diff --git a/admin/merge-gnulib b/admin/merge-gnulib
index 7e7971fe881..76918f3d34f 100755
--- a/admin/merge-gnulib
+++ b/admin/merge-gnulib
@@ -40,7 +40,7 @@ GNULIB_MODULES='
   sig2str socklen stat-time std-gnu11 stdalign stddef stdio
   stpcpy strftime strtoimax strtoumax symlink sys_stat
   sys_time time time_r time_rz timegm timer-time timespec-add timespec-sub
-  unsetenv update-copyright utimens
+  update-copyright utimens
   vla warnings
 '
 
@@ -97,7 +97,8 @@ test -x "$gnulib_srcdir"/gnulib-tool || {
 "$gnulib_srcdir"/gnulib-tool --dir="$src" $GNULIB_TOOL_FLAGS $GNULIB_MODULES &&
 rm -- "$src"lib/gl_openssl.h "$src"m4/fcntl-o.m4 \
       "$src"m4/gl-openssl.m4 \
-      "$src"m4/gnulib-cache.m4 "$src"m4/warn-on-use.m4 "$src"m4/wint_t.m4 &&
+      "$src"m4/gnulib-cache.m4 "$src"m4/gnulib-tool.m4 \
+      "$src"m4/warn-on-use.m4 "$src"m4/wint_t.m4 &&
 cp -- "$gnulib_srcdir"/build-aux/texinfo.tex "$src"doc/misc &&
 cp -- "$gnulib_srcdir"/build-aux/move-if-change "$src"build-aux &&
 { test -z "$src" || cd "$src"; } &&
diff --git a/lib/gnulib.mk b/lib/gnulib.mk
index e4aa90ecac9..7a0de1b440d 100644
--- a/lib/gnulib.mk
+++ b/lib/gnulib.mk
@@ -21,7 +21,7 @@
 # the same distribution terms as the rest of that program.
 #
 # Generated by gnulib-tool.
-# Reproduce by: gnulib-tool --import --lib=libgnu --source-base=lib --m4-base=m4 --doc-base=doc --tests-base=tests --aux-dir=build-aux --avoid=close --avoid=dup --avoid=fchdir --avoid=fstat --avoid=malloc-posix --avoid=msvc-inval --avoid=msvc-nothrow --avoid=open --avoid=openat-die --avoid=opendir --avoid=raise --avoid=save-cwd --avoid=select --avoid=setenv --avoid=sigprocmask --avoid=stdarg --avoid=stdbool --avoid=threadlib --avoid=unsetenv --makefile-name=gnulib.mk --conditional-dependencies --no-libtool --macro-prefix=gl --no-vc-files alloca-opt binary-io byteswap c-ctype c-strcase careadlinkat close-stream count-leading-zeros count-one-bits count-trailing-zeros crypto/md5 crypto/sha1 crypto/sha256 crypto/sha512 dtoastr dtotimespec dup2 environ execinfo faccessat fcntl fcntl-h fdatasync fdopendir filemode filevercmp flexmember fstatat fsync getloadavg getopt-gnu gettime gettimeofday gitlog-to-changelog ignore-value intprops largefile lstat manywarnings memrchr mkostemp mktime pipe2 pselect pthread_sigmask putenv qcopy-acl readlink readlinkat sig2str socklen stat-time std-gnu11 stdalign stddef stdio stpcpy strftime strtoimax strtoumax symlink sys_stat sys_time time time_r time_rz timegm timer-time timespec-add timespec-sub unsetenv update-copyright utimens vla warnings
+# Reproduce by: gnulib-tool --import --lib=libgnu --source-base=lib --m4-base=m4 --doc-base=doc --tests-base=tests --aux-dir=build-aux --avoid=close --avoid=dup --avoid=fchdir --avoid=fstat --avoid=malloc-posix --avoid=msvc-inval --avoid=msvc-nothrow --avoid=open --avoid=openat-die --avoid=opendir --avoid=raise --avoid=save-cwd --avoid=select --avoid=setenv --avoid=sigprocmask --avoid=stdarg --avoid=stdbool --avoid=threadlib --avoid=unsetenv --makefile-name=gnulib.mk --conditional-dependencies --no-libtool --macro-prefix=gl --no-vc-files alloca-opt binary-io byteswap c-ctype c-strcase careadlinkat close-stream count-leading-zeros count-one-bits count-trailing-zeros crypto/md5 crypto/sha1 crypto/sha256 crypto/sha512 dtoastr dtotimespec dup2 environ execinfo faccessat fcntl fcntl-h fdatasync fdopendir filemode filevercmp flexmember fstatat fsync getloadavg getopt-gnu gettime gettimeofday gitlog-to-changelog ignore-value intprops largefile lstat manywarnings memrchr mkostemp mktime pipe2 pselect pthread_sigmask putenv qcopy-acl readlink readlinkat sig2str socklen stat-time std-gnu11 stdalign stddef stdio stpcpy strftime strtoimax strtoumax symlink sys_stat sys_time time time_r time_rz timegm timer-time timespec-add timespec-sub update-copyright utimens vla warnings
 
 
 MOSTLYCLEANFILES += core *.stackdump
diff --git a/lib/unsetenv.c b/lib/unsetenv.c
deleted file mode 100644
index 6d742c15964..00000000000
--- a/lib/unsetenv.c
+++ /dev/null
@@ -1,128 +0,0 @@
-/* Copyright (C) 1992, 1995-2002, 2005-2017 Free Software Foundation,
-   Inc.
-   This file is part of the GNU C Library.
-
-   This program is free software: you can redistribute it and/or modify
-   it under the terms of the GNU General Public License as published by
-   the Free Software Foundation; either version 3 of the License, or
-   (at your option) any later version.
-
-   This program is distributed in the hope that it will be useful,
-   but WITHOUT ANY WARRANTY; without even the implied warranty of
-   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
-   GNU General Public License for more details.
-
-   You should have received a copy of the GNU General Public License
-   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
-
-/* Don't use __attribute__ __nonnull__ in this compilation unit.  Otherwise gcc
-   optimizes away the name == NULL test below.  */
-#define _GL_ARG_NONNULL(params)
-
-#include <config.h>
-
-/* Specification.  */
-#include <stdlib.h>
-
-#include <errno.h>
-#if !_LIBC
-# define __set_errno(ev) ((errno) = (ev))
-#endif
-
-#include <string.h>
-#include <unistd.h>
-
-#if !_LIBC
-# define __environ      environ
-#endif
-
-#if _LIBC
-/* This lock protects against simultaneous modifications of 'environ'.  */
-# include <bits/libc-lock.h>
-__libc_lock_define_initialized (static, envlock)
-# define LOCK   __libc_lock_lock (envlock)
-# define UNLOCK __libc_lock_unlock (envlock)
-#else
-# define LOCK
-# define UNLOCK
-#endif
-
-/* In the GNU C library we must keep the namespace clean.  */
-#ifdef _LIBC
-# define unsetenv __unsetenv
-#endif
-
-#if _LIBC || !HAVE_UNSETENV
-
-int
-unsetenv (const char *name)
-{
-  size_t len;
-  char **ep;
-
-  if (name == NULL || *name == '\0' || strchr (name, '=') != NULL)
-    {
-      __set_errno (EINVAL);
-      return -1;
-    }
-
-  len = strlen (name);
-
-  LOCK;
-
-  ep = __environ;
-  while (*ep != NULL)
-    if (!strncmp (*ep, name, len) && (*ep)[len] == '=')
-      {
-        /* Found it.  Remove this pointer by moving later ones back.  */
-        char **dp = ep;
-
-        do
-          dp[0] = dp[1];
-        while (*dp++);
-        /* Continue the loop in case NAME appears again.  */
-      }
-    else
-      ++ep;
-
-  UNLOCK;
-
-  return 0;
-}
-
-#ifdef _LIBC
-# undef unsetenv
-weak_alias (__unsetenv, unsetenv)
-#endif
-
-#else /* HAVE_UNSETENV */
-
-# undef unsetenv
-# if !HAVE_DECL_UNSETENV
-#  if VOID_UNSETENV
-extern void unsetenv (const char *);
-#  else
-extern int unsetenv (const char *);
-#  endif
-# endif
-
-/* Call the underlying unsetenv, in case there is hidden bookkeeping
-   that needs updating beyond just modifying environ.  */
-int
-rpl_unsetenv (const char *name)
-{
-  int result = 0;
-  if (!name || !*name || strchr (name, '='))
-    {
-      errno = EINVAL;
-      return -1;
-    }
-  while (getenv (name))
-# if !VOID_UNSETENV
-    result =
-# endif
-      unsetenv (name);
-  return result;
-}
-
-#endif /* HAVE_UNSETENV */
diff --git a/m4/gnulib-tool.m4 b/m4/gnulib-tool.m4
deleted file mode 100644
index 2e2d8f6dcdd..00000000000
--- a/m4/gnulib-tool.m4
+++ /dev/null
@@ -1,57 +0,0 @@
-# gnulib-tool.m4 serial 2
-dnl Copyright (C) 2004-2005, 2009-2017 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 The following macros need not be invoked explicitly.
-dnl Invoking them does nothing except to declare default arguments
-dnl for "gnulib-tool --import".
-
-dnl Usage: gl_LOCAL_DIR([DIR])
-AC_DEFUN([gl_LOCAL_DIR], [])
-
-dnl Usage: gl_MODULES([module1 module2 ...])
-AC_DEFUN([gl_MODULES], [])
-
-dnl Usage: gl_AVOID([module1 module2 ...])
-AC_DEFUN([gl_AVOID], [])
-
-dnl Usage: gl_SOURCE_BASE([DIR])
-AC_DEFUN([gl_SOURCE_BASE], [])
-
-dnl Usage: gl_M4_BASE([DIR])
-AC_DEFUN([gl_M4_BASE], [])
-
-dnl Usage: gl_PO_BASE([DIR])
-AC_DEFUN([gl_PO_BASE], [])
-
-dnl Usage: gl_DOC_BASE([DIR])
-AC_DEFUN([gl_DOC_BASE], [])
-
-dnl Usage: gl_TESTS_BASE([DIR])
-AC_DEFUN([gl_TESTS_BASE], [])
-
-dnl Usage: gl_WITH_TESTS
-AC_DEFUN([gl_WITH_TESTS], [])
-
-dnl Usage: gl_LIB([LIBNAME])
-AC_DEFUN([gl_LIB], [])
-
-dnl Usage: gl_LGPL or gl_LGPL([VERSION])
-AC_DEFUN([gl_LGPL], [])
-
-dnl Usage: gl_MAKEFILE_NAME([FILENAME])
-AC_DEFUN([gl_MAKEFILE_NAME], [])
-
-dnl Usage: gl_LIBTOOL
-AC_DEFUN([gl_LIBTOOL], [])
-
-dnl Usage: gl_MACRO_PREFIX([PREFIX])
-AC_DEFUN([gl_MACRO_PREFIX], [])
-
-dnl Usage: gl_PO_DOMAIN([DOMAIN])
-AC_DEFUN([gl_PO_DOMAIN], [])
-
-dnl Usage: gl_VC_FILES([BOOLEAN])
-AC_DEFUN([gl_VC_FILES], [])
diff --git a/m4/setenv.m4 b/m4/setenv.m4
deleted file mode 100644
index 005aa8cfeda..00000000000
--- a/m4/setenv.m4
+++ /dev/null
@@ -1,160 +0,0 @@
-# setenv.m4 serial 26
-dnl Copyright (C) 2001-2004, 2006-2017 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_SETENV],
-[
-  AC_REQUIRE([gl_FUNC_SETENV_SEPARATE])
-  AC_REQUIRE([AC_CANONICAL_HOST]) dnl for cross-compiles
-  if test $ac_cv_func_setenv = no; then
-    HAVE_SETENV=0
-  else
-    AC_CACHE_CHECK([whether setenv validates arguments],
-      [gl_cv_func_setenv_works],
-      [AC_RUN_IFELSE([AC_LANG_PROGRAM([[
-       #include <stdlib.h>
-       #include <errno.h>
-       #include <string.h>
-      ]], [[
-       int result = 0;
-       {
-         if (setenv ("", "", 0) != -1)
-           result |= 1;
-         else if (errno != EINVAL)
-           result |= 2;
-       }
-       {
-         if (setenv ("a", "=", 1) != 0)
-           result |= 4;
-         else if (strcmp (getenv ("a"), "=") != 0)
-           result |= 8;
-       }
-       return result;
-      ]])],
-      [gl_cv_func_setenv_works=yes], [gl_cv_func_setenv_works=no],
-      [case "$host_os" in
-                 # Guess yes on glibc systems.
-         *-gnu*) gl_cv_func_setenv_works="guessing yes" ;;
-                 # If we don't know, assume the worst.
-         *)      gl_cv_func_setenv_works="guessing no" ;;
-       esac
-      ])])
-    case "$gl_cv_func_setenv_works" in
-      *yes) ;;
-      *)
-        REPLACE_SETENV=1
-        ;;
-    esac
-  fi
-])
-
-# Like gl_FUNC_SETENV, except prepare for separate compilation
-# (no REPLACE_SETENV, no AC_LIBOBJ).
-AC_DEFUN([gl_FUNC_SETENV_SEPARATE],
-[
-  AC_REQUIRE([gl_STDLIB_H_DEFAULTS])
-  AC_CHECK_DECLS_ONCE([setenv])
-  if test $ac_cv_have_decl_setenv = no; then
-    HAVE_DECL_SETENV=0
-  fi
-  AC_CHECK_FUNCS_ONCE([setenv])
-  gl_PREREQ_SETENV
-])
-
-AC_DEFUN([gl_FUNC_UNSETENV],
-[
-  AC_REQUIRE([gl_STDLIB_H_DEFAULTS])
-  AC_REQUIRE([AC_CANONICAL_HOST]) dnl for cross-compiles
-  AC_CHECK_DECLS_ONCE([unsetenv])
-  if test $ac_cv_have_decl_unsetenv = no; then
-    HAVE_DECL_UNSETENV=0
-  fi
-  AC_CHECK_FUNCS([unsetenv])
-  if test $ac_cv_func_unsetenv = no; then
-    HAVE_UNSETENV=0
-  else
-    HAVE_UNSETENV=1
-    dnl Some BSDs return void, failing to do error checking.
-    AC_CACHE_CHECK([for unsetenv() return type], [gt_cv_func_unsetenv_ret],
-      [AC_COMPILE_IFELSE(
-         [AC_LANG_PROGRAM(
-            [[
-#undef _BSD
-#define _BSD 1 /* unhide unsetenv declaration in OSF/1 5.1 <stdlib.h> */
-#include <stdlib.h>
-extern
-#ifdef __cplusplus
-"C"
-#endif
-int unsetenv (const char *name);
-            ]],
-            [[]])],
-         [gt_cv_func_unsetenv_ret='int'],
-         [gt_cv_func_unsetenv_ret='void'])])
-    if test $gt_cv_func_unsetenv_ret = 'void'; then
-      AC_DEFINE([VOID_UNSETENV], [1], [Define to 1 if unsetenv returns void
-       instead of int.])
-      REPLACE_UNSETENV=1
-    fi
-
-    dnl Solaris 10 unsetenv does not remove all copies of a name.
-    dnl Haiku alpha 2 unsetenv gets confused by assignment to environ.
-    dnl OpenBSD 4.7 unsetenv("") does not fail.
-    AC_CACHE_CHECK([whether unsetenv obeys POSIX],
-      [gl_cv_func_unsetenv_works],
-      [AC_RUN_IFELSE([AC_LANG_PROGRAM([[
-       #include <stdlib.h>
-       #include <errno.h>
-       extern char **environ;
-      ]], [[
-       char entry1[] = "a=1";
-       char entry2[] = "b=2";
-       char *env[] = { entry1, entry2, NULL };
-       if (putenv ((char *) "a=1")) return 1;
-       if (putenv (entry2)) return 2;
-       entry2[0] = 'a';
-       unsetenv ("a");
-       if (getenv ("a")) return 3;
-       if (!unsetenv ("") || errno != EINVAL) return 4;
-       entry2[0] = 'b';
-       environ = env;
-       if (!getenv ("a")) return 5;
-       entry2[0] = 'a';
-       unsetenv ("a");
-       if (getenv ("a")) return 6;
-      ]])],
-      [gl_cv_func_unsetenv_works=yes], [gl_cv_func_unsetenv_works=no],
-      [case "$host_os" in
-                 # Guess yes on glibc systems.
-         *-gnu*) gl_cv_func_unsetenv_works="guessing yes" ;;
-                 # If we don't know, assume the worst.
-         *)      gl_cv_func_unsetenv_works="guessing no" ;;
-       esac
-      ])])
-    case "$gl_cv_func_unsetenv_works" in
-      *yes) ;;
-      *)
-        REPLACE_UNSETENV=1
-        ;;
-    esac
-  fi
-])
-
-# Prerequisites of lib/setenv.c.
-AC_DEFUN([gl_PREREQ_SETENV],
-[
-  AC_REQUIRE([AC_FUNC_ALLOCA])
-  AC_REQUIRE([gl_ENVIRON])
-  AC_CHECK_HEADERS_ONCE([unistd.h])
-  AC_CHECK_HEADERS([search.h])
-  AC_CHECK_FUNCS([tsearch])
-])
-
-# Prerequisites of lib/unsetenv.c.
-AC_DEFUN([gl_PREREQ_UNSETENV],
-[
-  AC_REQUIRE([gl_ENVIRON])
-  AC_CHECK_HEADERS_ONCE([unistd.h])
-])