2009-2021 Free Software Foundation,
 dnl Inc.
 dnl This file is free software; the Free Software Foundation
@@ -10,7 +10,7 @@ AC_DEFUN([gl_FUNC_MEMRCHR],
   dnl Persuade glibc <string.h> to declare memrchr().
   AC_REQUIRE([AC_USE_SYSTEM_EXTENSIONS])
 
-  AC_REQUIRE([gl_HEADER_STRING_H_DEFAULTS])
+  AC_REQUIRE([gl_STRING_H_DEFAULTS])
   AC_CHECK_DECLS_ONCE([memrchr])
   if test $ac_cv_have_decl_memrchr = no; then
     HAVE_DECL_MEMRCHR=0
diff --git a/m4/mktime.m4 b/m4/mktime.m4
index 245649e774a..721189af56e 100644
--- a/m4/mktime.m4
+++ b/m4/mktime.m4
@@ -1,4 +1,4 @@
-# serial 35
+# serial 36
 dnl Copyright (C) 2002-2003, 2005-2007, 2009-2021 Free Software Foundation,
 dnl Inc.
 dnl This file is free software; the Free Software Foundation
@@ -255,7 +255,7 @@ main ()
 dnl Main macro of module 'mktime'.
 AC_DEFUN([gl_FUNC_MKTIME],
 [
-  AC_REQUIRE([gl_HEADER_TIME_H_DEFAULTS])
+  AC_REQUIRE([gl_TIME_H_DEFAULTS])
   AC_REQUIRE([AC_CANONICAL_HOST])
   AC_REQUIRE([gl_FUNC_MKTIME_WORKS])
 
diff --git a/m4/nproc.m4 b/m4/nproc.m4
new file mode 100644
index 00000000000..887c66bee81
--- /dev/null
+++ b/m4/nproc.m4
@@ -0,0 +1,54 @@
+# nproc.m4 serial 5
+dnl Copyright (C) 2009-2021 Free Software Foundation, Inc.
+dnl This file is free software; the Free Software Foundation
+dnl gives unlimited permission to copy and/or distribute it,
+dnl with or without modifications, as long as this notice is preserved.
+
+AC_DEFUN([gl_NPROC],
+[
+  gl_PREREQ_NPROC
+])
+
+# Prerequisites of lib/nproc.c.
+AC_DEFUN([gl_PREREQ_NPROC],
+[
+  dnl Persuade glibc <sched.h> to declare CPU_SETSIZE, CPU_ISSET etc.
+  AC_REQUIRE([AC_USE_SYSTEM_EXTENSIONS])
+
+  AC_CHECK_HEADERS([sys/pstat.h sys/sysmp.h sys/param.h],,,
+    [AC_INCLUDES_DEFAULT])
+  dnl <sys/sysctl.h> requires <sys/param.h> on OpenBSD 4.0.
+  AC_CHECK_HEADERS([sys/sysctl.h],,,
+    [AC_INCLUDES_DEFAULT
+     #if HAVE_SYS_PARAM_H
+     # include <sys/param.h>
+     #endif
+    ])
+
+  AC_CHECK_FUNCS([sched_getaffinity sched_getaffinity_np \
+                  pstat_getdynamic sysmp sysctl])
+
+  dnl Test whether sched_getaffinity has the expected declaration.
+  dnl glibc 2.3.[0-2]:
+  dnl   int sched_getaffinity (pid_t, unsigned int, unsigned long int *);
+  dnl glibc 2.3.3:
+  dnl   int sched_getaffinity (pid_t, cpu_set_t *);
+  dnl glibc >= 2.3.4:
+  dnl   int sched_getaffinity (pid_t, size_t, cpu_set_t *);
+  if test $ac_cv_func_sched_getaffinity = yes; then
+    AC_CACHE_CHECK([for glibc compatible sched_getaffinity],
+      [gl_cv_func_sched_getaffinity3],
+      [AC_COMPILE_IFELSE(
+         [AC_LANG_PROGRAM(
+            [[#include <errno.h>
+              #include <sched.h>]],
+            [[sched_getaffinity (0, 0, (cpu_set_t *) 0);]])],
+         [gl_cv_func_sched_getaffinity3=yes],
+         [gl_cv_func_sched_getaffinity3=no])
+      ])
+    if test $gl_cv_func_sched_getaffinity3 = yes; then
+      AC_DEFINE([HAVE_SCHED_GETAFFINITY_LIKE_GLIBC], [1],
+        [Define to 1 if sched_getaffinity has a glibc compatible declaration.])
+    fi
+  fi
+])
diff --git a/m4/pselect.m4 b/m4/pselect.m4
index 538fe7dc122..9de63baf990 100644
--- a/m4/pselect.m4
+++ b/m4/pselect.m4
@@ -1,4 +1,4 @@
-# pselect.m4 serial 9
+# pselect.m4 serial 10
 dnl Copyright (C) 2011-2021 Free Software Foundation, Inc.
 dnl This file is free software; the Free Software Foundation
 dnl gives unlimited permission to copy and/or distribute it,
@@ -6,7 +6,7 @@ dnl with or without modifications, as long as this notice is preserved.
 
 AC_DEFUN([gl_FUNC_PSELECT],
 [
-  AC_REQUIRE([gl_HEADER_SYS_SELECT])
+  AC_REQUIRE([gl_SYS_SELECT_H])
   AC_REQUIRE([AC_C_RESTRICT])
   AC_REQUIRE([AC_CANONICAL_HOST]) dnl for cross-compiles
   AC_CHECK_FUNCS_ONCE([pselect])
diff --git a/m4/pthread_sigmask.m4 b/m4/pthread_sigmask.m4
index eb4c7849655..ff7fa9610e2 100644
--- a/m4/pthread_sigmask.m4
+++ b/m4/pthread_sigmask.m4
@@ -1,4 +1,4 @@
-# pthread_sigmask.m4 serial 19
+# pthread_sigmask.m4 serial 21
 dnl Copyright (C) 2011-2021 Free Software Foundation, Inc.
 dnl This file is free software; the Free Software Foundation
 dnl gives unlimited permission to copy and/or distribute it,
@@ -111,9 +111,9 @@ AC_DEFUN([gl_FUNC_PTHREAD_SIGMASK],
     AC_REQUIRE([AC_PROG_CC])
     AC_REQUIRE([AC_CANONICAL_HOST]) dnl for cross-compiles
 
-    dnl On FreeBSD 6.4, HP-UX 11.31, Solaris 9, in programs that are not linked
-    dnl with -lpthread, the pthread_sigmask() function always returns 0 and has
-    dnl no effect.
+    dnl On FreeBSD 13.0, MidnightBSD 1.1, HP-UX 11.31, Solaris 9, in programs
+    dnl that are not linked with -lpthread, the pthread_sigmask() function
+    dnl always returns 0 and has no effect.
     if test -z "$LIB_PTHREAD_SIGMASK"; then
       case " $LIBS " in
         *' -pthread '*) ;;
@@ -138,7 +138,7 @@ AC_DEFUN([gl_FUNC_PTHREAD_SIGMASK],
                 [
                  changequote(,)dnl
                  case "$host_os" in
-                   freebsd* | hpux* | solaris | solaris2.[2-9]*)
+                   freebsd* | midnightbsd* | hpux* | solaris | solaris2.[2-9]*)
                      gl_cv_func_pthread_sigmask_in_libc_works="guessing no";;
                    *)
                      gl_cv_func_pthread_sigmask_in_libc_works="guessing yes";;
diff --git a/m4/rawmemchr.m4 b/m4/rawmemchr.m4
index f92846543cc..452fab18f13 100644
--- a/m4/rawmemchr.m4
+++ b/m4/rawmemchr.m4
@@ -1,4 +1,4 @@
-# rawmemchr.m4 serial 2
+# rawmemchr.m4 serial 3
 dnl Copyright (C) 2003, 2007-2021 Free Software Foundation, Inc.
 dnl This file is free software; the Free Software Foundation
 dnl gives unlimited permission to copy and/or distribute it,
@@ -9,7 +9,7 @@ AC_DEFUN([gl_FUNC_RAWMEMCHR],
   dnl Persuade glibc <string.h> to declare rawmemchr().
   AC_REQUIRE([AC_USE_SYSTEM_EXTENSIONS])
 
-  AC_REQUIRE([gl_HEADER_STRING_H_DEFAULTS])
+  AC_REQUIRE([gl_STRING_H_DEFAULTS])
   AC_CHECK_FUNCS([rawmemchr])
   if test $ac_cv_func_rawmemchr = no; then
     HAVE_RAWMEMCHR=0
diff --git a/m4/realloc.m4 b/m4/realloc.m4
new file mode 100644
index 00000000000..0abc4185ed0
--- /dev/null
+++ b/m4/realloc.m4
@@ -0,0 +1,63 @@
+# realloc.m4 serial 24
+dnl Copyright (C) 2007, 2009-2021 Free Software Foundation, Inc.
+dnl This file is free software; the Free Software Foundation
+dnl gives unlimited permission to copy and/or distribute it,
+dnl with or without modifications, as long as this notice is preserved.
+
+# This is adapted with modifications from upstream Autoconf here:
+# https://git.savannah.gnu.org/cgit/autoconf.git/tree/lib/autoconf/functions.m4?id=v2.70#n1455
+AC_DEFUN([_AC_FUNC_REALLOC_IF],
+[
+  AC_REQUIRE([AC_CANONICAL_HOST])dnl for cross-compiles
+  AC_CACHE_CHECK([whether realloc (0, 0) returns nonnull],
+    [ac_cv_func_realloc_0_nonnull],
+    [AC_RUN_IFELSE(
+       [AC_LANG_PROGRAM(
+          [[#include <stdlib.h>
+          ]],
+          [[void *p = realloc (0, 0);
+            int result = !p;
+            free (p);
+            return result;]])
+       ],
+       [ac_cv_func_realloc_0_nonnull=yes],
+       [ac_cv_func_realloc_0_nonnull=no],
+       [case "$host_os" in
+          # Guess yes on platforms where we know the result.
+          *-gnu* | freebsd* | netbsd* | openbsd* | bitrig* \
+          | gnu* | *-musl* | midnightbsd* \
+          | hpux* | solaris* | cygwin* | mingw* | msys* )
+            ac_cv_func_realloc_0_nonnull="guessing yes" ;;
+          # If we don't know, obey --enable-cross-guesses.
+          *) ac_cv_func_realloc_0_nonnull="$gl_cross_guess_normal" ;;
+        esac
+       ])
+    ])
+  AS_CASE([$ac_cv_func_realloc_0_nonnull], [*yes], [$1], [$2])
+])# AC_FUNC_REALLOC
+
+# gl_FUNC_REALLOC_GNU
+# -------------------
+# Replace realloc if it is not compatible with GNU libc.
+AC_DEFUN([gl_FUNC_REALLOC_GNU],
+[
+  AC_REQUIRE([gl_STDLIB_H_DEFAULTS])
+  AC_REQUIRE([gl_FUNC_REALLOC_POSIX])
+  if test $REPLACE_REALLOC = 0; then
+    _AC_FUNC_REALLOC_IF([], [REPLACE_REALLOC=1])
+  fi
+])# gl_FUNC_REALLOC_GNU
+
+# gl_FUNC_REALLOC_POSIX
+# ---------------------
+# Test whether 'realloc' is POSIX compliant (sets errno to ENOMEM when it
+# fails, and doesn't mess up with ptrdiff_t overflow),
+# and replace realloc if it is not.
+AC_DEFUN([gl_FUNC_REALLOC_POSIX],
+[
+  AC_REQUIRE([gl_STDLIB_H_DEFAULTS])
+  AC_REQUIRE([gl_FUNC_MALLOC_POSIX])
+  if test $REPLACE_MALLOC = 1; then
+    REPLACE_REALLOC=1
+  fi
+])
diff --git a/m4/regex.m4 b/m4/regex.m4
index 850c572228a..1c7e562f6c6 100644
--- a/m4/regex.m4
+++ b/m4/regex.m4
@@ -1,4 +1,4 @@
-# serial 71
+# serial 73
 
 # Copyright (C) 1996-2001, 2003-2021 Free Software Foundation, Inc.
 #
@@ -246,7 +246,7 @@ AC_DEFUN([gl_REGEX],
                            & ~RE_CONTEXT_INVALID_DUP
                            & ~RE_NO_EMPTY_RANGES);
             memset (&regex, 0, sizeof regex);
-            s = re_compile_pattern ("[[:alnum:]_-]\\\\+$", 16, &regex);
+            s = re_compile_pattern ("[[:alnum:]_-]\\\\+\$", 16, &regex);
             if (s)
               result |= 32;
             else
@@ -264,14 +264,50 @@ AC_DEFUN([gl_REGEX],
                back reference.  */
             re_set_syntax (RE_SYNTAX_POSIX_EGREP);
             memset (&regex, 0, sizeof regex);
-            s = re_compile_pattern ("0|()0|\\1|0", 10, &regex);
+            s = re_compile_pattern ("0|()0|\\\\1|0", 10, &regex);
             if (!s)
-              result |= 64;
+              {
+                memset (&regs, 0, sizeof regs);
+                i = re_search (&regex, "x", 1, 0, 1, &regs);
+                if (i != -1)
+                  result |= 64;
+                if (0 <= i)
+                  {
+                    free (regs.start);
+                    free (regs.end);
+                  }
+                regfree (&regex);
+              }
             else
               {
                 if (strcmp (s, "Invalid back reference"))
                   result |= 64;
+              }
+
+            /* glibc bug 11053.  */
+            re_set_syntax (RE_SYNTAX_POSIX_BASIC);
+            memset (&regex, 0, sizeof regex);
+            static char const pat_sub2[] = "\\\\(a*\\\\)*a*\\\\1";
+            s = re_compile_pattern (pat_sub2, sizeof pat_sub2 - 1, &regex);
+            if (s)
+              result |= 64;
+            else
+              {
+                memset (&regs, 0, sizeof regs);
+                static char const data[] = "a";
+                int datalen = sizeof data - 1;
+                i = re_search (&regex, data, datalen, 0, datalen, &regs);
+                if (i != 0)
+                  result |= 64;
+                else if (regs.num_regs < 2)
+                  result |= 64;
+                else if (! (regs.start[0] == 0 && regs.end[0] == 1))
+                  result |= 64;
+                else if (! (regs.start[1] == 0 && regs.end[1] == 0))
+                  result |= 64;
                 regfree (&regex);
+                free (regs.start);
+                free (regs.end);
               }
 
 #if 0
diff --git a/m4/sigdescr_np.m4 b/m4/sigdescr_np.m4
index f6fa63140c4..17c22506cca 100644
--- a/m4/sigdescr_np.m4
+++ b/m4/sigdescr_np.m4
@@ -1,4 +1,4 @@
-# sigdescr_np.m4 serial 1
+# sigdescr_np.m4 serial 2
 dnl Copyright (C) 2020-2021 Free Software Foundation, Inc.
 dnl This file is free software; the Free Software Foundation
 dnl gives unlimited permission to copy and/or distribute it,
@@ -9,7 +9,7 @@ AC_DEFUN([gl_FUNC_SIGDESCR_NP],
   dnl Persuade glibc <string.h> to declare sigdescr_np().
   AC_REQUIRE([AC_USE_SYSTEM_EXTENSIONS])
 
-  AC_REQUIRE([gl_HEADER_STRING_H_DEFAULTS])
+  AC_REQUIRE([gl_STRING_H_DEFAULTS])
   AC_CHECK_FUNCS([sigdescr_np])
   if test $ac_cv_func_sigdescr_np = no; then
     HAVE_SIGDESCR_NP=0
diff --git a/m4/signal_h.m4 b/m4/signal_h.m4
index ff9f0251fd9..8b938809b7c 100644
--- a/m4/signal_h.m4
+++ b/m4/signal_h.m4
@@ -1,10 +1,10 @@
-# signal_h.m4 serial 19
+# signal_h.m4 serial 22
 dnl Copyright (C) 2007-2021 Free Software Foundation, Inc.
 dnl This file is free software; the Free Software Foundation
 dnl gives unlimited permission to copy and/or distribute it,
 dnl with or without modifications, as long as this notice is preserved.
 
-AC_DEFUN([gl_SIGNAL_H],
+AC_DEFUN_ONCE([gl_SIGNAL_H],
 [
   AC_REQUIRE([gl_SIGNAL_H_DEFAULTS])
   AC_REQUIRE([gl_CHECK_TYPE_SIGSET_T])
@@ -52,22 +52,37 @@ AC_DEFUN([gl_CHECK_TYPE_SIGSET_T],
   fi
 ])
 
+# gl_SIGNAL_MODULE_INDICATOR([modulename])
+# sets the shell variable that indicates the presence of the given module
+# to a C preprocessor expression that will evaluate to 1.
+# This macro invocation must not occur in macros that are AC_REQUIREd.
 AC_DEFUN([gl_SIGNAL_MODULE_INDICATOR],
 [
-  dnl Use AC_REQUIRE here, so that the default settings are expanded once only.
-  AC_REQUIRE([gl_SIGNAL_H_DEFAULTS])
+  dnl Ensure to expand the default settings once only.
+  gl_SIGNAL_H_REQUIRE_DEFAULTS
   gl_MODULE_INDICATOR_SET_VARIABLE([$1])
   dnl Define it also as a C macro, for the benefit of the unit tests.
   gl_MODULE_INDICATOR_FOR_TESTS([$1])
 ])
 
+# Initializes the default values for AC_SUBSTed shell variables.
+# This macro must not be AC_REQUIREd.  It must only be invoked, and only
+# outside of macros or in macros that are not AC_REQUIREd.
+AC_DEFUN([gl_SIGNAL_H_REQUIRE_DEFAULTS],
+[
+  m4_defun(GL_MODULE_INDICATOR_PREFIX[_SIGNAL_H_MODULE_INDICATOR_DEFAULTS], [
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_PTHREAD_SIGMASK])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_RAISE])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_SIGNAL_H_SIGPIPE])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_SIGPROCMASK])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_SIGACTION])
+  ])
+  m4_require(GL_MODULE_INDICATOR_PREFIX[_SIGNAL_H_MODULE_INDICATOR_DEFAULTS])
+  AC_REQUIRE([gl_SIGNAL_H_DEFAULTS])
+])
+
 AC_DEFUN([gl_SIGNAL_H_DEFAULTS],
 [
-  GNULIB_PTHREAD_SIGMASK=0;    AC_SUBST([GNULIB_PTHREAD_SIGMASK])
-  GNULIB_RAISE=0;              AC_SUBST([GNULIB_RAISE])
-  GNULIB_SIGNAL_H_SIGPIPE=0;   AC_SUBST([GNULIB_SIGNAL_H_SIGPIPE])
-  GNULIB_SIGPROCMASK=0;        AC_SUBST([GNULIB_SIGPROCMASK])
-  GNULIB_SIGACTION=0;          AC_SUBST([GNULIB_SIGACTION])
   dnl Assume proper GNU behavior unless another module says otherwise.
   HAVE_POSIX_SIGNALBLOCKING=1; AC_SUBST([HAVE_POSIX_SIGNALBLOCKING])
   HAVE_PTHREAD_SIGMASK=1;      AC_SUBST([HAVE_PTHREAD_SIGMASK])
diff --git a/m4/stdalign.m4 b/m4/stdalign.m4
index 8dcb634d55b..e22d7f78c06 100644
--- a/m4/stdalign.m4
+++ b/m4/stdalign.m4
@@ -13,7 +13,8 @@ AC_DEFUN([gl_STDALIGN_H],
     [gl_cv_header_working_stdalign_h],
     [AC_COMPILE_IFELSE(
        [AC_LANG_PROGRAM(
-          [[#include <stdalign.h>
+          [[#include <stdint.h>
+            #include <stdalign.h>
             #include <stddef.h>
 
             /* Test that alignof yields a result consistent with offsetof.
@@ -32,6 +33,7 @@ AC_DEFUN([gl_STDALIGN_H],
             /* Test _Alignas only on platforms where gnulib can help.  */
             #if \
                 ((defined __cplusplus && 201103 <= __cplusplus) \
+                 || (__TINYC__ && defined __attribute__) \
                  || (defined __APPLE__ && defined __MACH__ \
                      ? 4 < __GNUC__ + (1 <= __GNUC_MINOR__) \
                      : __GNUC__) \
diff --git a/m4/stddef_h.m4 b/m4/stddef_h.m4
index cd666c4a58c..1303d2e06c7 100644
--- a/m4/stddef_h.m4
+++ b/m4/stddef_h.m4
@@ -1,4 +1,4 @@
-# stddef_h.m4 serial 9
+# stddef_h.m4 serial 11
 dnl Copyright (C) 2009-2021 Free Software Foundation, Inc.
 dnl This file is free software; the Free Software Foundation
 dnl gives unlimited permission to copy and/or distribute it,
@@ -6,7 +6,7 @@ dnl with or without modifications, as long as this notice is preserved.
 
 dnl A placeholder for <stddef.h>, for platforms that have issues.
 
-AC_DEFUN([gl_STDDEF_H],
+AC_DEFUN_ONCE([gl_STDDEF_H],
 [
   AC_REQUIRE([gl_STDDEF_H_DEFAULTS])
   AC_REQUIRE([gt_TYPE_WCHAR_T])
@@ -68,13 +68,28 @@ AC_DEFUN([gl_STDDEF_H],
   fi
 ])
 
+# gl_STDDEF_MODULE_INDICATOR([modulename])
+# sets the shell variable that indicates the presence of the given module
+# to a C preprocessor expression that will evaluate to 1.
+# This macro invocation must not occur in macros that are AC_REQUIREd.
 AC_DEFUN([gl_STDDEF_MODULE_INDICATOR],
 [
-  dnl Use AC_REQUIRE here, so that the default settings are expanded once only.
-  AC_REQUIRE([gl_STDDEF_H_DEFAULTS])
+  dnl Ensure to expand the default settings once only.
+  gl_STDDEF_H_REQUIRE_DEFAULTS
   gl_MODULE_INDICATOR_SET_VARIABLE([$1])
 ])
 
+# Initializes the default values for AC_SUBSTed shell variables.
+# This macro must not be AC_REQUIREd.  It must only be invoked, and only
+# outside of macros or in macros that are not AC_REQUIREd.
+AC_DEFUN([gl_STDDEF_H_REQUIRE_DEFAULTS],
+[
+  m4_defun(GL_MODULE_INDICATOR_PREFIX[_STDDEF_H_MODULE_INDICATOR_DEFAULTS], [
+  ])
+  m4_require(GL_MODULE_INDICATOR_PREFIX[_STDDEF_H_MODULE_INDICATOR_DEFAULTS])
+  AC_REQUIRE([gl_STDDEF_H_DEFAULTS])
+])
+
 AC_DEFUN([gl_STDDEF_H_DEFAULTS],
 [
   dnl Assume proper GNU behavior unless another module says otherwise.
diff --git a/m4/stdint.m4 b/m4/stdint.m4
index a785b44ed17..2eb1652d8e2 100644
--- a/m4/stdint.m4
+++ b/m4/stdint.m4
@@ -1,4 +1,4 @@
-# stdint.m4 serial 58
+# stdint.m4 serial 60
 dnl Copyright (C) 2001-2021 Free Software Foundation, Inc.
 dnl This file is free software; the Free Software Foundation
 dnl gives unlimited permission to copy and/or distribute it,
@@ -170,7 +170,7 @@ struct s {
       PTRDIFF_MIN == TYPE_MINIMUM (ptrdiff_t)
       && PTRDIFF_MAX == TYPE_MAXIMUM (ptrdiff_t)
       ? 1 : -1;
-  /* Detect bug in FreeBSD 6.0 / ia64.  */
+  /* Detect bug in FreeBSD 6.0/ia64 and FreeBSD 13.0/arm64.  */
   int check_SIG_ATOMIC:
       SIG_ATOMIC_MIN == TYPE_MINIMUM (sig_atomic_t)
       && SIG_ATOMIC_MAX == TYPE_MAXIMUM (sig_atomic_t)
@@ -527,7 +527,7 @@ AC_DEFUN([gl_STDINT_TYPE_PROPERTIES],
   dnl requirement that wint_t is "unchanged by default argument promotions".
   dnl In this case gnulib's <wchar.h> and <wctype.h> override wint_t.
   dnl Set the variable BITSIZEOF_WINT_T accordingly.
-  if test $GNULIB_OVERRIDES_WINT_T = 1; then
+  if test $GNULIBHEADERS_OVERRIDE_WINT_T = 1; then
     BITSIZEOF_WINT_T=32
   fi
 ])
diff --git a/m4/stdio_h.m4 b/m4/stdio_h.m4
index 4c3f24accaa..e704383862d 100644
--- a/m4/stdio_h.m4
+++ b/m4/stdio_h.m4
@@ -1,11 +1,12 @@
-# stdio_h.m4 serial 52
+# stdio_h.m4 serial 56
 dnl Copyright (C) 2007-2021 Free Software Foundation, Inc.
 dnl This file is free software; the Free Software Foundation
 dnl gives unlimited permission to copy and/or distribute it,
 dnl with or without modifications, as long as this notice is preserved.
 
-AC_DEFUN([gl_STDIO_H],
+AC_DEFUN_ONCE([gl_STDIO_H],
 [
+  AC_REQUIRE([gl_STDIO_H_DEFAULTS])
   AH_VERBATIM([MINGW_ANSI_STDIO],
 [/* Use GNU style printf and scanf.  */
 #ifndef __USE_MINGW_ANSI_STDIO
@@ -13,7 +14,6 @@ AC_DEFUN([gl_STDIO_H],
 #endif
 ])
   AC_DEFINE([__USE_MINGW_ANSI_STDIO])
-  AC_REQUIRE([gl_STDIO_H_DEFAULTS])
   gl_NEXT_HEADERS([stdio.h])
 
   dnl Determine whether __USE_MINGW_ANSI_STDIO makes printf and
@@ -40,17 +40,6 @@ AC_DEFUN([gl_STDIO_H],
        attribute "__gnu_printf__" instead of "__printf__"])
   fi
 
-  dnl No need to create extra modules for these functions. Everyone who uses
-  dnl <stdio.h> likely needs them.
-  GNULIB_FSCANF=1
-  gl_MODULE_INDICATOR([fscanf])
-  GNULIB_SCANF=1
-  gl_MODULE_INDICATOR([scanf])
-  GNULIB_FGETC=1
-  GNULIB_GETC=1
-  GNULIB_GETCHAR=1
-  GNULIB_FGETS=1
-  GNULIB_FREAD=1
   dnl This ifdef is necessary to avoid an error "missing file lib/stdio-read.c"
   dnl "expected source file, required through AC_LIBSOURCES, not found". It is
   dnl also an optimization, to avoid performing a configure check whose result
@@ -64,18 +53,6 @@ AC_DEFUN([gl_STDIO_H],
     fi
   ])
 
-  dnl No need to create extra modules for these functions. Everyone who uses
-  dnl <stdio.h> likely needs them.
-  GNULIB_FPRINTF=1
-  GNULIB_PRINTF=1
-  GNULIB_VFPRINTF=1
-  GNULIB_VPRINTF=1
-  GNULIB_FPUTC=1
-  GNULIB_PUTC=1
-  GNULIB_PUTCHAR=1
-  GNULIB_FPUTS=1
-  GNULIB_PUTS=1
-  GNULIB_FWRITE=1
   dnl This ifdef is necessary to avoid an error "missing file lib/stdio-write.c"
   dnl "expected source file, required through AC_LIBSOURCES, not found". It is
   dnl also an optimization, to avoid performing a configure check whose result
@@ -116,77 +93,92 @@ AC_DEFUN([gl_STDIO_H],
   fi
 ])
 
+# gl_STDIO_MODULE_INDICATOR([modulename])
+# sets the shell variable that indicates the presence of the given module
+# to a C preprocessor expression that will evaluate to 1.
+# This macro invocation must not occur in macros that are AC_REQUIREd.
 AC_DEFUN([gl_STDIO_MODULE_INDICATOR],
 [
-  dnl Use AC_REQUIRE here, so that the default settings are expanded once only.
-  AC_REQUIRE([gl_STDIO_H_DEFAULTS])
+  dnl Ensure to expand the default settings once only.
+  gl_STDIO_H_REQUIRE_DEFAULTS
   gl_MODULE_INDICATOR_SET_VARIABLE([$1])
   dnl Define it also as a C macro, for the benefit of the unit tests.
   gl_MODULE_INDICATOR_FOR_TESTS([$1])
 ])
 
+# Initializes the default values for AC_SUBSTed shell variables.
+# This macro must not be AC_REQUIREd.  It must only be invoked, and only
+# outside of macros or in macros that are not AC_REQUIREd.
+AC_DEFUN([gl_STDIO_H_REQUIRE_DEFAULTS],
+[
+  m4_defun(GL_MODULE_INDICATOR_PREFIX[_STDIO_H_MODULE_INDICATOR_DEFAULTS], [
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_DPRINTF])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_FCLOSE])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_FDOPEN])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_FFLUSH])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_FGETC])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_FGETS])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_FOPEN])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_FPRINTF])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_FPRINTF_POSIX])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_FPURGE])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_FPUTC])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_FPUTS])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_FREAD])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_FREOPEN])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_FSCANF])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_FSEEK])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_FSEEKO])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_FTELL])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_FTELLO])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_FWRITE])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_GETC])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_GETCHAR])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_GETDELIM])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_GETLINE])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_OBSTACK_PRINTF])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_OBSTACK_PRINTF_POSIX])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_PCLOSE])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_PERROR])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_POPEN])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_PRINTF])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_PRINTF_POSIX])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_PUTC])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_PUTCHAR])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_PUTS])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_REMOVE])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_RENAME])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_RENAMEAT])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_SCANF])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_SNPRINTF])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_SPRINTF_POSIX])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_STDIO_H_NONBLOCKING])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_STDIO_H_SIGPIPE])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_TMPFILE])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_VASPRINTF])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_VFSCANF])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_VSCANF])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_VDPRINTF])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_VFPRINTF])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_VFPRINTF_POSIX])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_VPRINTF])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_VPRINTF_POSIX])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_VSNPRINTF])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_VSPRINTF_POSIX])
+    dnl Support Microsoft deprecated alias function names by default.
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_MDA_FCLOSEALL], [1])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_MDA_FDOPEN], [1])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_MDA_FILENO], [1])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_MDA_GETW], [1])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_MDA_PUTW], [1])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_MDA_TEMPNAM], [1])
+  ])
+  m4_require(GL_MODULE_INDICATOR_PREFIX[_STDIO_H_MODULE_INDICATOR_DEFAULTS])
+  AC_REQUIRE([gl_STDIO_H_DEFAULTS])
+])
+
 AC_DEFUN([gl_STDIO_H_DEFAULTS],
 [
-  GNULIB_DPRINTF=0;              AC_SUBST([GNULIB_DPRINTF])
-  GNULIB_FCLOSE=0;               AC_SUBST([GNULIB_FCLOSE])
-  GNULIB_FDOPEN=0;               AC_SUBST([GNULIB_FDOPEN])
-  GNULIB_FFLUSH=0;               AC_SUBST([GNULIB_FFLUSH])
-  GNULIB_FGETC=0;                AC_SUBST([GNULIB_FGETC])
-  GNULIB_FGETS=0;                AC_SUBST([GNULIB_FGETS])
-  GNULIB_FOPEN=0;                AC_SUBST([GNULIB_FOPEN])
-  GNULIB_FPRINTF=0;              AC_SUBST([GNULIB_FPRINTF])
-  GNULIB_FPRINTF_POSIX=0;        AC_SUBST([GNULIB_FPRINTF_POSIX])
-  GNULIB_FPURGE=0;               AC_SUBST([GNULIB_FPURGE])
-  GNULIB_FPUTC=0;                AC_SUBST([GNULIB_FPUTC])
-  GNULIB_FPUTS=0;                AC_SUBST([GNULIB_FPUTS])
-  GNULIB_FREAD=0;                AC_SUBST([GNULIB_FREAD])
-  GNULIB_FREOPEN=0;              AC_SUBST([GNULIB_FREOPEN])
-  GNULIB_FSCANF=0;               AC_SUBST([GNULIB_FSCANF])
-  GNULIB_FSEEK=0;                AC_SUBST([GNULIB_FSEEK])
-  GNULIB_FSEEKO=0;               AC_SUBST([GNULIB_FSEEKO])
-  GNULIB_FTELL=0;                AC_SUBST([GNULIB_FTELL])
-  GNULIB_FTELLO=0;               AC_SUBST([GNULIB_FTELLO])
-  GNULIB_FWRITE=0;               AC_SUBST([GNULIB_FWRITE])
-  GNULIB_GETC=0;                 AC_SUBST([GNULIB_GETC])
-  GNULIB_GETCHAR=0;              AC_SUBST([GNULIB_GETCHAR])
-  GNULIB_GETDELIM=0;             AC_SUBST([GNULIB_GETDELIM])
-  GNULIB_GETLINE=0;              AC_SUBST([GNULIB_GETLINE])
-  GNULIB_OBSTACK_PRINTF=0;       AC_SUBST([GNULIB_OBSTACK_PRINTF])
-  GNULIB_OBSTACK_PRINTF_POSIX=0; AC_SUBST([GNULIB_OBSTACK_PRINTF_POSIX])
-  GNULIB_PCLOSE=0;               AC_SUBST([GNULIB_PCLOSE])
-  GNULIB_PERROR=0;               AC_SUBST([GNULIB_PERROR])
-  GNULIB_POPEN=0;                AC_SUBST([GNULIB_POPEN])
-  GNULIB_PRINTF=0;               AC_SUBST([GNULIB_PRINTF])
-  GNULIB_PRINTF_POSIX=0;         AC_SUBST([GNULIB_PRINTF_POSIX])
-  GNULIB_PUTC=0;                 AC_SUBST([GNULIB_PUTC])
-  GNULIB_PUTCHAR=0;              AC_SUBST([GNULIB_PUTCHAR])
-  GNULIB_PUTS=0;                 AC_SUBST([GNULIB_PUTS])
-  GNULIB_REMOVE=0;               AC_SUBST([GNULIB_REMOVE])
-  GNULIB_RENAME=0;               AC_SUBST([GNULIB_RENAME])
-  GNULIB_RENAMEAT=0;             AC_SUBST([GNULIB_RENAMEAT])
-  GNULIB_SCANF=0;                AC_SUBST([GNULIB_SCANF])
-  GNULIB_SNPRINTF=0;             AC_SUBST([GNULIB_SNPRINTF])
-  GNULIB_SPRINTF_POSIX=0;        AC_SUBST([GNULIB_SPRINTF_POSIX])
-  GNULIB_STDIO_H_NONBLOCKING=0;  AC_SUBST([GNULIB_STDIO_H_NONBLOCKING])
-  GNULIB_STDIO_H_SIGPIPE=0;      AC_SUBST([GNULIB_STDIO_H_SIGPIPE])
-  GNULIB_TMPFILE=0;              AC_SUBST([GNULIB_TMPFILE])
-  GNULIB_VASPRINTF=0;            AC_SUBST([GNULIB_VASPRINTF])
-  GNULIB_VFSCANF=0;              AC_SUBST([GNULIB_VFSCANF])
-  GNULIB_VSCANF=0;               AC_SUBST([GNULIB_VSCANF])
-  GNULIB_VDPRINTF=0;             AC_SUBST([GNULIB_VDPRINTF])
-  GNULIB_VFPRINTF=0;             AC_SUBST([GNULIB_VFPRINTF])
-  GNULIB_VFPRINTF_POSIX=0;       AC_SUBST([GNULIB_VFPRINTF_POSIX])
-  GNULIB_VPRINTF=0;              AC_SUBST([GNULIB_VPRINTF])
-  GNULIB_VPRINTF_POSIX=0;        AC_SUBST([GNULIB_VPRINTF_POSIX])
-  GNULIB_VSNPRINTF=0;            AC_SUBST([GNULIB_VSNPRINTF])
-  GNULIB_VSPRINTF_POSIX=0;       AC_SUBST([GNULIB_VSPRINTF_POSIX])
-  dnl Support Microsoft deprecated alias function names by default.
-  GNULIB_MDA_FCLOSEALL=1;        AC_SUBST([GNULIB_MDA_FCLOSEALL])
-  GNULIB_MDA_FDOPEN=1;           AC_SUBST([GNULIB_MDA_FDOPEN])
-  GNULIB_MDA_FILENO=1;           AC_SUBST([GNULIB_MDA_FILENO])
-  GNULIB_MDA_GETW=1;             AC_SUBST([GNULIB_MDA_GETW])
-  GNULIB_MDA_PUTW=1;             AC_SUBST([GNULIB_MDA_PUTW])
-  GNULIB_MDA_TEMPNAM=1;          AC_SUBST([GNULIB_MDA_TEMPNAM])
   dnl Assume proper GNU behavior unless another module says otherwise.
   HAVE_DECL_FCLOSEALL=1;         AC_SUBST([HAVE_DECL_FCLOSEALL])
   HAVE_DECL_FPURGE=1;            AC_SUBST([HAVE_DECL_FPURGE])
diff --git a/m4/stdlib_h.m4 b/m4/stdlib_h.m4
index 5a02972e05d..9c1d1c76c13 100644
--- a/m4/stdlib_h.m4
+++ b/m4/stdlib_h.m4
@@ -1,10 +1,10 @@
-# stdlib_h.m4 serial 55
+# stdlib_h.m4 serial 63
 dnl Copyright (C) 2007-2021 Free Software Foundation, Inc.
 dnl This file is free software; the Free Software Foundation
 dnl gives unlimited permission to copy and/or distribute it,
 dnl with or without modifications, as long as this notice is preserved.
 
-AC_DEFUN([gl_STDLIB_H],
+AC_DEFUN_ONCE([gl_STDLIB_H],
 [
   AC_REQUIRE([gl_STDLIB_H_DEFAULTS])
   gl_NEXT_HEADERS([stdlib.h])
@@ -28,7 +28,7 @@ AC_DEFUN([gl_STDLIB_H],
     posix_memalign posix_openpt ptsname ptsname_r qsort_r
     random random_r reallocarray realpath rpmatch secure_getenv setenv
     setstate setstate_r srandom srandom_r
-    strtod strtold strtoll strtoull unlockpt unsetenv])
+    strtod strtol strtold strtoll strtoul strtoull unlockpt unsetenv])
 
   AC_REQUIRE([AC_C_RESTRICT])
 
@@ -46,61 +46,78 @@ AC_DEFUN([gl_STDLIB_H],
   fi
 ])
 
+# gl_STDLIB_MODULE_INDICATOR([modulename])
+# sets the shell variable that indicates the presence of the given module
+# to a C preprocessor expression that will evaluate to 1.
+# This macro invocation must not occur in macros that are AC_REQUIREd.
 AC_DEFUN([gl_STDLIB_MODULE_INDICATOR],
 [
-  dnl Use AC_REQUIRE here, so that the default settings are expanded once only.
-  AC_REQUIRE([gl_STDLIB_H_DEFAULTS])
+  dnl Ensure to expand the default settings once only.
+  gl_STDLIB_H_REQUIRE_DEFAULTS
   gl_MODULE_INDICATOR_SET_VARIABLE([$1])
   dnl Define it also as a C macro, for the benefit of the unit tests.
   gl_MODULE_INDICATOR_FOR_TESTS([$1])
 ])
 
+# Initializes the default values for AC_SUBSTed shell variables.
+# This macro must not be AC_REQUIREd.  It must only be invoked, and only
+# outside of macros or in macros that are not AC_REQUIREd.
+AC_DEFUN([gl_STDLIB_H_REQUIRE_DEFAULTS],
+[
+  m4_defun(GL_MODULE_INDICATOR_PREFIX[_STDLIB_H_MODULE_INDICATOR_DEFAULTS], [
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB__EXIT])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_ALIGNED_ALLOC])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_ATOLL])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_CALLOC_POSIX])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_CANONICALIZE_FILE_NAME])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_FREE_POSIX])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_GETLOADAVG])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_GETSUBOPT])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_GRANTPT])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_MALLOC_POSIX])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_MBTOWC])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_MKDTEMP])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_MKOSTEMP])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_MKOSTEMPS])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_MKSTEMP])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_MKSTEMPS])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_POSIX_MEMALIGN])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_POSIX_OPENPT])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_PTSNAME])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_PTSNAME_R])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_PUTENV])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_QSORT_R])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_RANDOM])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_RANDOM_R])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_REALLOCARRAY])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_REALLOC_POSIX])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_REALPATH])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_RPMATCH])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_SECURE_GETENV])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_SETENV])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_STRTOD])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_STRTOL])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_STRTOLD])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_STRTOLL])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_STRTOUL])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_STRTOULL])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_SYSTEM_POSIX])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_UNLOCKPT])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_UNSETENV])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_WCTOMB])
+    dnl Support Microsoft deprecated alias function names by default.
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_MDA_ECVT], [1])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_MDA_FCVT], [1])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_MDA_GCVT], [1])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_MDA_MKTEMP], [1])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_MDA_PUTENV], [1])
+  ])
+  m4_require(GL_MODULE_INDICATOR_PREFIX[_STDLIB_H_MODULE_INDICATOR_DEFAULTS])
+  AC_REQUIRE([gl_STDLIB_H_DEFAULTS])
+])
+
 AC_DEFUN([gl_STDLIB_H_DEFAULTS],
 [
-  GNULIB__EXIT=0;         AC_SUBST([GNULIB__EXIT])
-  GNULIB_ALIGNED_ALLOC=0; AC_SUBST([GNULIB_ALIGNED_ALLOC])
-  GNULIB_ATOLL=0;         AC_SUBST([GNULIB_ATOLL])
-  GNULIB_CALLOC_POSIX=0;  AC_SUBST([GNULIB_CALLOC_POSIX])
-  GNULIB_CANONICALIZE_FILE_NAME=0;  AC_SUBST([GNULIB_CANONICALIZE_FILE_NAME])
-  GNULIB_FREE_POSIX=0;    AC_SUBST([GNULIB_FREE_POSIX])
-  GNULIB_GETLOADAVG=0;    AC_SUBST([GNULIB_GETLOADAVG])
-  GNULIB_GETSUBOPT=0;     AC_SUBST([GNULIB_GETSUBOPT])
-  GNULIB_GRANTPT=0;       AC_SUBST([GNULIB_GRANTPT])
-  GNULIB_MALLOC_POSIX=0;  AC_SUBST([GNULIB_MALLOC_POSIX])
-  GNULIB_MBTOWC=0;        AC_SUBST([GNULIB_MBTOWC])
-  GNULIB_MKDTEMP=0;       AC_SUBST([GNULIB_MKDTEMP])
-  GNULIB_MKOSTEMP=0;      AC_SUBST([GNULIB_MKOSTEMP])
-  GNULIB_MKOSTEMPS=0;     AC_SUBST([GNULIB_MKOSTEMPS])
-  GNULIB_MKSTEMP=0;       AC_SUBST([GNULIB_MKSTEMP])
-  GNULIB_MKSTEMPS=0;      AC_SUBST([GNULIB_MKSTEMPS])
-  GNULIB_POSIX_MEMALIGN=0;AC_SUBST([GNULIB_POSIX_MEMALIGN])
-  GNULIB_POSIX_OPENPT=0;  AC_SUBST([GNULIB_POSIX_OPENPT])
-  GNULIB_PTSNAME=0;       AC_SUBST([GNULIB_PTSNAME])
-  GNULIB_PTSNAME_R=0;     AC_SUBST([GNULIB_PTSNAME_R])
-  GNULIB_PUTENV=0;        AC_SUBST([GNULIB_PUTENV])
-  GNULIB_QSORT_R=0;       AC_SUBST([GNULIB_QSORT_R])
-  GNULIB_RANDOM=0;        AC_SUBST([GNULIB_RANDOM])
-  GNULIB_RANDOM_R=0;      AC_SUBST([GNULIB_RANDOM_R])
-  GNULIB_REALLOCARRAY=0;  AC_SUBST([GNULIB_REALLOCARRAY])
-  GNULIB_REALLOC_POSIX=0; AC_SUBST([GNULIB_REALLOC_POSIX])
-  GNULIB_REALPATH=0;      AC_SUBST([GNULIB_REALPATH])
-  GNULIB_RPMATCH=0;       AC_SUBST([GNULIB_RPMATCH])
-  GNULIB_SECURE_GETENV=0; AC_SUBST([GNULIB_SECURE_GETENV])
-  GNULIB_SETENV=0;        AC_SUBST([GNULIB_SETENV])
-  GNULIB_STRTOD=0;        AC_SUBST([GNULIB_STRTOD])
-  GNULIB_STRTOLD=0;       AC_SUBST([GNULIB_STRTOLD])
-  GNULIB_STRTOLL=0;       AC_SUBST([GNULIB_STRTOLL])
-  GNULIB_STRTOULL=0;      AC_SUBST([GNULIB_STRTOULL])
-  GNULIB_SYSTEM_POSIX=0;  AC_SUBST([GNULIB_SYSTEM_POSIX])
-  GNULIB_UNLOCKPT=0;      AC_SUBST([GNULIB_UNLOCKPT])
-  GNULIB_UNSETENV=0;      AC_SUBST([GNULIB_UNSETENV])
-  GNULIB_WCTOMB=0;        AC_SUBST([GNULIB_WCTOMB])
-  dnl Support Microsoft deprecated alias function names by default.
-  GNULIB_MDA_ECVT=1;      AC_SUBST([GNULIB_MDA_ECVT])
-  GNULIB_MDA_FCVT=1;      AC_SUBST([GNULIB_MDA_FCVT])
-  GNULIB_MDA_GCVT=1;      AC_SUBST([GNULIB_MDA_GCVT])
-  GNULIB_MDA_MKTEMP=1;    AC_SUBST([GNULIB_MDA_MKTEMP])
-  GNULIB_MDA_PUTENV=1;    AC_SUBST([GNULIB_MDA_PUTENV])
   dnl Assume proper GNU behavior unless another module says otherwise.
   HAVE__EXIT=1;              AC_SUBST([HAVE__EXIT])
   HAVE_ALIGNED_ALLOC=1;      AC_SUBST([HAVE_ALIGNED_ALLOC])
@@ -137,8 +154,10 @@ AC_DEFUN([gl_STDLIB_H_DEFAULTS],
   HAVE_SETSTATE=1;           AC_SUBST([HAVE_SETSTATE])
   HAVE_DECL_SETSTATE=1;      AC_SUBST([HAVE_DECL_SETSTATE])
   HAVE_STRTOD=1;             AC_SUBST([HAVE_STRTOD])
+  HAVE_STRTOL=1;             AC_SUBST([HAVE_STRTOL])
   HAVE_STRTOLD=1;            AC_SUBST([HAVE_STRTOLD])
   HAVE_STRTOLL=1;            AC_SUBST([HAVE_STRTOLL])
+  HAVE_STRTOUL=1;            AC_SUBST([HAVE_STRTOUL])
   HAVE_STRTOULL=1;           AC_SUBST([HAVE_STRTOULL])
   HAVE_STRUCT_RANDOM_DATA=1; AC_SUBST([HAVE_STRUCT_RANDOM_DATA])
   HAVE_SYS_LOADAVG_H=0;      AC_SUBST([HAVE_SYS_LOADAVG_H])
@@ -160,11 +179,16 @@ AC_DEFUN([gl_STDLIB_H_DEFAULTS],
   REPLACE_RANDOM=0;          AC_SUBST([REPLACE_RANDOM])
   REPLACE_RANDOM_R=0;        AC_SUBST([REPLACE_RANDOM_R])
   REPLACE_REALLOC=0;         AC_SUBST([REPLACE_REALLOC])
+  REPLACE_REALLOCARRAY=0;    AC_SUBST([REPLACE_REALLOCARRAY])
   REPLACE_REALPATH=0;        AC_SUBST([REPLACE_REALPATH])
   REPLACE_SETENV=0;          AC_SUBST([REPLACE_SETENV])
   REPLACE_SETSTATE=0;        AC_SUBST([REPLACE_SETSTATE])
   REPLACE_STRTOD=0;          AC_SUBST([REPLACE_STRTOD])
+  REPLACE_STRTOL=0;          AC_SUBST([REPLACE_STRTOL])
   REPLACE_STRTOLD=0;         AC_SUBST([REPLACE_STRTOLD])
+  REPLACE_STRTOLL=0;         AC_SUBST([REPLACE_STRTOLL])
+  REPLACE_STRTOUL=0;         AC_SUBST([REPLACE_STRTOUL])
+  REPLACE_STRTOULL=0;        AC_SUBST([REPLACE_STRTOULL])
   REPLACE_UNSETENV=0;        AC_SUBST([REPLACE_UNSETENV])
   REPLACE_WCTOMB=0;          AC_SUBST([REPLACE_WCTOMB])
 ])
diff --git a/m4/stpcpy.m4 b/m4/stpcpy.m4
index 28db4f45dfe..eb44f03adba 100644
--- a/m4/stpcpy.m4
+++ b/m4/stpcpy.m4
@@ -1,4 +1,4 @@
-# stpcpy.m4 serial 8
+# stpcpy.m4 serial 9
 dnl Copyright (C) 2002, 2007, 2009-2021 Free Software Foundation, Inc.
 dnl This file is free software; the Free Software Foundation
 dnl gives unlimited permission to copy and/or distribute it,
@@ -12,7 +12,7 @@ AC_DEFUN([gl_FUNC_STPCPY],
   dnl The stpcpy() declaration in lib/string.in.h uses 'restrict'.
   AC_REQUIRE([AC_C_RESTRICT])
 
-  AC_REQUIRE([gl_HEADER_STRING_H_DEFAULTS])
+  AC_REQUIRE([gl_STRING_H_DEFAULTS])
   AC_CHECK_FUNCS([stpcpy])
   if test $ac_cv_func_stpcpy = no; then
     HAVE_STPCPY=0
diff --git a/m4/string_h.m4 b/m4/string_h.m4
index a4cc5b43783..e88ac9ca853 100644
--- a/m4/string_h.m4
+++ b/m4/string_h.m4
@@ -5,20 +5,15 @@
 # gives unlimited permission to copy and/or distribute it,
 # with or without modifications, as long as this notice is preserved.
 
-# serial 29
+# serial 34
 
 # Written by Paul Eggert.
 
-AC_DEFUN([gl_HEADER_STRING_H],
+AC_DEFUN_ONCE([gl_STRING_H],
 [
-  dnl Use AC_REQUIRE here, so that the default behavior below is expanded
-  dnl once only, before all statements that occur in other macros.
-  AC_REQUIRE([gl_HEADER_STRING_H_BODY])
-])
-
-AC_DEFUN([gl_HEADER_STRING_H_BODY],
-[
-  AC_REQUIRE([gl_HEADER_STRING_H_DEFAULTS])
+  dnl Ensure to expand the default settings once only, before all statements
+  dnl that occur in other macros.
+  AC_REQUIRE([gl_STRING_H_DEFAULTS])
   gl_NEXT_HEADERS([string.h])
 
   dnl Check for declarations of anything we want to poison if the
@@ -33,62 +28,79 @@ AC_DEFUN([gl_HEADER_STRING_H_BODY],
   AC_REQUIRE([AC_C_RESTRICT])
 ])
 
+# gl_STRING_MODULE_INDICATOR([modulename])
+# sets the shell variable that indicates the presence of the given module
+# to a C preprocessor expression that will evaluate to 1.
+# This macro invocation must not occur in macros that are AC_REQUIREd.
 AC_DEFUN([gl_STRING_MODULE_INDICATOR],
 [
-  dnl Use AC_REQUIRE here, so that the default settings are expanded once only.
-  AC_REQUIRE([gl_HEADER_STRING_H_DEFAULTS])
+  dnl Ensure to expand the default settings once only.
+  gl_STRING_H_REQUIRE_DEFAULTS
   gl_MODULE_INDICATOR_SET_VARIABLE([$1])
   dnl Define it also as a C macro, for the benefit of the unit tests.
   gl_MODULE_INDICATOR_FOR_TESTS([$1])
 ])
 
-AC_DEFUN([gl_HEADER_STRING_H_DEFAULTS],
+# Initializes the default values for AC_SUBSTed shell variables.
+# This macro must not be AC_REQUIREd.  It must only be invoked, and only
+# outside of macros or in macros that are not AC_REQUIREd.
+AC_DEFUN([gl_STRING_H_REQUIRE_DEFAULTS],
+[
+  m4_defun(GL_MODULE_INDICATOR_PREFIX[_STRING_H_MODULE_INDICATOR_DEFAULTS], [
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_EXPLICIT_BZERO])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_FFSL])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_FFSLL])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_MEMCHR])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_MEMMEM])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_MEMPCPY])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_MEMRCHR])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_RAWMEMCHR])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_STPCPY])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_STPNCPY])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_STRCHRNUL])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_STRDUP])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_STRNCAT])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_STRNDUP])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_STRNLEN])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_STRPBRK])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_STRSEP])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_STRSTR])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_STRCASESTR])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_STRTOK_R])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_MBSLEN])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_MBSNLEN])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_MBSCHR])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_MBSRCHR])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_MBSSTR])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_MBSCASECMP])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_MBSNCASECMP])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_MBSPCASECMP])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_MBSCASESTR])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_MBSCSPN])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_MBSPBRK])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_MBSSPN])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_MBSSEP])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_MBSTOK_R])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_STRERROR])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_STRERROR_R])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_STRERRORNAME_NP])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_SIGABBREV_NP])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_SIGDESCR_NP])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_STRSIGNAL])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_STRVERSCMP])
+    dnl Support Microsoft deprecated alias function names by default.
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_MDA_MEMCCPY], [1])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_MDA_STRDUP], [1])
+  ])
+  m4_require(GL_MODULE_INDICATOR_PREFIX[_STRING_H_MODULE_INDICATOR_DEFAULTS])
+  dnl Make sure the shell variable for GNULIB_FREE_POSIX is initialized.
+  gl_STDLIB_H_REQUIRE_DEFAULTS
+  AC_REQUIRE([gl_STRING_H_DEFAULTS])
+])
+
+AC_DEFUN([gl_STRING_H_DEFAULTS],
 [
-  GNULIB_EXPLICIT_BZERO=0;   AC_SUBST([GNULIB_EXPLICIT_BZERO])
-  GNULIB_FFSL=0;             AC_SUBST([GNULIB_FFSL])
-  GNULIB_FFSLL=0;            AC_SUBST([GNULIB_FFSLL])
-  GNULIB_MEMCHR=0;           AC_SUBST([GNULIB_MEMCHR])
-  GNULIB_MEMMEM=0;           AC_SUBST([GNULIB_MEMMEM])
-  GNULIB_MEMPCPY=0;          AC_SUBST([GNULIB_MEMPCPY])
-  GNULIB_MEMRCHR=0;          AC_SUBST([GNULIB_MEMRCHR])
-  GNULIB_RAWMEMCHR=0;        AC_SUBST([GNULIB_RAWMEMCHR])
-  GNULIB_STPCPY=0;           AC_SUBST([GNULIB_STPCPY])
-  GNULIB_STPNCPY=0;          AC_SUBST([GNULIB_STPNCPY])
-  GNULIB_STRCHRNUL=0;        AC_SUBST([GNULIB_STRCHRNUL])
-  GNULIB_STRDUP=0;           AC_SUBST([GNULIB_STRDUP])
-  GNULIB_STRNCAT=0;          AC_SUBST([GNULIB_STRNCAT])
-  GNULIB_STRNDUP=0;          AC_SUBST([GNULIB_STRNDUP])
-  GNULIB_STRNLEN=0;          AC_SUBST([GNULIB_STRNLEN])
-  GNULIB_STRPBRK=0;          AC_SUBST([GNULIB_STRPBRK])
-  GNULIB_STRSEP=0;           AC_SUBST([GNULIB_STRSEP])
-  GNULIB_STRSTR=0;           AC_SUBST([GNULIB_STRSTR])
-  GNULIB_STRCASESTR=0;       AC_SUBST([GNULIB_STRCASESTR])
-  GNULIB_STRTOK_R=0;         AC_SUBST([GNULIB_STRTOK_R])
-  GNULIB_MBSLEN=0;           AC_SUBST([GNULIB_MBSLEN])
-  GNULIB_MBSNLEN=0;          AC_SUBST([GNULIB_MBSNLEN])
-  GNULIB_MBSCHR=0;           AC_SUBST([GNULIB_MBSCHR])
-  GNULIB_MBSRCHR=0;          AC_SUBST([GNULIB_MBSRCHR])
-  GNULIB_MBSSTR=0;           AC_SUBST([GNULIB_MBSSTR])
-  GNULIB_MBSCASECMP=0;       AC_SUBST([GNULIB_MBSCASECMP])
-  GNULIB_MBSNCASECMP=0;      AC_SUBST([GNULIB_MBSNCASECMP])
-  GNULIB_MBSPCASECMP=0;      AC_SUBST([GNULIB_MBSPCASECMP])
-  GNULIB_MBSCASESTR=0;       AC_SUBST([GNULIB_MBSCASESTR])
-  GNULIB_MBSCSPN=0;          AC_SUBST([GNULIB_MBSCSPN])
-  GNULIB_MBSPBRK=0;          AC_SUBST([GNULIB_MBSPBRK])
-  GNULIB_MBSSPN=0;           AC_SUBST([GNULIB_MBSSPN])
-  GNULIB_MBSSEP=0;           AC_SUBST([GNULIB_MBSSEP])
-  GNULIB_MBSTOK_R=0;         AC_SUBST([GNULIB_MBSTOK_R])
-  GNULIB_STRERROR=0;         AC_SUBST([GNULIB_STRERROR])
-  GNULIB_STRERROR_R=0;       AC_SUBST([GNULIB_STRERROR_R])
-  GNULIB_STRERRORNAME_NP=0;  AC_SUBST([GNULIB_STRERRORNAME_NP])
-  GNULIB_SIGABBREV_NP=0;     AC_SUBST([GNULIB_SIGABBREV_NP])
-  GNULIB_SIGDESCR_NP=0;      AC_SUBST([GNULIB_SIGDESCR_NP])
-  GNULIB_STRSIGNAL=0;        AC_SUBST([GNULIB_STRSIGNAL])
-  GNULIB_STRVERSCMP=0;       AC_SUBST([GNULIB_STRVERSCMP])
   HAVE_MBSLEN=0;             AC_SUBST([HAVE_MBSLEN])
-  dnl Support Microsoft deprecated alias function names by default.
-  GNULIB_MDA_MEMCCPY=1;      AC_SUBST([GNULIB_MDA_MEMCCPY])
-  GNULIB_MDA_STRDUP=1;       AC_SUBST([GNULIB_MDA_STRDUP])
   dnl Assume proper GNU behavior unless another module says otherwise.
   HAVE_EXPLICIT_BZERO=1;        AC_SUBST([HAVE_EXPLICIT_BZERO])
   HAVE_FFSL=1;                  AC_SUBST([HAVE_FFSL])
diff --git a/m4/strnlen.m4 b/m4/strnlen.m4
index bb9a680fdc4..1d4f10616e2 100644
--- a/m4/strnlen.m4
+++ b/m4/strnlen.m4
@@ -1,4 +1,4 @@
-# strnlen.m4 serial 13
+# strnlen.m4 serial 14
 dnl Copyright (C) 2002-2003, 2005-2007, 2009-2021 Free Software Foundation,
 dnl Inc.
 dnl This file is free software; the Free Software Foundation
@@ -7,7 +7,7 @@ dnl with or without modifications, as long as this notice is preserved.
 
 AC_DEFUN([gl_FUNC_STRNLEN],
 [
-  AC_REQUIRE([gl_HEADER_STRING_H_DEFAULTS])
+  AC_REQUIRE([gl_STRING_H_DEFAULTS])
 
   dnl Persuade glibc <string.h> to declare strnlen().
   AC_REQUIRE([AC_USE_SYSTEM_EXTENSIONS])
diff --git a/m4/strtoll.m4 b/m4/strtoll.m4
index d2c9e5310d1..14455dc3db9 100644
--- a/m4/strtoll.m4
+++ b/m4/strtoll.m4
@@ -1,4 +1,4 @@
-# strtoll.m4 serial 8
+# strtoll.m4 serial 9
 dnl Copyright (C) 2002, 2004, 2006, 2008-2021 Free Software Foundation, Inc.
 dnl This file is free software; the Free Software Foundation
 dnl gives unlimited permission to copy and/or distribute it,
@@ -7,8 +7,40 @@ dnl with or without modifications, as long as this notice is preserved.
 AC_DEFUN([gl_FUNC_STRTOLL],
 [
   AC_REQUIRE([gl_STDLIB_H_DEFAULTS])
+  AC_REQUIRE([AC_CANONICAL_HOST])
   AC_CHECK_FUNCS([strtoll])
-  if test $ac_cv_func_strtoll = no; then
+  if test $ac_cv_func_strtoll = yes; then
+    AC_CACHE_CHECK([whether strtoll works],
+      [gl_cv_func_strtoll_works],
+      [AC_RUN_IFELSE(
+         [AC_LANG_PROGRAM(
+            [[#include <stdlib.h>]],
+            [[int result = 0;
+              char *term;
+              /* This test fails on Minix and native Windows.  */
+              {
+                const char input[] = "0x";
+                (void) strtoll (input, &term, 16);
+                if (term != input + 1)
+                  result |= 1;
+              }
+              return result;
+            ]])
+         ],
+         [gl_cv_func_strtoll_works=yes],
+         [gl_cv_func_strtoll_works=no],
+         [case "$host_os" in
+                    # Guess no on native Windows.
+            mingw*) gl_cv_func_strtoll_works="guessing no" ;;
+            *)      gl_cv_func_strtoll_works="$gl_cross_guess_normal" ;;
+          esac
+         ])
+    ])
+    case "$gl_cv_func_strtoll_works" in
+      *yes) ;;
+      *)    REPLACE_STRTOLL=1 ;;
+    esac
+  else
     HAVE_STRTOLL=0
   fi
 ])
diff --git a/m4/sys_random_h.m4 b/m4/sys_random_h.m4
index 45e0469ba05..37bc31606bd 100644
--- a/m4/sys_random_h.m4
+++ b/m4/sys_random_h.m4
@@ -1,10 +1,10 @@
-# sys_random_h.m4 serial 5
+# sys_random_h.m4 serial 8
 dnl Copyright (C) 2020-2021 Free Software Foundation, Inc.
 dnl This file is free software; the Free Software Foundation
 dnl gives unlimited permission to copy and/or distribute it,
 dnl with or without modifications, as long as this notice is preserved.
 
-AC_DEFUN([gl_HEADER_SYS_RANDOM],
+AC_DEFUN_ONCE([gl_SYS_RANDOM_H],
 [
   AC_REQUIRE([gl_SYS_RANDOM_H_DEFAULTS])
   dnl <sys/random.h> is always overridden, because of GNULIB_POSIXCHECK.
@@ -35,18 +35,33 @@ AC_DEFUN([gl_HEADER_SYS_RANDOM],
     [getrandom])
 ])
 
+# gl_SYS_RANDOM_MODULE_INDICATOR([modulename])
+# sets the shell variable that indicates the presence of the given module
+# to a C preprocessor expression that will evaluate to 1.
+# This macro invocation must not occur in macros that are AC_REQUIREd.
 AC_DEFUN([gl_SYS_RANDOM_MODULE_INDICATOR],
 [
-  dnl Use AC_REQUIRE here, so that the default settings are expanded once only.
-  AC_REQUIRE([gl_SYS_RANDOM_H_DEFAULTS])
+  dnl Ensure to expand the default settings once only.
+  gl_SYS_RANDOM_H_REQUIRE_DEFAULTS
   gl_MODULE_INDICATOR_SET_VARIABLE([$1])
   dnl Define it also as a C macro, for the benefit of the unit tests.
   gl_MODULE_INDICATOR_FOR_TESTS([$1])
 ])
 
+# Initializes the default values for AC_SUBSTed shell variables.
+# This macro must not be AC_REQUIREd.  It must only be invoked, and only
+# outside of macros or in macros that are not AC_REQUIREd.
+AC_DEFUN([gl_SYS_RANDOM_H_REQUIRE_DEFAULTS],
+[
+  m4_defun(GL_MODULE_INDICATOR_PREFIX[_SYS_RANDOM_H_MODULE_INDICATOR_DEFAULTS], [
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_GETRANDOM])
+  ])
+  m4_require(GL_MODULE_INDICATOR_PREFIX[_SYS_RANDOM_H_MODULE_INDICATOR_DEFAULTS])
+  AC_REQUIRE([gl_SYS_RANDOM_H_DEFAULTS])
+])
+
 AC_DEFUN([gl_SYS_RANDOM_H_DEFAULTS],
 [
-  GNULIB_GETRANDOM=0;     AC_SUBST([GNULIB_GETRANDOM])
   dnl Assume proper GNU behavior unless another module says otherwise.
   HAVE_GETRANDOM=1;       AC_SUBST([HAVE_GETRANDOM])
   REPLACE_GETRANDOM=0;    AC_SUBST([REPLACE_GETRANDOM])
diff --git a/m4/sys_select_h.m4 b/m4/sys_select_h.m4
index 4b33d312e55..2e7d140dee2 100644
--- a/m4/sys_select_h.m4
+++ b/m4/sys_select_h.m4
@@ -1,13 +1,13 @@
-# sys_select_h.m4 serial 20
+# sys_select_h.m4 serial 23
 dnl Copyright (C) 2006-2021 Free Software Foundation, Inc.
 dnl This file is free software; the Free Software Foundation
 dnl gives unlimited permission to copy and/or distribute it,
 dnl with or without modifications, as long as this notice is preserved.
 
-AC_DEFUN([gl_HEADER_SYS_SELECT],
+AC_DEFUN_ONCE([gl_SYS_SELECT_H],
 [
-  AC_REQUIRE([AC_C_RESTRICT])
   AC_REQUIRE([gl_SYS_SELECT_H_DEFAULTS])
+  AC_REQUIRE([AC_C_RESTRICT])
   AC_CACHE_CHECK([whether <sys/select.h> is self-contained],
     [gl_cv_header_sys_select_h_selfcontained],
     [
@@ -75,19 +75,34 @@ AC_DEFUN([gl_HEADER_SYS_SELECT],
     ]], [pselect select])
 ])
 
+# gl_SYS_SELECT_MODULE_INDICATOR([modulename])
+# sets the shell variable that indicates the presence of the given module
+# to a C preprocessor expression that will evaluate to 1.
+# This macro invocation must not occur in macros that are AC_REQUIREd.
 AC_DEFUN([gl_SYS_SELECT_MODULE_INDICATOR],
 [
-  dnl Use AC_REQUIRE here, so that the default settings are expanded once only.
-  AC_REQUIRE([gl_SYS_SELECT_H_DEFAULTS])
+  dnl Ensure to expand the default settings once only.
+  gl_SYS_SELECT_H_REQUIRE_DEFAULTS
   gl_MODULE_INDICATOR_SET_VARIABLE([$1])
   dnl Define it also as a C macro, for the benefit of the unit tests.
   gl_MODULE_INDICATOR_FOR_TESTS([$1])
 ])
 
+# Initializes the default values for AC_SUBSTed shell variables.
+# This macro must not be AC_REQUIREd.  It must only be invoked, and only
+# outside of macros or in macros that are not AC_REQUIREd.
+AC_DEFUN([gl_SYS_SELECT_H_REQUIRE_DEFAULTS],
+[
+  m4_defun(GL_MODULE_INDICATOR_PREFIX[_SYS_SELECT_H_MODULE_INDICATOR_DEFAULTS], [
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_PSELECT])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_SELECT])
+  ])
+  m4_require(GL_MODULE_INDICATOR_PREFIX[_SYS_SELECT_H_MODULE_INDICATOR_DEFAULTS])
+  AC_REQUIRE([gl_SYS_SELECT_H_DEFAULTS])
+])
+
 AC_DEFUN([gl_SYS_SELECT_H_DEFAULTS],
 [
-  GNULIB_PSELECT=0; AC_SUBST([GNULIB_PSELECT])
-  GNULIB_SELECT=0; AC_SUBST([GNULIB_SELECT])
   dnl Assume proper GNU behavior unless another module says otherwise.
   HAVE_PSELECT=1; AC_SUBST([HAVE_PSELECT])
   REPLACE_PSELECT=0; AC_SUBST([REPLACE_PSELECT])
diff --git a/m4/sys_socket_h.m4 b/m4/sys_socket_h.m4
index 503cb9668b7..5676a0d2170 100644
--- a/m4/sys_socket_h.m4
+++ b/m4/sys_socket_h.m4
@@ -1,4 +1,4 @@
-# sys_socket_h.m4 serial 25
+# sys_socket_h.m4 serial 28
 dnl Copyright (C) 2005-2021 Free Software Foundation, Inc.
 dnl This file is free software; the Free Software Foundation
 dnl gives unlimited permission to copy and/or distribute it,
@@ -6,7 +6,7 @@ dnl with or without modifications, as long as this notice is preserved.
 
 dnl From Simon Josefsson.
 
-AC_DEFUN([gl_HEADER_SYS_SOCKET],
+AC_DEFUN_ONCE([gl_SYS_SOCKET_H],
 [
   AC_REQUIRE([gl_SYS_SOCKET_H_DEFAULTS])
   AC_REQUIRE([AC_CANONICAL_HOST])
@@ -156,32 +156,47 @@ AC_DEFUN([gl_PREREQ_SYS_H_WS2TCPIP],
   AC_SUBST([HAVE_WS2TCPIP_H])
 ])
 
+# gl_SYS_SOCKET_MODULE_INDICATOR([modulename])
+# sets the shell variable that indicates the presence of the given module
+# to a C preprocessor expression that will evaluate to 1.
+# This macro invocation must not occur in macros that are AC_REQUIREd.
 AC_DEFUN([gl_SYS_SOCKET_MODULE_INDICATOR],
 [
-  dnl Use AC_REQUIRE here, so that the default settings are expanded once only.
-  AC_REQUIRE([gl_SYS_SOCKET_H_DEFAULTS])
+  dnl Ensure to expand the default settings once only.
+  gl_SYS_SOCKET_H_REQUIRE_DEFAULTS
   gl_MODULE_INDICATOR_SET_VARIABLE([$1])
   dnl Define it also as a C macro, for the benefit of the unit tests.
   gl_MODULE_INDICATOR_FOR_TESTS([$1])
 ])
 
+# Initializes the default values for AC_SUBSTed shell variables.
+# This macro must not be AC_REQUIREd.  It must only be invoked, and only
+# outside of macros or in macros that are not AC_REQUIREd.
+AC_DEFUN([gl_SYS_SOCKET_H_REQUIRE_DEFAULTS],
+[
+  m4_defun(GL_MODULE_INDICATOR_PREFIX[_SYS_SOCKET_H_MODULE_INDICATOR_DEFAULTS], [
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_SOCKET])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_CONNECT])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_ACCEPT])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_BIND])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_GETPEERNAME])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_GETSOCKNAME])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_GETSOCKOPT])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_LISTEN])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_RECV])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_SEND])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_RECVFROM])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_SENDTO])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_SETSOCKOPT])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_SHUTDOWN])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_ACCEPT4])
+  ])
+  m4_require(GL_MODULE_INDICATOR_PREFIX[_SYS_SOCKET_H_MODULE_INDICATOR_DEFAULTS])
+  AC_REQUIRE([gl_SYS_SOCKET_H_DEFAULTS])
+])
+
 AC_DEFUN([gl_SYS_SOCKET_H_DEFAULTS],
 [
-  GNULIB_SOCKET=0;      AC_SUBST([GNULIB_SOCKET])
-  GNULIB_CONNECT=0;     AC_SUBST([GNULIB_CONNECT])
-  GNULIB_ACCEPT=0;      AC_SUBST([GNULIB_ACCEPT])
-  GNULIB_BIND=0;        AC_SUBST([GNULIB_BIND])
-  GNULIB_GETPEERNAME=0; AC_SUBST([GNULIB_GETPEERNAME])
-  GNULIB_GETSOCKNAME=0; AC_SUBST([GNULIB_GETSOCKNAME])
-  GNULIB_GETSOCKOPT=0;  AC_SUBST([GNULIB_GETSOCKOPT])
-  GNULIB_LISTEN=0;      AC_SUBST([GNULIB_LISTEN])
-  GNULIB_RECV=0;        AC_SUBST([GNULIB_RECV])
-  GNULIB_SEND=0;        AC_SUBST([GNULIB_SEND])
-  GNULIB_RECVFROM=0;    AC_SUBST([GNULIB_RECVFROM])
-  GNULIB_SENDTO=0;      AC_SUBST([GNULIB_SENDTO])
-  GNULIB_SETSOCKOPT=0;  AC_SUBST([GNULIB_SETSOCKOPT])
-  GNULIB_SHUTDOWN=0;    AC_SUBST([GNULIB_SHUTDOWN])
-  GNULIB_ACCEPT4=0;     AC_SUBST([GNULIB_ACCEPT4])
   HAVE_STRUCT_SOCKADDR_STORAGE=1; AC_SUBST([HAVE_STRUCT_SOCKADDR_STORAGE])
   HAVE_STRUCT_SOCKADDR_STORAGE_SS_FAMILY=1;
                         AC_SUBST([HAVE_STRUCT_SOCKADDR_STORAGE_SS_FAMILY])
diff --git a/m4/sys_stat_h.m4 b/m4/sys_stat_h.m4
index 23cbdd28eb2..ac91d425bbb 100644
--- a/m4/sys_stat_h.m4
+++ b/m4/sys_stat_h.m4
@@ -1,4 +1,4 @@
-# sys_stat_h.m4 serial 38   -*- Autoconf -*-
+# sys_stat_h.m4 serial 41   -*- Autoconf -*-
 dnl Copyright (C) 2006-2021 Free Software Foundation, Inc.
 dnl This file is free software; the Free Software Foundation
 dnl gives unlimited permission to copy and/or distribute it,
@@ -7,7 +7,7 @@ dnl with or without modifications, as long as this notice is preserved.
 dnl From Eric Blake.
 dnl Provide a GNU-like <sys/stat.h>.
 
-AC_DEFUN([gl_HEADER_SYS_STAT_H],
+AC_DEFUN_ONCE([gl_SYS_STAT_H],
 [
   AC_REQUIRE([gl_SYS_STAT_H_DEFAULTS])
 
@@ -52,38 +52,53 @@ AC_DEFUN([gl_HEADER_SYS_STAT_H],
   AC_REQUIRE([AC_C_RESTRICT])
 ])
 
+# gl_SYS_STAT_MODULE_INDICATOR([modulename])
+# sets the shell variable that indicates the presence of the given module
+# to a C preprocessor expression that will evaluate to 1.
+# This macro invocation must not occur in macros that are AC_REQUIREd.
 AC_DEFUN([gl_SYS_STAT_MODULE_INDICATOR],
 [
-  dnl Use AC_REQUIRE here, so that the default settings are expanded once only.
-  AC_REQUIRE([gl_SYS_STAT_H_DEFAULTS])
+  dnl Ensure to expand the default settings once only.
+  gl_SYS_STAT_H_REQUIRE_DEFAULTS
   gl_MODULE_INDICATOR_SET_VARIABLE([$1])
   dnl Define it also as a C macro, for the benefit of the unit tests.
   gl_MODULE_INDICATOR_FOR_TESTS([$1])
 ])
 
+# Initializes the default values for AC_SUBSTed shell variables.
+# This macro must not be AC_REQUIREd.  It must only be invoked, and only
+# outside of macros or in macros that are not AC_REQUIREd.
+AC_DEFUN([gl_SYS_STAT_H_REQUIRE_DEFAULTS],
+[
+  m4_defun(GL_MODULE_INDICATOR_PREFIX[_SYS_STAT_H_MODULE_INDICATOR_DEFAULTS], [
+    gl_UNISTD_H_REQUIRE_DEFAULTS dnl for REPLACE_FCHDIR
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_FCHMODAT])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_FSTAT])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_FSTATAT])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_FUTIMENS])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_GETUMASK])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_LCHMOD])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_LSTAT])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_MKDIR])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_MKDIRAT])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_MKFIFO])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_MKFIFOAT])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_MKNOD])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_MKNODAT])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_STAT])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_UTIMENSAT])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_OVERRIDES_STRUCT_STAT])
+    dnl Support Microsoft deprecated alias function names by default.
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_MDA_CHMOD], [1])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_MDA_MKDIR], [1])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_MDA_UMASK], [1])
+  ])
+  m4_require(GL_MODULE_INDICATOR_PREFIX[_SYS_STAT_H_MODULE_INDICATOR_DEFAULTS])
+  AC_REQUIRE([gl_SYS_STAT_H_DEFAULTS])
+])
+
 AC_DEFUN([gl_SYS_STAT_H_DEFAULTS],
 [
-  AC_REQUIRE([gl_UNISTD_H_DEFAULTS]) dnl for REPLACE_FCHDIR
-  GNULIB_FCHMODAT=0;    AC_SUBST([GNULIB_FCHMODAT])
-  GNULIB_FSTAT=0;       AC_SUBST([GNULIB_FSTAT])
-  GNULIB_FSTATAT=0;     AC_SUBST([GNULIB_FSTATAT])
-  GNULIB_FUTIMENS=0;    AC_SUBST([GNULIB_FUTIMENS])
-  GNULIB_GETUMASK=0;    AC_SUBST([GNULIB_GETUMASK])
-  GNULIB_LCHMOD=0;      AC_SUBST([GNULIB_LCHMOD])
-  GNULIB_LSTAT=0;       AC_SUBST([GNULIB_LSTAT])
-  GNULIB_MKDIR=0;       AC_SUBST([GNULIB_MKDIR])
-  GNULIB_MKDIRAT=0;     AC_SUBST([GNULIB_MKDIRAT])
-  GNULIB_MKFIFO=0;      AC_SUBST([GNULIB_MKFIFO])
-  GNULIB_MKFIFOAT=0;    AC_SUBST([GNULIB_MKFIFOAT])
-  GNULIB_MKNOD=0;       AC_SUBST([GNULIB_MKNOD])
-  GNULIB_MKNODAT=0;     AC_SUBST([GNULIB_MKNODAT])
-  GNULIB_STAT=0;        AC_SUBST([GNULIB_STAT])
-  GNULIB_UTIMENSAT=0;   AC_SUBST([GNULIB_UTIMENSAT])
-  GNULIB_OVERRIDES_STRUCT_STAT=0; AC_SUBST([GNULIB_OVERRIDES_STRUCT_STAT])
-  dnl Support Microsoft deprecated alias function names by default.
-  GNULIB_MDA_CHMOD=1;   AC_SUBST([GNULIB_MDA_CHMOD])
-  GNULIB_MDA_MKDIR=1;   AC_SUBST([GNULIB_MDA_MKDIR])
-  GNULIB_MDA_UMASK=1;   AC_SUBST([GNULIB_MDA_UMASK])
   dnl Assume proper GNU behavior unless another module says otherwise.
   HAVE_FCHMODAT=1;      AC_SUBST([HAVE_FCHMODAT])
   HAVE_FSTATAT=1;       AC_SUBST([HAVE_FSTATAT])
diff --git a/m4/sys_time_h.m4 b/m4/sys_time_h.m4
index 64f133d5133..c425a9639a1 100644
--- a/m4/sys_time_h.m4
+++ b/m4/sys_time_h.m4
@@ -1,5 +1,5 @@
 # Configure a replacement for <sys/time.h>.
-# serial 9
+# serial 12
 
 # Copyright (C) 2007, 2009-2021 Free Software Foundation, Inc.
 # This file is free software; the Free Software Foundation
@@ -8,18 +8,13 @@
 
 # Written by Paul Eggert and Martin Lambers.
 
-AC_DEFUN([gl_HEADER_SYS_TIME_H],
+AC_DEFUN_ONCE([gl_SYS_TIME_H],
 [
   dnl Use AC_REQUIRE here, so that the REPLACE_GETTIMEOFDAY=0 statement
   dnl below is expanded once only, before all REPLACE_GETTIMEOFDAY=1
   dnl statements that occur in other macros.
-  AC_REQUIRE([gl_HEADER_SYS_TIME_H_BODY])
-])
-
-AC_DEFUN([gl_HEADER_SYS_TIME_H_BODY],
-[
+  AC_REQUIRE([gl_SYS_TIME_H_DEFAULTS])
   AC_REQUIRE([AC_C_RESTRICT])
-  AC_REQUIRE([gl_HEADER_SYS_TIME_H_DEFAULTS])
   AC_CHECK_HEADERS_ONCE([sys/time.h])
   gl_CHECK_NEXT_HEADERS([sys/time.h])
 
@@ -89,18 +84,33 @@ AC_DEFUN([gl_HEADER_SYS_TIME_H_BODY],
     ]], [gettimeofday])
 ])
 
+# gl_SYS_TIME_MODULE_INDICATOR([modulename])
+# sets the shell variable that indicates the presence of the given module
+# to a C preprocessor expression that will evaluate to 1.
+# This macro invocation must not occur in macros that are AC_REQUIREd.
 AC_DEFUN([gl_SYS_TIME_MODULE_INDICATOR],
 [
-  dnl Use AC_REQUIRE here, so that the default settings are expanded once only.
-  AC_REQUIRE([gl_HEADER_SYS_TIME_H_DEFAULTS])
+  dnl Ensure to expand the default settings once only.
+  gl_SYS_TIME_H_REQUIRE_DEFAULTS
   gl_MODULE_INDICATOR_SET_VARIABLE([$1])
   dnl Define it also as a C macro, for the benefit of the unit tests.
   gl_MODULE_INDICATOR_FOR_TESTS([$1])
 ])
 
-AC_DEFUN([gl_HEADER_SYS_TIME_H_DEFAULTS],
+# Initializes the default values for AC_SUBSTed shell variables.
+# This macro must not be AC_REQUIREd.  It must only be invoked, and only
+# outside of macros or in macros that are not AC_REQUIREd.
+AC_DEFUN([gl_SYS_TIME_H_REQUIRE_DEFAULTS],
+[
+  m4_defun(GL_MODULE_INDICATOR_PREFIX[_SYS_TIME_H_MODULE_INDICATOR_DEFAULTS], [
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_GETTIMEOFDAY])
+  ])
+  m4_require(GL_MODULE_INDICATOR_PREFIX[_SYS_TIME_H_MODULE_INDICATOR_DEFAULTS])
+  AC_REQUIRE([gl_SYS_TIME_H_DEFAULTS])
+])
+
+AC_DEFUN([gl_SYS_TIME_H_DEFAULTS],
 [
-  GNULIB_GETTIMEOFDAY=0;     AC_SUBST([GNULIB_GETTIMEOFDAY])
   dnl Assume POSIX behavior unless another module says otherwise.
   HAVE_GETTIMEOFDAY=1;       AC_SUBST([HAVE_GETTIMEOFDAY])
   HAVE_STRUCT_TIMEVAL=1;     AC_SUBST([HAVE_STRUCT_TIMEVAL])
diff --git a/m4/sys_types_h.m4 b/m4/sys_types_h.m4
index 2172c836d95..6dd6fee10c8 100644
--- a/m4/sys_types_h.m4
+++ b/m4/sys_types_h.m4
@@ -1,4 +1,4 @@
-# sys_types_h.m4 serial 11
+# sys_types_h.m4 serial 13
 dnl Copyright (C) 2011-2021 Free Software Foundation, Inc.
 dnl This file is free software; the Free Software Foundation
 dnl gives unlimited permission to copy and/or distribute it,
@@ -6,10 +6,11 @@ dnl with or without modifications, as long as this notice is preserved.
 
 AC_DEFUN_ONCE([gl_SYS_TYPES_H],
 [
+  AC_REQUIRE([gl_SYS_TYPES_H_DEFAULTS])
+
   dnl Use sane struct stat types in OpenVMS 8.2 and later.
   AC_DEFINE([_USE_STD_STAT], 1, [For standard stat data types on VMS.])
 
-  AC_REQUIRE([gl_SYS_TYPES_H_DEFAULTS])
   gl_NEXT_HEADERS([sys/types.h])
 
   dnl Ensure the type pid_t gets defined.
@@ -30,6 +31,17 @@ AC_DEFUN_ONCE([gl_SYS_TYPES_H],
   AC_SUBST([WINDOWS_STAT_INODES])
 ])
 
+# Initializes the default values for AC_SUBSTed shell variables.
+# This macro must not be AC_REQUIREd.  It must only be invoked, and only
+# outside of macros or in macros that are not AC_REQUIREd.
+AC_DEFUN([gl_SYS_TYPES_H_REQUIRE_DEFAULTS],
+[
+  m4_defun(GL_MODULE_INDICATOR_PREFIX[_SYS_TYPE_H_MODULE_INDICATOR_DEFAULTS], [
+  ])
+  m4_require(GL_MODULE_INDICATOR_PREFIX[_SYS_TYPE_H_MODULE_INDICATOR_DEFAULTS])
+  AC_REQUIRE([gl_SYS_TYPES_H_DEFAULTS])
+])
+
 AC_DEFUN([gl_SYS_TYPES_H_DEFAULTS],
 [
 ])
diff --git a/m4/time_h.m4 b/m4/time_h.m4
index b6a1aa3bc0f..b57474b48b3 100644
--- a/m4/time_h.m4
+++ b/m4/time_h.m4
@@ -2,7 +2,7 @@
 
 # Copyright (C) 2000-2001, 2003-2007, 2009-2021 Free Software Foundation, Inc.
 
-# serial 15
+# serial 18
 
 # This file is free software; the Free Software Foundation
 # gives unlimited permission to copy and/or distribute it,
@@ -10,16 +10,11 @@
 
 # Written by Paul Eggert and Jim Meyering.
 
-AC_DEFUN([gl_HEADER_TIME_H],
+AC_DEFUN_ONCE([gl_TIME_H],
 [
-  dnl Use AC_REQUIRE here, so that the default behavior below is expanded
-  dnl once only, before all statements that occur in other macros.
-  AC_REQUIRE([gl_HEADER_TIME_H_BODY])
-])
-
-AC_DEFUN([gl_HEADER_TIME_H_BODY],
-[
-  AC_REQUIRE([gl_HEADER_TIME_H_DEFAULTS])
+  dnl Ensure to expand the default settings once only, before all statements
+  dnl that occur in other macros.
+  AC_REQUIRE([gl_TIME_H_DEFAULTS])
 
   gl_NEXT_HEADERS([time.h])
   AC_REQUIRE([gl_CHECK_TYPE_STRUCT_TIMESPEC])
@@ -111,30 +106,45 @@ AC_DEFUN([gl_CHECK_TYPE_STRUCT_TIMESPEC],
   AC_SUBST([UNISTD_H_DEFINES_STRUCT_TIMESPEC])
 ])
 
+# gl_TIME_MODULE_INDICATOR([modulename])
+# sets the shell variable that indicates the presence of the given module
+# to a C preprocessor expression that will evaluate to 1.
+# This macro invocation must not occur in macros that are AC_REQUIREd.
 AC_DEFUN([gl_TIME_MODULE_INDICATOR],
 [
-  dnl Use AC_REQUIRE here, so that the default settings are expanded once only.
-  AC_REQUIRE([gl_HEADER_TIME_H_DEFAULTS])
+  dnl Ensure to expand the default settings once only.
+  gl_TIME_H_REQUIRE_DEFAULTS
   gl_MODULE_INDICATOR_SET_VARIABLE([$1])
   dnl Define it also as a C macro, for the benefit of the unit tests.
   gl_MODULE_INDICATOR_FOR_TESTS([$1])
 ])
 
-AC_DEFUN([gl_HEADER_TIME_H_DEFAULTS],
+# Initializes the default values for AC_SUBSTed shell variables.
+# This macro must not be AC_REQUIREd.  It must only be invoked, and only
+# outside of macros or in macros that are not AC_REQUIREd.
+AC_DEFUN([gl_TIME_H_REQUIRE_DEFAULTS],
+[
+  m4_defun(GL_MODULE_INDICATOR_PREFIX[_TIME_H_MODULE_INDICATOR_DEFAULTS], [
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_CTIME])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_MKTIME])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_LOCALTIME])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_NANOSLEEP])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_STRFTIME])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_STRPTIME])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_TIMEGM])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_TIMESPEC_GET])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_TIME_R])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_TIME_RZ])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_TZSET])
+    dnl Support Microsoft deprecated alias function names by default.
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_MDA_TZSET], [1])
+  ])
+  m4_require(GL_MODULE_INDICATOR_PREFIX[_TIME_H_MODULE_INDICATOR_DEFAULTS])
+  AC_REQUIRE([gl_TIME_H_DEFAULTS])
+])
+
+AC_DEFUN([gl_TIME_H_DEFAULTS],
 [
-  GNULIB_CTIME=0;                        AC_SUBST([GNULIB_CTIME])
-  GNULIB_MKTIME=0;                       AC_SUBST([GNULIB_MKTIME])
-  GNULIB_LOCALTIME=0;                    AC_SUBST([GNULIB_LOCALTIME])
-  GNULIB_NANOSLEEP=0;                    AC_SUBST([GNULIB_NANOSLEEP])
-  GNULIB_STRFTIME=0;                     AC_SUBST([GNULIB_STRFTIME])
-  GNULIB_STRPTIME=0;                     AC_SUBST([GNULIB_STRPTIME])
-  GNULIB_TIMEGM=0;                       AC_SUBST([GNULIB_TIMEGM])
-  GNULIB_TIMESPEC_GET=0;                 AC_SUBST([GNULIB_TIMESPEC_GET])
-  GNULIB_TIME_R=0;                       AC_SUBST([GNULIB_TIME_R])
-  GNULIB_TIME_RZ=0;                      AC_SUBST([GNULIB_TIME_RZ])
-  GNULIB_TZSET=0;                        AC_SUBST([GNULIB_TZSET])
-  dnl Support Microsoft deprecated alias function names by default.
-  GNULIB_MDA_TZSET=1;                    AC_SUBST([GNULIB_MDA_TZSET])
   dnl Assume proper GNU behavior unless another module says otherwise.
   HAVE_DECL_LOCALTIME_R=1;               AC_SUBST([HAVE_DECL_LOCALTIME_R])
   HAVE_NANOSLEEP=1;                      AC_SUBST([HAVE_NANOSLEEP])
diff --git a/m4/time_r.m4 b/m4/time_r.m4
index 713e93ac263..2d49b64f12c 100644
--- a/m4/time_r.m4
+++ b/m4/time_r.m4
@@ -12,7 +12,7 @@ AC_DEFUN([gl_TIME_R],
   dnl Persuade glibc and Solaris <time.h> to declare localtime_r.
   AC_REQUIRE([gl_USE_SYSTEM_EXTENSIONS])
 
-  AC_REQUIRE([gl_HEADER_TIME_H_DEFAULTS])
+  AC_REQUIRE([gl_TIME_H_DEFAULTS])
   AC_REQUIRE([AC_C_RESTRICT])
 
   dnl Some systems don't declare localtime_r() and gmtime_r() if _REENTRANT is
diff --git a/m4/time_rz.m4 b/m4/time_rz.m4
index 34ef0bab4b9..c5e85dc625e 100644
--- a/m4/time_rz.m4
+++ b/m4/time_rz.m4
@@ -10,7 +10,7 @@ dnl Written by Paul Eggert.
 AC_DEFUN([gl_TIME_RZ],
 [
   AC_REQUIRE([gl_USE_SYSTEM_EXTENSIONS])
-  AC_REQUIRE([gl_HEADER_TIME_H_DEFAULTS])
+  AC_REQUIRE([gl_TIME_H_DEFAULTS])
   AC_REQUIRE([AC_STRUCT_TIMEZONE])
 
   # On Mac OS X 10.6, localtime loops forever with some time_t values.
diff --git a/m4/timegm.m4 b/m4/timegm.m4
index 098c857e7f2..58123beb0cc 100644
--- a/m4/timegm.m4
+++ b/m4/timegm.m4
@@ -1,4 +1,4 @@
-# timegm.m4 serial 12
+# timegm.m4 serial 13
 dnl Copyright (C) 2003, 2007, 2009-2021 Free Software Foundation, Inc.
 dnl This file is free software; the Free Software Foundation
 dnl gives unlimited permission to copy and/or distribute it,
@@ -6,7 +6,7 @@ dnl with or without modifications, as long as this notice is preserved.
 
 AC_DEFUN([gl_FUNC_TIMEGM],
 [
-  AC_REQUIRE([gl_HEADER_TIME_H_DEFAULTS])
+  AC_REQUIRE([gl_TIME_H_DEFAULTS])
   AC_REQUIRE([gl_FUNC_MKTIME_WORKS])
   REPLACE_TIMEGM=0
   AC_CHECK_FUNCS_ONCE([timegm])
diff --git a/m4/timer_time.m4 b/m4/timer_time.m4
index f0e5785e9aa..003e36e9d14 100644
--- a/m4/timer_time.m4
+++ b/m4/timer_time.m4
@@ -1,4 +1,4 @@
-# timer_time.m4 serial 4
+# timer_time.m4 serial 5
 dnl Copyright (C) 2011-2021 Free Software Foundation, Inc.
 dnl This file is free software; the Free Software Foundation
 dnl gives unlimited permission to copy and/or distribute it,
@@ -18,9 +18,13 @@ AC_DEFUN([gl_TIMER_TIME],
   dnl the threadlib.m4 file that is installed in $PREFIX/share/aclocal/.
   m4_ifdef([gl_][PTHREADLIB], [AC_REQUIRE([gl_][PTHREADLIB])])
 
+  AC_CHECK_DECL([timer_settime], [], [],
+                [[#include <time.h>
+                ]])
   LIB_TIMER_TIME=
   AC_SUBST([LIB_TIMER_TIME])
-  gl_saved_libs=$LIBS
+  AS_IF([test "$ac_cv_have_decl_timer_settime" = yes], [
+    gl_saved_libs=$LIBS
     AC_SEARCH_LIBS([timer_settime], [rt posix4],
                    [test "$ac_cv_search_timer_settime" = "none required" ||
                     LIB_TIMER_TIME=$ac_cv_search_timer_settime])
@@ -40,5 +44,6 @@ AC_DEFUN([gl_TIMER_TIME],
          ],
          [LIB_TIMER_TIME="$LIB_TIMER_TIME $LIBPMULTITHREAD"])])
     AC_CHECK_FUNCS([timer_settime])
-  LIBS=$gl_saved_libs
+    LIBS=$gl_saved_libs
+  ])
 ])
diff --git a/m4/unistd_h.m4 b/m4/unistd_h.m4
index 0f26fb908d3..0ce4ea4511f 100644
--- a/m4/unistd_h.m4
+++ b/m4/unistd_h.m4
@@ -1,4 +1,4 @@
-# unistd_h.m4 serial 85
+# unistd_h.m4 serial 89
 dnl Copyright (C) 2006-2021 Free Software Foundation, Inc.
 dnl This file is free software; the Free Software Foundation
 dnl gives unlimited permission to copy and/or distribute it,
@@ -6,10 +6,10 @@ dnl with or without modifications, as long as this notice is preserved.
 
 dnl Written by Simon Josefsson, Bruno Haible.
 
-AC_DEFUN([gl_UNISTD_H],
+AC_DEFUN_ONCE([gl_UNISTD_H],
 [
-  dnl Use AC_REQUIRE here, so that the default behavior below is expanded
-  dnl once only, before all statements that occur in other macros.
+  dnl Ensure to expand the default settings once only, before all statements
+  dnl that occur in other macros.
   AC_REQUIRE([gl_UNISTD_H_DEFAULTS])
 
   gl_CHECK_NEXT_HEADERS([unistd.h])
@@ -59,100 +59,116 @@ AC_DEFUN([gl_UNISTD_H],
   fi
 ])
 
+# gl_UNISTD_MODULE_INDICATOR([modulename])
+# sets the shell variable that indicates the presence of the given module
+# to a C preprocessor expression that will evaluate to 1.
+# This macro invocation must not occur in macros that are AC_REQUIREd.
 AC_DEFUN([gl_UNISTD_MODULE_INDICATOR],
 [
-  dnl Use AC_REQUIRE here, so that the default settings are expanded once only.
-  AC_REQUIRE([gl_UNISTD_H_DEFAULTS])
+  dnl Ensure to expand the default settings once only.
+  gl_UNISTD_H_REQUIRE_DEFAULTS
   gl_MODULE_INDICATOR_SET_VARIABLE([$1])
   dnl Define it also as a C macro, for the benefit of the unit tests.
   gl_MODULE_INDICATOR_FOR_TESTS([$1])
 ])
 
+# Initializes the default values for AC_SUBSTed shell variables.
+# This macro must not be AC_REQUIREd.  It must only be invoked, and only
+# outside of macros or in macros that are not AC_REQUIREd.
+AC_DEFUN([gl_UNISTD_H_REQUIRE_DEFAULTS],
+[
+  m4_defun(GL_MODULE_INDICATOR_PREFIX[_UNISTD_H_MODULE_INDICATOR_DEFAULTS], [
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_ACCESS])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_CHDIR])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_CHOWN])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_CLOSE])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_COPY_FILE_RANGE])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_DUP])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_DUP2])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_DUP3])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_ENVIRON])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_EUIDACCESS])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_EXECL])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_EXECLE])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_EXECLP])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_EXECV])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_EXECVE])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_EXECVP])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_EXECVPE])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_FACCESSAT])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_FCHDIR])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_FCHOWNAT])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_FDATASYNC])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_FSYNC])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_FTRUNCATE])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_GETCWD])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_GETDOMAINNAME])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_GETDTABLESIZE])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_GETENTROPY])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_GETGROUPS])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_GETHOSTNAME])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_GETLOGIN])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_GETLOGIN_R])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_GETOPT_POSIX])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_GETPAGESIZE])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_GETPASS])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_GETUSERSHELL])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_GROUP_MEMBER])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_ISATTY])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_LCHOWN])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_LINK])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_LINKAT])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_LSEEK])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_PIPE])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_PIPE2])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_PREAD])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_PWRITE])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_READ])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_READLINK])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_READLINKAT])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_RMDIR])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_SETHOSTNAME])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_SLEEP])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_SYMLINK])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_SYMLINKAT])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_TRUNCATE])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_TTYNAME_R])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_UNISTD_H_GETOPT])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_UNISTD_H_NONBLOCKING])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_UNISTD_H_SIGPIPE])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_UNLINK])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_UNLINKAT])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_USLEEP])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_WRITE])
+    dnl Support Microsoft deprecated alias function names by default.
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_MDA_ACCESS], [1])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_MDA_CHDIR], [1])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_MDA_CLOSE], [1])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_MDA_DUP], [1])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_MDA_DUP2], [1])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_MDA_EXECL], [1])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_MDA_EXECLE], [1])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_MDA_EXECLP], [1])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_MDA_EXECV], [1])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_MDA_EXECVE], [1])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_MDA_EXECVP], [1])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_MDA_EXECVPE], [1])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_MDA_GETCWD], [1])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_MDA_GETPID], [1])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_MDA_ISATTY], [1])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_MDA_LSEEK], [1])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_MDA_READ], [1])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_MDA_RMDIR], [1])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_MDA_SWAB], [1])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_MDA_UNLINK], [1])
+    gl_MODULE_INDICATOR_INIT_VARIABLE([GNULIB_MDA_WRITE], [1])
+  ])
+  m4_require(GL_MODULE_INDICATOR_PREFIX[_UNISTD_H_MODULE_INDICATOR_DEFAULTS])
+  AC_REQUIRE([gl_UNISTD_H_DEFAULTS])
+])
+
 AC_DEFUN([gl_UNISTD_H_DEFAULTS],
 [
-  GNULIB_ACCESS=0;               AC_SUBST([GNULIB_ACCESS])
-  GNULIB_CHDIR=0;                AC_SUBST([GNULIB_CHDIR])
-  GNULIB_CHOWN=0;                AC_SUBST([GNULIB_CHOWN])
-  GNULIB_CLOSE=0;                AC_SUBST([GNULIB_CLOSE])
-  GNULIB_COPY_FILE_RANGE=0;      AC_SUBST([GNULIB_COPY_FILE_RANGE])
-  GNULIB_DUP=0;                  AC_SUBST([GNULIB_DUP])
-  GNULIB_DUP2=0;                 AC_SUBST([GNULIB_DUP2])
-  GNULIB_DUP3=0;                 AC_SUBST([GNULIB_DUP3])
-  GNULIB_ENVIRON=0;              AC_SUBST([GNULIB_ENVIRON])
-  GNULIB_EUIDACCESS=0;           AC_SUBST([GNULIB_EUIDACCESS])
-  GNULIB_EXECL=0;                AC_SUBST([GNULIB_EXECL])
-  GNULIB_EXECLE=0;               AC_SUBST([GNULIB_EXECLE])
-  GNULIB_EXECLP=0;               AC_SUBST([GNULIB_EXECLP])
-  GNULIB_EXECV=0;                AC_SUBST([GNULIB_EXECV])
-  GNULIB_EXECVE=0;               AC_SUBST([GNULIB_EXECVE])
-  GNULIB_EXECVP=0;               AC_SUBST([GNULIB_EXECVP])
-  GNULIB_EXECVPE=0;              AC_SUBST([GNULIB_EXECVPE])
-  GNULIB_FACCESSAT=0;            AC_SUBST([GNULIB_FACCESSAT])
-  GNULIB_FCHDIR=0;               AC_SUBST([GNULIB_FCHDIR])
-  GNULIB_FCHOWNAT=0;             AC_SUBST([GNULIB_FCHOWNAT])
-  GNULIB_FDATASYNC=0;            AC_SUBST([GNULIB_FDATASYNC])
-  GNULIB_FSYNC=0;                AC_SUBST([GNULIB_FSYNC])
-  GNULIB_FTRUNCATE=0;            AC_SUBST([GNULIB_FTRUNCATE])
-  GNULIB_GETCWD=0;               AC_SUBST([GNULIB_GETCWD])
-  GNULIB_GETDOMAINNAME=0;        AC_SUBST([GNULIB_GETDOMAINNAME])
-  GNULIB_GETDTABLESIZE=0;        AC_SUBST([GNULIB_GETDTABLESIZE])
-  GNULIB_GETENTROPY=0;           AC_SUBST([GNULIB_GETENTROPY])
-  GNULIB_GETGROUPS=0;            AC_SUBST([GNULIB_GETGROUPS])
-  GNULIB_GETHOSTNAME=0;          AC_SUBST([GNULIB_GETHOSTNAME])
-  GNULIB_GETLOGIN=0;             AC_SUBST([GNULIB_GETLOGIN])
-  GNULIB_GETLOGIN_R=0;           AC_SUBST([GNULIB_GETLOGIN_R])
-  GNULIB_GETOPT_POSIX=0;         AC_SUBST([GNULIB_GETOPT_POSIX])
-  GNULIB_GETPAGESIZE=0;          AC_SUBST([GNULIB_GETPAGESIZE])
-  GNULIB_GETPASS=0;              AC_SUBST([GNULIB_GETPASS])
-  GNULIB_GETUSERSHELL=0;         AC_SUBST([GNULIB_GETUSERSHELL])
-  GNULIB_GROUP_MEMBER=0;         AC_SUBST([GNULIB_GROUP_MEMBER])
-  GNULIB_ISATTY=0;               AC_SUBST([GNULIB_ISATTY])
-  GNULIB_LCHOWN=0;               AC_SUBST([GNULIB_LCHOWN])
-  GNULIB_LINK=0;                 AC_SUBST([GNULIB_LINK])
-  GNULIB_LINKAT=0;               AC_SUBST([GNULIB_LINKAT])
-  GNULIB_LSEEK=0;                AC_SUBST([GNULIB_LSEEK])
-  GNULIB_PIPE=0;                 AC_SUBST([GNULIB_PIPE])
-  GNULIB_PIPE2=0;                AC_SUBST([GNULIB_PIPE2])
-  GNULIB_PREAD=0;                AC_SUBST([GNULIB_PREAD])
-  GNULIB_PWRITE=0;               AC_SUBST([GNULIB_PWRITE])
-  GNULIB_READ=0;                 AC_SUBST([GNULIB_READ])
-  GNULIB_READLINK=0;             AC_SUBST([GNULIB_READLINK])
-  GNULIB_READLINKAT=0;           AC_SUBST([GNULIB_READLINKAT])
-  GNULIB_RMDIR=0;                AC_SUBST([GNULIB_RMDIR])
-  GNULIB_SETHOSTNAME=0;          AC_SUBST([GNULIB_SETHOSTNAME])
-  GNULIB_SLEEP=0;                AC_SUBST([GNULIB_SLEEP])
-  GNULIB_SYMLINK=0;              AC_SUBST([GNULIB_SYMLINK])
-  GNULIB_SYMLINKAT=0;            AC_SUBST([GNULIB_SYMLINKAT])
-  GNULIB_TRUNCATE=0;             AC_SUBST([GNULIB_TRUNCATE])
-  GNULIB_TTYNAME_R=0;            AC_SUBST([GNULIB_TTYNAME_R])
-  GNULIB_UNISTD_H_NONBLOCKING=0; AC_SUBST([GNULIB_UNISTD_H_NONBLOCKING])
-  GNULIB_UNISTD_H_SIGPIPE=0;     AC_SUBST([GNULIB_UNISTD_H_SIGPIPE])
-  GNULIB_UNLINK=0;               AC_SUBST([GNULIB_UNLINK])
-  GNULIB_UNLINKAT=0;             AC_SUBST([GNULIB_UNLINKAT])
-  GNULIB_USLEEP=0;               AC_SUBST([GNULIB_USLEEP])
-  GNULIB_WRITE=0;                AC_SUBST([GNULIB_WRITE])
-  dnl Support Microsoft deprecated alias function names by default.
-  GNULIB_MDA_ACCESS=1;           AC_SUBST([GNULIB_MDA_ACCESS])
-  GNULIB_MDA_CHDIR=1;            AC_SUBST([GNULIB_MDA_CHDIR])
-  GNULIB_MDA_CLOSE=1;            AC_SUBST([GNULIB_MDA_CLOSE])
-  GNULIB_MDA_DUP=1;              AC_SUBST([GNULIB_MDA_DUP])
-  GNULIB_MDA_DUP2=1;             AC_SUBST([GNULIB_MDA_DUP2])
-  GNULIB_MDA_EXECL=1;            AC_SUBST([GNULIB_MDA_EXECL])
-  GNULIB_MDA_EXECLE=1;           AC_SUBST([GNULIB_MDA_EXECLE])
-  GNULIB_MDA_EXECLP=1;           AC_SUBST([GNULIB_MDA_EXECLP])
-  GNULIB_MDA_EXECV=1;            AC_SUBST([GNULIB_MDA_EXECV])
-  GNULIB_MDA_EXECVE=1;           AC_SUBST([GNULIB_MDA_EXECVE])
-  GNULIB_MDA_EXECVP=1;           AC_SUBST([GNULIB_MDA_EXECVP])
-  GNULIB_MDA_EXECVPE=1;          AC_SUBST([GNULIB_MDA_EXECVPE])
-  GNULIB_MDA_GETCWD=1;           AC_SUBST([GNULIB_MDA_GETCWD])
-  GNULIB_MDA_GETPID=1;           AC_SUBST([GNULIB_MDA_GETPID])
-  GNULIB_MDA_ISATTY=1;           AC_SUBST([GNULIB_MDA_ISATTY])
-  GNULIB_MDA_LSEEK=1;            AC_SUBST([GNULIB_MDA_LSEEK])
-  GNULIB_MDA_READ=1;             AC_SUBST([GNULIB_MDA_READ])
-  GNULIB_MDA_RMDIR=1;            AC_SUBST([GNULIB_MDA_RMDIR])
-  GNULIB_MDA_SWAB=1;             AC_SUBST([GNULIB_MDA_SWAB])
-  GNULIB_MDA_UNLINK=1;           AC_SUBST([GNULIB_MDA_UNLINK])
-  GNULIB_MDA_WRITE=1;            AC_SUBST([GNULIB_MDA_WRITE])
   dnl Assume proper GNU behavior unless another module says otherwise.
   HAVE_CHOWN=1;           AC_SUBST([HAVE_CHOWN])
   HAVE_COPY_FILE_RANGE=1; AC_SUBST([HAVE_COPY_FILE_RANGE])
diff --git a/m4/unlocked-io.m4 b/m4/unlocked-io.m4
index a2dc8a144af..b689020ff49 100644
--- a/m4/unlocked-io.m4
+++ b/m4/unlocked-io.m4
@@ -1,4 +1,4 @@
-# unlocked-io.m4 serial 15
+# unlocked-io.m4 serial 16
 
 # Copyright (C) 1998-2006, 2009-2021 Free Software Foundation, Inc.
 #
@@ -16,11 +16,6 @@ dnl on Solaris 2.6).
 
 AC_DEFUN([gl_FUNC_GLIBC_UNLOCKED_IO],
 [
-  AC_DEFINE([USE_UNLOCKED_IO], [1],
-    [Define to 1 if you want getc etc. to use unlocked I/O if available.
-     Unlocked I/O can improve performance in unithreaded apps,
-     but it is not safe for multithreaded apps.])
-
   dnl Persuade glibc and Solaris <stdio.h> to declare
   dnl fgets_unlocked(), fputs_unlocked() etc.
   AC_REQUIRE([gl_USE_SYSTEM_EXTENSIONS])
diff --git a/m4/year2038.m4 b/m4/year2038.m4
new file mode 100644
index 00000000000..da0f8d73030
--- /dev/null
+++ b/m4/year2038.m4
@@ -0,0 +1,124 @@
+# year2038.m4 serial 7
+dnl Copyright (C) 2017-2021 Free Software Foundation, Inc.
+dnl This file is free software; the Free Software Foundation
+dnl gives unlimited permission to copy and/or distribute it,
+dnl with or without modifications, as long as this notice is preserved.
+
+dnl Attempt to ensure that 'time_t' can go past the year 2038 and that
+dnl the functions 'time', 'stat', etc. work with post-2038 timestamps.
+
+AC_DEFUN([gl_YEAR2038_EARLY],
+[
+  AC_REQUIRE([AC_CANONICAL_HOST])
+  case "$host_os" in
+    mingw*)
+      AC_DEFINE([__MINGW_USE_VC2005_COMPAT], [1],
+        [For 64-bit time_t on 32-bit mingw.])
+      ;;
+  esac
+])
+
+# gl_YEAR2038_TEST_INCLUDES
+# -------------------------
+AC_DEFUN([gl_YEAR2038_TEST_INCLUDES],
+[[
+  #include <time.h>
+  /* Check that time_t can represent 2**32 - 1 correctly.  */
+  #define LARGE_TIME_T \\
+    ((time_t) (((time_t) 1 << 30) - 1 + 3 * ((time_t) 1 << 30)))
+  int verify_time_t_range[(LARGE_TIME_T / 65537 == 65535
+                           && LARGE_TIME_T % 65537 == 0)
+                          ? 1 : -1];
+]])
+
+# gl_YEAR2038_BODY(REQUIRE-YEAR2038-SAFE)
+-----------------------------------------
+AC_DEFUN([gl_YEAR2038_BODY],
+[
+ AC_ARG_ENABLE([year2038],
+   [  --disable-year2038      omit support for timestamps past the year 2038])
+ AS_IF([test "$enable_year2038" != no],
+ [
+  dnl On many systems, time_t is already a 64-bit type.
+  dnl On those systems where time_t is still 32-bit, it requires kernel
+  dnl and libc support to make it 64-bit. For glibc 2.34 and later on Linux,
+  dnl defining _TIME_BITS=64 and _FILE_OFFSET_BITS=64 is needed on x86 and ARM.
+  dnl
+  dnl On native Windows, the system include files define types __time32_t
+  dnl and __time64_t. By default, time_t is an alias of
+  dnl   - __time32_t on 32-bit mingw,
+  dnl   - __time64_t on 64-bit mingw and on MSVC (since MSVC 8).
+  dnl But when compiling with -D__MINGW_USE_VC2005_COMPAT, time_t is an
+  dnl alias of __time64_t.
+  dnl And when compiling with -D_USE_32BIT_TIME_T, time_t is an alias of
+  dnl __time32_t.
+  AC_CACHE_CHECK([for time_t past the year 2038], [gl_cv_type_time_t_y2038],
+    [AC_COMPILE_IFELSE(
+       [AC_LANG_SOURCE([gl_YEAR2038_TEST_INCLUDES])],
+       [gl_cv_type_time_t_y2038=yes], [gl_cv_type_time_t_y2038=no])
+    ])
+  if test "$gl_cv_type_time_t_y2038" = no; then
+    AC_CACHE_CHECK([for 64-bit time_t with _TIME_BITS=64],
+      [gl_cv_type_time_t_bits_macro],
+      [AC_COMPILE_IFELSE(
+         [AC_LANG_SOURCE([[#define _TIME_BITS 64
+                           #define _FILE_OFFSET_BITS 64
+                           ]gl_YEAR2038_TEST_INCLUDES])],
+         [gl_cv_type_time_t_bits_macro=yes],
+         [gl_cv_type_time_t_bits_macro=no])
+      ])
+    if test "$gl_cv_type_time_t_bits_macro" = yes; then
+      AC_DEFINE([_TIME_BITS], [64],
+        [Number of bits in a timestamp, on hosts where this is settable.])
+      dnl AC_SYS_LARGFILE also defines this; it's OK if we do too.
+      AC_DEFINE([_FILE_OFFSET_BITS], [64],
+        [Number of bits in a file offset, on hosts where this is settable.])
+      gl_cv_type_time_t_y2038=yes
+    fi
+  fi
+  if test $gl_cv_type_time_t_y2038 = no; then
+    AC_COMPILE_IFELSE(
+      [AC_LANG_SOURCE(
+         [[#ifdef _USE_32BIT_TIME_T
+             int ok;
+           #else
+             error fail
+           #endif
+         ]])],
+      [AC_MSG_FAILURE(
+         [The 'time_t' type stops working after January 2038.
+          Remove _USE_32BIT_TIME_T from the compiler flags.])],
+      [# If not cross-compiling and $1 says we should check,
+       # and 'touch' works with a large timestamp, then evidently wider time_t
+       # is desired and supported, so fail and ask the builder to fix the
+       # problem.  Otherwise, just warn the builder.
+       m4_ifval([$1],
+         [if test $cross_compiling = no \
+             && TZ=UTC0 touch -t 210602070628.15 conftest.time 2>/dev/null; then
+            case `TZ=UTC0 LC_ALL=C ls -l conftest.time 2>/dev/null` in
+              *'Feb  7  2106'* | *'Feb  7 17:10'*)
+                AC_MSG_FAILURE(
+                  [The 'time_t' type stops working after January 2038,
+                   and your system appears to support a wider 'time_t'.
+                   Try configuring with 'CC="${CC} -m64"'.
+                   To build with a 32-bit time_t anyway (not recommended),
+                   configure with '--disable-year2038'.]);;
+            esac
+            rm -f conftest.time
+          fi])
+       if test "$gl_warned_about_y2038" != yes; then
+         AC_MSG_WARN(
+           [The 'time_t' type stops working after January 2038,
+            and this package needs a wider 'time_t' type
+            if there is any way to access timestamps after that.
+            Configure with 'CC="${CC} -m64"' perhaps?])
+         gl_warned_about_y2038=yes
+       fi
+      ])
+  fi])
+])
+
+AC_DEFUN([gl_YEAR2038],
+[
+  gl_YEAR2038_BODY([require-year2038-safe])
+])