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[libmicrohttpd] 02/04: Updated M4 macros


From: gnunet
Subject: [libmicrohttpd] 02/04: Updated M4 macros
Date: Mon, 18 Jan 2021 21:25:23 +0100

This is an automated email from the git hooks/post-receive script.

karlson2k pushed a commit to branch master
in repository libmicrohttpd.

commit 3b64c6bd5fee56db2618b84573d9885db8adbf9a
Author: Evgeny Grin (Karlson2k) <k2k@narod.ru>
AuthorDate: Mon Jan 18 22:49:55 2021 +0300

    Updated M4 macros
    
    extern-inline.m4 is removed from the repo as it's not needed and may
    conflict with host version
---
 m4/extern-inline.m4  | 102 --------
 m4/fcntl-o.m4        |  22 +-
 m4/gettext.m4        |  72 ++----
 m4/host-cpu-c-abi.m4 | 675 +++++++++++++++++++++++++++++++++++++++++++++++++++
 m4/iconv.m4          | 112 +++++----
 m4/intlmacosx.m4     |  37 +--
 m4/lcmessage.m4      |  10 +-
 m4/lib-ld.m4         | 163 ++++++++-----
 m4/lib-link.m4       | 184 ++++++++------
 m4/lib-prefix.m4     | 241 ++++++++++++------
 m4/libcurl.m4        |   4 +-
 m4/lock.m4           |  11 +-
 m4/longlong.m4       |  22 +-
 m4/nls.m4            |  10 +-
 m4/po.m4             |  63 +++--
 m4/progtest.m4       |  16 +-
 m4/search_h.m4       |  10 +-
 m4/size_max.m4       |  16 +-
 m4/threadlib.m4      | 633 ++++++++++++++++++++++++++++++++---------------
 m4/tsearch.m4        |  15 +-
 m4/visibility.m4     |  74 +++---
 m4/wint_t.m4         |  49 +++-
 22 files changed, 1779 insertions(+), 762 deletions(-)

diff --git a/m4/extern-inline.m4 b/m4/extern-inline.m4
deleted file mode 100644
index 1e578f3d..00000000
--- a/m4/extern-inline.m4
+++ /dev/null
@@ -1,102 +0,0 @@
-dnl 'extern inline' a la ISO C99.
-
-dnl Copyright 2012-2016 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_EXTERN_INLINE],
-[
-  AH_VERBATIM([extern_inline],
-[/* Please see the Gnulib manual for how to use these macros.
-
-   Suppress extern inline with HP-UX cc, as it appears to be broken; see
-   <http://lists.gnu.org/archive/html/bug-texinfo/2013-02/msg00030.html>.
-
-   Suppress extern inline with Sun C in standards-conformance mode, as it
-   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.
-
-   Suppress extern inline (with or without __attribute__ ((__gnu_inline__)))
-   on configurations that mistakenly use 'static inline' to implement
-   functions or macros in standard C headers like <ctype.h>.  For example,
-   if isdigit is mistakenly implemented via a static inline function,
-   a program containing an extern inline function that calls isdigit
-   may not work since the C standard prohibits extern inline functions
-   from calling static functions.  This bug is known to occur on:
-
-     OS X 10.8 and earlier; see:
-     http://lists.gnu.org/archive/html/bug-gnulib/2012-12/msg00023.html
-
-     DragonFly; see
-     
http://muscles.dragonflybsd.org/bulk/bleeding-edge-potential/latest-per-pkg/ah-tty-0.3.12.log
-
-     FreeBSD; see:
-     http://lists.gnu.org/archive/html/bug-gnulib/2014-07/msg00104.html
-
-   OS X 10.9 has a macro __header_inline indicating the bug is fixed for C and
-   for clang but remains for g++; see <http://trac.macports.org/ticket/41033>.
-   Assume DragonFly and FreeBSD will be similar.  */
-#if (((defined __APPLE__ && defined __MACH__) \
-      || defined __DragonFly__ || defined __FreeBSD__) \
-     && (defined __header_inline \
-         ? (defined __cplusplus && defined __GNUC_STDC_INLINE__ \
-            && ! defined __clang__) \
-         : ((! defined _DONT_USE_CTYPE_INLINE_ \
-             && (defined __GNUC__ || defined __cplusplus)) \
-            || (defined _FORTIFY_SOURCE && 0 < _FORTIFY_SOURCE \
-                && defined __GNUC__ && ! defined __cplusplus))))
-# define _GL_EXTERN_INLINE_STDHEADER_BUG
-#endif
-#if ((__GNUC__ \
-      ? defined __GNUC_STDC_INLINE__ && __GNUC_STDC_INLINE__ \
-      : (199901L <= __STDC_VERSION__ \
-         && !defined __HP_cc \
-         && !defined __PGI \
-         && !(defined __SUNPRO_C && __STDC__))) \
-     && !defined _GL_EXTERN_INLINE_STDHEADER_BUG)
-# define _GL_INLINE inline
-# define _GL_EXTERN_INLINE extern inline
-# define _GL_EXTERN_INLINE_IN_USE
-#elif (2 < __GNUC__ + (7 <= __GNUC_MINOR__) && !defined __STRICT_ANSI__ \
-       && !defined _GL_EXTERN_INLINE_STDHEADER_BUG)
-# if defined __GNUC_GNU_INLINE__ && __GNUC_GNU_INLINE__
-   /* __gnu_inline__ suppresses a GCC 4.2 diagnostic.  */
-#  define _GL_INLINE extern inline __attribute__ ((__gnu_inline__))
-# else
-#  define _GL_INLINE extern inline
-# endif
-# 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
-#endif
-
-/* In GCC 4.6 (inclusive) to 5.1 (exclusive),
-   suppress bogus "no previous prototype for 'FOO'"
-   and "no previous declaration for 'FOO'" diagnostics,
-   when FOO is an inline function in the header; see
-   <https://gcc.gnu.org/bugzilla/show_bug.cgi?id=54113> and
-   <https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63877>.  */
-#if __GNUC__ == 4 && 6 <= __GNUC_MINOR__
-# if defined __GNUC_STDC_INLINE__ && __GNUC_STDC_INLINE__
-#  define _GL_INLINE_HEADER_CONST_PRAGMA
-# else
-#  define _GL_INLINE_HEADER_CONST_PRAGMA \
-     _Pragma ("GCC diagnostic ignored \"-Wsuggest-attribute=const\"")
-# endif
-# define _GL_INLINE_HEADER_BEGIN \
-    _Pragma ("GCC diagnostic push") \
-    _Pragma ("GCC diagnostic ignored \"-Wmissing-prototypes\"") \
-    _Pragma ("GCC diagnostic ignored \"-Wmissing-declarations\"") \
-    _GL_INLINE_HEADER_CONST_PRAGMA
-# define _GL_INLINE_HEADER_END \
-    _Pragma ("GCC diagnostic pop")
-#else
-# define _GL_INLINE_HEADER_BEGIN
-# define _GL_INLINE_HEADER_END
-#endif])
-])
diff --git a/m4/fcntl-o.m4 b/m4/fcntl-o.m4
index 24fcf88d..7c459ad1 100644
--- a/m4/fcntl-o.m4
+++ b/m4/fcntl-o.m4
@@ -1,23 +1,22 @@
-# fcntl-o.m4 serial 4
-dnl Copyright (C) 2006, 2009-2016 Free Software Foundation, Inc.
+# fcntl-o.m4 serial 7
+dnl Copyright (C) 2006, 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 Written by Paul Eggert.
 
+AC_PREREQ([2.60])
+
 # Test whether the flags O_NOATIME and O_NOFOLLOW actually work.
 # Define HAVE_WORKING_O_NOATIME to 1 if O_NOATIME works, or to 0 otherwise.
 # Define HAVE_WORKING_O_NOFOLLOW to 1 if O_NOFOLLOW works, or to 0 otherwise.
 AC_DEFUN([gl_FCNTL_O_FLAGS],
 [
   dnl Persuade glibc <fcntl.h> to define O_NOATIME and O_NOFOLLOW.
-  dnl AC_USE_SYSTEM_EXTENSIONS was introduced in autoconf 2.60 and obsoletes
-  dnl AC_GNU_SOURCE.
-  m4_ifdef([AC_USE_SYSTEM_EXTENSIONS],
-    [AC_REQUIRE([AC_USE_SYSTEM_EXTENSIONS])],
-    [AC_REQUIRE([AC_GNU_SOURCE])])
+  AC_REQUIRE([AC_USE_SYSTEM_EXTENSIONS])
 
+  AC_REQUIRE([AC_CANONICAL_HOST]) dnl for cross-compiles
   AC_CHECK_HEADERS_ONCE([unistd.h])
   AC_CHECK_FUNCS_ONCE([symlink])
   AC_CACHE_CHECK([for working fcntl.h], [gl_cv_header_working_fcntl_h],
@@ -33,6 +32,7 @@ AC_DEFUN([gl_FCNTL_O_FLAGS],
            # defined sleep(n) _sleep ((n) * 1000)
            #endif
            #include <fcntl.h>
+           ]GL_MDA_DEFINES[
            #ifndef O_NOATIME
             #define O_NOATIME 0
            #endif
@@ -116,7 +116,13 @@ AC_DEFUN([gl_FCNTL_O_FLAGS],
         68) gl_cv_header_working_fcntl_h='no (bad O_NOATIME, O_NOFOLLOW)';; #(
          *) gl_cv_header_working_fcntl_h='no';;
         esac],
-       [gl_cv_header_working_fcntl_h=cross-compiling])])
+       [case "$host_os" in
+                  # Guess 'no' on native Windows.
+          mingw*) gl_cv_header_working_fcntl_h='no' ;;
+          *)      gl_cv_header_working_fcntl_h=cross-compiling ;;
+        esac
+       ])
+    ])
 
   case $gl_cv_header_working_fcntl_h in #(
   *O_NOATIME* | no | cross-compiling) ac_val=0;; #(
diff --git a/m4/gettext.m4 b/m4/gettext.m4
index eef5073b..c7f54609 100644
--- a/m4/gettext.m4
+++ b/m4/gettext.m4
@@ -1,15 +1,15 @@
-# gettext.m4 serial 68 (gettext-0.19.8)
-dnl Copyright (C) 1995-2014, 2016 Free Software Foundation, Inc.
+# gettext.m4 serial 71 (gettext-0.20.2)
+dnl Copyright (C) 1995-2014, 2016, 2018-2021 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
 dnl This file can be used in projects which are not available under
-dnl the GNU General Public License or the GNU Library General Public
+dnl the GNU General Public License or the GNU Lesser General Public
 dnl License but which still want to provide support for the GNU gettext
 dnl functionality.
 dnl Please note that the actual code of the GNU gettext library is covered
-dnl by the GNU Library General Public License, and the rest of the GNU
+dnl by the GNU Lesser General Public License, and the rest of the GNU
 dnl gettext package is covered by the GNU General Public License.
 dnl They are *not* in the public domain.
 
@@ -20,15 +20,13 @@ dnl   Bruno Haible <haible@clisp.cons.org>, 2000-2006, 
2008-2010.
 dnl Macro to add for using GNU gettext.
 
 dnl Usage: AM_GNU_GETTEXT([INTLSYMBOL], [NEEDSYMBOL], [INTLDIR]).
-dnl INTLSYMBOL can be one of 'external', 'no-libtool', 'use-libtool'. The
-dnl    default (if it is not specified or empty) is 'no-libtool'.
-dnl    INTLSYMBOL should be 'external' for packages with no intl directory,
-dnl    and 'no-libtool' or 'use-libtool' for packages with an intl directory.
+dnl INTLSYMBOL must be one of 'external', 'use-libtool'.
+dnl    INTLSYMBOL should be 'external' for packages other than GNU gettext, and
+dnl    'use-libtool' for the packages 'gettext-runtime' and 'gettext-tools'.
 dnl    If INTLSYMBOL is 'use-libtool', then a libtool library
 dnl    $(top_builddir)/intl/libintl.la will be created (shared and/or static,
 dnl    depending on --{enable,disable}-{shared,static} and on the presence of
-dnl    AM-DISABLE-SHARED). If INTLSYMBOL is 'no-libtool', a static library
-dnl    $(top_builddir)/intl/libintl.a will be created.
+dnl    AM-DISABLE-SHARED).
 dnl If NEEDSYMBOL is specified and is 'need-ngettext', then GNU gettext
 dnl    implementations (in libc or libintl) without the ngettext() function
 dnl    will be ignored.  If NEEDSYMBOL is specified and is
@@ -57,19 +55,17 @@ dnl
 AC_DEFUN([AM_GNU_GETTEXT],
 [
   dnl Argument checking.
-  ifelse([$1], [], , [ifelse([$1], [external], , [ifelse([$1], [no-libtool], , 
[ifelse([$1], [use-libtool], ,
+  ifelse([$1], [], , [ifelse([$1], [external], , [ifelse([$1], [use-libtool], ,
     [errprint([ERROR: invalid first argument to AM_GNU_GETTEXT
-])])])])])
+])])])])
   ifelse(ifelse([$1], [], [old])[]ifelse([$1], [no-libtool], [old]), [old],
-    [AC_DIAGNOSE([obsolete], [Use of AM_GNU_GETTEXT without [external] 
argument is deprecated.])])
+    [errprint([ERROR: Use of AM_GNU_GETTEXT without [external] argument is no 
longer supported.
+])])
   ifelse([$2], [], , [ifelse([$2], [need-ngettext], , [ifelse([$2], 
[need-formatstring-macros], ,
     [errprint([ERROR: invalid second argument to AM_GNU_GETTEXT
 ])])])])
   define([gt_included_intl],
-    ifelse([$1], [external],
-      ifdef([AM_GNU_GETTEXT_][INTL_SUBDIR], [yes], [no]),
-      [yes]))
-  define([gt_libtool_suffix_prefix], ifelse([$1], [use-libtool], [l], []))
+    ifelse([$1], [external], [no], [yes]))
   gt_NEEDS_INIT
   AM_GNU_GETTEXT_NEED([$2])
 
@@ -91,8 +87,7 @@ AC_DEFUN([AM_GNU_GETTEXT],
   dnl again, outside any 'if'. There are two solutions:
   dnl - Invoke AM_ICONV_LINKFLAGS_BODY here, outside any 'if'.
   dnl - Control the expansions in more detail using AC_PROVIDE_IFELSE.
-  dnl Since AC_PROVIDE_IFELSE is only in autoconf >= 2.52 and not
-  dnl documented, we avoid it.
+  dnl Since AC_PROVIDE_IFELSE is not documented, we avoid it.
   ifelse(gt_included_intl, yes, , [
     AC_REQUIRE([AM_ICONV_LINKFLAGS_BODY])
   ])
@@ -278,8 +273,8 @@ return * gettext ("")$gt_expression_test_code + 
__GNU_GETTEXT_SYMBOL_EXPRESSION
         dnl Mark actions used to generate GNU NLS library.
         BUILD_INCLUDED_LIBINTL=yes
         USE_INCLUDED_LIBINTL=yes
-        
LIBINTL="ifelse([$3],[],\${top_builddir}/intl,[$3])/libintl.[]gt_libtool_suffix_prefix[]a
 $LIBICONV $LIBTHREAD"
-        
LTLIBINTL="ifelse([$3],[],\${top_builddir}/intl,[$3])/libintl.[]gt_libtool_suffix_prefix[]a
 $LTLIBICONV $LTLIBTHREAD"
+        LIBINTL="ifelse([$3],[],\${top_builddir}/intl,[$3])/libintl.la 
$LIBICONV $LIBTHREAD"
+        LTLIBINTL="ifelse([$3],[],\${top_builddir}/intl,[$3])/libintl.la 
$LTLIBICONV $LTLIBTHREAD"
         LIBS=`echo " $LIBS " | sed -e 's/ -lintl / /' -e 's/^ //' -e 's/ $//'`
       fi
 
@@ -347,43 +342,14 @@ return * gettext ("")$gt_expression_test_code + 
__GNU_GETTEXT_SYMBOL_EXPRESSION
   fi
 
   ifelse(gt_included_intl, yes, [
-    dnl If this is used in GNU gettext we have to set BUILD_INCLUDED_LIBINTL
-    dnl to 'yes' because some of the testsuite requires it.
-    if test "$PACKAGE" = gettext-runtime || test "$PACKAGE" = gettext-tools; 
then
-      BUILD_INCLUDED_LIBINTL=yes
-    fi
+    dnl In GNU gettext we have to set BUILD_INCLUDED_LIBINTL to 'yes'
+    dnl because some of the testsuite requires it.
+    BUILD_INCLUDED_LIBINTL=yes
 
     dnl Make all variables we use known to autoconf.
     AC_SUBST([BUILD_INCLUDED_LIBINTL])
     AC_SUBST([USE_INCLUDED_LIBINTL])
     AC_SUBST([CATOBJEXT])
-
-    dnl For backward compatibility. Some configure.ins may be using this.
-    nls_cv_header_intl=
-    nls_cv_header_libgt=
-
-    dnl For backward compatibility. Some Makefiles may be using this.
-    DATADIRNAME=share
-    AC_SUBST([DATADIRNAME])
-
-    dnl For backward compatibility. Some Makefiles may be using this.
-    INSTOBJEXT=.mo
-    AC_SUBST([INSTOBJEXT])
-
-    dnl For backward compatibility. Some Makefiles may be using this.
-    GENCAT=gencat
-    AC_SUBST([GENCAT])
-
-    dnl For backward compatibility. Some Makefiles may be using this.
-    INTLOBJS=
-    if test "$USE_INCLUDED_LIBINTL" = yes; then
-      INTLOBJS="\$(GETTOBJS)"
-    fi
-    AC_SUBST([INTLOBJS])
-
-    dnl Enable libtool support if the surrounding package wishes it.
-    INTL_LIBTOOL_SUFFIX_PREFIX=gt_libtool_suffix_prefix
-    AC_SUBST([INTL_LIBTOOL_SUFFIX_PREFIX])
   ])
 
   dnl For backward compatibility. Some Makefiles may be using this.
diff --git a/m4/host-cpu-c-abi.m4 b/m4/host-cpu-c-abi.m4
new file mode 100644
index 00000000..7dc830ef
--- /dev/null
+++ b/m4/host-cpu-c-abi.m4
@@ -0,0 +1,675 @@
+# host-cpu-c-abi.m4 serial 13
+dnl Copyright (C) 2002-2021 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 From Bruno Haible and Sam Steingold.
+
+dnl Sets the HOST_CPU variable to the canonical name of the CPU.
+dnl Sets the HOST_CPU_C_ABI variable to the canonical name of the CPU with its
+dnl C language ABI (application binary interface).
+dnl Also defines __${HOST_CPU}__ and __${HOST_CPU_C_ABI}__ as C macros in
+dnl config.h.
+dnl
+dnl This canonical name can be used to select a particular assembly language
+dnl source file that will interoperate with C code on the given host.
+dnl
+dnl For example:
+dnl * 'i386' and 'sparc' are different canonical names, because code for i386
+dnl   will not run on SPARC CPUs and vice versa. They have different
+dnl   instruction sets.
+dnl * 'sparc' and 'sparc64' are different canonical names, because code for
+dnl   'sparc' and code for 'sparc64' cannot be linked together: 'sparc' code
+dnl   contains 32-bit instructions, whereas 'sparc64' code contains 64-bit
+dnl   instructions. A process on a SPARC CPU can be in 32-bit mode or in 64-bit
+dnl   mode, but not both.
+dnl * 'mips' and 'mipsn32' are different canonical names, because they use
+dnl   different argument passing and return conventions for C functions, and
+dnl   although the instruction set of 'mips' is a large subset of the
+dnl   instruction set of 'mipsn32'.
+dnl * 'mipsn32' and 'mips64' are different canonical names, because they use
+dnl   different sizes for the C types like 'int' and 'void *', and although
+dnl   the instruction sets of 'mipsn32' and 'mips64' are the same.
+dnl * The same canonical name is used for different endiannesses. You can
+dnl   determine the endianness through preprocessor symbols:
+dnl   - 'arm': test __ARMEL__.
+dnl   - 'mips', 'mipsn32', 'mips64': test _MIPSEB vs. _MIPSEL.
+dnl   - 'powerpc64': test _BIG_ENDIAN vs. _LITTLE_ENDIAN.
+dnl * The same name 'i386' is used for CPUs of type i386, i486, i586
+dnl   (Pentium), AMD K7, Pentium II, Pentium IV, etc., because
+dnl   - Instructions that do not exist on all of these CPUs (cmpxchg,
+dnl     MMX, SSE, SSE2, 3DNow! etc.) are not frequently used. If your
+dnl     assembly language source files use such instructions, you will
+dnl     need to make the distinction.
+dnl   - Speed of execution of the common instruction set is reasonable across
+dnl     the entire family of CPUs. If you have assembly language source files
+dnl     that are optimized for particular CPU types (like GNU gmp has), you
+dnl     will need to make the distinction.
+dnl   See <https://en.wikipedia.org/wiki/X86_instruction_listings>.
+AC_DEFUN([gl_HOST_CPU_C_ABI],
+[
+  AC_REQUIRE([AC_CANONICAL_HOST])
+  AC_REQUIRE([gl_C_ASM])
+  AC_CACHE_CHECK([host CPU and C ABI], [gl_cv_host_cpu_c_abi],
+    [case "$host_cpu" in
+
+changequote(,)dnl
+       i[34567]86 )
+changequote([,])dnl
+         gl_cv_host_cpu_c_abi=i386
+         ;;
+
+       x86_64 )
+         # On x86_64 systems, the C compiler may be generating code in one of
+         # these ABIs:
+         # - 64-bit instruction set, 64-bit pointers, 64-bit 'long': x86_64.
+         # - 64-bit instruction set, 64-bit pointers, 32-bit 'long': x86_64
+         #   with native Windows (mingw, MSVC).
+         # - 64-bit instruction set, 32-bit pointers, 32-bit 'long': 
x86_64-x32.
+         # - 32-bit instruction set, 32-bit pointers, 32-bit 'long': i386.
+         AC_COMPILE_IFELSE(
+           [AC_LANG_SOURCE(
+              [[#if (defined __x86_64__ || defined __amd64__ \
+                     || defined _M_X64 || defined _M_AMD64)
+                 int ok;
+                #else
+                 error fail
+                #endif
+              ]])],
+           [AC_COMPILE_IFELSE(
+              [AC_LANG_SOURCE(
+                 [[#if defined __ILP32__ || defined _ILP32
+                    int ok;
+                   #else
+                    error fail
+                   #endif
+                 ]])],
+              [gl_cv_host_cpu_c_abi=x86_64-x32],
+              [gl_cv_host_cpu_c_abi=x86_64])],
+           [gl_cv_host_cpu_c_abi=i386])
+         ;;
+
+changequote(,)dnl
+       alphaev[4-8] | alphaev56 | alphapca5[67] | alphaev6[78] )
+changequote([,])dnl
+         gl_cv_host_cpu_c_abi=alpha
+         ;;
+
+       arm* | aarch64 )
+         # Assume arm with EABI.
+         # On arm64 systems, the C compiler may be generating code in one of
+         # these ABIs:
+         # - aarch64 instruction set, 64-bit pointers, 64-bit 'long': arm64.
+         # - aarch64 instruction set, 32-bit pointers, 32-bit 'long': 
arm64-ilp32.
+         # - 32-bit instruction set, 32-bit pointers, 32-bit 'long': arm or 
armhf.
+         AC_COMPILE_IFELSE(
+           [AC_LANG_SOURCE(
+              [[#ifdef __aarch64__
+                 int ok;
+                #else
+                 error fail
+                #endif
+              ]])],
+           [AC_COMPILE_IFELSE(
+              [AC_LANG_SOURCE(
+                [[#if defined __ILP32__ || defined _ILP32
+                   int ok;
+                  #else
+                   error fail
+                  #endif
+                ]])],
+              [gl_cv_host_cpu_c_abi=arm64-ilp32],
+              [gl_cv_host_cpu_c_abi=arm64])],
+           [# Don't distinguish little-endian and big-endian arm, since they
+            # don't require different machine code for simple operations and
+            # since the user can distinguish them through the preprocessor
+            # defines __ARMEL__ vs. __ARMEB__.
+            # But distinguish arm which passes floating-point arguments and
+            # return values in integer registers (r0, r1, ...) - this is
+            # gcc -mfloat-abi=soft or gcc -mfloat-abi=softfp - from arm which
+            # passes them in float registers (s0, s1, ...) and double registers
+            # (d0, d1, ...) - this is gcc -mfloat-abi=hard. GCC 4.6 or newer
+            # sets the preprocessor defines __ARM_PCS (for the first case) and
+            # __ARM_PCS_VFP (for the second case), but older GCC does not.
+            echo 'double ddd; void func (double dd) { ddd = dd; }' > conftest.c
+            # Look for a reference to the register d0 in the .s file.
+            AC_TRY_COMMAND(${CC-cc} $CFLAGS $CPPFLAGS $gl_c_asm_opt 
conftest.c) >/dev/null 2>&1
+            if LC_ALL=C grep 'd0,' conftest.$gl_asmext >/dev/null; then
+              gl_cv_host_cpu_c_abi=armhf
+            else
+              gl_cv_host_cpu_c_abi=arm
+            fi
+            rm -f conftest*
+           ])
+         ;;
+
+       hppa1.0 | hppa1.1 | hppa2.0* | hppa64 )
+         # On hppa, the C compiler may be generating 32-bit code or 64-bit
+         # code. In the latter case, it defines _LP64 and __LP64__.
+         AC_COMPILE_IFELSE(
+           [AC_LANG_SOURCE(
+              [[#ifdef __LP64__
+                 int ok;
+                #else
+                 error fail
+                #endif
+              ]])],
+           [gl_cv_host_cpu_c_abi=hppa64],
+           [gl_cv_host_cpu_c_abi=hppa])
+         ;;
+
+       ia64* )
+         # On ia64 on HP-UX, the C compiler may be generating 64-bit code or
+         # 32-bit code. In the latter case, it defines _ILP32.
+         AC_COMPILE_IFELSE(
+           [AC_LANG_SOURCE(
+              [[#ifdef _ILP32
+                 int ok;
+                #else
+                 error fail
+                #endif
+              ]])],
+           [gl_cv_host_cpu_c_abi=ia64-ilp32],
+           [gl_cv_host_cpu_c_abi=ia64])
+         ;;
+
+       mips* )
+         # We should also check for (_MIPS_SZPTR == 64), but gcc keeps this
+         # at 32.
+         AC_COMPILE_IFELSE(
+           [AC_LANG_SOURCE(
+              [[#if defined _MIPS_SZLONG && (_MIPS_SZLONG == 64)
+                 int ok;
+                #else
+                 error fail
+                #endif
+              ]])],
+           [gl_cv_host_cpu_c_abi=mips64],
+           [# In the n32 ABI, _ABIN32 is defined, _ABIO32 is not defined (but
+            # may later get defined by <sgidefs.h>), and _MIPS_SIM == _ABIN32.
+            # In the 32 ABI, _ABIO32 is defined, _ABIN32 is not defined (but
+            # may later get defined by <sgidefs.h>), and _MIPS_SIM == _ABIO32.
+            AC_COMPILE_IFELSE(
+              [AC_LANG_SOURCE(
+                 [[#if (_MIPS_SIM == _ABIN32)
+                    int ok;
+                   #else
+                    error fail
+                   #endif
+                 ]])],
+              [gl_cv_host_cpu_c_abi=mipsn32],
+              [gl_cv_host_cpu_c_abi=mips])])
+         ;;
+
+       powerpc* )
+         # Different ABIs are in use on AIX vs. Mac OS X vs. Linux,*BSD.
+         # No need to distinguish them here; the caller may distinguish
+         # them based on the OS.
+         # On powerpc64 systems, the C compiler may still be generating
+         # 32-bit code. And on powerpc-ibm-aix systems, the C compiler may
+         # be generating 64-bit code.
+         AC_COMPILE_IFELSE(
+           [AC_LANG_SOURCE(
+              [[#if defined __powerpc64__ || defined _ARCH_PPC64
+                 int ok;
+                #else
+                 error fail
+                #endif
+              ]])],
+           [# On powerpc64, there are two ABIs on Linux: The AIX compatible
+            # one and the ELFv2 one. The latter defines _CALL_ELF=2.
+            AC_COMPILE_IFELSE(
+              [AC_LANG_SOURCE(
+                 [[#if defined _CALL_ELF && _CALL_ELF == 2
+                    int ok;
+                   #else
+                    error fail
+                   #endif
+                 ]])],
+              [gl_cv_host_cpu_c_abi=powerpc64-elfv2],
+              [gl_cv_host_cpu_c_abi=powerpc64])
+           ],
+           [gl_cv_host_cpu_c_abi=powerpc])
+         ;;
+
+       rs6000 )
+         gl_cv_host_cpu_c_abi=powerpc
+         ;;
+
+       riscv32 | riscv64 )
+         # There are 2 architectures (with variants): rv32* and rv64*.
+         AC_COMPILE_IFELSE(
+           [AC_LANG_SOURCE(
+              [[#if __riscv_xlen == 64
+                  int ok;
+                #else
+                  error fail
+                #endif
+              ]])],
+           [cpu=riscv64],
+           [cpu=riscv32])
+         # There are 6 ABIs: ilp32, ilp32f, ilp32d, lp64, lp64f, lp64d.
+         # Size of 'long' and 'void *':
+         AC_COMPILE_IFELSE(
+           [AC_LANG_SOURCE(
+              [[#if defined __LP64__
+                  int ok;
+                #else
+                  error fail
+                #endif
+              ]])],
+           [main_abi=lp64],
+           [main_abi=ilp32])
+         # Float ABIs:
+         # __riscv_float_abi_double:
+         #   'float' and 'double' are passed in floating-point registers.
+         # __riscv_float_abi_single:
+         #   'float' are passed in floating-point registers.
+         # __riscv_float_abi_soft:
+         #   No values are passed in floating-point registers.
+         AC_COMPILE_IFELSE(
+           [AC_LANG_SOURCE(
+              [[#if defined __riscv_float_abi_double
+                  int ok;
+                #else
+                  error fail
+                #endif
+              ]])],
+           [float_abi=d],
+           [AC_COMPILE_IFELSE(
+              [AC_LANG_SOURCE(
+                 [[#if defined __riscv_float_abi_single
+                     int ok;
+                   #else
+                     error fail
+                   #endif
+                 ]])],
+              [float_abi=f],
+              [float_abi=''])
+           ])
+         gl_cv_host_cpu_c_abi="${cpu}-${main_abi}${float_abi}"
+         ;;
+
+       s390* )
+         # On s390x, the C compiler may be generating 64-bit (= s390x) code
+         # or 31-bit (= s390) code.
+         AC_COMPILE_IFELSE(
+           [AC_LANG_SOURCE(
+              [[#if defined __LP64__ || defined __s390x__
+                  int ok;
+                #else
+                  error fail
+                #endif
+              ]])],
+           [gl_cv_host_cpu_c_abi=s390x],
+           [gl_cv_host_cpu_c_abi=s390])
+         ;;
+
+       sparc | sparc64 )
+         # UltraSPARCs running Linux have `uname -m` = "sparc64", but the
+         # C compiler still generates 32-bit code.
+         AC_COMPILE_IFELSE(
+           [AC_LANG_SOURCE(
+              [[#if defined __sparcv9 || defined __arch64__
+                 int ok;
+                #else
+                 error fail
+                #endif
+              ]])],
+           [gl_cv_host_cpu_c_abi=sparc64],
+           [gl_cv_host_cpu_c_abi=sparc])
+         ;;
+
+       *)
+         gl_cv_host_cpu_c_abi="$host_cpu"
+         ;;
+     esac
+    ])
+
+  dnl In most cases, $HOST_CPU and $HOST_CPU_C_ABI are the same.
+  HOST_CPU=`echo "$gl_cv_host_cpu_c_abi" | sed -e 's/-.*//'`
+  HOST_CPU_C_ABI="$gl_cv_host_cpu_c_abi"
+  AC_SUBST([HOST_CPU])
+  AC_SUBST([HOST_CPU_C_ABI])
+
+  # This was
+  #   AC_DEFINE_UNQUOTED([__${HOST_CPU}__])
+  #   AC_DEFINE_UNQUOTED([__${HOST_CPU_C_ABI}__])
+  # earlier, but KAI C++ 3.2d doesn't like this.
+  sed -e 's/-/_/g' >> confdefs.h <<EOF
+#ifndef __${HOST_CPU}__
+#define __${HOST_CPU}__ 1
+#endif
+#ifndef __${HOST_CPU_C_ABI}__
+#define __${HOST_CPU_C_ABI}__ 1
+#endif
+EOF
+  AH_TOP([/* CPU and C ABI indicator */
+#ifndef __i386__
+#undef __i386__
+#endif
+#ifndef __x86_64_x32__
+#undef __x86_64_x32__
+#endif
+#ifndef __x86_64__
+#undef __x86_64__
+#endif
+#ifndef __alpha__
+#undef __alpha__
+#endif
+#ifndef __arm__
+#undef __arm__
+#endif
+#ifndef __armhf__
+#undef __armhf__
+#endif
+#ifndef __arm64_ilp32__
+#undef __arm64_ilp32__
+#endif
+#ifndef __arm64__
+#undef __arm64__
+#endif
+#ifndef __hppa__
+#undef __hppa__
+#endif
+#ifndef __hppa64__
+#undef __hppa64__
+#endif
+#ifndef __ia64_ilp32__
+#undef __ia64_ilp32__
+#endif
+#ifndef __ia64__
+#undef __ia64__
+#endif
+#ifndef __m68k__
+#undef __m68k__
+#endif
+#ifndef __mips__
+#undef __mips__
+#endif
+#ifndef __mipsn32__
+#undef __mipsn32__
+#endif
+#ifndef __mips64__
+#undef __mips64__
+#endif
+#ifndef __powerpc__
+#undef __powerpc__
+#endif
+#ifndef __powerpc64__
+#undef __powerpc64__
+#endif
+#ifndef __powerpc64_elfv2__
+#undef __powerpc64_elfv2__
+#endif
+#ifndef __riscv32__
+#undef __riscv32__
+#endif
+#ifndef __riscv64__
+#undef __riscv64__
+#endif
+#ifndef __riscv32_ilp32__
+#undef __riscv32_ilp32__
+#endif
+#ifndef __riscv32_ilp32f__
+#undef __riscv32_ilp32f__
+#endif
+#ifndef __riscv32_ilp32d__
+#undef __riscv32_ilp32d__
+#endif
+#ifndef __riscv64_ilp32__
+#undef __riscv64_ilp32__
+#endif
+#ifndef __riscv64_ilp32f__
+#undef __riscv64_ilp32f__
+#endif
+#ifndef __riscv64_ilp32d__
+#undef __riscv64_ilp32d__
+#endif
+#ifndef __riscv64_lp64__
+#undef __riscv64_lp64__
+#endif
+#ifndef __riscv64_lp64f__
+#undef __riscv64_lp64f__
+#endif
+#ifndef __riscv64_lp64d__
+#undef __riscv64_lp64d__
+#endif
+#ifndef __s390__
+#undef __s390__
+#endif
+#ifndef __s390x__
+#undef __s390x__
+#endif
+#ifndef __sh__
+#undef __sh__
+#endif
+#ifndef __sparc__
+#undef __sparc__
+#endif
+#ifndef __sparc64__
+#undef __sparc64__
+#endif
+])
+
+])
+
+
+dnl Sets the HOST_CPU_C_ABI_32BIT variable to 'yes' if the C language ABI
+dnl (application binary interface) is a 32-bit one, to 'no' if it is a 64-bit
+dnl one, or to 'unknown' if unknown.
+dnl This is a simplified variant of gl_HOST_CPU_C_ABI.
+AC_DEFUN([gl_HOST_CPU_C_ABI_32BIT],
+[
+  AC_REQUIRE([AC_CANONICAL_HOST])
+  AC_CACHE_CHECK([32-bit host C ABI], [gl_cv_host_cpu_c_abi_32bit],
+    [if test -n "$gl_cv_host_cpu_c_abi"; then
+       case "$gl_cv_host_cpu_c_abi" in
+         i386 | x86_64-x32 | arm | armhf | arm64-ilp32 | hppa | ia64-ilp32 | 
mips | mipsn32 | powerpc | riscv*-ilp32* | s390 | sparc)
+           gl_cv_host_cpu_c_abi_32bit=yes ;;
+         x86_64 | alpha | arm64 | hppa64 | ia64 | mips64 | powerpc64 | 
powerpc64-elfv2 | riscv*-lp64* | s390x | sparc64 )
+           gl_cv_host_cpu_c_abi_32bit=no ;;
+         *)
+           gl_cv_host_cpu_c_abi_32bit=unknown ;;
+       esac
+     else
+       case "$host_cpu" in
+
+         # CPUs that only support a 32-bit ABI.
+         arc \
+         | bfin \
+         | cris* \
+         | csky \
+         | epiphany \
+         | ft32 \
+         | h8300 \
+         | m68k \
+         | microblaze | microblazeel \
+         | nds32 | nds32le | nds32be \
+         | nios2 | nios2eb | nios2el \
+         | or1k* \
+         | or32 \
+         | sh | sh[1234] | sh[1234]e[lb] \
+         | tic6x \
+         | xtensa* )
+           gl_cv_host_cpu_c_abi_32bit=yes
+           ;;
+
+         # CPUs that only support a 64-bit ABI.
+changequote(,)dnl
+         alpha | alphaev[4-8] | alphaev56 | alphapca5[67] | alphaev6[78] \
+         | mmix )
+changequote([,])dnl
+           gl_cv_host_cpu_c_abi_32bit=no
+           ;;
+
+changequote(,)dnl
+         i[34567]86 )
+changequote([,])dnl
+           gl_cv_host_cpu_c_abi_32bit=yes
+           ;;
+
+         x86_64 )
+           # On x86_64 systems, the C compiler may be generating code in one of
+           # these ABIs:
+           # - 64-bit instruction set, 64-bit pointers, 64-bit 'long': x86_64.
+           # - 64-bit instruction set, 64-bit pointers, 32-bit 'long': x86_64
+           #   with native Windows (mingw, MSVC).
+           # - 64-bit instruction set, 32-bit pointers, 32-bit 'long': 
x86_64-x32.
+           # - 32-bit instruction set, 32-bit pointers, 32-bit 'long': i386.
+           AC_COMPILE_IFELSE(
+             [AC_LANG_SOURCE(
+                [[#if (defined __x86_64__ || defined __amd64__ \
+                       || defined _M_X64 || defined _M_AMD64) \
+                      && !(defined __ILP32__ || defined _ILP32)
+                   int ok;
+                  #else
+                   error fail
+                  #endif
+                ]])],
+             [gl_cv_host_cpu_c_abi_32bit=no],
+             [gl_cv_host_cpu_c_abi_32bit=yes])
+           ;;
+
+         arm* | aarch64 )
+           # Assume arm with EABI.
+           # On arm64 systems, the C compiler may be generating code in one of
+           # these ABIs:
+           # - aarch64 instruction set, 64-bit pointers, 64-bit 'long': arm64.
+           # - aarch64 instruction set, 32-bit pointers, 32-bit 'long': 
arm64-ilp32.
+           # - 32-bit instruction set, 32-bit pointers, 32-bit 'long': arm or 
armhf.
+           AC_COMPILE_IFELSE(
+             [AC_LANG_SOURCE(
+                [[#if defined __aarch64__ && !(defined __ILP32__ || defined 
_ILP32)
+                   int ok;
+                  #else
+                   error fail
+                  #endif
+                ]])],
+             [gl_cv_host_cpu_c_abi_32bit=no],
+             [gl_cv_host_cpu_c_abi_32bit=yes])
+           ;;
+
+         hppa1.0 | hppa1.1 | hppa2.0* | hppa64 )
+           # On hppa, the C compiler may be generating 32-bit code or 64-bit
+           # code. In the latter case, it defines _LP64 and __LP64__.
+           AC_COMPILE_IFELSE(
+             [AC_LANG_SOURCE(
+                [[#ifdef __LP64__
+                   int ok;
+                  #else
+                   error fail
+                  #endif
+                ]])],
+             [gl_cv_host_cpu_c_abi_32bit=no],
+             [gl_cv_host_cpu_c_abi_32bit=yes])
+           ;;
+
+         ia64* )
+           # On ia64 on HP-UX, the C compiler may be generating 64-bit code or
+           # 32-bit code. In the latter case, it defines _ILP32.
+           AC_COMPILE_IFELSE(
+             [AC_LANG_SOURCE(
+                [[#ifdef _ILP32
+                   int ok;
+                  #else
+                   error fail
+                  #endif
+                ]])],
+             [gl_cv_host_cpu_c_abi_32bit=yes],
+             [gl_cv_host_cpu_c_abi_32bit=no])
+           ;;
+
+         mips* )
+           # We should also check for (_MIPS_SZPTR == 64), but gcc keeps this
+           # at 32.
+           AC_COMPILE_IFELSE(
+             [AC_LANG_SOURCE(
+                [[#if defined _MIPS_SZLONG && (_MIPS_SZLONG == 64)
+                   int ok;
+                  #else
+                   error fail
+                  #endif
+                ]])],
+             [gl_cv_host_cpu_c_abi_32bit=no],
+             [gl_cv_host_cpu_c_abi_32bit=yes])
+           ;;
+
+         powerpc* )
+           # Different ABIs are in use on AIX vs. Mac OS X vs. Linux,*BSD.
+           # No need to distinguish them here; the caller may distinguish
+           # them based on the OS.
+           # On powerpc64 systems, the C compiler may still be generating
+           # 32-bit code. And on powerpc-ibm-aix systems, the C compiler may
+           # be generating 64-bit code.
+           AC_COMPILE_IFELSE(
+             [AC_LANG_SOURCE(
+                [[#if defined __powerpc64__ || defined _ARCH_PPC64
+                   int ok;
+                  #else
+                   error fail
+                  #endif
+                ]])],
+             [gl_cv_host_cpu_c_abi_32bit=no],
+             [gl_cv_host_cpu_c_abi_32bit=yes])
+           ;;
+
+         rs6000 )
+           gl_cv_host_cpu_c_abi_32bit=yes
+           ;;
+
+         riscv32 | riscv64 )
+           # There are 6 ABIs: ilp32, ilp32f, ilp32d, lp64, lp64f, lp64d.
+           # Size of 'long' and 'void *':
+           AC_COMPILE_IFELSE(
+             [AC_LANG_SOURCE(
+                [[#if defined __LP64__
+                    int ok;
+                  #else
+                    error fail
+                  #endif
+                ]])],
+             [gl_cv_host_cpu_c_abi_32bit=no],
+             [gl_cv_host_cpu_c_abi_32bit=yes])
+           ;;
+
+         s390* )
+           # On s390x, the C compiler may be generating 64-bit (= s390x) code
+           # or 31-bit (= s390) code.
+           AC_COMPILE_IFELSE(
+             [AC_LANG_SOURCE(
+                [[#if defined __LP64__ || defined __s390x__
+                    int ok;
+                  #else
+                    error fail
+                  #endif
+                ]])],
+             [gl_cv_host_cpu_c_abi_32bit=no],
+             [gl_cv_host_cpu_c_abi_32bit=yes])
+           ;;
+
+         sparc | sparc64 )
+           # UltraSPARCs running Linux have `uname -m` = "sparc64", but the
+           # C compiler still generates 32-bit code.
+           AC_COMPILE_IFELSE(
+             [AC_LANG_SOURCE(
+                [[#if defined __sparcv9 || defined __arch64__
+                   int ok;
+                  #else
+                   error fail
+                  #endif
+                ]])],
+             [gl_cv_host_cpu_c_abi_32bit=no],
+             [gl_cv_host_cpu_c_abi_32bit=yes])
+           ;;
+
+         *)
+           gl_cv_host_cpu_c_abi_32bit=unknown
+           ;;
+       esac
+     fi
+    ])
+
+  HOST_CPU_C_ABI_32BIT="$gl_cv_host_cpu_c_abi_32bit"
+])
diff --git a/m4/iconv.m4 b/m4/iconv.m4
index aa159c53..d0e61de2 100644
--- a/m4/iconv.m4
+++ b/m4/iconv.m4
@@ -1,11 +1,18 @@
-# iconv.m4 serial 19 (gettext-0.18.2)
-dnl Copyright (C) 2000-2002, 2007-2014, 2016 Free Software Foundation, Inc.
+# iconv.m4 serial 24
+dnl Copyright (C) 2000-2002, 2007-2014, 2016-2021 Free Software Foundation,
+dnl 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 From Bruno Haible.
 
+AC_PREREQ([2.64])
+
+dnl Note: AM_ICONV is documented in the GNU gettext manual
+dnl <https://www.gnu.org/software/gettext/manual/html_node/AM_005fICONV.html>.
+dnl Don't make changes that are incompatible with that documentation!
+
 AC_DEFUN([AM_ICONV_LINKFLAGS_BODY],
 [
   dnl Prerequisites of AC_LIB_LINKFLAGS_BODY.
@@ -85,8 +92,9 @@ AC_DEFUN([AM_ICONV_LINK],
 #endif
              ]],
              [[int result = 0;
-  /* Test against AIX 5.1 bug: Failures are not distinguishable from successful
-     returns.  */
+  /* Test against AIX 5.1...7.2 bug: Failures are not distinguishable from
+     successful returns.  This is even documented in
+     
<https://www.ibm.com/support/knowledgecenter/ssw_aix_72/i_bostechref/iconv.html>
 */
   {
     iconv_t cd_utf8_to_88591 = iconv_open ("ISO8859-1", "UTF-8");
     if (cd_utf8_to_88591 != (iconv_t)(-1))
@@ -167,15 +175,27 @@ AC_DEFUN([AM_ICONV_LINK],
 #endif
   /* Test against HP-UX 11.11 bug: No converter from EUC-JP to UTF-8 is
      provided.  */
-  if (/* Try standardized names.  */
-      iconv_open ("UTF-8", "EUC-JP") == (iconv_t)(-1)
-      /* Try IRIX, OSF/1 names.  */
-      && iconv_open ("UTF-8", "eucJP") == (iconv_t)(-1)
-      /* Try AIX names.  */
-      && iconv_open ("UTF-8", "IBM-eucJP") == (iconv_t)(-1)
-      /* Try HP-UX names.  */
-      && iconv_open ("utf8", "eucJP") == (iconv_t)(-1))
-    result |= 16;
+  {
+    /* Try standardized names.  */
+    iconv_t cd1 = iconv_open ("UTF-8", "EUC-JP");
+    /* Try IRIX, OSF/1 names.  */
+    iconv_t cd2 = iconv_open ("UTF-8", "eucJP");
+    /* Try AIX names.  */
+    iconv_t cd3 = iconv_open ("UTF-8", "IBM-eucJP");
+    /* Try HP-UX names.  */
+    iconv_t cd4 = iconv_open ("utf8", "eucJP");
+    if (cd1 == (iconv_t)(-1) && cd2 == (iconv_t)(-1)
+        && cd3 == (iconv_t)(-1) && cd4 == (iconv_t)(-1))
+      result |= 16;
+    if (cd1 != (iconv_t)(-1))
+      iconv_close (cd1);
+    if (cd2 != (iconv_t)(-1))
+      iconv_close (cd2);
+    if (cd3 != (iconv_t)(-1))
+      iconv_close (cd3);
+    if (cd4 != (iconv_t)(-1))
+      iconv_close (cd4);
+  }
   return result;
 ]])],
           [am_cv_func_iconv_works=yes], ,
@@ -212,8 +232,7 @@ AC_DEFUN([AM_ICONV_LINK],
   AC_SUBST([LTLIBICONV])
 ])
 
-dnl Define AM_ICONV using AC_DEFUN_ONCE for Autoconf >= 2.64, in order to
-dnl avoid warnings like
+dnl Define AM_ICONV using AC_DEFUN_ONCE, in order to avoid warnings like
 dnl "warning: AC_REQUIRE: `AM_ICONV' was expanded before it was required".
 dnl This is tricky because of the way 'aclocal' is implemented:
 dnl - It requires defining an auxiliary macro whose name ends in AC_DEFUN.
@@ -221,51 +240,44 @@ dnl   Otherwise aclocal's initial scan pass would miss 
the macro definition.
 dnl - It requires a line break inside the AC_DEFUN_ONCE and AC_DEFUN 
expansions.
 dnl   Otherwise aclocal would emit many "Use of uninitialized value $1"
 dnl   warnings.
-m4_define([gl_iconv_AC_DEFUN],
-  m4_version_prereq([2.64],
-    [[AC_DEFUN_ONCE(
-        [$1], [$2])]],
-    [m4_ifdef([gl_00GNULIB],
-       [[AC_DEFUN_ONCE(
-           [$1], [$2])]],
-       [[AC_DEFUN(
-           [$1], [$2])]])]))
-gl_iconv_AC_DEFUN([AM_ICONV],
+AC_DEFUN_ONCE([AM_ICONV],
 [
   AM_ICONV_LINK
   if test "$am_cv_func_iconv" = yes; then
-    AC_MSG_CHECKING([for iconv declaration])
-    AC_CACHE_VAL([am_cv_proto_iconv], [
-      AC_COMPILE_IFELSE(
-        [AC_LANG_PROGRAM(
-           [[
+    AC_CACHE_CHECK([whether iconv is compatible with its POSIX signature],
+      [gl_cv_iconv_nonconst],
+      [AC_COMPILE_IFELSE(
+         [AC_LANG_PROGRAM(
+            [[
 #include <stdlib.h>
 #include <iconv.h>
 extern
 #ifdef __cplusplus
 "C"
 #endif
-#if defined(__STDC__) || defined(_MSC_VER) || defined(__cplusplus)
 size_t iconv (iconv_t cd, char * *inbuf, size_t *inbytesleft, char * *outbuf, 
size_t *outbytesleft);
-#else
-size_t iconv();
-#endif
-           ]],
-           [[]])],
-        [am_cv_proto_iconv_arg1=""],
-        [am_cv_proto_iconv_arg1="const"])
-      am_cv_proto_iconv="extern size_t iconv (iconv_t cd, 
$am_cv_proto_iconv_arg1 char * *inbuf, size_t *inbytesleft, char * *outbuf, 
size_t *outbytesleft);"])
-    am_cv_proto_iconv=`echo "[$]am_cv_proto_iconv" | tr -s ' ' | sed -e 's/( 
/(/'`
-    AC_MSG_RESULT([
-         $am_cv_proto_iconv])
-    AC_DEFINE_UNQUOTED([ICONV_CONST], [$am_cv_proto_iconv_arg1],
-      [Define as const if the declaration of iconv() needs const.])
-    dnl Also substitute ICONV_CONST in the gnulib generated <iconv.h>.
-    m4_ifdef([gl_ICONV_H_DEFAULTS],
-      [AC_REQUIRE([gl_ICONV_H_DEFAULTS])
-       if test -n "$am_cv_proto_iconv_arg1"; then
-         ICONV_CONST="const"
-       fi
+            ]],
+            [[]])],
+         [gl_cv_iconv_nonconst=yes],
+         [gl_cv_iconv_nonconst=no])
       ])
+  else
+    dnl When compiling GNU libiconv on a system that does not have iconv yet,
+    dnl pick the POSIX compliant declaration without 'const'.
+    gl_cv_iconv_nonconst=yes
   fi
+  if test $gl_cv_iconv_nonconst = yes; then
+    iconv_arg1=""
+  else
+    iconv_arg1="const"
+  fi
+  AC_DEFINE_UNQUOTED([ICONV_CONST], [$iconv_arg1],
+    [Define as const if the declaration of iconv() needs const.])
+  dnl Also substitute ICONV_CONST in the gnulib generated <iconv.h>.
+  m4_ifdef([gl_ICONV_H_DEFAULTS],
+    [AC_REQUIRE([gl_ICONV_H_DEFAULTS])
+     if test $gl_cv_iconv_nonconst != yes; then
+       ICONV_CONST="const"
+     fi
+    ])
 ])
diff --git a/m4/intlmacosx.m4 b/m4/intlmacosx.m4
index aca924c6..4ae0d128 100644
--- a/m4/intlmacosx.m4
+++ b/m4/intlmacosx.m4
@@ -1,15 +1,15 @@
-# intlmacosx.m4 serial 5 (gettext-0.18.2)
-dnl Copyright (C) 2004-2014, 2016 Free Software Foundation, Inc.
+# intlmacosx.m4 serial 8 (gettext-0.20.2)
+dnl Copyright (C) 2004-2014, 2016, 2019-2021 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
 dnl This file can be used in projects which are not available under
-dnl the GNU General Public License or the GNU Library General Public
+dnl the GNU General Public License or the GNU Lesser General Public
 dnl License but which still want to provide support for the GNU gettext
 dnl functionality.
 dnl Please note that the actual code of the GNU gettext library is covered
-dnl by the GNU Library General Public License, and the rest of the GNU
+dnl by the GNU Lesser General Public License, and the rest of the GNU
 dnl gettext package is covered by the GNU General Public License.
 dnl They are *not* in the public domain.
 
@@ -17,7 +17,7 @@ dnl Checks for special options needed on Mac OS X.
 dnl Defines INTL_MACOSX_LIBS.
 AC_DEFUN([gt_INTL_MACOSX],
 [
-  dnl Check for API introduced in Mac OS X 10.2.
+  dnl Check for API introduced in Mac OS X 10.4.
   AC_CACHE_CHECK([for CFPreferencesCopyAppValue],
     [gt_cv_func_CFPreferencesCopyAppValue],
     [gt_save_LIBS="$LIBS"
@@ -33,23 +33,32 @@ AC_DEFUN([gt_INTL_MACOSX],
     AC_DEFINE([HAVE_CFPREFERENCESCOPYAPPVALUE], [1],
       [Define to 1 if you have the Mac OS X function CFPreferencesCopyAppValue 
in the CoreFoundation framework.])
   fi
-  dnl Check for API introduced in Mac OS X 10.3.
-  AC_CACHE_CHECK([for CFLocaleCopyCurrent], [gt_cv_func_CFLocaleCopyCurrent],
+  dnl Don't check for the API introduced in Mac OS X 10.5, CFLocaleCopyCurrent,
+  dnl because in macOS 10.13.4 it has the following behaviour:
+  dnl When two or more languages are specified in the
+  dnl "System Preferences > Language & Region > Preferred Languages" panel,
+  dnl it returns en_CC where CC is the territory (even when English is not 
among
+  dnl the preferred languages!).  What we want instead is what
+  dnl CFLocaleCopyCurrent returned in earlier macOS releases and what
+  dnl CFPreferencesCopyAppValue still returns, namely ll_CC where ll is the
+  dnl first among the preferred languages and CC is the territory.
+  AC_CACHE_CHECK([for CFLocaleCopyPreferredLanguages], 
[gt_cv_func_CFLocaleCopyPreferredLanguages],
     [gt_save_LIBS="$LIBS"
      LIBS="$LIBS -Wl,-framework -Wl,CoreFoundation"
      AC_LINK_IFELSE(
        [AC_LANG_PROGRAM(
           [[#include <CoreFoundation/CFLocale.h>]],
-          [[CFLocaleCopyCurrent();]])],
-       [gt_cv_func_CFLocaleCopyCurrent=yes],
-       [gt_cv_func_CFLocaleCopyCurrent=no])
+          [[CFLocaleCopyPreferredLanguages();]])],
+       [gt_cv_func_CFLocaleCopyPreferredLanguages=yes],
+       [gt_cv_func_CFLocaleCopyPreferredLanguages=no])
      LIBS="$gt_save_LIBS"])
-  if test $gt_cv_func_CFLocaleCopyCurrent = yes; then
-    AC_DEFINE([HAVE_CFLOCALECOPYCURRENT], [1],
-      [Define to 1 if you have the Mac OS X function CFLocaleCopyCurrent in 
the CoreFoundation framework.])
+  if test $gt_cv_func_CFLocaleCopyPreferredLanguages = yes; then
+    AC_DEFINE([HAVE_CFLOCALECOPYPREFERREDLANGUAGES], [1],
+      [Define to 1 if you have the Mac OS X function 
CFLocaleCopyPreferredLanguages in the CoreFoundation framework.])
   fi
   INTL_MACOSX_LIBS=
-  if test $gt_cv_func_CFPreferencesCopyAppValue = yes || test 
$gt_cv_func_CFLocaleCopyCurrent = yes; then
+  if test $gt_cv_func_CFPreferencesCopyAppValue = yes \
+     || test $gt_cv_func_CFLocaleCopyPreferredLanguages = yes; then
     INTL_MACOSX_LIBS="-Wl,-framework -Wl,CoreFoundation"
   fi
   AC_SUBST([INTL_MACOSX_LIBS])
diff --git a/m4/lcmessage.m4 b/m4/lcmessage.m4
index 1c24d6d9..a52700e7 100644
--- a/m4/lcmessage.m4
+++ b/m4/lcmessage.m4
@@ -1,16 +1,16 @@
-# lcmessage.m4 serial 7 (gettext-0.18.2)
-dnl Copyright (C) 1995-2002, 2004-2005, 2008-2014, 2016 Free Software
-dnl Foundation, Inc.
+# lcmessage.m4 serial 8
+dnl Copyright (C) 1995-2002, 2004-2005, 2008-2014, 2016, 2019-2021 Free
+dnl 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
 dnl This file can be used in projects which are not available under
-dnl the GNU General Public License or the GNU Library General Public
+dnl the GNU General Public License or the GNU Lesser General Public
 dnl License but which still want to provide support for the GNU gettext
 dnl functionality.
 dnl Please note that the actual code of the GNU gettext library is covered
-dnl by the GNU Library General Public License, and the rest of the GNU
+dnl by the GNU Lesser General Public License, and the rest of the GNU
 dnl gettext package is covered by the GNU General Public License.
 dnl They are *not* in the public domain.
 
diff --git a/m4/lib-ld.m4 b/m4/lib-ld.m4
index 6209de65..aa07cb4b 100644
--- a/m4/lib-ld.m4
+++ b/m4/lib-ld.m4
@@ -1,5 +1,5 @@
-# lib-ld.m4 serial 6
-dnl Copyright (C) 1996-2003, 2009-2016 Free Software Foundation, Inc.
+# lib-ld.m4 serial 9
+dnl Copyright (C) 1996-2003, 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.
@@ -47,73 +47,122 @@ if test "${PATH_SEPARATOR+set}" != set; then
        }
 fi
 
-ac_prog=ld
-if test "$GCC" = yes; then
-  # Check if gcc -print-prog-name=ld gives a path.
+if test -n "$LD"; then
+  AC_MSG_CHECKING([for ld])
+elif test "$GCC" = yes; then
   AC_MSG_CHECKING([for ld used by $CC])
-  case $host in
-  *-*-mingw*)
-    # gcc leaves a trailing carriage return which upsets mingw
-    ac_prog=`($CC -print-prog-name=ld) 2>&5 | tr -d '\015'` ;;
-  *)
-    ac_prog=`($CC -print-prog-name=ld) 2>&5` ;;
-  esac
-  case $ac_prog in
-    # Accept absolute paths.
-    [[\\/]]* | ?:[[\\/]]*)
-      re_direlt='/[[^/]][[^/]]*/\.\./'
-      # Canonicalize the pathname of ld
-      ac_prog=`echo "$ac_prog"| sed 's%\\\\%/%g'`
-      while echo "$ac_prog" | grep "$re_direlt" > /dev/null 2>&1; do
-        ac_prog=`echo $ac_prog| sed "s%$re_direlt%/%"`
-      done
-      test -z "$LD" && LD="$ac_prog"
-      ;;
-  "")
-    # If it fails, then pretend we aren't using GCC.
-    ac_prog=ld
-    ;;
-  *)
-    # If it is relative, then search for the first ld in PATH.
-    with_gnu_ld=unknown
-    ;;
-  esac
 elif test "$with_gnu_ld" = yes; then
   AC_MSG_CHECKING([for GNU ld])
 else
   AC_MSG_CHECKING([for non-GNU ld])
 fi
-AC_CACHE_VAL([acl_cv_path_LD],
-[if test -z "$LD"; then
-  acl_save_ifs="$IFS"; IFS=$PATH_SEPARATOR
-  for ac_dir in $PATH; do
-    IFS="$acl_save_ifs"
-    test -z "$ac_dir" && ac_dir=.
-    if test -f "$ac_dir/$ac_prog" || test -f "$ac_dir/$ac_prog$ac_exeext"; then
-      acl_cv_path_LD="$ac_dir/$ac_prog"
-      # Check to see if the program is GNU ld.  I'd rather use --version,
-      # but apparently some variants of GNU ld only accept -v.
-      # Break only if it was the GNU/non-GNU ld that we prefer.
-      case `"$acl_cv_path_LD" -v 2>&1 </dev/null` in
-      *GNU* | *'with BFD'*)
-        test "$with_gnu_ld" != no && break
-        ;;
-      *)
-        test "$with_gnu_ld" != yes && break
-        ;;
+if test -n "$LD"; then
+  # Let the user override the test with a path.
+  :
+else
+  AC_CACHE_VAL([acl_cv_path_LD],
+  [
+    acl_cv_path_LD= # Final result of this test
+    ac_prog=ld # Program to search in $PATH
+    if test "$GCC" = yes; then
+      # Check if gcc -print-prog-name=ld gives a path.
+      case $host in
+        *-*-mingw*)
+          # gcc leaves a trailing carriage return which upsets mingw
+          acl_output=`($CC -print-prog-name=ld) 2>&5 | tr -d '\015'` ;;
+        *)
+          acl_output=`($CC -print-prog-name=ld) 2>&5` ;;
+      esac
+      case $acl_output in
+        # Accept absolute paths.
+        [[\\/]]* | ?:[[\\/]]*)
+          re_direlt='/[[^/]][[^/]]*/\.\./'
+          # Canonicalize the pathname of ld
+          acl_output=`echo "$acl_output" | sed 's%\\\\%/%g'`
+          while echo "$acl_output" | grep "$re_direlt" > /dev/null 2>&1; do
+            acl_output=`echo $acl_output | sed "s%$re_direlt%/%"`
+          done
+          # Got the pathname. No search in PATH is needed.
+          acl_cv_path_LD="$acl_output"
+          ac_prog=
+          ;;
+        "")
+          # If it fails, then pretend we aren't using GCC.
+          ;;
+        *)
+          # If it is relative, then search for the first ld in PATH.
+          with_gnu_ld=unknown
+          ;;
       esac
     fi
-  done
-  IFS="$acl_save_ifs"
-else
-  acl_cv_path_LD="$LD" # Let the user override the test with a path.
-fi])
-LD="$acl_cv_path_LD"
+    if test -n "$ac_prog"; then
+      # Search for $ac_prog in $PATH.
+      acl_save_ifs="$IFS"; IFS=$PATH_SEPARATOR
+      for ac_dir in $PATH; do
+        IFS="$acl_save_ifs"
+        test -z "$ac_dir" && ac_dir=.
+        if test -f "$ac_dir/$ac_prog" || test -f "$ac_dir/$ac_prog$ac_exeext"; 
then
+          acl_cv_path_LD="$ac_dir/$ac_prog"
+          # Check to see if the program is GNU ld.  I'd rather use --version,
+          # but apparently some variants of GNU ld only accept -v.
+          # Break only if it was the GNU/non-GNU ld that we prefer.
+          case `"$acl_cv_path_LD" -v 2>&1 </dev/null` in
+            *GNU* | *'with BFD'*)
+              test "$with_gnu_ld" != no && break
+              ;;
+            *)
+              test "$with_gnu_ld" != yes && break
+              ;;
+          esac
+        fi
+      done
+      IFS="$acl_save_ifs"
+    fi
+    case $host in
+      *-*-aix*)
+        AC_COMPILE_IFELSE(
+          [AC_LANG_SOURCE(
+             [[#if defined __powerpc64__ || defined _ARCH_PPC64
+                int ok;
+               #else
+                error fail
+               #endif
+             ]])],
+          [# The compiler produces 64-bit code. Add option '-b64' so that the
+           # linker groks 64-bit object files.
+           case "$acl_cv_path_LD " in
+             *" -b64 "*) ;;
+             *) acl_cv_path_LD="$acl_cv_path_LD -b64" ;;
+           esac
+          ], [])
+        ;;
+      sparc64-*-netbsd*)
+        AC_COMPILE_IFELSE(
+          [AC_LANG_SOURCE(
+             [[#if defined __sparcv9 || defined __arch64__
+                int ok;
+               #else
+                error fail
+               #endif
+             ]])],
+          [],
+          [# The compiler produces 32-bit code. Add option '-m elf32_sparc'
+           # so that the linker groks 32-bit object files.
+           case "$acl_cv_path_LD " in
+             *" -m elf32_sparc "*) ;;
+             *) acl_cv_path_LD="$acl_cv_path_LD -m elf32_sparc" ;;
+           esac
+          ])
+        ;;
+    esac
+  ])
+  LD="$acl_cv_path_LD"
+fi
 if test -n "$LD"; then
   AC_MSG_RESULT([$LD])
 else
   AC_MSG_RESULT([no])
+  AC_MSG_ERROR([no acceptable ld found in \$PATH])
 fi
-test -z "$LD" && AC_MSG_ERROR([no acceptable ld found in \$PATH])
 AC_LIB_PROG_LD_GNU
 ])
diff --git a/m4/lib-link.m4 b/m4/lib-link.m4
index 2f518553..787efab2 100644
--- a/m4/lib-link.m4
+++ b/m4/lib-link.m4
@@ -1,12 +1,12 @@
-# lib-link.m4 serial 26 (gettext-0.18.2)
-dnl Copyright (C) 2001-2016 Free Software Foundation, Inc.
+# lib-link.m4 serial 32
+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,
 dnl with or without modifications, as long as this notice is preserved.
 
 dnl From Bruno Haible.
 
-AC_PREREQ([2.54])
+AC_PREREQ([2.61])
 
 dnl AC_LIB_LINKFLAGS(name [, dependencies]) searches for libname and
 dnl the libraries corresponding to explicit and implicit dependencies.
@@ -124,8 +124,8 @@ dnl   acl_hardcode_direct,
 dnl   acl_hardcode_minus_L.
 AC_DEFUN([AC_LIB_RPATH],
 [
-  dnl Tell automake >= 1.10 to complain if config.rpath is missing.
-  m4_ifdef([AC_REQUIRE_AUX_FILE], [AC_REQUIRE_AUX_FILE([config.rpath])])
+  dnl Complain if config.rpath is missing.
+  AC_REQUIRE_AUX_FILE([config.rpath])
   AC_REQUIRE([AC_PROG_CC])                dnl we use $CC, $GCC, $LDFLAGS
   AC_REQUIRE([AC_LIB_PROG_LD])            dnl we use $LD, $with_gnu_ld
   AC_REQUIRE([AC_CANONICAL_HOST])         dnl we use $host
@@ -187,17 +187,17 @@ AC_DEFUN([AC_LIB_LINKFLAGS_BODY],
   pushdef([PACKUP],[m4_translit(PACK,[abcdefghijklmnopqrstuvwxyz./+-],
                                      [ABCDEFGHIJKLMNOPQRSTUVWXYZ____])])
   pushdef([PACKLIBS],[m4_ifdef([acl_frompackage_]NAME, 
[acl_libsinpackage_]PACKUP, lib[$1])])
-  dnl Autoconf >= 2.61 supports dots in --with options.
-  
pushdef([P_A_C_K],[m4_if(m4_version_compare(m4_defn([m4_PACKAGE_VERSION]),[2.61]),[-1],[m4_translit(PACK,[.],[_])],PACK)])
   dnl By default, look in $includedir and $libdir.
   use_additional=yes
   AC_LIB_WITH_FINAL_PREFIX([
     eval additional_includedir=\"$includedir\"
     eval additional_libdir=\"$libdir\"
+    eval additional_libdir2=\"$exec_prefix/$acl_libdirstem2\"
+    eval additional_libdir3=\"$exec_prefix/$acl_libdirstem3\"
   ])
-  AC_ARG_WITH(P_A_C_K[-prefix],
-[[  --with-]]P_A_C_K[[-prefix[=DIR]  search for ]PACKLIBS[ in DIR/include and 
DIR/lib
-  --without-]]P_A_C_K[[-prefix     don't search for ]PACKLIBS[ in includedir 
and libdir]],
+  AC_ARG_WITH(PACK[-prefix],
+[[  --with-]]PACK[[-prefix[=DIR]  search for ]PACKLIBS[ in DIR/include and 
DIR/lib
+  --without-]]PACK[[-prefix     don't search for ]PACKLIBS[ in includedir and 
libdir]],
 [
     if test "X$withval" = "Xno"; then
       use_additional=no
@@ -206,17 +206,23 @@ AC_DEFUN([AC_LIB_LINKFLAGS_BODY],
         AC_LIB_WITH_FINAL_PREFIX([
           eval additional_includedir=\"$includedir\"
           eval additional_libdir=\"$libdir\"
+          eval additional_libdir2=\"$exec_prefix/$acl_libdirstem2\"
+          eval additional_libdir3=\"$exec_prefix/$acl_libdirstem3\"
         ])
       else
         additional_includedir="$withval/include"
         additional_libdir="$withval/$acl_libdirstem"
-        if test "$acl_libdirstem2" != "$acl_libdirstem" \
-           && ! test -d "$withval/$acl_libdirstem"; then
-          additional_libdir="$withval/$acl_libdirstem2"
-        fi
+        additional_libdir2="$withval/$acl_libdirstem2"
+        additional_libdir3="$withval/$acl_libdirstem3"
       fi
     fi
 ])
+  if test "X$additional_libdir2" = "X$additional_libdir"; then
+    additional_libdir2=
+  fi
+  if test "X$additional_libdir3" = "X$additional_libdir"; then
+    additional_libdir3=
+  fi
   dnl Search the library and its dependencies in $additional_libdir and
   dnl $LDFLAGS. Using breadth-first-seach.
   LIB[]NAME=
@@ -272,48 +278,54 @@ AC_DEFUN([AC_LIB_LINKFLAGS_BODY],
             shrext=
           fi
           if test $use_additional = yes; then
-            dir="$additional_libdir"
-            dnl The same code as in the loop below:
-            dnl First look for a shared library.
-            if test -n "$acl_shlibext"; then
-              if test -f "$dir/$libname$shrext"; then
-                found_dir="$dir"
-                found_so="$dir/$libname$shrext"
-              else
-                if test "$acl_library_names_spec" = 
'$libname$shrext$versuffix'; then
-                  ver=`(cd "$dir" && \
-                        for f in "$libname$shrext".*; do echo "$f"; done \
-                        | sed -e "s,^$libname$shrext\\\\.,," \
-                        | sort -t '.' -n -r -k1,1 -k2,2 -k3,3 -k4,4 -k5,5 \
-                        | sed 1q ) 2>/dev/null`
-                  if test -n "$ver" && test -f "$dir/$libname$shrext.$ver"; 
then
-                    found_dir="$dir"
-                    found_so="$dir/$libname$shrext.$ver"
+            for additional_libdir_variable in additional_libdir 
additional_libdir2 additional_libdir3; do
+              if test "X$found_dir" = "X"; then
+                eval dir=\$$additional_libdir_variable
+                if test -n "$dir"; then
+                  dnl The same code as in the loop below:
+                  dnl First look for a shared library.
+                  if test -n "$acl_shlibext"; then
+                    if test -f "$dir/$libname$shrext" && 
acl_is_expected_elfclass < "$dir/$libname$shrext"; then
+                      found_dir="$dir"
+                      found_so="$dir/$libname$shrext"
+                    else
+                      if test "$acl_library_names_spec" = 
'$libname$shrext$versuffix'; then
+                        ver=`(cd "$dir" && \
+                              for f in "$libname$shrext".*; do echo "$f"; done 
\
+                              | sed -e "s,^$libname$shrext\\\\.,," \
+                              | sort -t '.' -n -r -k1,1 -k2,2 -k3,3 -k4,4 
-k5,5 \
+                              | sed 1q ) 2>/dev/null`
+                        if test -n "$ver" && test -f 
"$dir/$libname$shrext.$ver" && acl_is_expected_elfclass < 
"$dir/$libname$shrext.$ver"; then
+                          found_dir="$dir"
+                          found_so="$dir/$libname$shrext.$ver"
+                        fi
+                      else
+                        eval library_names=\"$acl_library_names_spec\"
+                        for f in $library_names; do
+                          if test -f "$dir/$f" && acl_is_expected_elfclass < 
"$dir/$f"; then
+                            found_dir="$dir"
+                            found_so="$dir/$f"
+                            break
+                          fi
+                        done
+                      fi
+                    fi
                   fi
-                else
-                  eval library_names=\"$acl_library_names_spec\"
-                  for f in $library_names; do
-                    if test -f "$dir/$f"; then
+                  dnl Then look for a static library.
+                  if test "X$found_dir" = "X"; then
+                    if test -f "$dir/$libname.$acl_libext" && ${AR-ar} -p 
"$dir/$libname.$acl_libext" | acl_is_expected_elfclass; then
                       found_dir="$dir"
-                      found_so="$dir/$f"
-                      break
+                      found_a="$dir/$libname.$acl_libext"
                     fi
-                  done
+                  fi
+                  if test "X$found_dir" != "X"; then
+                    if test -f "$dir/$libname.la"; then
+                      found_la="$dir/$libname.la"
+                    fi
+                  fi
                 fi
               fi
-            fi
-            dnl Then look for a static library.
-            if test "X$found_dir" = "X"; then
-              if test -f "$dir/$libname.$acl_libext"; then
-                found_dir="$dir"
-                found_a="$dir/$libname.$acl_libext"
-              fi
-            fi
-            if test "X$found_dir" != "X"; then
-              if test -f "$dir/$libname.la"; then
-                found_la="$dir/$libname.la"
-              fi
-            fi
+            done
           fi
           if test "X$found_dir" = "X"; then
             for x in $LDFLAGS $LTLIB[]NAME; do
@@ -323,7 +335,7 @@ AC_DEFUN([AC_LIB_LINKFLAGS_BODY],
                   dir=`echo "X$x" | sed -e 's/^X-L//'`
                   dnl First look for a shared library.
                   if test -n "$acl_shlibext"; then
-                    if test -f "$dir/$libname$shrext"; then
+                    if test -f "$dir/$libname$shrext" && 
acl_is_expected_elfclass < "$dir/$libname$shrext"; then
                       found_dir="$dir"
                       found_so="$dir/$libname$shrext"
                     else
@@ -333,14 +345,14 @@ AC_DEFUN([AC_LIB_LINKFLAGS_BODY],
                               | sed -e "s,^$libname$shrext\\\\.,," \
                               | sort -t '.' -n -r -k1,1 -k2,2 -k3,3 -k4,4 
-k5,5 \
                               | sed 1q ) 2>/dev/null`
-                        if test -n "$ver" && test -f 
"$dir/$libname$shrext.$ver"; then
+                        if test -n "$ver" && test -f 
"$dir/$libname$shrext.$ver" && acl_is_expected_elfclass < 
"$dir/$libname$shrext.$ver"; then
                           found_dir="$dir"
                           found_so="$dir/$libname$shrext.$ver"
                         fi
                       else
                         eval library_names=\"$acl_library_names_spec\"
                         for f in $library_names; do
-                          if test -f "$dir/$f"; then
+                          if test -f "$dir/$f" && acl_is_expected_elfclass < 
"$dir/$f"; then
                             found_dir="$dir"
                             found_so="$dir/$f"
                             break
@@ -351,7 +363,7 @@ AC_DEFUN([AC_LIB_LINKFLAGS_BODY],
                   fi
                   dnl Then look for a static library.
                   if test "X$found_dir" = "X"; then
-                    if test -f "$dir/$libname.$acl_libext"; then
+                    if test -f "$dir/$libname.$acl_libext" && ${AR-ar} -p 
"$dir/$libname.$acl_libext" | acl_is_expected_elfclass; then
                       found_dir="$dir"
                       found_a="$dir/$libname.$acl_libext"
                     fi
@@ -377,7 +389,8 @@ AC_DEFUN([AC_LIB_LINKFLAGS_BODY],
               dnl standard /usr/lib.
               if test "$enable_rpath" = no \
                  || test "X$found_dir" = "X/usr/$acl_libdirstem" \
-                 || test "X$found_dir" = "X/usr/$acl_libdirstem2"; then
+                 || test "X$found_dir" = "X/usr/$acl_libdirstem2" \
+                 || test "X$found_dir" = "X/usr/$acl_libdirstem3"; then
                 dnl No hardcoding is needed.
                 LIB[]NAME="${LIB[]NAME}${LIB[]NAME:+ }$found_so"
               else
@@ -477,6 +490,13 @@ AC_DEFUN([AC_LIB_LINKFLAGS_BODY],
                 fi
                 additional_includedir="$basedir/include"
                 ;;
+              */$acl_libdirstem3 | */$acl_libdirstem3/)
+                basedir=`echo "X$found_dir" | sed -e 's,^X,,' -e 
"s,/$acl_libdirstem3/"'*$,,'`
+                if test "$name" = '$1'; then
+                  LIB[]NAME[]_PREFIX="$basedir"
+                fi
+                additional_includedir="$basedir/include"
+                ;;
             esac
             if test "X$additional_includedir" != "X"; then
               dnl Potentially add $additional_includedir to $INCNAME.
@@ -527,19 +547,21 @@ AC_DEFUN([AC_LIB_LINKFLAGS_BODY],
               for dep in $dependency_libs; do
                 case "$dep" in
                   -L*)
-                    additional_libdir=`echo "X$dep" | sed -e 's/^X-L//'`
-                    dnl Potentially add $additional_libdir to $LIBNAME and 
$LTLIBNAME.
+                    dependency_libdir=`echo "X$dep" | sed -e 's/^X-L//'`
+                    dnl Potentially add $dependency_libdir to $LIBNAME and 
$LTLIBNAME.
                     dnl But don't add it
                     dnl   1. if it's the standard /usr/lib,
                     dnl   2. if it's /usr/local/lib and we are using GCC on 
Linux,
                     dnl   3. if it's already present in $LDFLAGS or the already
                     dnl      constructed $LIBNAME,
                     dnl   4. if it doesn't exist as a directory.
-                    if test "X$additional_libdir" != "X/usr/$acl_libdirstem" \
-                       && test "X$additional_libdir" != 
"X/usr/$acl_libdirstem2"; then
+                    if test "X$dependency_libdir" != "X/usr/$acl_libdirstem" \
+                       && test "X$dependency_libdir" != 
"X/usr/$acl_libdirstem2" \
+                       && test "X$dependency_libdir" != 
"X/usr/$acl_libdirstem3"; then
                       haveit=
-                      if test "X$additional_libdir" = 
"X/usr/local/$acl_libdirstem" \
-                         || test "X$additional_libdir" = 
"X/usr/local/$acl_libdirstem2"; then
+                      if test "X$dependency_libdir" = 
"X/usr/local/$acl_libdirstem" \
+                         || test "X$dependency_libdir" = 
"X/usr/local/$acl_libdirstem2" \
+                         || test "X$dependency_libdir" = 
"X/usr/local/$acl_libdirstem3"; then
                         if test -n "$GCC"; then
                           case $host_os in
                             linux* | gnu* | k*bsd*-gnu) haveit=yes;;
@@ -550,29 +572,29 @@ AC_DEFUN([AC_LIB_LINKFLAGS_BODY],
                         haveit=
                         for x in $LDFLAGS $LIB[]NAME; do
                           AC_LIB_WITH_FINAL_PREFIX([eval x=\"$x\"])
-                          if test "X$x" = "X-L$additional_libdir"; then
+                          if test "X$x" = "X-L$dependency_libdir"; then
                             haveit=yes
                             break
                           fi
                         done
                         if test -z "$haveit"; then
-                          if test -d "$additional_libdir"; then
-                            dnl Really add $additional_libdir to $LIBNAME.
-                            LIB[]NAME="${LIB[]NAME}${LIB[]NAME:+ 
}-L$additional_libdir"
+                          if test -d "$dependency_libdir"; then
+                            dnl Really add $dependency_libdir to $LIBNAME.
+                            LIB[]NAME="${LIB[]NAME}${LIB[]NAME:+ 
}-L$dependency_libdir"
                           fi
                         fi
                         haveit=
                         for x in $LDFLAGS $LTLIB[]NAME; do
                           AC_LIB_WITH_FINAL_PREFIX([eval x=\"$x\"])
-                          if test "X$x" = "X-L$additional_libdir"; then
+                          if test "X$x" = "X-L$dependency_libdir"; then
                             haveit=yes
                             break
                           fi
                         done
                         if test -z "$haveit"; then
-                          if test -d "$additional_libdir"; then
-                            dnl Really add $additional_libdir to $LTLIBNAME.
-                            LTLIB[]NAME="${LTLIB[]NAME}${LTLIB[]NAME:+ 
}-L$additional_libdir"
+                          if test -d "$dependency_libdir"; then
+                            dnl Really add $dependency_libdir to $LTLIBNAME.
+                            LTLIB[]NAME="${LTLIB[]NAME}${LTLIB[]NAME:+ 
}-L$dependency_libdir"
                           fi
                         fi
                       fi
@@ -609,7 +631,20 @@ AC_DEFUN([AC_LIB_LINKFLAGS_BODY],
                     ;;
                   -l*)
                     dnl Handle this in the next round.
-                    names_next_round="$names_next_round "`echo "X$dep" | sed 
-e 's/^X-l//'`
+                    dnl But on GNU systems, ignore -lc options, because
+                    dnl   - linking with libc is the default anyway,
+                    dnl   - linking with libc.a may produce an error
+                    dnl     "/usr/bin/ld: dynamic STT_GNU_IFUNC symbol 
`strcmp' with pointer equality in `/usr/lib/libc.a(strcmp.o)' can not be used 
when making an executable; recompile with -fPIE and relink with -pie"
+                    dnl     or may produce an executable that always crashes, 
see
+                    dnl     
<https://lists.gnu.org/archive/html/grep-devel/2020-09/msg00052.html>.
+                    dep=`echo "X$dep" | sed -e 's/^X-l//'`
+                    if test "X$dep" != Xc \
+                       || case $host_os in
+                            linux* | gnu* | k*bsd*-gnu) false ;;
+                            *)                          true ;;
+                          esac; then
+                      names_next_round="$names_next_round $dep"
+                    fi
                     ;;
                   *.la)
                     dnl Handle this in the next round. Throw away the .la's
@@ -670,7 +705,6 @@ AC_DEFUN([AC_LIB_LINKFLAGS_BODY],
       LTLIB[]NAME="${LTLIB[]NAME}${LTLIB[]NAME:+ }-R$found_dir"
     done
   fi
-  popdef([P_A_C_K])
   popdef([PACKLIBS])
   popdef([PACKUP])
   popdef([PACK])
@@ -721,7 +755,8 @@ AC_DEFUN([AC_LIB_LINKFLAGS_FROM_LIBS],
           dir="$next"
           dnl No need to hardcode the standard /usr/lib.
           if test "X$dir" != "X/usr/$acl_libdirstem" \
-             && test "X$dir" != "X/usr/$acl_libdirstem2"; then
+             && test "X$dir" != "X/usr/$acl_libdirstem2" \
+             && test "X$dir" != "X/usr/$acl_libdirstem3"; then
             rpathdirs="$rpathdirs $dir"
           fi
           next=
@@ -731,7 +766,8 @@ AC_DEFUN([AC_LIB_LINKFLAGS_FROM_LIBS],
             -L*) dir=`echo "X$opt" | sed -e 's,^X-L,,'`
                  dnl No need to hardcode the standard /usr/lib.
                  if test "X$dir" != "X/usr/$acl_libdirstem" \
-                    && test "X$dir" != "X/usr/$acl_libdirstem2"; then
+                    && test "X$dir" != "X/usr/$acl_libdirstem2" \
+                    && test "X$dir" != "X/usr/$acl_libdirstem3"; then
                    rpathdirs="$rpathdirs $dir"
                  fi
                  next= ;;
diff --git a/m4/lib-prefix.m4 b/m4/lib-prefix.m4
index 6851031d..3c94db0a 100644
--- a/m4/lib-prefix.m4
+++ b/m4/lib-prefix.m4
@@ -1,18 +1,11 @@
-# lib-prefix.m4 serial 7 (gettext-0.18)
-dnl Copyright (C) 2001-2005, 2008-2016 Free Software Foundation, Inc.
+# lib-prefix.m4 serial 19
+dnl Copyright (C) 2001-2005, 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,
 dnl with or without modifications, as long as this notice is preserved.
 
 dnl From Bruno Haible.
 
-dnl AC_LIB_ARG_WITH is synonymous to AC_ARG_WITH in autoconf-2.13, and
-dnl similar to AC_ARG_WITH in autoconf 2.52...2.57 except that is doesn't
-dnl require excessive bracketing.
-ifdef([AC_HELP_STRING],
-[AC_DEFUN([AC_LIB_ARG_WITH], [AC_ARG_WITH([$1],[[$2]],[$3],[$4])])],
-[AC_DEFUN([AC_][LIB_ARG_WITH], [AC_ARG_WITH([$1],[$2],[$3],[$4])])])
-
 dnl AC_LIB_PREFIX adds to the CPPFLAGS and LDFLAGS the flags that are needed
 dnl to access previously installed libraries. The basic assumption is that
 dnl a user will want packages to use other packages he previously installed
@@ -32,9 +25,9 @@ AC_DEFUN([AC_LIB_PREFIX],
     eval additional_includedir=\"$includedir\"
     eval additional_libdir=\"$libdir\"
   ])
-  AC_LIB_ARG_WITH([lib-prefix],
-[  --with-lib-prefix[=DIR] search for libraries in DIR/include and DIR/lib
-  --without-lib-prefix    don't search for libraries in includedir and libdir],
+  AC_ARG_WITH([lib-prefix],
+[[  --with-lib-prefix[=DIR] search for libraries in DIR/include and DIR/lib
+  --without-lib-prefix    don't search for libraries in includedir and 
libdir]],
 [
     if test "X$withval" = "Xno"; then
       use_additional=no
@@ -154,71 +147,177 @@ AC_DEFUN([AC_LIB_WITH_FINAL_PREFIX],
 ])
 
 dnl AC_LIB_PREPARE_MULTILIB creates
-dnl - a variable acl_libdirstem, containing the basename of the libdir, either
-dnl   "lib" or "lib64" or "lib/64",
-dnl - a variable acl_libdirstem2, as a secondary possible value for
-dnl   acl_libdirstem, either the same as acl_libdirstem or "lib/sparcv9" or
-dnl   "lib/amd64".
+dnl - a function acl_is_expected_elfclass, that tests whether standard input
+dn;   has a 32-bit or 64-bit ELF header, depending on the host CPU ABI,
+dnl - 3 variables acl_libdirstem, acl_libdirstem2, acl_libdirstem3, containing
+dnl   the basename of the libdir to try in turn, either "lib" or "lib64" or
+dnl   "lib/64" or "lib32" or "lib/sparcv9" or "lib/amd64" or similar.
 AC_DEFUN([AC_LIB_PREPARE_MULTILIB],
 [
-  dnl There is no formal standard regarding lib and lib64.
-  dnl On glibc systems, the current practice is that on a system supporting
+  dnl There is no formal standard regarding lib, lib32, and lib64.
+  dnl On most glibc systems, the current practice is that on a system 
supporting
   dnl 32-bit and 64-bit instruction sets or ABIs, 64-bit libraries go under
-  dnl $prefix/lib64 and 32-bit libraries go under $prefix/lib. We determine
-  dnl the compiler's default mode by looking at the compiler's library search
-  dnl path. If at least one of its elements ends in /lib64 or points to a
-  dnl directory whose absolute pathname ends in /lib64, we assume a 64-bit ABI.
-  dnl Otherwise we use the default, namely "lib".
+  dnl $prefix/lib64 and 32-bit libraries go under $prefix/lib. However, on
+  dnl Arch Linux based distributions, it's the opposite: 32-bit libraries go
+  dnl under $prefix/lib32 and 64-bit libraries go under $prefix/lib.
+  dnl We determine the compiler's default mode by looking at the compiler's
+  dnl library search path. If at least one of its elements ends in /lib64 or
+  dnl points to a directory whose absolute pathname ends in /lib64, we use that
+  dnl for 64-bit ABIs. Similarly for 32-bit ABIs. Otherwise we use the default,
+  dnl namely "lib".
   dnl On Solaris systems, the current practice is that on a system supporting
   dnl 32-bit and 64-bit instruction sets or ABIs, 64-bit libraries go under
   dnl $prefix/lib/64 (which is a symlink to either $prefix/lib/sparcv9 or
   dnl $prefix/lib/amd64) and 32-bit libraries go under $prefix/lib.
   AC_REQUIRE([AC_CANONICAL_HOST])
-  acl_libdirstem=lib
-  acl_libdirstem2=
-  case "$host_os" in
-    solaris*)
-      dnl See Solaris 10 Software Developer Collection > Solaris 64-bit 
Developer's Guide > The Development Environment
-      dnl <http://docs.sun.com/app/docs/doc/816-5138/dev-env?l=en&a=view>.
-      dnl "Portable Makefiles should refer to any library directories using 
the 64 symbolic link."
-      dnl But we want to recognize the sparcv9 or amd64 subdirectory also if 
the
-      dnl symlink is missing, so we set acl_libdirstem2 too.
-      AC_CACHE_CHECK([for 64-bit host], [gl_cv_solaris_64bit],
-        [AC_EGREP_CPP([sixtyfour bits], [
-#ifdef _LP64
-sixtyfour bits
-#endif
-           ], [gl_cv_solaris_64bit=yes], [gl_cv_solaris_64bit=no])
-        ])
-      if test $gl_cv_solaris_64bit = yes; then
-        acl_libdirstem=lib/64
-        case "$host_cpu" in
-          sparc*)        acl_libdirstem2=lib/sparcv9 ;;
-          i*86 | x86_64) acl_libdirstem2=lib/amd64 ;;
-        esac
-      fi
-      ;;
-    *)
-      searchpath=`(LC_ALL=C $CC -print-search-dirs) 2>/dev/null | sed -n -e 
's,^libraries: ,,p' | sed -e 's,^=,,'`
-      if test -n "$searchpath"; then
-        acl_save_IFS="${IFS=   }"; IFS=":"
-        for searchdir in $searchpath; do
-          if test -d "$searchdir"; then
-            case "$searchdir" in
-              */lib64/ | */lib64 ) acl_libdirstem=lib64 ;;
-              */../ | */.. )
-                # Better ignore directories of this form. They are misleading.
-                ;;
-              *) searchdir=`cd "$searchdir" && pwd`
-                 case "$searchdir" in
-                   */lib64 ) acl_libdirstem=lib64 ;;
-                 esac ;;
-            esac
-          fi
-        done
-        IFS="$acl_save_IFS"
-      fi
-      ;;
-  esac
-  test -n "$acl_libdirstem2" || acl_libdirstem2="$acl_libdirstem"
+  AC_REQUIRE([gl_HOST_CPU_C_ABI_32BIT])
+
+  AC_CACHE_CHECK([for ELF binary format], [gl_cv_elf],
+    [AC_EGREP_CPP([Extensible Linking Format],
+       [#ifdef __ELF__
+        Extensible Linking Format
+        #endif
+       ],
+       [gl_cv_elf=yes],
+       [gl_cv_elf=no])
+    ])
+  if test $gl_cv_elf = yes; then
+    # Extract the ELF class of a file (5th byte) in decimal.
+    # Cf. 
https://en.wikipedia.org/wiki/Executable_and_Linkable_Format#File_header
+    if od -A x < /dev/null >/dev/null 2>/dev/null; then
+      # Use POSIX od.
+      func_elfclass ()
+      {
+        od -A n -t d1 -j 4 -N 1
+      }
+    else
+      # Use BSD hexdump.
+      func_elfclass ()
+      {
+        dd bs=1 count=1 skip=4 2>/dev/null | hexdump -e '1/1 "%3d "'
+        echo
+      }
+    fi
+    # Use 'expr', not 'test', to compare the values of func_elfclass, because 
on
+    # Solaris 11 OpenIndiana and Solaris 11 OmniOS, the result is 001 or 002,
+    # not 1 or 2.
+changequote(,)dnl
+    case $HOST_CPU_C_ABI_32BIT in
+      yes)
+        # 32-bit ABI.
+        acl_is_expected_elfclass ()
+        {
+          expr "`func_elfclass | sed -e 's/[   ]//g'`" = 1 > /dev/null
+        }
+        ;;
+      no)
+        # 64-bit ABI.
+        acl_is_expected_elfclass ()
+        {
+          expr "`func_elfclass | sed -e 's/[   ]//g'`" = 2 > /dev/null
+        }
+        ;;
+      *)
+        # Unknown.
+        acl_is_expected_elfclass ()
+        {
+          :
+        }
+        ;;
+    esac
+changequote([,])dnl
+  else
+    acl_is_expected_elfclass ()
+    {
+      :
+    }
+  fi
+
+  dnl Allow the user to override the result by setting acl_cv_libdirstems.
+  AC_CACHE_CHECK([for the common suffixes of directories in the library search 
path],
+    [acl_cv_libdirstems],
+    [dnl Try 'lib' first, because that's the default for libdir in GNU, see
+     dnl 
<https://www.gnu.org/prep/standards/html_node/Directory-Variables.html>.
+     acl_libdirstem=lib
+     acl_libdirstem2=
+     acl_libdirstem3=
+     case "$host_os" in
+       solaris*)
+         dnl See Solaris 10 Software Developer Collection > Solaris 64-bit 
Developer's Guide > The Development Environment
+         dnl 
<https://docs.oracle.com/cd/E19253-01/816-5138/dev-env/index.html>.
+         dnl "Portable Makefiles should refer to any library directories using 
the 64 symbolic link."
+         dnl But we want to recognize the sparcv9 or amd64 subdirectory also 
if the
+         dnl symlink is missing, so we set acl_libdirstem2 too.
+         if test $HOST_CPU_C_ABI_32BIT = no; then
+           acl_libdirstem2=lib/64
+           case "$host_cpu" in
+             sparc*)        acl_libdirstem3=lib/sparcv9 ;;
+             i*86 | x86_64) acl_libdirstem3=lib/amd64 ;;
+           esac
+         fi
+         ;;
+       *)
+         dnl If $CC generates code for a 32-bit ABI, the libraries are
+         dnl surely under $prefix/lib or $prefix/lib32, not $prefix/lib64.
+         dnl Similarly, if $CC generates code for a 64-bit ABI, the libraries
+         dnl are surely under $prefix/lib or $prefix/lib64, not $prefix/lib32.
+         dnl Find the compiler's search path. However, non-system compilers
+         dnl sometimes have odd library search paths. But we can't simply 
invoke
+         dnl '/usr/bin/gcc -print-search-dirs' because that would not take into
+         dnl account the -m32/-m31 or -m64 options from the $CC or $CFLAGS.
+         searchpath=`(LC_ALL=C $CC $CPPFLAGS $CFLAGS -print-search-dirs) 
2>/dev/null \
+                     | sed -n -e 's,^libraries: ,,p' | sed -e 's,^=,,'`
+         if test $HOST_CPU_C_ABI_32BIT != no; then
+           # 32-bit or unknown ABI.
+           if test -d /usr/lib32; then
+             acl_libdirstem2=lib32
+           fi
+         fi
+         if test $HOST_CPU_C_ABI_32BIT != yes; then
+           # 64-bit or unknown ABI.
+           if test -d /usr/lib64; then
+             acl_libdirstem3=lib64
+           fi
+         fi
+         if test -n "$searchpath"; then
+           acl_save_IFS="${IFS=        }"; IFS=":"
+           for searchdir in $searchpath; do
+             if test -d "$searchdir"; then
+               case "$searchdir" in
+                 */lib32/ | */lib32 ) acl_libdirstem2=lib32 ;;
+                 */lib64/ | */lib64 ) acl_libdirstem3=lib64 ;;
+                 */../ | */.. )
+                   # Better ignore directories of this form. They are 
misleading.
+                   ;;
+                 *) searchdir=`cd "$searchdir" && pwd`
+                    case "$searchdir" in
+                      */lib32 ) acl_libdirstem2=lib32 ;;
+                      */lib64 ) acl_libdirstem3=lib64 ;;
+                    esac ;;
+               esac
+             fi
+           done
+           IFS="$acl_save_IFS"
+           if test $HOST_CPU_C_ABI_32BIT = yes; then
+             # 32-bit ABI.
+             acl_libdirstem3=
+           fi
+           if test $HOST_CPU_C_ABI_32BIT = no; then
+             # 64-bit ABI.
+             acl_libdirstem2=
+           fi
+         fi
+         ;;
+     esac
+     test -n "$acl_libdirstem2" || acl_libdirstem2="$acl_libdirstem"
+     test -n "$acl_libdirstem3" || acl_libdirstem3="$acl_libdirstem"
+     acl_cv_libdirstems="$acl_libdirstem,$acl_libdirstem2,$acl_libdirstem3"
+    ])
+  dnl Decompose acl_cv_libdirstems into acl_libdirstem, acl_libdirstem2, and
+  dnl acl_libdirstem3.
+changequote(,)dnl
+  acl_libdirstem=`echo "$acl_cv_libdirstems" | sed -e 's/,.*//'`
+  acl_libdirstem2=`echo "$acl_cv_libdirstems" | sed -e 's/^[^,]*,//' -e 
's/,.*//'`
+  acl_libdirstem3=`echo "$acl_cv_libdirstems" | sed -e 's/^[^,]*,[^,]*,//' -e 
's/,.*//'`
+changequote([,])dnl
 ])
diff --git a/m4/libcurl.m4 b/m4/libcurl.m4
index 53d694d0..ad53a444 100644
--- a/m4/libcurl.m4
+++ b/m4/libcurl.m4
@@ -5,11 +5,11 @@
 #                            | (__| |_| |  _ <| |___
 #                             \___|\___/|_| \_\_____|
 #
-# Copyright (C) 2006, David Shaw <dshaw@jabberwocky.com>
+# Copyright (C) 2006 - 2020, David Shaw <dshaw@jabberwocky.com>
 #
 # This software is licensed as described in the file COPYING, which
 # you should have received as part of this distribution. The terms
-# are also available at https://curl.haxx.se/docs/copyright.html.
+# are also available at https://curl.se/docs/copyright.html.
 #
 # You may opt to use, copy, modify, merge, publish, distribute and/or sell
 # copies of the Software, and permit persons to whom the Software is
diff --git a/m4/lock.m4 b/m4/lock.m4
index 1e83e236..d68c12d0 100644
--- a/m4/lock.m4
+++ b/m4/lock.m4
@@ -1,5 +1,5 @@
-# lock.m4 serial 13 (gettext-0.18.2)
-dnl Copyright (C) 2005-2016 Free Software Foundation, Inc.
+# lock.m4 serial 14
+dnl Copyright (C) 2005-2021 Free Software Foundation, Inc.
 dnl This file is free software; the Free Software Foundation
 dnl gives unlimited permission to copy and/or distribute it,
 dnl with or without modifications, as long as this notice is preserved.
@@ -12,11 +12,16 @@ AC_DEFUN([gl_LOCK],
   if test "$gl_threads_api" = posix; then
     # OSF/1 4.0 and Mac OS X 10.1 lack the pthread_rwlock_t type and the
     # pthread_rwlock_* functions.
+    has_rwlock=false
     AC_CHECK_TYPE([pthread_rwlock_t],
-      [AC_DEFINE([HAVE_PTHREAD_RWLOCK], [1],
+      [has_rwlock=true
+       AC_DEFINE([HAVE_PTHREAD_RWLOCK], [1],
          [Define if the POSIX multithreading library has read/write locks.])],
       [],
       [#include <pthread.h>])
+    if $has_rwlock; then
+      gl_PTHREAD_RWLOCK_RDLOCK_PREFER_WRITER
+    fi
     # glibc defines PTHREAD_MUTEX_RECURSIVE as enum, not as a macro.
     AC_COMPILE_IFELSE([
       AC_LANG_PROGRAM(
diff --git a/m4/longlong.m4 b/m4/longlong.m4
index 36d8b124..7559db59 100644
--- a/m4/longlong.m4
+++ b/m4/longlong.m4
@@ -1,14 +1,15 @@
-# longlong.m4 serial 17
-dnl Copyright (C) 1999-2007, 2009-2016 Free Software Foundation, Inc.
+# longlong.m4 serial 19
+dnl Copyright (C) 1999-2007, 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 From Paul Eggert.
 
+AC_PREREQ([2.62])
+
 # Define HAVE_LONG_LONG_INT if 'long long int' works.
-# This fixes a bug in Autoconf 2.61, and can be faster
-# than what's in Autoconf 2.62 through 2.68.
+# This can be faster than what's in Autoconf 2.62 through 2.68.
 
 # Note: If the type 'long long int' exists but is only 32 bits large
 # (as on some very old compilers), HAVE_LONG_LONG_INT will not be
@@ -27,12 +28,12 @@ AC_DEFUN([AC_TYPE_LONG_LONG_INT],
           dnl nobody cross compiles for this platform as far as we know.
           AC_RUN_IFELSE(
             [AC_LANG_PROGRAM(
-               [[@%:@include <limits.h>
-                 @%:@ifndef LLONG_MAX
-                 @%:@ define HALF \
+               [[#include <limits.h>
+                 #ifndef LLONG_MAX
+                 # define HALF \
                           (1LL << (sizeof (long long int) * CHAR_BIT - 2))
-                 @%:@ define LLONG_MAX (HALF - 1 + HALF)
-                 @%:@endif]],
+                 # define LLONG_MAX (HALF - 1 + HALF)
+                 #endif]],
                [[long long int n = 1;
                  int i;
                  for (i = 0; ; i++)
@@ -56,8 +57,7 @@ AC_DEFUN([AC_TYPE_LONG_LONG_INT],
 ])
 
 # Define HAVE_UNSIGNED_LONG_LONG_INT if 'unsigned long long int' works.
-# This fixes a bug in Autoconf 2.61, and can be faster
-# than what's in Autoconf 2.62 through 2.68.
+# This can be faster than what's in Autoconf 2.62 through 2.68.
 
 # Note: If the type 'unsigned long long int' exists but is only 32 bits
 # large (as on some very old compilers), AC_TYPE_UNSIGNED_LONG_LONG_INT
diff --git a/m4/nls.m4 b/m4/nls.m4
index afdb9cac..f4f6b801 100644
--- a/m4/nls.m4
+++ b/m4/nls.m4
@@ -1,16 +1,16 @@
-# nls.m4 serial 5 (gettext-0.18)
-dnl Copyright (C) 1995-2003, 2005-2006, 2008-2014, 2016 Free Software
-dnl Foundation, Inc.
+# nls.m4 serial 6 (gettext-0.20.2)
+dnl Copyright (C) 1995-2003, 2005-2006, 2008-2014, 2016, 2019-2021 Free
+dnl 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
 dnl This file can be used in projects which are not available under
-dnl the GNU General Public License or the GNU Library General Public
+dnl the GNU General Public License or the GNU Lesser General Public
 dnl License but which still want to provide support for the GNU gettext
 dnl functionality.
 dnl Please note that the actual code of the GNU gettext library is covered
-dnl by the GNU Library General Public License, and the rest of the GNU
+dnl by the GNU Lesser General Public License, and the rest of the GNU
 dnl gettext package is covered by the GNU General Public License.
 dnl They are *not* in the public domain.
 
diff --git a/m4/po.m4 b/m4/po.m4
index c5a2f6bf..66bea3e6 100644
--- a/m4/po.m4
+++ b/m4/po.m4
@@ -1,15 +1,15 @@
-# po.m4 serial 24 (gettext-0.19)
-dnl Copyright (C) 1995-2014, 2016 Free Software Foundation, Inc.
+# po.m4 serial 31 (gettext-0.20.2)
+dnl Copyright (C) 1995-2014, 2016, 2018-2021 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
 dnl This file can be used in projects which are not available under
-dnl the GNU General Public License or the GNU Library General Public
+dnl the GNU General Public License or the GNU Lesser General Public
 dnl License but which still want to provide support for the GNU gettext
 dnl functionality.
 dnl Please note that the actual code of the GNU gettext library is covered
-dnl by the GNU Library General Public License, and the rest of the GNU
+dnl by the GNU Lesser General Public License, and the rest of the GNU
 dnl gettext package is covered by the GNU General Public License.
 dnl They are *not* in the public domain.
 
@@ -30,7 +30,7 @@ AC_DEFUN([AM_PO_SUBDIRS],
 
   dnl Release version of the gettext macros. This is used to ensure that
   dnl the gettext macros and po/Makefile.in.in are in sync.
-  AC_SUBST([GETTEXT_MACRO_VERSION], [0.19])
+  AC_SUBST([GETTEXT_MACRO_VERSION], [0.20])
 
   dnl Perform the following tests also if --disable-nls has been given,
   dnl because they are needed for "make dist" to work.
@@ -45,13 +45,6 @@ AC_DEFUN([AM_PO_SUBDIRS],
   AC_PATH_PROG([GMSGFMT], [gmsgfmt], [$MSGFMT])
 
   dnl Test whether it is GNU msgfmt >= 0.15.
-changequote(,)dnl
-  case `$MSGFMT --version | sed 1q | sed -e 's,^[^0-9]*,,'` in
-    '' | 0.[0-9] | 0.[0-9].* | 0.1[0-4] | 0.1[0-4].*) MSGFMT_015=: ;;
-    *) MSGFMT_015=$MSGFMT ;;
-  esac
-changequote([,])dnl
-  AC_SUBST([MSGFMT_015])
 changequote(,)dnl
   case `$GMSGFMT --version | sed 1q | sed -e 's,^[^0-9]*,,'` in
     '' | 0.[0-9] | 0.[0-9].* | 0.1[0-4] | 0.1[0-4].*) GMSGFMT_015=: ;;
@@ -83,11 +76,21 @@ changequote([,])dnl
   AM_PATH_PROG_WITH_TEST(MSGMERGE, msgmerge,
     [$ac_dir/$ac_word --update -q /dev/null /dev/null >&]AS_MESSAGE_LOG_FD[ 
2>&1], :)
 
-  dnl Installation directories.
-  dnl Autoconf >= 2.60 defines localedir. For older versions of autoconf, we
-  dnl have to define it here, so that it can be used in po/Makefile.
-  test -n "$localedir" || localedir='${datadir}/locale'
-  AC_SUBST([localedir])
+  dnl Test whether it is GNU msgmerge >= 0.20.
+  if LC_ALL=C $MSGMERGE --help | grep ' --for-msgfmt ' >/dev/null; then
+    MSGMERGE_FOR_MSGFMT_OPTION='--for-msgfmt'
+  else
+    dnl Test whether it is GNU msgmerge >= 0.12.
+    if LC_ALL=C $MSGMERGE --help | grep ' --no-fuzzy-matching ' >/dev/null; 
then
+      MSGMERGE_FOR_MSGFMT_OPTION='--no-fuzzy-matching --no-location --quiet'
+    else
+      dnl With these old versions, $(MSGMERGE) $(MSGMERGE_FOR_MSGFMT_OPTION) is
+      dnl slow. But this is not a big problem, as such old gettext versions are
+      dnl hardly in use any more.
+      MSGMERGE_FOR_MSGFMT_OPTION='--no-location --quiet'
+    fi
+  fi
+  AC_SUBST([MSGMERGE_FOR_MSGFMT_OPTION])
 
   dnl Support for AM_XGETTEXT_OPTION.
   test -n "${XGETTEXT_EXTRA_OPTIONS+set}" || XGETTEXT_EXTRA_OPTIONS=
@@ -130,14 +133,11 @@ changequote([,])dnl
             if test -n "$OBSOLETE_ALL_LINGUAS"; then
               test -n "$as_me" && echo "$as_me: setting ALL_LINGUAS in 
configure.in is obsolete" || echo "setting ALL_LINGUAS in configure.in is 
obsolete"
             fi
-            ALL_LINGUAS_=`sed -e "/^#/d" -e "s/#.*//" 
"$ac_given_srcdir/$ac_dir/LINGUAS"`
-            # Hide the ALL_LINGUAS assignment from automake < 1.5.
-            eval 'ALL_LINGUAS''=$ALL_LINGUAS_'
+            ALL_LINGUAS=`sed -e "/^#/d" -e "s/#.*//" 
"$ac_given_srcdir/$ac_dir/LINGUAS"`
             POMAKEFILEDEPS="$POMAKEFILEDEPS LINGUAS"
           else
             # The set of available languages was given in configure.in.
-            # Hide the ALL_LINGUAS assignment from automake < 1.5.
-            eval 'ALL_LINGUAS''=$OBSOLETE_ALL_LINGUAS'
+            ALL_LINGUAS=$OBSOLETE_ALL_LINGUAS
           fi
           # Compute POFILES
           # as      $(foreach lang, $(ALL_LINGUAS), $(srcdir)/$(lang).po)
@@ -208,9 +208,8 @@ changequote([,])dnl
       esac
     done]],
    [# Capture the value of obsolete ALL_LINGUAS because we need it to compute
-    # POFILES, UPDATEPOFILES, DUMMYPOFILES, GMOFILES, CATALOGS. But hide it
-    # from automake < 1.5.
-    eval 'OBSOLETE_ALL_LINGUAS''="$ALL_LINGUAS"'
+    # POFILES, UPDATEPOFILES, DUMMYPOFILES, GMOFILES, CATALOGS.
+    OBSOLETE_ALL_LINGUAS="$ALL_LINGUAS"
     # Capture the value of LINGUAS because we need it to compute CATALOGS.
     LINGUAS="${LINGUAS-%UNSET%}"
    ])
@@ -311,15 +310,13 @@ changequote([,])dnl
   fi
   if test -f "$ac_given_srcdir/$ac_dir/LINGUAS"; then
     # The LINGUAS file contains the set of available languages.
-    ALL_LINGUAS_=`sed -e "/^#/d" -e "s/#.*//" 
"$ac_given_srcdir/$ac_dir/LINGUAS"`
+    ALL_LINGUAS=`sed -e "/^#/d" -e "s/#.*//" 
"$ac_given_srcdir/$ac_dir/LINGUAS"`
     POMAKEFILEDEPS="$POMAKEFILEDEPS LINGUAS"
   else
     # Set ALL_LINGUAS to the value of the Makefile variable LINGUAS.
     sed_x_LINGUAS=`$gt_echo "$sed_x_variable" | sed -e '/^ *#/d' -e 
's/VARIABLE/LINGUAS/g'`
-    ALL_LINGUAS_=`sed -n -e "$sed_x_LINGUAS" < "$ac_file"`
+    ALL_LINGUAS=`sed -n -e "$sed_x_LINGUAS" < "$ac_file"`
   fi
-  # Hide the ALL_LINGUAS assignment from automake < 1.5.
-  eval 'ALL_LINGUAS''=$ALL_LINGUAS_'
   # Compute POFILES
   # as      $(foreach lang, $(ALL_LINGUAS), $(srcdir)/$(lang).po)
   # Compute UPDATEPOFILES
@@ -329,9 +326,9 @@ changequote([,])dnl
   # Compute GMOFILES
   # as      $(foreach lang, $(ALL_LINGUAS), $(srcdir)/$(lang).gmo)
   # Compute PROPERTIESFILES
-  # as      $(foreach lang, $(ALL_LINGUAS), 
$(top_srcdir)/$(DOMAIN)_$(lang).properties)
+  # as      $(foreach lang, $(ALL_LINGUAS), 
$(srcdir)/$(DOMAIN)_$(lang).properties)
   # Compute CLASSFILES
-  # as      $(foreach lang, $(ALL_LINGUAS), 
$(top_srcdir)/$(DOMAIN)_$(lang).class)
+  # as      $(foreach lang, $(ALL_LINGUAS), $(srcdir)/$(DOMAIN)_$(lang).class)
   # Compute QMFILES
   # as      $(foreach lang, $(ALL_LINGUAS), $(srcdir)/$(lang).qm)
   # Compute MSGFILES
@@ -356,8 +353,8 @@ changequote([,])dnl
     UPDATEPOFILES="$UPDATEPOFILES $lang.po-update"
     DUMMYPOFILES="$DUMMYPOFILES $lang.nop"
     GMOFILES="$GMOFILES $srcdirpre$lang.gmo"
-    PROPERTIESFILES="$PROPERTIESFILES 
\$(top_srcdir)/\$(DOMAIN)_$lang.properties"
-    CLASSFILES="$CLASSFILES \$(top_srcdir)/\$(DOMAIN)_$lang.class"
+    PROPERTIESFILES="$PROPERTIESFILES \$(srcdir)/\$(DOMAIN)_$lang.properties"
+    CLASSFILES="$CLASSFILES \$(srcdir)/\$(DOMAIN)_$lang.class"
     QMFILES="$QMFILES $srcdirpre$lang.qm"
     frobbedlang=`echo $lang | sed -e 's/\..*$//' -e 
'y/ABCDEFGHIJKLMNOPQRSTUVWXYZ/abcdefghijklmnopqrstuvwxyz/'`
     MSGFILES="$MSGFILES $srcdirpre$frobbedlang.msg"
diff --git a/m4/progtest.m4 b/m4/progtest.m4
index 9ace7c34..9e8823c2 100644
--- a/m4/progtest.m4
+++ b/m4/progtest.m4
@@ -1,22 +1,22 @@
-# progtest.m4 serial 7 (gettext-0.18.2)
-dnl Copyright (C) 1996-2003, 2005, 2008-2016 Free Software Foundation, Inc.
+# progtest.m4 serial 9 (gettext-0.21.1)
+dnl Copyright (C) 1996-2003, 2005, 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,
 dnl with or without modifications, as long as this notice is preserved.
 dnl
 dnl This file can be used in projects which are not available under
-dnl the GNU General Public License or the GNU Library General Public
+dnl the GNU General Public License or the GNU Lesser General Public
 dnl License but which still want to provide support for the GNU gettext
 dnl functionality.
 dnl Please note that the actual code of the GNU gettext library is covered
-dnl by the GNU Library General Public License, and the rest of the GNU
+dnl by the GNU Lesser General Public License, and the rest of the GNU
 dnl gettext package is covered by the GNU General Public License.
 dnl They are *not* in the public domain.
 
 dnl Authors:
 dnl   Ulrich Drepper <drepper@cygnus.com>, 1996.
 
-AC_PREREQ([2.50])
+AC_PREREQ([2.53])
 
 # Search path for a program which passes the given test.
 
@@ -61,7 +61,7 @@ AC_CACHE_VAL([ac_cv_path_$1],
     ;;
   *)
     ac_save_IFS="$IFS"; IFS=$PATH_SEPARATOR
-    for ac_dir in ifelse([$5], , $PATH, [$5]); do
+    for ac_dir in m4_if([$5], , $PATH, [$5]); do
       IFS="$ac_save_IFS"
       test -z "$ac_dir" && ac_dir=.
       for ac_exec_ext in '' $ac_executable_extensions; do
@@ -77,12 +77,12 @@ AC_CACHE_VAL([ac_cv_path_$1],
     IFS="$ac_save_IFS"
 dnl If no 4th arg is given, leave the cache variable unset,
 dnl so AC_PATH_PROGS will keep looking.
-ifelse([$4], , , [  test -z "[$]ac_cv_path_$1" && ac_cv_path_$1="$4"
+m4_if([$4], , , [  test -z "[$]ac_cv_path_$1" && ac_cv_path_$1="$4"
 ])dnl
     ;;
 esac])dnl
 $1="$ac_cv_path_$1"
-if test ifelse([$4], , [-n "[$]$1"], ["[$]$1" != "$4"]); then
+if test m4_if([$4], , [-n "[$]$1"], ["[$]$1" != "$4"]); then
   AC_MSG_RESULT([$][$1])
 else
   AC_MSG_RESULT([no])
diff --git a/m4/search_h.m4 b/m4/search_h.m4
index 6aaaf36e..9fafc716 100644
--- a/m4/search_h.m4
+++ b/m4/search_h.m4
@@ -1,5 +1,5 @@
-# search_h.m4 serial 9
-dnl Copyright (C) 2007-2017 Free Software Foundation, Inc.
+# search_h.m4 serial 12
+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.
@@ -40,6 +40,8 @@ AC_DEFUN([gl_SEARCH_H],
   dnl corresponding gnulib module is not in use.
   gl_WARN_ON_USE_PREPARE([[#include <search.h>
     ]], [tdelete tfind tsearch twalk])
+
+  AC_REQUIRE([AC_C_RESTRICT])
 ])
 
 AC_DEFUN([gl_SEARCH_MODULE_INDICATOR],
@@ -54,7 +56,11 @@ AC_DEFUN([gl_SEARCH_MODULE_INDICATOR],
 AC_DEFUN([gl_SEARCH_H_DEFAULTS],
 [
   GNULIB_TSEARCH=0; AC_SUBST([GNULIB_TSEARCH])
+  dnl Support Microsoft deprecated alias function names by default.
+  GNULIB_MDA_LFIND=1;   AC_SUBST([GNULIB_MDA_LFIND])
+  GNULIB_MDA_LSEARCH=1; AC_SUBST([GNULIB_MDA_LSEARCH])
   dnl Assume proper GNU behavior unless another module says otherwise.
   HAVE_TSEARCH=1;    AC_SUBST([HAVE_TSEARCH])
+  HAVE_TWALK=1;      AC_SUBST([HAVE_TWALK])
   REPLACE_TSEARCH=0; AC_SUBST([REPLACE_TSEARCH])
 ])
diff --git a/m4/size_max.m4 b/m4/size_max.m4
index de69025d..1d41ce9a 100644
--- a/m4/size_max.m4
+++ b/m4/size_max.m4
@@ -1,17 +1,19 @@
-# size_max.m4 serial 10
-dnl Copyright (C) 2003, 2005-2006, 2008-2016 Free Software Foundation, Inc.
+# size_max.m4 serial 12
+dnl Copyright (C) 2003, 2005-2006, 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,
 dnl with or without modifications, as long as this notice is preserved.
 
 dnl From Bruno Haible.
 
+AC_PREREQ([2.61])
+
 AC_DEFUN([gl_SIZE_MAX],
 [
   AC_CHECK_HEADERS([stdint.h])
   dnl First test whether the system already has SIZE_MAX.
   AC_CACHE_CHECK([for SIZE_MAX], [gl_cv_size_max], [
-    gl_cv_size_max=
+    gl_cv_size_max=no
     AC_EGREP_CPP([Found it], [
 #include <limits.h>
 #if HAVE_STDINT_H
@@ -21,7 +23,7 @@ AC_DEFUN([gl_SIZE_MAX],
 Found it
 #endif
 ], [gl_cv_size_max=yes])
-    if test -z "$gl_cv_size_max"; then
+    if test $gl_cv_size_max != yes; then
       dnl Define it ourselves. Here we assume that the type 'size_t' is not 
wider
       dnl than the type 'unsigned long'. Try hard to find a definition that can
       dnl be used in a preprocessor #if, i.e. doesn't contain a cast.
@@ -71,9 +73,3 @@ Found it
 # undef SIZE_MAX
 #endif])
 ])
-
-dnl Autoconf >= 2.61 has AC_COMPUTE_INT built-in.
-dnl Remove this when we can assume autoconf >= 2.61.
-m4_ifdef([AC_COMPUTE_INT], [], [
-  AC_DEFUN([AC_COMPUTE_INT], [_AC_COMPUTE_INT([$2],[$1],[$3],[$4])])
-])
diff --git a/m4/threadlib.m4 b/m4/threadlib.m4
index b43534ea..20b383a8 100644
--- a/m4/threadlib.m4
+++ b/m4/threadlib.m4
@@ -1,11 +1,351 @@
-# threadlib.m4 serial 11 (gettext-0.18.2)
-dnl Copyright (C) 2005-2016 Free Software Foundation, Inc.
+# threadlib.m4 serial 29
+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,
 dnl with or without modifications, as long as this notice is preserved.
 
 dnl From Bruno Haible.
 
+AC_PREREQ([2.60])
+
+dnl The general structure of the multithreading modules in gnulib is that we
+dnl have three set of modules:
+dnl
+dnl   * POSIX API:
+dnl     pthread, which combines
+dnl       pthread-h
+dnl       pthread-thread
+dnl       pthread-once
+dnl       pthread-mutex
+dnl       pthread-rwlock
+dnl       pthread-cond
+dnl       pthread-tss
+dnl       pthread-spin
+dnl     sched_yield
+dnl
+dnl   * ISO C API:
+dnl     threads, which combines
+dnl       threads-h
+dnl       thrd
+dnl       mtx
+dnl       cnd
+dnl       tss
+dnl
+dnl   * Gnulib API, with an implementation that can be chosen at configure
+dnl     time through the option --enable-threads=...
+dnl       thread
+dnl       lock
+dnl       cond
+dnl       tls
+dnl       yield
+dnl
+dnl They are independent, except for the fact that
+dnl   - the implementation of the ISO C API may use the POSIX (or some other
+dnl     platform dependent) API,
+dnl   - the implementation of the Gnulib API may use the POSIX or ISO C or
+dnl     some other platform dependent API, depending on the --enable-threads
+dnl     option.
+dnl
+dnl This file contains macros for all of these APIs!
+
+dnl 
============================================================================
+dnl Macros for all thread APIs
+
+AC_DEFUN([gl_ANYTHREADLIB_EARLY],
+[
+  AC_REQUIRE([AC_CANONICAL_HOST])
+  if test -z "$gl_anythreadlib_early_done"; then
+    case "$host_os" in
+      osf*)
+        # On OSF/1, the compiler needs the flag -D_REENTRANT so that it
+        # groks <pthread.h>. cc also understands the flag -pthread, but
+        # we don't use it because 1. gcc-2.95 doesn't understand -pthread,
+        # 2. putting a flag into CPPFLAGS that has an effect on the linker
+        # causes the AC_LINK_IFELSE test below to succeed unexpectedly,
+        # leading to wrong values of LIBTHREAD and LTLIBTHREAD.
+        CPPFLAGS="$CPPFLAGS -D_REENTRANT"
+        ;;
+    esac
+    # Some systems optimize for single-threaded programs by default, and
+    # need special flags to disable these optimizations. For example, the
+    # definition of 'errno' in <errno.h>.
+    case "$host_os" in
+      aix* | freebsd*) CPPFLAGS="$CPPFLAGS -D_THREAD_SAFE" ;;
+      solaris*) CPPFLAGS="$CPPFLAGS -D_REENTRANT" ;;
+    esac
+    gl_anythreadlib_early_done=done
+  fi
+])
+
+dnl Checks whether the compiler and linker support weak declarations of 
symbols.
+
+AC_DEFUN([gl_WEAK_SYMBOLS],
+[
+  AC_REQUIRE([AC_CANONICAL_HOST])
+  AC_CACHE_CHECK([whether imported symbols can be declared weak],
+    [gl_cv_have_weak],
+    [gl_cv_have_weak=no
+     dnl First, test whether the compiler accepts it syntactically.
+     AC_LINK_IFELSE(
+       [AC_LANG_PROGRAM(
+          [[extern void xyzzy ();
+#pragma weak xyzzy]],
+          [[xyzzy();]])],
+       [gl_cv_have_weak=maybe])
+     if test $gl_cv_have_weak = maybe; then
+       dnl Second, test whether it actually works. On Cygwin 1.7.2, with
+       dnl gcc 4.3, symbols declared weak always evaluate to the address 0.
+       AC_RUN_IFELSE(
+         [AC_LANG_SOURCE([[
+#include <stdio.h>
+#pragma weak fputs
+int main ()
+{
+  return (fputs == NULL);
+}]])],
+         [gl_cv_have_weak=yes],
+         [gl_cv_have_weak=no],
+         [dnl When cross-compiling, assume that only ELF platforms support
+          dnl weak symbols.
+          AC_EGREP_CPP([Extensible Linking Format],
+            [#ifdef __ELF__
+             Extensible Linking Format
+             #endif
+            ],
+            [gl_cv_have_weak="guessing yes"],
+            [gl_cv_have_weak="guessing no"])
+         ])
+     fi
+     dnl But when linking statically, weak symbols don't work.
+     case " $LDFLAGS " in
+       *" -static "*) gl_cv_have_weak=no ;;
+     esac
+     dnl Test for a bug in FreeBSD 11: A link error occurs when using a weak
+     dnl symbol and linking against a shared library that has a dependency on
+     dnl the shared library that defines the symbol.
+     case "$gl_cv_have_weak" in
+       *yes)
+         case "$host_os" in
+           freebsd* | dragonfly*)
+             : > conftest1.c
+             $CC $CPPFLAGS $CFLAGS $LDFLAGS -fPIC -shared -o libempty.so 
conftest1.c -lpthread >&AS_MESSAGE_LOG_FD 2>&1
+             cat <<EOF > conftest2.c
+#include <pthread.h>
+#pragma weak pthread_mutexattr_gettype
+int main ()
+{
+  return (pthread_mutexattr_gettype != NULL);
+}
+EOF
+             $CC $CPPFLAGS $CFLAGS $LDFLAGS -o conftest conftest2.c 
libempty.so >&AS_MESSAGE_LOG_FD 2>&1 \
+               || gl_cv_have_weak=no
+             rm -f conftest1.c libempty.so conftest2.c conftest
+             ;;
+         esac
+         ;;
+     esac
+    ])
+  case "$gl_cv_have_weak" in
+    *yes)
+      AC_DEFINE([HAVE_WEAK_SYMBOLS], [1],
+        [Define to 1 if the compiler and linker support weak declarations of 
symbols.])
+      ;;
+  esac
+])
+
+dnl 
============================================================================
+dnl Macros for the POSIX API
+
+dnl gl_PTHREADLIB
+dnl -------------
+dnl Tests for the libraries needs for using the POSIX threads API.
+dnl Sets the variable LIBPTHREAD to the linker options for use in a Makefile.
+dnl Sets the variable LIBPMULTITHREAD, for programs that really need
+dnl multithread functionality. The difference between LIBPTHREAD and
+dnl LIBPMULTITHREAD is that on platforms supporting weak symbols, typically
+dnl LIBPTHREAD is empty whereas LIBPMULTITHREAD is not.
+dnl Sets the variable LIB_SCHED_YIELD to the linker options needed to use the
+dnl sched_yield() function.
+dnl Adds to CPPFLAGS the flag -D_REENTRANT or -D_THREAD_SAFE if needed for
+dnl multithread-safe programs.
+dnl Defines the C macro HAVE_PTHREAD_API if (at least parts of) the POSIX
+dnl threads API is available.
+
+dnl The guts of gl_PTHREADLIB. Needs to be expanded only once.
+
+AC_DEFUN([gl_PTHREADLIB_BODY],
+[
+  AC_REQUIRE([gl_ANYTHREADLIB_EARLY])
+  if test -z "$gl_pthreadlib_body_done"; then
+    gl_pthread_api=no
+    LIBPTHREAD=
+    LIBPMULTITHREAD=
+    # On OSF/1, the compiler needs the flag -pthread or -D_REENTRANT so that
+    # it groks <pthread.h>. It's added above, in gl_ANYTHREADLIB_EARLY.
+    AC_CHECK_HEADER([pthread.h],
+      [gl_have_pthread_h=yes], [gl_have_pthread_h=no])
+    if test "$gl_have_pthread_h" = yes; then
+      # Other possible tests:
+      #   -lpthreads (FSU threads, PCthreads)
+      #   -lgthreads
+      # Test whether both pthread_mutex_lock and pthread_mutexattr_init exist
+      # in libc. IRIX 6.5 has the first one in both libc and libpthread, but
+      # the second one only in libpthread, and lock.c needs it.
+      #
+      # If -pthread works, prefer it to -lpthread, since Ubuntu 14.04
+      # needs -pthread for some reason.  See:
+      # https://lists.gnu.org/r/bug-gnulib/2014-09/msg00023.html
+      save_LIBS=$LIBS
+      for gl_pthread in '' '-pthread'; do
+        LIBS="$LIBS $gl_pthread"
+        AC_LINK_IFELSE(
+          [AC_LANG_PROGRAM(
+             [[#include <pthread.h>
+               pthread_mutex_t m;
+               pthread_mutexattr_t ma;
+             ]],
+             [[pthread_mutex_lock (&m);
+               pthread_mutexattr_init (&ma);]])],
+          [gl_pthread_api=yes
+           LIBPTHREAD=$gl_pthread
+           LIBPMULTITHREAD=$gl_pthread])
+        LIBS=$save_LIBS
+        test $gl_pthread_api = yes && break
+      done
+
+      # Test for libpthread by looking for pthread_kill. (Not pthread_self,
+      # since it is defined as a macro on OSF/1.)
+      if test $gl_pthread_api = yes && test -z "$LIBPTHREAD"; then
+        # The program links fine without libpthread. But it may actually
+        # need to link with libpthread in order to create multiple threads.
+        AC_CHECK_LIB([pthread], [pthread_kill],
+          [LIBPMULTITHREAD=-lpthread
+           # On Solaris and HP-UX, most pthread functions exist also in libc.
+           # Therefore pthread_in_use() needs to actually try to create a
+           # thread: pthread_create from libc will fail, whereas
+           # pthread_create will actually create a thread.
+           # On Solaris 10 or newer, this test is no longer needed, because
+           # libc contains the fully functional pthread functions.
+           case "$host_os" in
+             solaris | solaris2.[1-9] | solaris2.[1-9].* | hpux*)
+               AC_DEFINE([PTHREAD_IN_USE_DETECTION_HARD], [1],
+                 [Define if the pthread_in_use() detection is hard.])
+           esac
+          ])
+      elif test $gl_pthread_api != yes; then
+        # Some library is needed. Try libpthread and libc_r.
+        AC_CHECK_LIB([pthread], [pthread_kill],
+          [gl_pthread_api=yes
+           LIBPTHREAD=-lpthread
+           LIBPMULTITHREAD=-lpthread])
+        if test $gl_pthread_api != yes; then
+          # For FreeBSD 4.
+          AC_CHECK_LIB([c_r], [pthread_kill],
+            [gl_pthread_api=yes
+             LIBPTHREAD=-lc_r
+             LIBPMULTITHREAD=-lc_r])
+        fi
+      fi
+    fi
+    AC_MSG_CHECKING([whether POSIX threads API is available])
+    AC_MSG_RESULT([$gl_pthread_api])
+    AC_SUBST([LIBPTHREAD])
+    AC_SUBST([LIBPMULTITHREAD])
+    if test $gl_pthread_api = yes; then
+      AC_DEFINE([HAVE_PTHREAD_API], [1],
+        [Define if you have the <pthread.h> header and the POSIX threads API.])
+    fi
+
+    dnl On some systems, sched_yield is in librt, rather than in libpthread.
+    AC_LINK_IFELSE(
+      [AC_LANG_PROGRAM(
+         [[#include <sched.h>]],
+         [[sched_yield ();]])],
+      [LIB_SCHED_YIELD=
+      ],
+      [dnl Solaris 7...10 has sched_yield in librt, not in libpthread or libc.
+       AC_CHECK_LIB([rt], [sched_yield], [LIB_SCHED_YIELD=-lrt],
+         [dnl Solaris 2.5.1, 2.6 has sched_yield in libposix4, not librt.
+          AC_CHECK_LIB([posix4], [sched_yield], [LIB_SCHED_YIELD=-lposix4])])
+      ])
+    AC_SUBST([LIB_SCHED_YIELD])
+
+    gl_pthreadlib_body_done=done
+  fi
+])
+
+AC_DEFUN([gl_PTHREADLIB],
+[
+  AC_REQUIRE([gl_ANYTHREADLIB_EARLY])
+  gl_PTHREADLIB_BODY
+])
+
+dnl 
============================================================================
+dnl Macros for the ISO C API
+
+dnl gl_STDTHREADLIB
+dnl ---------------
+dnl Tests for the libraries needs for using the ISO C threads API.
+dnl Sets the variable LIBSTDTHREAD to the linker options for use in a Makefile.
+dnl Adds to CPPFLAGS the flag -D_REENTRANT or -D_THREAD_SAFE if needed for
+dnl multithread-safe programs.
+dnl Defines the C macro HAVE_THREADS_H if (at least parts of) the ISO C threads
+dnl API is available.
+
+dnl The guts of gl_STDTHREADLIB. Needs to be expanded only once.
+
+AC_DEFUN([gl_STDTHREADLIB_BODY],
+[
+  AC_REQUIRE([gl_ANYTHREADLIB_EARLY])
+  AC_REQUIRE([AC_CANONICAL_HOST])
+  if test -z "$gl_stdthreadlib_body_done"; then
+    AC_CHECK_HEADERS_ONCE([threads.h])
+
+    case "$host_os" in
+      mingw*)
+        LIBSTDTHREAD=
+        ;;
+      *)
+        gl_PTHREADLIB_BODY
+        if test $ac_cv_header_threads_h = yes; then
+          dnl glibc >= 2.29 has thrd_create in libpthread.
+          dnl FreeBSD >= 10 has thrd_create in libstdthreads; this library 
depends
+          dnl on libpthread (for the symbol 'pthread_mutexattr_gettype').
+          dnl AIX >= 7.1 and Solaris >= 11.4 have thrd_create in libc.
+          AC_CHECK_FUNCS([thrd_create])
+          if test $ac_cv_func_thrd_create = yes; then
+            LIBSTDTHREAD=
+          else
+            AC_CHECK_LIB([stdthreads], [thrd_create], [
+              LIBSTDTHREAD='-lstdthreads -lpthread'
+            ], [
+              dnl Guess that thrd_create is in libpthread.
+              LIBSTDTHREAD="$LIBPMULTITHREAD"
+            ])
+          fi
+        else
+          dnl Libraries needed by thrd.c, mtx.c, cnd.c, tss.c.
+          LIBSTDTHREAD="$LIBPMULTITHREAD $LIB_SCHED_YIELD"
+        fi
+        ;;
+    esac
+    AC_SUBST([LIBSTDTHREAD])
+
+    AC_MSG_CHECKING([whether ISO C threads API is available])
+    AC_MSG_RESULT([$ac_cv_header_threads_h])
+    gl_stdthreadlib_body_done=done
+  fi
+])
+
+AC_DEFUN([gl_STDTHREADLIB],
+[
+  AC_REQUIRE([gl_ANYTHREADLIB_EARLY])
+  gl_STDTHREADLIB_BODY
+])
+
+dnl 
============================================================================
+dnl Macros for the Gnulib API
+
 dnl gl_THREADLIB
 dnl ------------
 dnl Tests for a multithreading library to be used.
@@ -14,8 +354,13 @@ dnl (it must be placed before the invocation of 
gl_THREADLIB_EARLY!), then the
 dnl default is 'no', otherwise it is system dependent. In both cases, the user
 dnl can change the choice through the options --enable-threads=choice or
 dnl --disable-threads.
-dnl Defines at most one of the macros USE_POSIX_THREADS, USE_SOLARIS_THREADS,
-dnl USE_PTH_THREADS, USE_WINDOWS_THREADS
+dnl Defines at most one of the macros USE_ISOC_THREADS, USE_POSIX_THREADS,
+dnl USE_ISOC_AND_POSIX_THREADS, USE_WINDOWS_THREADS.
+dnl The choice --enable-threads=isoc+posix is available only on platforms that
+dnl have both the ISO C and the POSIX threads APIs. It has the effect of using
+dnl the ISO C API for most things and the POSIX API only for creating and
+dnl controlling threads (because there is no equivalent to pthread_atfork in
+dnl the ISO C API).
 dnl Sets the variables LIBTHREAD and LTLIBTHREAD to the linker options for use
 dnl in a Makefile (LIBTHREAD for use without libtool, LTLIBTHREAD for use with
 dnl libtool).
@@ -25,6 +370,9 @@ dnl between LIBTHREAD and LIBMULTITHREAD is that on 
platforms supporting weak
 dnl symbols, typically LIBTHREAD is empty whereas LIBMULTITHREAD is not.
 dnl Adds to CPPFLAGS the flag -D_REENTRANT or -D_THREAD_SAFE if needed for
 dnl multithread-safe programs.
+dnl Since support for GNU pth was removed, $LTLIBTHREAD and $LIBTHREAD have the
+dnl same value, and similarly $LTLIBMULTITHREAD and $LIBMULTITHREAD have the
+dnl same value. Only system libraries are needed.
 
 AC_DEFUN([gl_THREADLIB_EARLY],
 [
@@ -43,18 +391,15 @@ AC_DEFUN([gl_THREADLIB_EARLY_BODY],
 
   AC_REQUIRE([AC_CANONICAL_HOST])
   dnl _GNU_SOURCE is needed for pthread_rwlock_t on glibc systems.
-  dnl AC_USE_SYSTEM_EXTENSIONS was introduced in autoconf 2.60 and obsoletes
-  dnl AC_GNU_SOURCE.
-  m4_ifdef([AC_USE_SYSTEM_EXTENSIONS],
-    [AC_REQUIRE([AC_USE_SYSTEM_EXTENSIONS])],
-    [AC_REQUIRE([AC_GNU_SOURCE])])
+  AC_REQUIRE([AC_USE_SYSTEM_EXTENSIONS])
   dnl Check for multithreading.
   m4_ifdef([gl_THREADLIB_DEFAULT_NO],
     [m4_divert_text([DEFAULTS], [gl_use_threads_default=no])],
     [m4_divert_text([DEFAULTS], [gl_use_threads_default=])])
+  m4_divert_text([DEFAULTS], [gl_use_winpthreads_default=])
   AC_ARG_ENABLE([threads],
-AC_HELP_STRING([--enable-threads={posix|solaris|pth|windows}], [specify 
multithreading API])m4_ifdef([gl_THREADLIB_DEFAULT_NO], [], [
-AC_HELP_STRING([--disable-threads], [build without multithread safety])]),
+AS_HELP_STRING([--enable-threads={isoc|posix|isoc+posix|windows}], [specify 
multithreading API])m4_ifdef([gl_THREADLIB_DEFAULT_NO], [], [
+AS_HELP_STRING([--disable-threads], [build without multithread safety])]),
     [gl_use_threads=$enableval],
     [if test -n "$gl_use_threads_default"; then
        gl_use_threads="$gl_use_threads_default"
@@ -64,41 +409,35 @@ changequote(,)dnl
          dnl Disable multithreading by default on OSF/1, because it interferes
          dnl with fork()/exec(): When msgexec is linked with -lpthread, its
          dnl child process gets an endless segmentation fault inside execvp().
+         osf*) gl_use_threads=no ;;
          dnl Disable multithreading by default on Cygwin 1.5.x, because it has
          dnl bugs that lead to endless loops or crashes. See
-         dnl <http://cygwin.com/ml/cygwin/2009-08/msg00283.html>.
-         osf*) gl_use_threads=no ;;
+         dnl <https://cygwin.com/ml/cygwin/2009-08/msg00283.html>.
          cygwin*)
                case `uname -r` in
                  1.[0-5].*) gl_use_threads=no ;;
                  *)         gl_use_threads=yes ;;
                esac
                ;;
+         dnl Obey gl_AVOID_WINPTHREAD on mingw.
+         mingw*)
+               case "$gl_use_winpthreads_default" in
+                 yes) gl_use_threads=posix ;;
+                 no)  gl_use_threads=windows ;;
+                 *)   gl_use_threads=yes ;;
+               esac
+               ;;
          *)    gl_use_threads=yes ;;
        esac
 changequote([,])dnl
      fi
     ])
-  if test "$gl_use_threads" = yes || test "$gl_use_threads" = posix; then
-    # For using <pthread.h>:
-    case "$host_os" in
-      osf*)
-        # On OSF/1, the compiler needs the flag -D_REENTRANT so that it
-        # groks <pthread.h>. cc also understands the flag -pthread, but
-        # we don't use it because 1. gcc-2.95 doesn't understand -pthread,
-        # 2. putting a flag into CPPFLAGS that has an effect on the linker
-        # causes the AC_LINK_IFELSE test below to succeed unexpectedly,
-        # leading to wrong values of LIBTHREAD and LTLIBTHREAD.
-        CPPFLAGS="$CPPFLAGS -D_REENTRANT"
-        ;;
-    esac
-    # Some systems optimize for single-threaded programs by default, and
-    # need special flags to disable these optimizations. For example, the
-    # definition of 'errno' in <errno.h>.
-    case "$host_os" in
-      aix* | freebsd*) CPPFLAGS="$CPPFLAGS -D_THREAD_SAFE" ;;
-      solaris*) CPPFLAGS="$CPPFLAGS -D_REENTRANT" ;;
-    esac
+  if test "$gl_use_threads" = yes \
+     || test "$gl_use_threads" = isoc \
+     || test "$gl_use_threads" = posix \
+     || test "$gl_use_threads" = isoc+posix; then
+    # For using <threads.h> or <pthread.h>:
+    gl_ANYTHREADLIB_EARLY
   fi
 ])
 
@@ -114,108 +453,31 @@ AC_DEFUN([gl_THREADLIB_BODY],
   LTLIBMULTITHREAD=
   if test "$gl_use_threads" != no; then
     dnl Check whether the compiler and linker support weak declarations.
-    AC_CACHE_CHECK([whether imported symbols can be declared weak],
-      [gl_cv_have_weak],
-      [gl_cv_have_weak=no
-       dnl First, test whether the compiler accepts it syntactically.
-       AC_LINK_IFELSE(
-         [AC_LANG_PROGRAM(
-            [[extern void xyzzy ();
-#pragma weak xyzzy]],
-            [[xyzzy();]])],
-         [gl_cv_have_weak=maybe])
-       if test $gl_cv_have_weak = maybe; then
-         dnl Second, test whether it actually works. On Cygwin 1.7.2, with
-         dnl gcc 4.3, symbols declared weak always evaluate to the address 0.
-         AC_RUN_IFELSE(
-           [AC_LANG_SOURCE([[
-#include <stdio.h>
-#pragma weak fputs
-int main ()
-{
-  return (fputs == NULL);
-}]])],
-           [gl_cv_have_weak=yes],
-           [gl_cv_have_weak=no],
-           [dnl When cross-compiling, assume that only ELF platforms support
-            dnl weak symbols.
-            AC_EGREP_CPP([Extensible Linking Format],
-              [#ifdef __ELF__
-               Extensible Linking Format
-               #endif
-              ],
-              [gl_cv_have_weak="guessing yes"],
-              [gl_cv_have_weak="guessing no"])
-           ])
-       fi
-      ])
-    if test "$gl_use_threads" = yes || test "$gl_use_threads" = posix; then
-      # On OSF/1, the compiler needs the flag -pthread or -D_REENTRANT so that
-      # it groks <pthread.h>. It's added above, in gl_THREADLIB_EARLY_BODY.
-      AC_CHECK_HEADER([pthread.h],
-        [gl_have_pthread_h=yes], [gl_have_pthread_h=no])
-      if test "$gl_have_pthread_h" = yes; then
-        # Other possible tests:
-        #   -lpthreads (FSU threads, PCthreads)
-        #   -lgthreads
-        gl_have_pthread=
-        # Test whether both pthread_mutex_lock and pthread_mutexattr_init exist
-        # in libc. IRIX 6.5 has the first one in both libc and libpthread, but
-        # the second one only in libpthread, and lock.c needs it.
-        #
-        # If -pthread works, prefer it to -lpthread, since Ubuntu 14.04
-        # needs -pthread for some reason.  See:
-        # http://lists.gnu.org/archive/html/bug-gnulib/2014-09/msg00023.html
-        save_LIBS=$LIBS
-        for gl_pthread in '' '-pthread'; do
-          LIBS="$LIBS $gl_pthread"
-          AC_LINK_IFELSE(
-            [AC_LANG_PROGRAM(
-               [[#include <pthread.h>
-                 pthread_mutex_t m;
-                 pthread_mutexattr_t ma;
-               ]],
-               [[pthread_mutex_lock (&m);
-                 pthread_mutexattr_init (&ma);]])],
-            [gl_have_pthread=yes
-             LIBTHREAD=$gl_pthread LTLIBTHREAD=$gl_pthread
-             LIBMULTITHREAD=$gl_pthread LTLIBMULTITHREAD=$gl_pthread])
-          LIBS=$save_LIBS
-          test -n "$gl_have_pthread" && break
-        done
-
-        # Test for libpthread by looking for pthread_kill. (Not pthread_self,
-        # since it is defined as a macro on OSF/1.)
-        if test -n "$gl_have_pthread" && test -z "$LIBTHREAD"; then
-          # The program links fine without libpthread. But it may actually
-          # need to link with libpthread in order to create multiple threads.
-          AC_CHECK_LIB([pthread], [pthread_kill],
-            [LIBMULTITHREAD=-lpthread LTLIBMULTITHREAD=-lpthread
-             # On Solaris and HP-UX, most pthread functions exist also in libc.
-             # Therefore pthread_in_use() needs to actually try to create a
-             # thread: pthread_create from libc will fail, whereas
-             # pthread_create will actually create a thread.
-             case "$host_os" in
-               solaris* | hpux*)
-                 AC_DEFINE([PTHREAD_IN_USE_DETECTION_HARD], [1],
-                   [Define if the pthread_in_use() detection is hard.])
-             esac
-            ])
-        elif test -z "$gl_have_pthread"; then
-          # Some library is needed. Try libpthread and libc_r.
-          AC_CHECK_LIB([pthread], [pthread_kill],
-            [gl_have_pthread=yes
-             LIBTHREAD=-lpthread LTLIBTHREAD=-lpthread
-             LIBMULTITHREAD=-lpthread LTLIBMULTITHREAD=-lpthread])
-          if test -z "$gl_have_pthread"; then
-            # For FreeBSD 4.
-            AC_CHECK_LIB([c_r], [pthread_kill],
-              [gl_have_pthread=yes
-               LIBTHREAD=-lc_r LTLIBTHREAD=-lc_r
-               LIBMULTITHREAD=-lc_r LTLIBMULTITHREAD=-lc_r])
-          fi
-        fi
-        if test -n "$gl_have_pthread"; then
+    gl_WEAK_SYMBOLS
+    if case "$gl_cv_have_weak" in *yes) true;; *) false;; esac; then
+      dnl If we use weak symbols to implement pthread_in_use / pth_in_use /
+      dnl thread_in_use, we also need to test whether the ISO C 11 thrd_create
+      dnl facility is in use.
+      AC_CHECK_HEADERS_ONCE([threads.h])
+      :
+    fi
+    if test "$gl_use_threads" = isoc || test "$gl_use_threads" = isoc+posix; 
then
+      AC_CHECK_HEADERS_ONCE([threads.h])
+      gl_have_isoc_threads="$ac_cv_header_threads_h"
+    fi
+    if test "$gl_use_threads" = yes \
+       || test "$gl_use_threads" = posix \
+       || test "$gl_use_threads" = isoc+posix; then
+      gl_PTHREADLIB_BODY
+      LIBTHREAD=$LIBPTHREAD LTLIBTHREAD=$LIBPTHREAD
+      LIBMULTITHREAD=$LIBPMULTITHREAD LTLIBMULTITHREAD=$LIBPMULTITHREAD
+      if test $gl_pthread_api = yes; then
+        if test "$gl_use_threads" = isoc+posix && test "$gl_have_isoc_threads" 
= yes; then
+          gl_threads_api='isoc+posix'
+          AC_DEFINE([USE_ISOC_AND_POSIX_THREADS], [1],
+            [Define if the combination of the ISO C and POSIX multithreading 
APIs can be used.])
+          LIBTHREAD= LTLIBTHREAD=
+        else
           gl_threads_api=posix
           AC_DEFINE([USE_POSIX_THREADS], [1],
             [Define if the POSIX multithreading library can be used.])
@@ -223,75 +485,34 @@ int main ()
             if case "$gl_cv_have_weak" in *yes) true;; *) false;; esac; then
               AC_DEFINE([USE_POSIX_THREADS_WEAK], [1],
                 [Define if references to the POSIX multithreading library 
should be made weak.])
-              LIBTHREAD=
-              LTLIBTHREAD=
+              LIBTHREAD= LTLIBTHREAD=
+            else
+              case "$host_os" in
+                freebsd* | dragonfly*)
+                  if test "x$LIBTHREAD" != "x$LIBMULTITHREAD"; then
+                    dnl If weak symbols can't tell whether pthread_create(), 
pthread_key_create()
+                    dnl etc. will succeed, we need a runtime test.
+                    AC_DEFINE([PTHREAD_IN_USE_DETECTION_HARD], [1],
+                      [Define if the pthread_in_use() detection is hard.])
+                  fi
+                  ;;
+              esac
             fi
           fi
         fi
       fi
     fi
-    if test -z "$gl_have_pthread"; then
-      if test "$gl_use_threads" = yes || test "$gl_use_threads" = solaris; then
-        gl_have_solaristhread=
-        gl_save_LIBS="$LIBS"
-        LIBS="$LIBS -lthread"
-        AC_LINK_IFELSE(
-          [AC_LANG_PROGRAM(
-             [[
-#include <thread.h>
-#include <synch.h>
-             ]],
-             [[thr_self();]])],
-          [gl_have_solaristhread=yes])
-        LIBS="$gl_save_LIBS"
-        if test -n "$gl_have_solaristhread"; then
-          gl_threads_api=solaris
-          LIBTHREAD=-lthread
-          LTLIBTHREAD=-lthread
-          LIBMULTITHREAD="$LIBTHREAD"
-          LTLIBMULTITHREAD="$LTLIBTHREAD"
-          AC_DEFINE([USE_SOLARIS_THREADS], [1],
-            [Define if the old Solaris multithreading library can be used.])
-          if case "$gl_cv_have_weak" in *yes) true;; *) false;; esac; then
-            AC_DEFINE([USE_SOLARIS_THREADS_WEAK], [1],
-              [Define if references to the old Solaris multithreading library 
should be made weak.])
-            LIBTHREAD=
-            LTLIBTHREAD=
-          fi
-        fi
-      fi
-    fi
-    if test "$gl_use_threads" = pth; then
-      gl_save_CPPFLAGS="$CPPFLAGS"
-      AC_LIB_LINKFLAGS([pth])
-      gl_have_pth=
-      gl_save_LIBS="$LIBS"
-      LIBS="$LIBS $LIBPTH"
-      AC_LINK_IFELSE(
-        [AC_LANG_PROGRAM([[#include <pth.h>]], [[pth_self();]])],
-        [gl_have_pth=yes])
-      LIBS="$gl_save_LIBS"
-      if test -n "$gl_have_pth"; then
-        gl_threads_api=pth
-        LIBTHREAD="$LIBPTH"
-        LTLIBTHREAD="$LTLIBPTH"
-        LIBMULTITHREAD="$LIBTHREAD"
-        LTLIBMULTITHREAD="$LTLIBTHREAD"
-        AC_DEFINE([USE_PTH_THREADS], [1],
-          [Define if the GNU Pth multithreading library can be used.])
-        if test -n "$LIBMULTITHREAD" || test -n "$LTLIBMULTITHREAD"; then
-          if case "$gl_cv_have_weak" in *yes) true;; *) false;; esac; then
-            AC_DEFINE([USE_PTH_THREADS_WEAK], [1],
-              [Define if references to the GNU Pth multithreading library 
should be made weak.])
-            LIBTHREAD=
-            LTLIBTHREAD=
-          fi
-        fi
-      else
-        CPPFLAGS="$gl_save_CPPFLAGS"
+    if test $gl_threads_api = none; then
+      if test "$gl_use_threads" = isoc && test "$gl_have_isoc_threads" = yes; 
then
+        gl_STDTHREADLIB_BODY
+        LIBTHREAD=$LIBSTDTHREAD LTLIBTHREAD=$LIBSTDTHREAD
+        LIBMULTITHREAD=$LIBSTDTHREAD LTLIBMULTITHREAD=$LIBSTDTHREAD
+        gl_threads_api=isoc
+        AC_DEFINE([USE_ISOC_THREADS], [1],
+          [Define if the ISO C multithreading library can be used.])
       fi
     fi
-    if test -z "$gl_have_pthread"; then
+    if test $gl_threads_api = none; then
       case "$gl_use_threads" in
         yes | windows | win32) # The 'win32' is for backward compatibility.
           if { case "$host_os" in
@@ -333,6 +554,21 @@ AC_DEFUN([gl_DISABLE_THREADS], [
 ])
 
 
+dnl gl_AVOID_WINPTHREAD
+dnl -------------------
+dnl Sets the gl_THREADLIB default so that on mingw, a dependency to the
+dnl libwinpthread DLL (mingw-w64 winpthreads library) is avoided.
+dnl The user can still override it at installation time, by using the
+dnl configure option '--enable-threads'.
+
+AC_DEFUN([gl_AVOID_WINPTHREAD], [
+  m4_divert_text([INIT_PREPARE], [gl_use_winpthreads_default=no])
+])
+
+
+dnl 
============================================================================
+
+
 dnl Survey of platforms:
 dnl
 dnl Platform           Available  Compiler    Supports   test-lock
@@ -362,7 +598,6 @@ dnl
 dnl Mac OS X 10.[123]  posix      -lpthread       Y      OK
 dnl
 dnl Solaris 7,8,9      posix      -lpthread       Y      Sol 7,8: 0.0; Sol 9: 
OK
-dnl                    solaris    -lthread        Y      Sol 7,8: 0.0; Sol 9: 
OK
 dnl
 dnl HP-UX 11           posix      -lpthread       N (cc) OK
 dnl                                               Y (gcc)
@@ -376,8 +611,6 @@ dnl                               -lpthread (gcc) Y
 dnl
 dnl Cygwin             posix      -lpthread       Y      OK
 dnl
-dnl Any of the above   pth        -lpth                  0.0
-dnl
 dnl Mingw              windows                    N      OK
 dnl
 dnl BeOS 5             --
diff --git a/m4/tsearch.m4 b/m4/tsearch.m4
index 24b35ce2..9f8782e4 100644
--- a/m4/tsearch.m4
+++ b/m4/tsearch.m4
@@ -1,5 +1,5 @@
-# tsearch.m4 serial 6
-dnl Copyright (C) 2006-2017 Free Software Foundation, Inc.
+# tsearch.m4 serial 8
+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.
@@ -7,7 +7,7 @@ dnl with or without modifications, as long as this notice is 
preserved.
 AC_DEFUN([gl_FUNC_TSEARCH],
 [
   AC_REQUIRE([gl_SEARCH_H_DEFAULTS])
-  AC_CHECK_FUNCS([tsearch])
+  AC_CHECK_FUNCS([tsearch twalk])
   if test $ac_cv_func_tsearch = yes; then
     dnl On OpenBSD 4.0, the return value of tdelete() is incorrect.
     AC_REQUIRE([AC_PROG_CC])
@@ -38,8 +38,10 @@ main ()
   return result;
 }]])], [gl_cv_func_tdelete_works=yes], [gl_cv_func_tdelete_works=no],
             [case "$host_os" in
-               openbsd*) gl_cv_func_tdelete_works="guessing no";;
-               *)        gl_cv_func_tdelete_works="guessing yes";;
+               openbsd*) gl_cv_func_tdelete_works="guessing no" ;;
+                         # Guess yes on native Windows.
+               mingw*)   gl_cv_func_tdelete_works="guessing yes" ;;
+               *)        gl_cv_func_tdelete_works="guessing yes" ;;
              esac
             ])
       ])
@@ -51,6 +53,9 @@ main ()
   else
     HAVE_TSEARCH=0
   fi
+  if test $ac_cv_func_twalk != yes; then
+    HAVE_TWALK=0
+  fi
 ])
 
 # Prerequisites of lib/tsearch.c.
diff --git a/m4/visibility.m4 b/m4/visibility.m4
index e99e3fba..6e4b4615 100644
--- a/m4/visibility.m4
+++ b/m4/visibility.m4
@@ -1,5 +1,5 @@
-# visibility.m4 serial 5 (gettext-0.18.2)
-dnl Copyright (C) 2005, 2008, 2010-2016 Free Software Foundation, Inc.
+# visibility.m4 serial 6
+dnl Copyright (C) 2005, 2008, 2010-2021 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.
@@ -29,42 +29,42 @@ AC_DEFUN([gl_VISIBILITY],
     dnl First, check whether -Werror can be added to the command line, or
     dnl whether it leads to an error because of some other option that the
     dnl user has put into $CC $CFLAGS $CPPFLAGS.
-    AC_MSG_CHECKING([whether the -Werror option is usable])
-    AC_CACHE_VAL([gl_cv_cc_vis_werror], [
-      gl_save_CFLAGS="$CFLAGS"
-      CFLAGS="$CFLAGS -Werror"
-      AC_COMPILE_IFELSE(
-        [AC_LANG_PROGRAM([[]], [[]])],
-        [gl_cv_cc_vis_werror=yes],
-        [gl_cv_cc_vis_werror=no])
-      CFLAGS="$gl_save_CFLAGS"])
-    AC_MSG_RESULT([$gl_cv_cc_vis_werror])
+    AC_CACHE_CHECK([whether the -Werror option is usable],
+      [gl_cv_cc_vis_werror],
+      [gl_save_CFLAGS="$CFLAGS"
+       CFLAGS="$CFLAGS -Werror"
+       AC_COMPILE_IFELSE(
+         [AC_LANG_PROGRAM([[]], [[]])],
+         [gl_cv_cc_vis_werror=yes],
+         [gl_cv_cc_vis_werror=no])
+       CFLAGS="$gl_save_CFLAGS"
+      ])
     dnl Now check whether visibility declarations are supported.
-    AC_MSG_CHECKING([for simple visibility declarations])
-    AC_CACHE_VAL([gl_cv_cc_visibility], [
-      gl_save_CFLAGS="$CFLAGS"
-      CFLAGS="$CFLAGS -fvisibility=hidden"
-      dnl We use the option -Werror and a function dummyfunc, because on some
-      dnl platforms (Cygwin 1.7) the use of -fvisibility triggers a warning
-      dnl "visibility attribute not supported in this configuration; ignored"
-      dnl at the first function definition in every compilation unit, and we
-      dnl don't want to use the option in this case.
-      if test $gl_cv_cc_vis_werror = yes; then
-        CFLAGS="$CFLAGS -Werror"
-      fi
-      AC_COMPILE_IFELSE(
-        [AC_LANG_PROGRAM(
-           [[extern __attribute__((__visibility__("hidden"))) int hiddenvar;
-             extern __attribute__((__visibility__("default"))) int exportedvar;
-             extern __attribute__((__visibility__("hidden"))) int hiddenfunc 
(void);
-             extern __attribute__((__visibility__("default"))) int 
exportedfunc (void);
-             void dummyfunc (void) {}
-           ]],
-           [[]])],
-        [gl_cv_cc_visibility=yes],
-        [gl_cv_cc_visibility=no])
-      CFLAGS="$gl_save_CFLAGS"])
-    AC_MSG_RESULT([$gl_cv_cc_visibility])
+    AC_CACHE_CHECK([for simple visibility declarations],
+      [gl_cv_cc_visibility],
+      [gl_save_CFLAGS="$CFLAGS"
+       CFLAGS="$CFLAGS -fvisibility=hidden"
+       dnl We use the option -Werror and a function dummyfunc, because on some
+       dnl platforms (Cygwin 1.7) the use of -fvisibility triggers a warning
+       dnl "visibility attribute not supported in this configuration; ignored"
+       dnl at the first function definition in every compilation unit, and we
+       dnl don't want to use the option in this case.
+       if test $gl_cv_cc_vis_werror = yes; then
+         CFLAGS="$CFLAGS -Werror"
+       fi
+       AC_COMPILE_IFELSE(
+         [AC_LANG_PROGRAM(
+            [[extern __attribute__((__visibility__("hidden"))) int hiddenvar;
+              extern __attribute__((__visibility__("default"))) int 
exportedvar;
+              extern __attribute__((__visibility__("hidden"))) int hiddenfunc 
(void);
+              extern __attribute__((__visibility__("default"))) int 
exportedfunc (void);
+              void dummyfunc (void) {}
+            ]],
+            [[]])],
+         [gl_cv_cc_visibility=yes],
+         [gl_cv_cc_visibility=no])
+       CFLAGS="$gl_save_CFLAGS"
+      ])
     if test $gl_cv_cc_visibility = yes; then
       CFLAG_VISIBILITY="-fvisibility=hidden"
       HAVE_VISIBILITY=1
diff --git a/m4/wint_t.m4 b/m4/wint_t.m4
index 8ff2a5b5..2fc7467f 100644
--- a/m4/wint_t.m4
+++ b/m4/wint_t.m4
@@ -1,11 +1,12 @@
-# wint_t.m4 serial 5 (gettext-0.18.2)
-dnl Copyright (C) 2003, 2007-2016 Free Software Foundation, Inc.
+# wint_t.m4 serial 10
+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,
 dnl with or without modifications, as long as this notice is preserved.
 
 dnl From Bruno Haible.
-dnl Test whether <wchar.h> has the 'wint_t' type.
+dnl Test whether <wchar.h> has the 'wint_t' type and whether gnulib's
+dnl <wchar.h> or <wctype.h> would, if present, override 'wint_t'.
 dnl Prerequisite: AC_PROG_CC
 
 AC_DEFUN([gt_TYPE_WINT_T],
@@ -13,20 +14,44 @@ AC_DEFUN([gt_TYPE_WINT_T],
   AC_CACHE_CHECK([for wint_t], [gt_cv_c_wint_t],
     [AC_COMPILE_IFELSE(
        [AC_LANG_PROGRAM(
-          [[
-/* 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>
             wint_t foo = (wchar_t)'\0';]],
           [[]])],
        [gt_cv_c_wint_t=yes],
        [gt_cv_c_wint_t=no])])
   if test $gt_cv_c_wint_t = yes; then
     AC_DEFINE([HAVE_WINT_T], [1], [Define if you have the 'wint_t' type.])
+
+    dnl Determine whether gnulib's <wchar.h> or <wctype.h> would, if present,
+    dnl override 'wint_t'.
+    AC_CACHE_CHECK([whether wint_t is large enough],
+      [gl_cv_type_wint_t_large_enough],
+      [AC_COMPILE_IFELSE(
+         [AC_LANG_PROGRAM(
+            [[#include <wchar.h>
+              int verify[sizeof (wint_t) < sizeof (int) ? -1 : 1];
+            ]])],
+         [gl_cv_type_wint_t_large_enough=yes],
+         [gl_cv_type_wint_t_large_enough=no])])
+    if test $gl_cv_type_wint_t_large_enough = no; then
+      GNULIB_OVERRIDES_WINT_T=1
+    else
+      GNULIB_OVERRIDES_WINT_T=0
+    fi
+  else
+    GNULIB_OVERRIDES_WINT_T=0
+  fi
+  AC_SUBST([GNULIB_OVERRIDES_WINT_T])
+])
+
+dnl Prerequisites of the 'wint_t' override.
+AC_DEFUN([gl_TYPE_WINT_T_PREREQ],
+[
+  AC_CHECK_HEADERS_ONCE([crtdefs.h])
+  if test $ac_cv_header_crtdefs_h = yes; then
+    HAVE_CRTDEFS_H=1
+  else
+    HAVE_CRTDEFS_H=0
   fi
+  AC_SUBST([HAVE_CRTDEFS_H])
 ])

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