Update Gnulib.

All changes in this commit are autogenerated by running
admin/merge-gnulib.

21 files changed, 481 insertions, 196 deletions

diff --git a/m4/alloca.m4 b/m4/alloca.m4
index d8414896308..e3c377c9e2c 100644
--- a/m4/alloca.m4
+++ b/m4/alloca.m4
@@ -1,4 +1,4 @@
-# alloca.m4 serial 18
+# alloca.m4 serial 20
 dnl Copyright (C) 2002-2004, 2006-2007, 2009-2020 Free Software Foundation,
 dnl Inc.
 dnl This file is free software; the Free Software Foundation
@@ -104,5 +104,5 @@ AH_VERBATIM([STACK_DIRECTION],
         STACK_DIRECTION = 0 => direction of growth unknown */
 #undef STACK_DIRECTION])dnl
 AC_DEFINE_UNQUOTED(STACK_DIRECTION, $ac_cv_c_stack_direction)
-])
+])# _AC_LIBOBJ_ALLOCA
 ])
diff --git a/m4/extensions.m4 b/m4/extensions.m4
index d7c95effdac..44be1d15cbf 100644
--- a/m4/extensions.m4
+++ b/m4/extensions.m4
@@ -1,4 +1,4 @@
-# serial 18  -*- Autoconf -*-
+# serial 21  -*- Autoconf -*-
 # Enable extensions on systems that normally disable them.
 
 # Copyright (C) 2003, 2006-2020 Free Software Foundation, Inc.
@@ -6,9 +6,14 @@
 # gives unlimited permission to copy and/or distribute it,
 # with or without modifications, as long as this notice is preserved.
 
+dnl Define to empty for the benefit of Autoconf 2.69 and earlier, so that
+dnl AC_USE_SYSTEM_EXTENSIONS (below) can be used unchanged from Autoconf 2.70+.
+m4_ifndef([AC_CHECK_INCLUDES_DEFAULT],
+  [AC_DEFUN([AC_CHECK_INCLUDES_DEFAULT], [])])
+
 # This definition of AC_USE_SYSTEM_EXTENSIONS is stolen from git
 # Autoconf.  Perhaps we can remove this once we can assume Autoconf
-# 2.70 or later everywhere, but since Autoconf mutates rapidly
+# is recent-enough everywhere, but since Autoconf mutates rapidly
 # enough in this area it's likely we'll need to redefine
 # AC_USE_SYSTEM_EXTENSIONS for quite some time.
 
@@ -26,36 +31,27 @@
 #      its dependencies. This will ensure that the gl_USE_SYSTEM_EXTENSIONS
 #      invocation occurs in gl_EARLY, not in gl_INIT.
 
+m4_version_prereq([2.70.1], [], [
+
 # AC_USE_SYSTEM_EXTENSIONS
 # ------------------------
 # Enable extensions on systems that normally disable them,
 # typically due to standards-conformance issues.
-#
-# Remember that #undef in AH_VERBATIM gets replaced with #define by
-# AC_DEFINE.  The goal here is to define all known feature-enabling
-# macros, then, if reports of conflicts are made, disable macros that
-# cause problems on some platforms (such as __EXTENSIONS__).
+# We unconditionally define as many of the known feature-enabling
+# as possible, reserving conditional behavior for macros that are
+# known to cause problems on some platforms (such as __EXTENSIONS__).
 AC_DEFUN_ONCE([AC_USE_SYSTEM_EXTENSIONS],
-[AC_BEFORE([$0], [AC_COMPILE_IFELSE])dnl
+[AC_BEFORE([$0], [AC_PREPROC_IFELSE])dnl
+AC_BEFORE([$0], [AC_COMPILE_IFELSE])dnl
+AC_BEFORE([$0], [AC_LINK_IFELSE])dnl
 AC_BEFORE([$0], [AC_RUN_IFELSE])dnl
-
-  AC_CHECK_HEADER([minix/config.h], [MINIX=yes], [MINIX=])
-  if test "$MINIX" = yes; then
-    AC_DEFINE([_POSIX_SOURCE], [1],
-      [Define to 1 if you need to in order for 'stat' and other
-       things to work.])
-    AC_DEFINE([_POSIX_1_SOURCE], [2],
-      [Define to 2 if the system does not provide POSIX.1 features
-       except with this defined.])
-    AC_DEFINE([_MINIX], [1],
-      [Define to 1 if on MINIX.])
-    AC_DEFINE([_NETBSD_SOURCE], [1],
-      [Define to 1 to make NetBSD features available.  MINIX 3 needs this.])
-  fi
-
+AC_BEFORE([$0], [AC_CHECK_INCLUDES_DEFAULT])dnl
+dnl #undef in AH_VERBATIM gets replaced with #define by AC_DEFINE.
 dnl Use a different key than __EXTENSIONS__, as that name broke existing
 dnl configure.ac when using autoheader 2.62.
-  AH_VERBATIM([USE_SYSTEM_EXTENSIONS],
+dnl The macros below are in alphabetical order ignoring leading _ or __
+dnl prefixes.
+AH_VERBATIM([USE_SYSTEM_EXTENSIONS],
 [/* Enable extensions on AIX 3, Interix.  */
 #ifndef _ALL_SOURCE
 # undef _ALL_SOURCE
@@ -64,19 +60,44 @@ dnl configure.ac when using autoheader 2.62.
 #ifndef _DARWIN_C_SOURCE
 # undef _DARWIN_C_SOURCE
 #endif
+/* Enable general extensions on Solaris.  */
+#ifndef __EXTENSIONS__
+# undef __EXTENSIONS__
+#endif
 /* Enable GNU extensions on systems that have them.  */
 #ifndef _GNU_SOURCE
 # undef _GNU_SOURCE
 #endif
-/* Enable NetBSD extensions on NetBSD.  */
+/* Enable X/Open compliant socket functions that do not require linking
+   with -lxnet on HP-UX 11.11.  */
+#ifndef _HPUX_ALT_XOPEN_SOCKET_API
+# undef _HPUX_ALT_XOPEN_SOCKET_API
+#endif
+/* Identify the host operating system as Minix.
+   This macro does not affect the system headers' behavior.
+   A future release of Autoconf may stop defining this macro.  */
+#ifndef _MINIX
+# undef _MINIX
+#endif
+/* Enable general extensions on NetBSD.
+   Enable NetBSD compatibility extensions on Minix.  */
 #ifndef _NETBSD_SOURCE
 # undef _NETBSD_SOURCE
 #endif
-/* Enable OpenBSD extensions on NetBSD.  */
+/* Enable OpenBSD compatibility extensions on NetBSD.
+   Oddly enough, this does nothing on OpenBSD.  */
 #ifndef _OPENBSD_SOURCE
 # undef _OPENBSD_SOURCE
 #endif
-/* Enable threading extensions on Solaris.  */
+/* Define to 1 if needed for POSIX-compatible behavior.  */
+#ifndef _POSIX_SOURCE
+# undef _POSIX_SOURCE
+#endif
+/* Define to 2 if needed for POSIX-compatible behavior.  */
+#ifndef _POSIX_1_SOURCE
+# undef _POSIX_1_SOURCE
+#endif
+/* Enable POSIX-compatible threading on Solaris.  */
 #ifndef _POSIX_PTHREAD_SEMANTICS
 # undef _POSIX_PTHREAD_SEMANTICS
 #endif
@@ -112,22 +133,19 @@ dnl configure.ac when using autoheader 2.62.
 #ifndef _TANDEM_SOURCE
 # undef _TANDEM_SOURCE
 #endif
-/* Enable X/Open extensions if necessary.  HP-UX 11.11 defines
-   mbstate_t only if _XOPEN_SOURCE is defined to 500, regardless of
-   whether compiling with -Ae or -D_HPUX_SOURCE=1.  */
+/* Enable X/Open extensions.  Define to 500 only if necessary
+   to make mbstate_t available.  */
 #ifndef _XOPEN_SOURCE
 # undef _XOPEN_SOURCE
 #endif
-/* Enable X/Open compliant socket functions that do not require linking
-   with -lxnet on HP-UX 11.11.  */
-#ifndef _HPUX_ALT_XOPEN_SOCKET_API
-# undef _HPUX_ALT_XOPEN_SOCKET_API
-#endif
-/* Enable general extensions on Solaris.  */
-#ifndef __EXTENSIONS__
-# undef __EXTENSIONS__
-#endif
-])
+])dnl
+
+  AC_REQUIRE([AC_CHECK_INCLUDES_DEFAULT])dnl
+  _AC_CHECK_HEADER_ONCE([wchar.h])
+  _AC_CHECK_HEADER_ONCE([minix/config.h])
+
+dnl Defining __EXTENSIONS__ may break the system headers on some systems.
+dnl (FIXME: Which ones?)
   AC_CACHE_CHECK([whether it is safe to define __EXTENSIONS__],
     [ac_cv_safe_to_define___extensions__],
     [AC_COMPILE_IFELSE(
@@ -136,11 +154,33 @@ dnl configure.ac when using autoheader 2.62.
           ]AC_INCLUDES_DEFAULT])],
        [ac_cv_safe_to_define___extensions__=yes],
        [ac_cv_safe_to_define___extensions__=no])])
-  test $ac_cv_safe_to_define___extensions__ = yes &&
-    AC_DEFINE([__EXTENSIONS__])
+
+dnl HP-UX 11.11 defines mbstate_t only if _XOPEN_SOURCE is defined to
+dnl 500, regardless of whether compiling with -Ae or -D_HPUX_SOURCE=1.
+dnl But defining _XOPEN_SOURCE may turn *off* extensions on platforms
+dnl not covered by turn-on-extensions macros (notably Dragonfly, Free,
+dnl and OpenBSD, which don't have any equivalent of _NETBSD_SOURCE) so
+dnl it should only be defined when necessary.
+  AC_CACHE_CHECK([whether _XOPEN_SOURCE should be defined],
+    [ac_cv_should_define__xopen_source],
+    [ac_cv_should_define__xopen_source=no
+    AS_IF([test $ac_cv_header_wchar_h = yes],
+      [AC_COMPILE_IFELSE(
+        [AC_LANG_PROGRAM([[
+          #include <wchar.h>
+          mbstate_t x;]])],
+        [],
+        [AC_COMPILE_IFELSE(
+          [AC_LANG_PROGRAM([[
+            #define _XOPEN_SOURCE 500
+            #include <wchar.h>
+            mbstate_t x;]])],
+          [ac_cv_should_define__xopen_source=yes])])])])
+
   AC_DEFINE([_ALL_SOURCE])
   AC_DEFINE([_DARWIN_C_SOURCE])
   AC_DEFINE([_GNU_SOURCE])
+  AC_DEFINE([_HPUX_ALT_XOPEN_SOCKET_API])
   AC_DEFINE([_NETBSD_SOURCE])
   AC_DEFINE([_OPENBSD_SOURCE])
   AC_DEFINE([_POSIX_PTHREAD_SEMANTICS])
@@ -152,24 +192,18 @@ dnl configure.ac when using autoheader 2.62.
   AC_DEFINE([__STDC_WANT_LIB_EXT2__])
   AC_DEFINE([__STDC_WANT_MATH_SPEC_FUNCS__])
   AC_DEFINE([_TANDEM_SOURCE])
-  AC_CACHE_CHECK([whether _XOPEN_SOURCE should be defined],
-    [ac_cv_should_define__xopen_source],
-    [ac_cv_should_define__xopen_source=no
-     AC_COMPILE_IFELSE(
-       [AC_LANG_PROGRAM([[
-          #include <wchar.h>
-          mbstate_t x;]])],
-       [],
-       [AC_COMPILE_IFELSE(
-          [AC_LANG_PROGRAM([[
-             #define _XOPEN_SOURCE 500
-             #include <wchar.h>
-             mbstate_t x;]])],
-          [ac_cv_should_define__xopen_source=yes])])])
-  test $ac_cv_should_define__xopen_source = yes &&
-    AC_DEFINE([_XOPEN_SOURCE], [500])
-  AC_DEFINE([_HPUX_ALT_XOPEN_SOCKET_API])
+  AS_IF([test $ac_cv_header_minix_config_h = yes],
+    [MINIX=yes
+    AC_DEFINE([_MINIX])
+    AC_DEFINE([_POSIX_SOURCE])
+    AC_DEFINE([_POSIX_1_SOURCE], [2])],
+    [MINIX=])
+  AS_IF([test $ac_cv_safe_to_define___extensions__ = yes],
+    [AC_DEFINE([__EXTENSIONS__])])
+  AS_IF([test $ac_cv_should_define__xopen_source = yes],
+    [AC_DEFINE([_XOPEN_SOURCE], [500])])
 ])# AC_USE_SYSTEM_EXTENSIONS
+])
 
 # gl_USE_SYSTEM_EXTENSIONS
 # ------------------------
@@ -177,13 +211,5 @@ dnl configure.ac when using autoheader 2.62.
 # typically due to standards-conformance issues.
 AC_DEFUN_ONCE([gl_USE_SYSTEM_EXTENSIONS],
 [
-  dnl Require this macro before AC_USE_SYSTEM_EXTENSIONS.
-  dnl gnulib does not need it. But if it gets required by third-party macros
-  dnl after AC_USE_SYSTEM_EXTENSIONS is required, autoconf 2.62..2.63 emit a
-  dnl warning: "AC_COMPILE_IFELSE was called before AC_USE_SYSTEM_EXTENSIONS".
-  dnl Note: We can do this only for one of the macros AC_AIX, AC_GNU_SOURCE,
-  dnl AC_MINIX. If people still use AC_AIX or AC_MINIX, they are out of luck.
-  AC_REQUIRE([AC_GNU_SOURCE])
-
   AC_REQUIRE([AC_USE_SYSTEM_EXTENSIONS])
 ])
diff --git a/m4/fcntl.m4 b/m4/fcntl.m4
index ea24f3d64ef..547ff40b804 100644
--- a/m4/fcntl.m4
+++ b/m4/fcntl.m4
@@ -1,4 +1,4 @@
-# fcntl.m4 serial 10
+# fcntl.m4 serial 11
 dnl Copyright (C) 2009-2020 Free Software Foundation, Inc.
 dnl This file is free software; the Free Software Foundation
 dnl gives unlimited permission to copy and/or distribute it,
@@ -81,15 +81,29 @@ AC_DEFUN([gl_FUNC_FCNTL],
           behavior does not match POSIX]) ;;
     esac
 
-    dnl Many systems lack F_DUPFD_CLOEXEC
+    dnl Many systems lack F_DUPFD_CLOEXEC.
+    dnl NetBSD 9.0 declares F_DUPFD_CLOEXEC but it works only like F_DUPFD.
     AC_CACHE_CHECK([whether fcntl understands F_DUPFD_CLOEXEC],
       [gl_cv_func_fcntl_f_dupfd_cloexec],
-      [AC_COMPILE_IFELSE([AC_LANG_PROGRAM([[
-#include <fcntl.h>
-#ifndef F_DUPFD_CLOEXEC
-choke me
-#endif
-         ]])],
+      [AC_RUN_IFELSE(
+         [AC_LANG_SOURCE(
+            [[#include <fcntl.h>
+              #include <unistd.h>
+              int main (int argc, char *argv[])
+              {
+                if (argc == 1)
+                  /* parent process */
+                  {
+                    if (fcntl (1, F_DUPFD_CLOEXEC, 10) < 0)
+                      return 1;
+                    return execl ("./conftest", "./conftest", "child", NULL);
+                  }
+                else
+                  /* child process */
+                  return (fcntl (10, F_GETFL) < 0 ? 0 : 42);
+              }
+            ]])
+         ],
          [AC_COMPILE_IFELSE([AC_LANG_PROGRAM([[
 #ifdef __linux__
 /* The Linux kernel only added F_DUPFD_CLOEXEC in 2.6.24, so we always replace
@@ -98,12 +112,22 @@ choke me
 #endif
            ]])],
            [gl_cv_func_fcntl_f_dupfd_cloexec=yes],
-           [gl_cv_func_fcntl_f_dupfd_cloexec="needs runtime check"])],
-         [gl_cv_func_fcntl_f_dupfd_cloexec=no])])
-    if test "$gl_cv_func_fcntl_f_dupfd_cloexec" != yes; then
-      gl_REPLACE_FCNTL
-      dnl No witness macro needed for this bug.
-    fi
+           [gl_cv_func_fcntl_f_dupfd_cloexec="needs runtime check"])
+         ],
+         [gl_cv_func_fcntl_f_dupfd_cloexec=no],
+         [case "$host_os" in
+                     # Guess no on NetBSD.
+            netbsd*) gl_cv_func_fcntl_f_dupfd_cloexec="guessing no" ;;
+            *)       gl_cv_func_fcntl_f_dupfd_cloexec="$gl_cross_guess_normal" ;;
+          esac
+         ])
+      ])
+    case "$gl_cv_func_fcntl_f_dupfd_cloexec" in
+      *yes) ;;
+      *)    gl_REPLACE_FCNTL
+            dnl No witness macro needed for this bug.
+            ;;
+    esac
   fi
   dnl Replace fcntl() for supporting the gnulib-defined fchdir() function,
   dnl to keep fchdir's bookkeeping up-to-date.
diff --git a/m4/filemode.m4 b/m4/filemode.m4
index 5aaaa1a167d..8bbfcdbafe0 100644
--- a/m4/filemode.m4
+++ b/m4/filemode.m4
@@ -1,4 +1,4 @@
-# filemode.m4 serial 8
+# filemode.m4 serial 9
 dnl Copyright (C) 2002, 2005-2006, 2009-2020 Free Software Foundation, Inc.
 dnl This file is free software; the Free Software Foundation
 dnl gives unlimited permission to copy and/or distribute it,
@@ -6,6 +6,5 @@ dnl with or without modifications, as long as this notice is preserved.
 
 AC_DEFUN([gl_FILEMODE],
 [
-  AC_REQUIRE([AC_STRUCT_ST_DM_MODE])
   AC_CHECK_DECLS_ONCE([strmode])
 ])
diff --git a/m4/free.m4 b/m4/free.m4
new file mode 100644
index 00000000000..bf9fc31d9b4
--- /dev/null
+++ b/m4/free.m4
@@ -0,0 +1,49 @@
+# free.m4 serial 5
+# Copyright (C) 2003-2005, 2009-2020 Free Software Foundation, Inc.
+# This file is free software; the Free Software Foundation
+# gives unlimited permission to copy and/or distribute it,
+# with or without modifications, as long as this notice is preserved.
+
+# Written by Paul Eggert and Bruno Haible.
+
+AC_DEFUN([gl_FUNC_FREE],
+[
+  AC_REQUIRE([gl_STDLIB_H_DEFAULTS])
+
+  dnl In the next release of POSIX, free must preserve errno.
+  dnl https://www.austingroupbugs.net/view.php?id=385
+  dnl https://sourceware.org/bugzilla/show_bug.cgi?id=17924
+  dnl So far, we know of three platforms that do this:
+  dnl * glibc >= 2.33, thanks to the fix for this bug:
+  dnl   <https://sourceware.org/bugzilla/show_bug.cgi?id=17924>
+  dnl * OpenBSD >= 4.5, thanks to this commit:
+  dnl   <https://cvsweb.openbsd.org/cgi-bin/cvsweb/src/lib/libc/stdlib/malloc.c.diff?r1=1.100&r2=1.101&f=h>
+  dnl * Solaris, because its malloc() implementation is based on brk(),
+  dnl   not mmap(); hence its free() implementation makes no system calls.
+  dnl For other platforms, you can only be sure if they state it in their
+  dnl documentation, or by code inspection of the free() implementation in libc.
+  AC_CACHE_CHECK([whether free is known to preserve errno],
+    [gl_cv_func_free_preserves_errno],
+    [AC_COMPILE_IFELSE(
+       [AC_LANG_PROGRAM(
+          [[#include <stdlib.h>
+          ]],
+          [[#if 2 < __GLIBC__ + (33 <= __GLIBC_MINOR__)
+            #elif defined __OpenBSD__
+            #elif defined __sun
+            #else
+              #error "'free' is not known to preserve errno"
+            #endif
+          ]])],
+       [gl_cv_func_free_preserves_errno=yes],
+       [gl_cv_func_free_preserves_errno=no])
+    ])
+
+  case $gl_cv_func_free_preserves_errno in
+   *yes) ;;
+   *) REPLACE_FREE=1 ;;
+  esac
+])
+
+# Prerequisites of lib/free.c.
+AC_DEFUN([gl_PREREQ_FREE], [:])
diff --git a/m4/fsusage.m4 b/m4/fsusage.m4
index 0bc62066aab..c15cfca4d3e 100644
--- a/m4/fsusage.m4
+++ b/m4/fsusage.m4
@@ -1,4 +1,4 @@
-# serial 34
+# serial 35
 # Obtaining file system usage information.
 
 # Copyright (C) 1997-1998, 2000-2001, 2003-2020 Free Software Foundation, Inc.
@@ -36,7 +36,6 @@ AC_DEFUN([gl_FILE_SYSTEM_USAGE],
   dnl Mac OS X >= 10.5 (32-bit mode).
   AC_REQUIRE([AC_SYS_LARGEFILE])
 
-  AC_MSG_CHECKING([how to get file system space usage])
   ac_fsusage_space=no
 
   # Perform only the link test since it seems there are no variants of the
diff --git a/m4/gnulib-common.m4 b/m4/gnulib-common.m4
index 33e56faa98e..2c0ae9bef40 100644
--- a/m4/gnulib-common.m4
+++ b/m4/gnulib-common.m4
@@ -1,4 +1,4 @@
-# gnulib-common.m4 serial 57
+# gnulib-common.m4 serial 63
 dnl Copyright (C) 2007-2020 Free Software Foundation, Inc.
 dnl This file is free software; the Free Software Foundation
 dnl gives unlimited permission to copy and/or distribute it,
@@ -483,23 +483,17 @@ AC_DEFUN([gl_FEATURES_H],
 # gl_PROG_CC_C99
 # Modifies the value of the shell variable CC in an attempt to make $CC
 # understand ISO C99 source code.
-# This is like AC_PROG_CC_C99, except that
-# - AC_PROG_CC_C99 does not mix well with AC_PROG_CC_STDC
-#   <https://lists.gnu.org/r/bug-gnulib/2011-09/msg00367.html>,
-#   but many more packages use AC_PROG_CC_STDC than AC_PROG_CC_C99
-#   <https://lists.gnu.org/r/bug-gnulib/2011-09/msg00441.html>.
-# Remaining problems:
-# - When AC_PROG_CC_STDC is invoked twice, it adds the C99 enabling options
-#   to CC twice
-#   <https://lists.gnu.org/r/bug-gnulib/2011-09/msg00431.html>.
-# - AC_PROG_CC_STDC is likely to change now that C11 is an ISO standard.
 AC_DEFUN([gl_PROG_CC_C99],
 [
-  dnl Change that version number to the minimum Autoconf version that supports
-  dnl mixing AC_PROG_CC_C99 calls with AC_PROG_CC_STDC calls.
-  m4_version_prereq([9.0],
-    [AC_REQUIRE([AC_PROG_CC_C99])],
-    [AC_REQUIRE([AC_PROG_CC_STDC])])
+  dnl Just use AC_PROG_CC_C99.
+  dnl When AC_PROG_CC_C99 and AC_PROG_CC_STDC are used together, the substituted
+  dnl value of CC will contain the C99 enabling options twice. But this is only
+  dnl a cosmetic problem.
+  dnl With Autoconf >= 2.70, use AC_PROG_CC since it implies AC_PROG_CC_C99;
+  dnl this avoids a "warning: The macro `AC_PROG_CC_C99' is obsolete."
+  m4_version_prereq([2.70],
+    [AC_REQUIRE([AC_PROG_CC])],
+    [AC_REQUIRE([AC_PROG_CC_C99])])
 ])
 
 # gl_PROG_AR_RANLIB
@@ -573,16 +567,16 @@ Amsterdam
 ])
 
 # AC_C_RESTRICT
-# This definition is copied from post-2.69 Autoconf and overrides the
-# AC_C_RESTRICT macro from autoconf 2.60..2.69.  It can be removed
-# once autoconf >= 2.70 can be assumed.  It's painful to check version
-# numbers, and in practice this macro is more up-to-date than Autoconf
-# is, so override Autoconf unconditionally.
+# This definition is copied from post-2.70 Autoconf and overrides the
+# AC_C_RESTRICT macro from autoconf 2.60..2.70.
+m4_version_prereq([2.70.1], [], [
 AC_DEFUN([AC_C_RESTRICT],
 [AC_CACHE_CHECK([for C/C++ restrict keyword], [ac_cv_c_restrict],
   [ac_cv_c_restrict=no
-   # The order here caters to the fact that C++ does not require restrict.
-   for ac_kw in __restrict __restrict__ _Restrict restrict; do
+   # Put '__restrict__' first, to avoid problems with glibc and non-GCC; see:
+   # https://lists.gnu.org/archive/html/bug-autoconf/2016-02/msg00006.html
+   # Put 'restrict' last, because C++ lacks it.
+   for ac_kw in __restrict__ __restrict _Restrict restrict; do
      AC_COMPILE_IFELSE(
       [AC_LANG_PROGRAM(
          [[typedef int *int_ptr;
@@ -602,7 +596,7 @@ AC_DEFUN([AC_C_RESTRICT],
  AH_VERBATIM([restrict],
 [/* Define to the equivalent of the C99 'restrict' keyword, or to
    nothing if this is not supported.  Do not define if restrict is
-   supported directly.  */
+   supported only directly.  */
 #undef restrict
 /* Work around a bug in older versions of Sun C++, which did not
    #define __restrict__ or support _Restrict or __restrict__
@@ -620,6 +614,7 @@ AC_DEFUN([AC_C_RESTRICT],
    *)  AC_DEFINE_UNQUOTED([restrict], [$ac_cv_c_restrict]) ;;
  esac
 ])# AC_C_RESTRICT
+])
 
 # gl_BIGENDIAN
 # is like AC_C_BIGENDIAN, except that it can be AC_REQUIREd.
@@ -630,13 +625,20 @@ AC_DEFUN([gl_BIGENDIAN],
   AC_C_BIGENDIAN
 ])
 
+# A temporary file descriptor.
+# Must be less than 10, because dash 0.5.8 does not support redirections
+# with multi-digit file descriptors.
+m4_define([GL_TMP_FD], 9)
+
 # gl_SILENT(command)
 # executes command, but without the normal configure output.
+# This is useful when you want to invoke AC_CACHE_CHECK (or AC_CHECK_FUNC etc.)
+# inside another AC_CACHE_CHECK.
 AC_DEFUN([gl_SILENT],
 [
-  {
-    $1
-  } AS_MESSAGE_FD>/dev/null
+  exec GL_TMP_FD>&AS_MESSAGE_FD AS_MESSAGE_FD>/dev/null
+  $1
+  exec AS_MESSAGE_FD>&GL_TMP_FD GL_TMP_FD>&-
 ])
 
 # gl_CACHE_VAL_SILENT(cache-id, command-to-set-it)
@@ -646,10 +648,9 @@ AC_DEFUN([gl_SILENT],
 # by an AC_MSG_CHECKING/AC_MSG_RESULT pair.
 AC_DEFUN([gl_CACHE_VAL_SILENT],
 [
-  saved_as_echo_n="$as_echo_n"
-  as_echo_n=':'
-  AC_CACHE_VAL([$1], [$2])
-  as_echo_n="$saved_as_echo_n"
+  gl_SILENT([
+    AC_CACHE_VAL([$1], [$2])
+  ])
 ])
 
 dnl Expands to some code for use in .c programs that, on native Windows, defines
diff --git a/m4/gnulib-comp.m4 b/m4/gnulib-comp.m4
index d2fdbd82e73..beb9817d266 100644
--- a/m4/gnulib-comp.m4
+++ b/m4/gnulib-comp.m4
@@ -94,6 +94,7 @@ AC_DEFUN([gl_EARLY],
   # Code from module fpending:
   # Code from module fpieee:
   AC_REQUIRE([gl_FP_IEEE])
+  # Code from module free-posix:
   # Code from module fstatat:
   # Code from module fsusage:
   # Code from module fsync:
@@ -109,6 +110,7 @@ AC_DEFUN([gl_EARLY],
   # Code from module gettimeofday:
   # Code from module gitlog-to-changelog:
   # Code from module group-member:
+  # Code from module idx:
   # Code from module ieee754-h:
   # Code from module ignore-value:
   # Code from module include_next:
@@ -121,7 +123,6 @@ AC_DEFUN([gl_EARLY],
   # Code from module libgmp:
   # Code from module limits-h:
   # Code from module lstat:
-  # Code from module malloca:
   # Code from module manywarnings:
   # Code from module memmem-simple:
   # Code from module mempcpy:
@@ -140,10 +141,12 @@ AC_DEFUN([gl_EARLY],
   # Code from module pselect:
   # Code from module pthread_sigmask:
   # Code from module qcopy-acl:
+  # Code from module rawmemchr:
   # Code from module readlink:
   # Code from module readlinkat:
   # Code from module regex:
   # Code from module root-uid:
+  # Code from module scratch_buffer:
   # Code from module sig2str:
   # Code from module sigdescr_np:
   # Code from module signal-h:
@@ -508,16 +511,19 @@ AC_DEFUN([gl_INIT],
   gl_gnulib_enabled_cloexec=false
   gl_gnulib_enabled_dirfd=false
   gl_gnulib_enabled_euidaccess=false
+  gl_gnulib_enabled_ef07dc4b3077c11ea9cef586db4e5955=false
   gl_gnulib_enabled_getdtablesize=false
   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_malloca=false
   gl_gnulib_enabled_5264294aa0a5557541b53c8c741f7f31=false
   gl_gnulib_enabled_open=false
   gl_gnulib_enabled_03e0aaad4cb89ca757653bd367a6ccb7=false
+  gl_gnulib_enabled_rawmemchr=false
   gl_gnulib_enabled_6099e9737f757db36c47fa9d9f02e88c=false
+  gl_gnulib_enabled_scratch_buffer=false
   gl_gnulib_enabled_strtoll=false
   gl_gnulib_enabled_utimens=false
   gl_gnulib_enabled_682e609604ccaac6be382e4ee3a4eaec=false
@@ -567,6 +573,18 @@ AC_DEFUN([gl_INIT],
       func_gl_gnulib_m4code_6099e9737f757db36c47fa9d9f02e88c
     fi
   }
+  func_gl_gnulib_m4code_ef07dc4b3077c11ea9cef586db4e5955 ()
+  {
+    if ! $gl_gnulib_enabled_ef07dc4b3077c11ea9cef586db4e5955; then
+      gl_FUNC_FREE
+      if test $REPLACE_FREE = 1; then
+        AC_LIBOBJ([free])
+        gl_PREREQ_FREE
+      fi
+      gl_STDLIB_MODULE_INDICATOR([free-posix])
+      gl_gnulib_enabled_ef07dc4b3077c11ea9cef586db4e5955=true
+    fi
+  }
   func_gl_gnulib_m4code_getdtablesize ()
   {
     if ! $gl_gnulib_enabled_getdtablesize; then
@@ -616,6 +634,12 @@ AC_DEFUN([gl_INIT],
       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
@@ -628,14 +652,6 @@ AC_DEFUN([gl_INIT],
       gl_gnulib_enabled_lchmod=true
     fi
   }
-  func_gl_gnulib_m4code_malloca ()
-  {
-    if ! $gl_gnulib_enabled_malloca; then
-      gl_MALLOCA
-      gl_gnulib_enabled_malloca=true
-      func_gl_gnulib_m4code_682e609604ccaac6be382e4ee3a4eaec
-    fi
-  }
   func_gl_gnulib_m4code_5264294aa0a5557541b53c8c741f7f31 ()
   {
     if ! $gl_gnulib_enabled_5264294aa0a5557541b53c8c741f7f31; then
@@ -668,12 +684,30 @@ AC_DEFUN([gl_INIT],
       gl_gnulib_enabled_03e0aaad4cb89ca757653bd367a6ccb7=true
     fi
   }
+  func_gl_gnulib_m4code_rawmemchr ()
+  {
+    if ! $gl_gnulib_enabled_rawmemchr; then
+      gl_FUNC_RAWMEMCHR
+      if test $HAVE_RAWMEMCHR = 0; then
+        AC_LIBOBJ([rawmemchr])
+        gl_PREREQ_RAWMEMCHR
+      fi
+      gl_STRING_MODULE_INDICATOR([rawmemchr])
+      gl_gnulib_enabled_rawmemchr=true
+    fi
+  }
   func_gl_gnulib_m4code_6099e9737f757db36c47fa9d9f02e88c ()
   {
     if ! $gl_gnulib_enabled_6099e9737f757db36c47fa9d9f02e88c; then
       gl_gnulib_enabled_6099e9737f757db36c47fa9d9f02e88c=true
     fi
   }
+  func_gl_gnulib_m4code_scratch_buffer ()
+  {
+    if ! $gl_gnulib_enabled_scratch_buffer; then
+      gl_gnulib_enabled_scratch_buffer=true
+    fi
+  }
   func_gl_gnulib_m4code_strtoll ()
   {
     if ! $gl_gnulib_enabled_strtoll; then
@@ -700,7 +734,16 @@ AC_DEFUN([gl_INIT],
     fi
   }
   if test $HAVE_CANONICALIZE_FILE_NAME = 0 || test $REPLACE_CANONICALIZE_FILE_NAME = 1; then
-    func_gl_gnulib_m4code_malloca
+    func_gl_gnulib_m4code_ef07dc4b3077c11ea9cef586db4e5955
+  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
+    func_gl_gnulib_m4code_scratch_buffer
   fi
   if test $HAVE_FACCESSAT = 0 || test $REPLACE_FACCESSAT = 1; then
     func_gl_gnulib_m4code_260941c0e5dc67ec9e87d1fb321c300b
@@ -747,15 +790,18 @@ AC_DEFUN([gl_INIT],
   if case $host_os in mingw*) false;; *) test $HAVE_GETRANDOM = 0 || test $REPLACE_GETRANDOM = 1;; esac; then
     func_gl_gnulib_m4code_open
   fi
-  if test $HAVE_READLINKAT = 0; then
+  if test $HAVE_READLINKAT = 0 || test $REPLACE_READLINKAT = 1; then
     func_gl_gnulib_m4code_260941c0e5dc67ec9e87d1fb321c300b
   fi
-  if test $HAVE_READLINKAT = 0; then
+  if test $HAVE_READLINKAT = 0 || test $REPLACE_READLINKAT = 1; then
     func_gl_gnulib_m4code_03e0aaad4cb89ca757653bd367a6ccb7
   fi
   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 $REPLACE_TIMEGM = 1; then
     func_gl_gnulib_m4code_5264294aa0a5557541b53c8c741f7f31
   fi
@@ -773,16 +819,19 @@ AC_DEFUN([gl_INIT],
   AM_CONDITIONAL([gl_GNULIB_ENABLED_cloexec], [$gl_gnulib_enabled_cloexec])
   AM_CONDITIONAL([gl_GNULIB_ENABLED_dirfd], [$gl_gnulib_enabled_dirfd])
   AM_CONDITIONAL([gl_GNULIB_ENABLED_euidaccess], [$gl_gnulib_enabled_euidaccess])
+  AM_CONDITIONAL([gl_GNULIB_ENABLED_ef07dc4b3077c11ea9cef586db4e5955], [$gl_gnulib_enabled_ef07dc4b3077c11ea9cef586db4e5955])
   AM_CONDITIONAL([gl_GNULIB_ENABLED_getdtablesize], [$gl_gnulib_enabled_getdtablesize])
   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], [$gl_gnulib_enabled_lchmod])
-  AM_CONDITIONAL([gl_GNULIB_ENABLED_malloca], [$gl_gnulib_enabled_malloca])
   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_6099e9737f757db36c47fa9d9f02e88c], [$gl_gnulib_enabled_6099e9737f757db36c47fa9d9f02e88c])
+  AM_CONDITIONAL([gl_GNULIB_ENABLED_scratch_buffer], [$gl_gnulib_enabled_scratch_buffer])
   AM_CONDITIONAL([gl_GNULIB_ENABLED_strtoll], [$gl_gnulib_enabled_strtoll])
   AM_CONDITIONAL([gl_GNULIB_ENABLED_utimens], [$gl_gnulib_enabled_utimens])
   AM_CONDITIONAL([gl_GNULIB_ENABLED_682e609604ccaac6be382e4ee3a4eaec], [$gl_gnulib_enabled_682e609604ccaac6be382e4ee3a4eaec])
@@ -989,6 +1038,7 @@ AC_DEFUN([gl_FILE_LIST], [
   lib/flexmember.h
   lib/fpending.c
   lib/fpending.h
+  lib/free.c
   lib/fstatat.c
   lib/fsusage.c
   lib/fsusage.h
@@ -1015,6 +1065,7 @@ AC_DEFUN([gl_FILE_LIST], [
   lib/gettimeofday.c
   lib/gl_openssl.h
   lib/group-member.c
+  lib/idx.h
   lib/ieee754.in.h
   lib/ignore-value.h
   lib/intprops.h
@@ -1023,8 +1074,10 @@ AC_DEFUN([gl_FILE_LIST], [
   lib/libc-config.h
   lib/limits.in.h
   lib/lstat.c
-  lib/malloca.c
-  lib/malloca.h
+  lib/malloc/scratch_buffer.h
+  lib/malloc/scratch_buffer_grow.c
+  lib/malloc/scratch_buffer_grow_preserve.c
+  lib/malloc/scratch_buffer_set_array_size.c
   lib/md5.c
   lib/md5.h
   lib/memmem.c
@@ -1047,6 +1100,8 @@ AC_DEFUN([gl_FILE_LIST], [
   lib/pselect.c
   lib/pthread_sigmask.c
   lib/qcopy-acl.c
+  lib/rawmemchr.c
+  lib/rawmemchr.valgrind
   lib/readlink.c
   lib/readlinkat.c
   lib/regcomp.c
@@ -1056,6 +1111,7 @@ AC_DEFUN([gl_FILE_LIST], [
   lib/regex_internal.h
   lib/regexec.c
   lib/root-uid.h
+  lib/scratch_buffer.h
   lib/set-permissions.c
   lib/sha1.c
   lib/sha1.h
@@ -1145,6 +1201,7 @@ AC_DEFUN([gl_FILE_LIST], [
   m4/flexmember.m4
   m4/fpending.m4
   m4/fpieee.m4
+  m4/free.m4
   m4/fstatat.m4
   m4/fsusage.m4
   m4/fsync.m4
@@ -1168,7 +1225,6 @@ AC_DEFUN([gl_FILE_LIST], [
   m4/libgmp.m4
   m4/limits-h.m4
   m4/lstat.m4
-  m4/malloca.m4
   m4/manywarnings-c++.m4
   m4/manywarnings.m4
   m4/mbstate_t.m4
@@ -1192,6 +1248,7 @@ AC_DEFUN([gl_FILE_LIST], [
   m4/pipe2.m4
   m4/pselect.m4
   m4/pthread_sigmask.m4
+  m4/rawmemchr.m4
   m4/readlink.m4
   m4/readlinkat.m4
   m4/regex.m4
@@ -1203,7 +1260,6 @@ AC_DEFUN([gl_FILE_LIST], [
   m4/signal_h.m4
   m4/socklen.m4
   m4/ssize_t.m4
-  m4/st_dm_mode.m4
   m4/stat-time.m4
   m4/std-gnu11.m4
   m4/stdalign.m4
diff --git a/m4/largefile.m4 b/m4/largefile.m4
index f4c5d3a5cea..c4cc835bea0 100644
--- a/m4/largefile.m4
+++ b/m4/largefile.m4
@@ -25,7 +25,7 @@ AC_DEFUN([gl_SET_LARGEFILE_SOURCE],
 # The following implementation works 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], [] ,[
+m4_version_prereq([2.70], [], [
 
 # _AC_SYS_LARGEFILE_TEST_INCLUDES
 # -------------------------------
diff --git a/m4/mbstate_t.m4 b/m4/mbstate_t.m4
index 057ce12ebe6..226f1228dde 100644
--- a/m4/mbstate_t.m4
+++ b/m4/mbstate_t.m4
@@ -1,4 +1,4 @@
-# mbstate_t.m4 serial 13
+# mbstate_t.m4 serial 14
 dnl Copyright (C) 2000-2002, 2008-2020 Free Software Foundation, Inc.
 dnl This file is free software; the Free Software Foundation
 dnl gives unlimited permission to copy and/or distribute it,
@@ -20,14 +20,7 @@ AC_DEFUN([AC_TYPE_MBSTATE_T],
      [AC_COMPILE_IFELSE(
         [AC_LANG_PROGRAM(
            [AC_INCLUDES_DEFAULT[
-/* Tru64 with Desktop Toolkit C has a bug: <stdio.h> must be included before
-   <wchar.h>.
-   BSD/OS 4.0.1 has a bug: <stddef.h>, <stdio.h> and <time.h> must be
-   included before <wchar.h>.  */
-#include <stddef.h>
-#include <stdio.h>
-#include <time.h>
-#include <wchar.h>]],
+             #include <wchar.h>]],
            [[mbstate_t x; return sizeof x;]])],
         [ac_cv_type_mbstate_t=yes],
         [ac_cv_type_mbstate_t=no])])
diff --git a/m4/pid_t.m4 b/m4/pid_t.m4
new file mode 100644
index 00000000000..c7abceeecba
--- /dev/null
+++ b/m4/pid_t.m4
@@ -0,0 +1,38 @@
+# pid_t.m4 serial 4
+dnl Copyright (C) 2020 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.
+
+# The following implementation works around a problem in autoconf <= 2.69.
+m4_version_prereq([2.70], [], [
+
+dnl Define pid_t if the headers don't define it.
+AC_DEFUN([AC_TYPE_PID_T],
+[
+  AC_CHECK_TYPE([pid_t],
+    [],
+    [dnl On 64-bit native Windows, define it to the equivalent of 'intptr_t'
+     dnl (= 'long long' = '__int64'), because that is the return type
+     dnl of the _spawnv* functions
+     dnl <https://docs.microsoft.com/en-us/cpp/c-runtime-library/reference/spawnvp-wspawnvp>
+     dnl and the argument type of the _cwait function
+     dnl <https://docs.microsoft.com/en-us/cpp/c-runtime-library/reference/cwait>.
+     dnl Otherwise (on 32-bit Windows and on old Unix platforms), define it
+     dnl to 'int'.
+     AC_COMPILE_IFELSE(
+       [AC_LANG_PROGRAM([[
+          #if defined _WIN64 && !defined __CYGWIN__
+          LLP64
+          #endif
+          ]])
+       ],
+       [gl_pid_type='int'],
+       [gl_pid_type='__int64'])
+     AC_DEFINE_UNQUOTED([pid_t], [$gl_pid_type],
+       [Define as a signed integer type capable of holding a process identifier.])
+    ],
+    [AC_INCLUDES_DEFAULT])
+])
+
+])# m4_version_prereq 2.70
diff --git a/m4/rawmemchr.m4 b/m4/rawmemchr.m4
new file mode 100644
index 00000000000..c5bf04189c6
--- /dev/null
+++ b/m4/rawmemchr.m4
@@ -0,0 +1,20 @@
+# rawmemchr.m4 serial 2
+dnl Copyright (C) 2003, 2007-2020 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_FUNC_RAWMEMCHR],
+[
+  dnl Persuade glibc <string.h> to declare rawmemchr().
+  AC_REQUIRE([AC_USE_SYSTEM_EXTENSIONS])
+
+  AC_REQUIRE([gl_HEADER_STRING_H_DEFAULTS])
+  AC_CHECK_FUNCS([rawmemchr])
+  if test $ac_cv_func_rawmemchr = no; then
+    HAVE_RAWMEMCHR=0
+  fi
+])
+
+# Prerequisites of lib/strchrnul.c.
+AC_DEFUN([gl_PREREQ_RAWMEMCHR], [:])
diff --git a/m4/readlink.m4 b/m4/readlink.m4
index 9aa9e46da8c..c7f436a3125 100644
--- a/m4/readlink.m4
+++ b/m4/readlink.m4
@@ -1,4 +1,4 @@
-# readlink.m4 serial 15
+# readlink.m4 serial 16
 dnl Copyright (C) 2003, 2007, 2009-2020 Free Software Foundation, Inc.
 dnl This file is free software; the Free Software Foundation
 dnl gives unlimited permission to copy and/or distribute it,
@@ -23,7 +23,7 @@ AC_DEFUN([gl_FUNC_READLINK],
     dnl Solaris 9 ignores trailing slash.
     dnl FreeBSD 7.2 dereferences only one level of links with trailing slash.
     AC_CACHE_CHECK([whether readlink handles trailing slash correctly],
-      [gl_cv_func_readlink_works],
+      [gl_cv_func_readlink_trailing_slash],
       [# We have readlink, so assume ln -s works.
        ln -s conftest.no-such conftest.link
        ln -s conftest.link conftest.lnk2
@@ -32,18 +32,22 @@ AC_DEFUN([gl_FUNC_READLINK],
            [[#include <unistd.h>
 ]], [[char buf[20];
       return readlink ("conftest.lnk2/", buf, sizeof buf) != -1;]])],
-         [gl_cv_func_readlink_works=yes], [gl_cv_func_readlink_works=no],
+         [gl_cv_func_readlink_trailing_slash=yes],
+         [gl_cv_func_readlink_trailing_slash=no],
          [case "$host_os" in
-                             # Guess yes on Linux systems.
-            linux-* | linux) gl_cv_func_readlink_works="guessing yes" ;;
-                             # Guess yes on glibc systems.
-            *-gnu* | gnu*)   gl_cv_func_readlink_works="guessing yes" ;;
-                             # If we don't know, obey --enable-cross-guesses.
-            *)               gl_cv_func_readlink_works="$gl_cross_guess_normal" ;;
+            # Guess yes on Linux or glibc systems.
+            linux-* | linux | *-gnu* | gnu*)
+              gl_cv_func_readlink_trailing_slash="guessing yes" ;;
+            # Guess no on AIX or HP-UX.
+            aix* | hpux*)
+              gl_cv_func_readlink_trailing_slash="guessing no" ;;
+            # If we don't know, obey --enable-cross-guesses.
+            *)
+              gl_cv_func_readlink_trailing_slash="$gl_cross_guess_normal" ;;
           esac
          ])
       rm -f conftest.link conftest.lnk2])
-    case "$gl_cv_func_readlink_works" in
+    case "$gl_cv_func_readlink_trailing_slash" in
       *yes)
         if test "$gl_cv_decl_readlink_works" != yes; then
           REPLACE_READLINK=1
@@ -55,6 +59,43 @@ AC_DEFUN([gl_FUNC_READLINK],
         REPLACE_READLINK=1
         ;;
     esac
+
+    AC_CACHE_CHECK([whether readlink truncates results correctly],
+      [gl_cv_func_readlink_truncate],
+      [# We have readlink, so assume ln -s works.
+       ln -s ab conftest.link
+       AC_RUN_IFELSE(
+         [AC_LANG_PROGRAM(
+           [[#include <unistd.h>
+]], [[char c;
+      return readlink ("conftest.link", &c, 1) != 1;]])],
+         [gl_cv_func_readlink_truncate=yes],
+         [gl_cv_func_readlink_truncate=no],
+         [case "$host_os" in
+            # Guess yes on Linux or glibc systems.
+            linux-* | linux | *-gnu* | gnu*)
+              gl_cv_func_readlink_truncate="guessing yes" ;;
+            # Guess no on AIX or HP-UX.
+            aix* | hpux*)
+              gl_cv_func_readlink_truncate="guessing no" ;;
+            # If we don't know, obey --enable-cross-guesses.
+            *)
+              gl_cv_func_readlink_truncate="$gl_cross_guess_normal" ;;
+          esac
+         ])
+      rm -f conftest.link conftest.lnk2])
+    case $gl_cv_func_readlink_truncate in
+      *yes)
+        if test "$gl_cv_decl_readlink_works" != yes; then
+          REPLACE_READLINK=1
+        fi
+        ;;
+      *)
+        AC_DEFINE([READLINK_TRUNCATE_BUG], [1], [Define to 1 if readlink
+          sets errno instead of truncating a too-long link.])
+        REPLACE_READLINK=1
+        ;;
+    esac
   fi
 ])
 
diff --git a/m4/readlinkat.m4 b/m4/readlinkat.m4
index 6ef1f590c06..73e343f746d 100644
--- a/m4/readlinkat.m4
+++ b/m4/readlinkat.m4
@@ -1,4 +1,4 @@
-# serial 5
+# serial 6
 # See if we need to provide readlinkat replacement.
 
 dnl Copyright (C) 2009-2020 Free Software Foundation, Inc.
@@ -26,13 +26,10 @@ AC_DEFUN([gl_FUNC_READLINKAT],
              ssize_t readlinkat (int, char const *, char *, size_t);]])],
          [gl_cv_decl_readlinkat_works=yes],
          [gl_cv_decl_readlinkat_works=no])])
-    # Assume readinkat has the same trailing slash bug as readlink,
-    # as is the case on Mac Os X 10.10
-    case "$gl_cv_func_readlink_works" in
-      *yes)
-        if test "$gl_cv_decl_readlinkat_works" != yes; then
-          REPLACE_READLINKAT=1
-        fi
+    # Assume readlinkat has the same bugs as readlink,
+    # as is the case on OS X 10.10 with trailing slashes.
+    case $gl_cv_decl_readlinkat_works,$gl_cv_func_readlink_trailing_slash,$gl_cv_func_readlink_truncate in
+      *yes,*yes,*yes)
         ;;
       *)
         REPLACE_READLINKAT=1
diff --git a/m4/std-gnu11.m4 b/m4/std-gnu11.m4
index db833d820f3..b5ab8abed02 100644
--- a/m4/std-gnu11.m4
+++ b/m4/std-gnu11.m4
@@ -6,6 +6,8 @@
 # This implementation will be obsolete once we can assume Autoconf 2.70
 # or later is installed everywhere a Gnulib program might be developed.
 
+m4_version_prereq([2.70], [], [
+
 
 # Copyright (C) 2001-2020 Free Software Foundation, Inc.
 
@@ -822,3 +824,6 @@ dnl Tru64	N/A (no support)
 dnl with extended modes being tried first.
 [[-std=gnu++11 -std=c++11 -std=gnu++0x -std=c++0x -qlanglvl=extended0x -AA]], [$1], [$2])[]dnl
 ])# _AC_PROG_CXX_CXX11
+
+
+])# m4_version_prereq
diff --git a/m4/stdint.m4 b/m4/stdint.m4
index d5f5d6133a9..adaea3e5826 100644
--- a/m4/stdint.m4
+++ b/m4/stdint.m4
@@ -1,4 +1,4 @@
-# stdint.m4 serial 56
+# stdint.m4 serial 58
 dnl Copyright (C) 2001-2020 Free Software Foundation, Inc.
 dnl This file is free software; the Free Software Foundation
 dnl gives unlimited permission to copy and/or distribute it,
@@ -34,7 +34,7 @@ AC_DEFUN_ONCE([gl_STDINT_H],
   AC_SUBST([HAVE_WCHAR_H])
 
   dnl Check for <inttypes.h>.
-  dnl AC_INCLUDES_DEFAULT defines $ac_cv_header_inttypes_h.
+  AC_CHECK_HEADERS_ONCE([inttypes.h])
   if test $ac_cv_header_inttypes_h = yes; then
     HAVE_INTTYPES_H=1
   else
@@ -43,7 +43,7 @@ AC_DEFUN_ONCE([gl_STDINT_H],
   AC_SUBST([HAVE_INTTYPES_H])
 
   dnl Check for <sys/types.h>.
-  dnl AC_INCLUDES_DEFAULT defines $ac_cv_header_sys_types_h.
+  AC_CHECK_HEADERS_ONCE([sys/types.h])
   if test $ac_cv_header_sys_types_h = yes; then
     HAVE_SYS_TYPES_H=1
   else
@@ -493,13 +493,9 @@ AC_DEFUN([gl_INTEGER_TYPE_SUFFIX],
 dnl gl_STDINT_INCLUDES
 AC_DEFUN([gl_STDINT_INCLUDES],
 [[
-  /* BSD/OS 4.0.1 has a bug: <stddef.h>, <stdio.h> and <time.h> must be
-     included before <wchar.h>.  */
   #include <stddef.h>
   #include <signal.h>
   #if HAVE_WCHAR_H
-  # include <stdio.h>
-  # include <time.h>
   # include <wchar.h>
   #endif
 ]])
diff --git a/m4/stdio_h.m4 b/m4/stdio_h.m4
index 5f968bc26a5..6003a31b382 100644
--- a/m4/stdio_h.m4
+++ b/m4/stdio_h.m4
@@ -1,4 +1,4 @@
-# stdio_h.m4 serial 50
+# stdio_h.m4 serial 51
 dnl Copyright (C) 2007-2020 Free Software Foundation, Inc.
 dnl This file is free software; the Free Software Foundation
 dnl gives unlimited permission to copy and/or distribute it,
@@ -109,6 +109,11 @@ AC_DEFUN([gl_STDIO_H],
     renameat snprintf tmpfile vdprintf vsnprintf])
 
   AC_REQUIRE([AC_C_RESTRICT])
+
+  AC_CHECK_DECLS_ONCE([fcloseall])
+  if test $ac_cv_have_decl_fcloseall = no; then
+    HAVE_DECL_FCLOSEALL=0
+  fi
 ])
 
 AC_DEFUN([gl_STDIO_MODULE_INDICATOR],
@@ -176,6 +181,7 @@ AC_DEFUN([gl_STDIO_H_DEFAULTS],
   GNULIB_VSNPRINTF=0;            AC_SUBST([GNULIB_VSNPRINTF])
   GNULIB_VSPRINTF_POSIX=0;       AC_SUBST([GNULIB_VSPRINTF_POSIX])
   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])
   HAVE_DECL_FSEEKO=1;            AC_SUBST([HAVE_DECL_FSEEKO])
   HAVE_DECL_FTELLO=1;            AC_SUBST([HAVE_DECL_FTELLO])
diff --git a/m4/stdlib_h.m4 b/m4/stdlib_h.m4
index 743066a6336..7e03b9a6d58 100644
--- a/m4/stdlib_h.m4
+++ b/m4/stdlib_h.m4
@@ -1,4 +1,4 @@
-# stdlib_h.m4 serial 49
+# stdlib_h.m4 serial 54
 dnl Copyright (C) 2007-2020 Free Software Foundation, Inc.
 dnl This file is free software; the Free Software Foundation
 dnl gives unlimited permission to copy and/or distribute it,
@@ -22,13 +22,28 @@ AC_DEFUN([gl_STDLIB_H],
 #if HAVE_RANDOM_H
 # include <random.h>
 #endif
-    ]], [_Exit atoll canonicalize_file_name getloadavg getsubopt grantpt
+    ]], [_Exit aligned_alloc atoll canonicalize_file_name free
+    getloadavg getsubopt grantpt
     initstate initstate_r mbtowc mkdtemp mkostemp mkostemps mkstemp mkstemps
-    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])
+    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])
 
   AC_REQUIRE([AC_C_RESTRICT])
+
+  AC_CHECK_DECLS_ONCE([ecvt])
+  if test $ac_cv_have_decl_ecvt = no; then
+    HAVE_DECL_ECVT=0
+  fi
+  AC_CHECK_DECLS_ONCE([fcvt])
+  if test $ac_cv_have_decl_fcvt = no; then
+    HAVE_DECL_FCVT=0
+  fi
+  AC_CHECK_DECLS_ONCE([gcvt])
+  if test $ac_cv_have_decl_gcvt = no; then
+    HAVE_DECL_GCVT=0
+  fi
 ])
 
 AC_DEFUN([gl_STDLIB_MODULE_INDICATOR],
@@ -43,9 +58,11 @@ AC_DEFUN([gl_STDLIB_MODULE_INDICATOR],
 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])
@@ -56,6 +73,7 @@ AC_DEFUN([gl_STDLIB_H_DEFAULTS],
   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])
@@ -79,8 +97,12 @@ AC_DEFUN([gl_STDLIB_H_DEFAULTS],
   GNULIB_WCTOMB=0;        AC_SUBST([GNULIB_WCTOMB])
   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])
   HAVE_ATOLL=1;              AC_SUBST([HAVE_ATOLL])
   HAVE_CANONICALIZE_FILE_NAME=1;  AC_SUBST([HAVE_CANONICALIZE_FILE_NAME])
+  HAVE_DECL_ECVT=1;          AC_SUBST([HAVE_DECL_ECVT])
+  HAVE_DECL_FCVT=1;          AC_SUBST([HAVE_DECL_FCVT])
+  HAVE_DECL_GCVT=1;          AC_SUBST([HAVE_DECL_GCVT])
   HAVE_DECL_GETLOADAVG=1;    AC_SUBST([HAVE_DECL_GETLOADAVG])
   HAVE_GETSUBOPT=1;          AC_SUBST([HAVE_GETSUBOPT])
   HAVE_GRANTPT=1;            AC_SUBST([HAVE_GRANTPT])
@@ -92,6 +114,7 @@ AC_DEFUN([gl_STDLIB_H_DEFAULTS],
   HAVE_MKOSTEMPS=1;          AC_SUBST([HAVE_MKOSTEMPS])
   HAVE_MKSTEMP=1;            AC_SUBST([HAVE_MKSTEMP])
   HAVE_MKSTEMPS=1;           AC_SUBST([HAVE_MKSTEMPS])
+  HAVE_POSIX_MEMALIGN=1;     AC_SUBST([HAVE_POSIX_MEMALIGN])
   HAVE_POSIX_OPENPT=1;       AC_SUBST([HAVE_POSIX_OPENPT])
   HAVE_PTSNAME=1;            AC_SUBST([HAVE_PTSNAME])
   HAVE_PTSNAME_R=1;          AC_SUBST([HAVE_PTSNAME_R])
@@ -115,12 +138,15 @@ AC_DEFUN([gl_STDLIB_H_DEFAULTS],
   HAVE_SYS_LOADAVG_H=0;      AC_SUBST([HAVE_SYS_LOADAVG_H])
   HAVE_UNLOCKPT=1;           AC_SUBST([HAVE_UNLOCKPT])
   HAVE_DECL_UNSETENV=1;      AC_SUBST([HAVE_DECL_UNSETENV])
+  REPLACE_ALIGNED_ALLOC=0;   AC_SUBST([REPLACE_ALIGNED_ALLOC])
   REPLACE_CALLOC=0;          AC_SUBST([REPLACE_CALLOC])
   REPLACE_CANONICALIZE_FILE_NAME=0;  AC_SUBST([REPLACE_CANONICALIZE_FILE_NAME])
+  REPLACE_FREE=0;            AC_SUBST([REPLACE_FREE])
   REPLACE_INITSTATE=0;       AC_SUBST([REPLACE_INITSTATE])
   REPLACE_MALLOC=0;          AC_SUBST([REPLACE_MALLOC])
   REPLACE_MBTOWC=0;          AC_SUBST([REPLACE_MBTOWC])
   REPLACE_MKSTEMP=0;         AC_SUBST([REPLACE_MKSTEMP])
+  REPLACE_POSIX_MEMALIGN=0;  AC_SUBST([REPLACE_POSIX_MEMALIGN])
   REPLACE_PTSNAME=0;         AC_SUBST([REPLACE_PTSNAME])
   REPLACE_PTSNAME_R=0;       AC_SUBST([REPLACE_PTSNAME_R])
   REPLACE_PUTENV=0;          AC_SUBST([REPLACE_PUTENV])
diff --git a/m4/sys_types_h.m4 b/m4/sys_types_h.m4
index be918dc0d8b..c3a691becdf 100644
--- a/m4/sys_types_h.m4
+++ b/m4/sys_types_h.m4
@@ -1,4 +1,4 @@
-# sys_types_h.m4 serial 9
+# sys_types_h.m4 serial 11
 dnl Copyright (C) 2011-2020 Free Software Foundation, Inc.
 dnl This file is free software; the Free Software Foundation
 dnl gives unlimited permission to copy and/or distribute it,
@@ -36,25 +36,23 @@ AC_DEFUN([gl_SYS_TYPES_H_DEFAULTS],
 
 # This works around a buggy version in autoconf <= 2.69.
 # See <https://lists.gnu.org/r/autoconf/2016-08/msg00014.html>
+# The 2.70 version isn't quoted properly, so override it too.
 
-m4_version_prereq([2.70], [], [
-
-# This is taken from the following Autoconf patch:
-# https://git.savannah.gnu.org/cgit/autoconf.git/commit/?id=e17a30e987d7ee695fb4294a82d987ec3dc9b974
+m4_version_prereq([2.70.1], [], [
 
 m4_undefine([AC_HEADER_MAJOR])
 AC_DEFUN([AC_HEADER_MAJOR],
 [AC_CHECK_HEADERS_ONCE([sys/types.h])
 AC_CHECK_HEADER([sys/mkdev.h],
-  [AC_DEFINE([MAJOR_IN_MKDEV], [1],
-    [Define to 1 if `major', `minor', and `makedev' are declared in
-     <mkdev.h>.])])
+                [AC_DEFINE([MAJOR_IN_MKDEV], [1],
+                           [Define to 1 if `major', `minor', and `makedev' are
+                            declared in <mkdev.h>.])])
 if test $ac_cv_header_sys_mkdev_h = no; then
   AC_CHECK_HEADER([sys/sysmacros.h],
-    [AC_DEFINE([MAJOR_IN_SYSMACROS], [1],
-      [Define to 1 if `major', `minor', and `makedev' are declared in
-       <sysmacros.h>.])])
+                  [AC_DEFINE([MAJOR_IN_SYSMACROS], [1],
+                             [Define to 1 if `major', `minor', and `makedev'
+                              are declared in <sysmacros.h>.])])
 fi
-])
+])# AC_HEADER_MAJOR
 
 ])
diff --git a/m4/unistd_h.m4 b/m4/unistd_h.m4
index b4734daf603..b26d2c88dde 100644
--- a/m4/unistd_h.m4
+++ b/m4/unistd_h.m4
@@ -1,4 +1,4 @@
-# unistd_h.m4 serial 81
+# unistd_h.m4 serial 83
 dnl Copyright (C) 2006-2020 Free Software Foundation, Inc.
 dnl This file is free software; the Free Software Foundation
 dnl gives unlimited permission to copy and/or distribute it,
@@ -41,7 +41,8 @@ AC_DEFUN([gl_UNISTD_H],
 #  include <io.h>
 # endif
 #endif
-    ]], [access chdir chown dup dup2 dup3 environ euidaccess faccessat fchdir
+    ]], [access chdir chown copy_file_range dup dup2 dup3 environ euidaccess
+    faccessat fchdir
     fchownat fdatasync fsync ftruncate getcwd getdomainname getdtablesize
     getentropy getgroups gethostname getlogin getlogin_r getpagesize getpass
     getusershell setusershell endusershell
@@ -50,6 +51,11 @@ AC_DEFUN([gl_UNISTD_H],
     truncate ttyname_r unlink unlinkat usleep])
 
   AC_REQUIRE([AC_C_RESTRICT])
+
+  AC_CHECK_DECLS_ONCE([execvpe])
+  if test $ac_cv_have_decl_execvpe = no; then
+    HAVE_DECL_EXECVPE=0
+  fi
 ])
 
 AC_DEFUN([gl_UNISTD_MODULE_INDICATOR],
@@ -152,6 +158,7 @@ AC_DEFUN([gl_UNISTD_H_DEFAULTS],
   HAVE_UNLINKAT=1;        AC_SUBST([HAVE_UNLINKAT])
   HAVE_USLEEP=1;          AC_SUBST([HAVE_USLEEP])
   HAVE_DECL_ENVIRON=1;    AC_SUBST([HAVE_DECL_ENVIRON])
+  HAVE_DECL_EXECVPE=1;    AC_SUBST([HAVE_DECL_EXECVPE])
   HAVE_DECL_FCHDIR=1;     AC_SUBST([HAVE_DECL_FCHDIR])
   HAVE_DECL_FDATASYNC=1;  AC_SUBST([HAVE_DECL_FDATASYNC])
   HAVE_DECL_GETDOMAINNAME=1; AC_SUBST([HAVE_DECL_GETDOMAINNAME])
diff --git a/m4/vararrays.m4 b/m4/vararrays.m4
index 49ded2efe0d..9524a6ddd33 100644
--- a/m4/vararrays.m4
+++ b/m4/vararrays.m4
@@ -1,6 +1,6 @@
 # Check for variable-length arrays.
 
-# serial 5
+# serial 6
 
 # From Paul Eggert
 
@@ -9,9 +9,11 @@
 # gives unlimited permission to copy and/or distribute it,
 # with or without modifications, as long as this notice is preserved.
 
-# This is a copy of AC_C_VARARRAYS from a recent development version
-# of Autoconf.  It replaces Autoconf's version, or for pre-2.61 autoconf
-# it defines the macro that Autoconf lacks.
+m4_version_prereq([2.70], [], [
+
+# AC_C_VARARRAYS
+# --------------
+# Check whether the C compiler supports variable-length arrays.
 AC_DEFUN([AC_C_VARARRAYS],
 [
   AC_CACHE_CHECK([for variable-length arrays],
@@ -27,7 +29,7 @@ AC_DEFUN([AC_C_VARARRAYS],
              [[/* Test for VLA support.  This test is partly inspired
                   from examples in the C standard.  Use at least two VLA
                   functions to detect the GCC 3.4.3 bug described in:
-                  https://lists.gnu.org/r/bug-gnulib/2014-08/msg00014.html
+                  https://lists.gnu.org/archive/html/bug-gnulib/2014-08/msg00014.html
                   */
                #ifdef __STDC_NO_VLA__
                 syntax error;
@@ -66,3 +68,5 @@ AC_DEFUN([AC_C_VARARRAYS],
        if the compiler does not already define this.])
   fi
 ])
+
+])