Re: building the docs

[Paul Eggert <eggert@cs.ucla.edu>]

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On 5/29/19 8:04 AM, Eli Zaretskii wrote:
> Paul imports the Gnulib version regularly, and Karl Berry said that
> version had a problem.

I ran 'admin/update-gnulib' and installed the resulting patch. This 
upgrades master to the latest version in Gnulib, which Karl updated 
recently, and so should fix the problem.


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From 8986dbe3a8edb9296bdd83323b1138a756da2f7a Mon Sep 17 00:00:00 2001
From: Paul Eggert <eggert@cs.ucla.edu>
Date: Wed, 29 May 2019 16:33:51 -0700
Subject: [PATCH] Update from Gnulib

This incorporates:
2019-05-24 flexmember: update comments
2019-05-18 pthread_sigmask: fix --enable-threads=windows compilation
2019-05-14 close-stream, closein, closeout: simplify
2019-05-09 verify: remove verify_true
2019-05-09 verify: support C2X and C++17 static_assert
* build-aux/config.guess, build-aux/config.sub:
* doc/misc/texinfo.tex, lib/flexmember.h, lib/verify.h:
* m4/flexmember.m4, m4/pthread_sigmask.m4:
Copy from Gnulib
* m4/gnulib-comp.m4: Regenerate.

2019-05-26  Paul Eggert  <eggert@cs.ucla.edu>

Update author/maintainer info
This mostly updates email addresses and fixes spellings of
author and maintainer names.
---
 build-aux/config.guess |  61 +++++++++---------
 build-aux/config.sub   |   4 +-
 doc/misc/texinfo.tex   |  17 ++++-
 lib/flexmember.h       |  25 ++++++--
 lib/verify.h           | 110 ++++++++++++++++----------------
 m4/flexmember.m4       |   8 +--
 m4/gnulib-comp.m4      |   2 -
 m4/pthread_sigmask.m4  | 140 ++++++++++++++++++++---------------------
 8 files changed, 195 insertions(+), 172 deletions(-)

diff --git a/build-aux/config.guess b/build-aux/config.guess
index 4cd9454b35..ae713942d8 100755
--- a/build-aux/config.guess
+++ b/build-aux/config.guess
@@ -2,7 +2,7 @@
 # Attempt to guess a canonical system name.
 #   Copyright 1992-2019 Free Software Foundation, Inc.
 
-timestamp='2019-04-28'
+timestamp='2019-05-28'
 
 # This file is free software; you can redistribute it and/or modify it
 # under the terms of the GNU General Public License as published by
@@ -1325,38 +1325,39 @@ 	main ()
 	echo "$UNAME_MACHINE"-apple-rhapsody"$UNAME_RELEASE"
 	exit ;;
     *:Darwin:*:*)
-	UNAME_PROCESSOR=`uname -p` || UNAME_PROCESSOR=unknown
-	set_cc_for_build
-	if test "$UNAME_PROCESSOR" = unknown ; then
-	    UNAME_PROCESSOR=powerpc
+	UNAME_PROCESSOR=`uname -p`
+	case $UNAME_PROCESSOR in
+	    unknown) UNAME_PROCESSOR=powerpc ;;
+	esac
+	if command -v xcode-select > /dev/null 2> /dev/null && \
+		! xcode-select --print-path > /dev/null 2> /dev/null ; then
+	    # Avoid executing cc if there is no toolchain installed as
+	    # cc will be a stub that puts up a graphical alert
+	    # prompting the user to install developer tools.
+	    CC_FOR_BUILD=no_compiler_found
+	else
+	    set_cc_for_build
 	fi
-	if test "`echo "$UNAME_RELEASE" | sed -e 's/\..*//'`" -le 10 ; then
-	    if [ "$CC_FOR_BUILD" != no_compiler_found ]; then
-		if (echo '#ifdef __LP64__'; echo IS_64BIT_ARCH; echo '#endif') | \
-		       (CCOPTS="" $CC_FOR_BUILD -E - 2>/dev/null) | \
-		       grep IS_64BIT_ARCH >/dev/null
-		then
-		    case $UNAME_PROCESSOR in
-			i386) UNAME_PROCESSOR=x86_64 ;;
-			powerpc) UNAME_PROCESSOR=powerpc64 ;;
-		    esac
-		fi
-		# On 10.4-10.6 one might compile for PowerPC via gcc -arch ppc
-		if (echo '#ifdef __POWERPC__'; echo IS_PPC; echo '#endif') | \
-		       (CCOPTS="" $CC_FOR_BUILD -E - 2>/dev/null) | \
-		       grep IS_PPC >/dev/null
-		then
-		    UNAME_PROCESSOR=powerpc
-		fi
+	if [ "$CC_FOR_BUILD" != no_compiler_found ]; then
+	    if (echo '#ifdef __LP64__'; echo IS_64BIT_ARCH; echo '#endif') | \
+		   (CCOPTS="" $CC_FOR_BUILD -E - 2>/dev/null) | \
+		   grep IS_64BIT_ARCH >/dev/null
+	    then
+		case $UNAME_PROCESSOR in
+		    i386) UNAME_PROCESSOR=x86_64 ;;
+		    powerpc) UNAME_PROCESSOR=powerpc64 ;;
+		esac
+	    fi
+	    # On 10.4-10.6 one might compile for PowerPC via gcc -arch ppc
+	    if (echo '#ifdef __POWERPC__'; echo IS_PPC; echo '#endif') | \
+		   (CCOPTS="" $CC_FOR_BUILD -E - 2>/dev/null) | \
+		   grep IS_PPC >/dev/null
+	    then
+		UNAME_PROCESSOR=powerpc
 	    fi
 	elif test "$UNAME_PROCESSOR" = i386 ; then
-	    # Avoid executing cc on OS X 10.9, as it ships with a stub
-	    # that puts up a graphical alert prompting to install
-	    # developer tools.  Any system running Mac OS X 10.7 or
-	    # later (Darwin 11 and later) is required to have a 64-bit
-	    # processor. This is not true of the ARM version of Darwin
-	    # that Apple uses in portable devices.
-	    UNAME_PROCESSOR=x86_64
+	    # uname -m returns i386 or x86_64
+	    UNAME_PROCESSOR=$UNAME_MACHINE
 	fi
 	echo "$UNAME_PROCESSOR"-apple-darwin"$UNAME_RELEASE"
 	exit ;;
diff --git a/build-aux/config.sub b/build-aux/config.sub
index f53af5a2da..5b158ac41c 100755
--- a/build-aux/config.sub
+++ b/build-aux/config.sub
@@ -2,7 +2,7 @@
 # Configuration validation subroutine script.
 #   Copyright 1992-2019 Free Software Foundation, Inc.
 
-timestamp='2019-01-05'
+timestamp='2019-05-23'
 
 # This file is free software; you can redistribute it and/or modify it
 # under the terms of the GNU General Public License as published by
@@ -1172,7 +1172,7 @@ IFS=
 			| asmjs \
 			| ba \
 			| be32 | be64 \
-			| bfin | bs2000 \
+			| bfin | bpf | bs2000 \
 			| c[123]* | c30 | [cjt]90 | c4x \
 			| c8051 | clipper | craynv | csky | cydra \
 			| d10v | d30v | dlx | dsp16xx \
diff --git a/doc/misc/texinfo.tex b/doc/misc/texinfo.tex
index ccd112941a..53f2fc4835 100644
--- a/doc/misc/texinfo.tex
+++ b/doc/misc/texinfo.tex
@@ -3,7 +3,7 @@
 % Load plain if necessary, i.e., if running under initex.
 \expandafter\ifx\csname fmtname\endcsname\relax\input plain\fi
 %
-\def\texinfoversion{2019-04-12.13}
+\def\texinfoversion{2019-05-18.15}
 %
 % Copyright 1985, 1986, 1988, 1990-2019 Free Software Foundation, Inc.
 %
@@ -4952,6 +4952,8 @@
   \definedummyword\sup
   \definedummyword\textdegree
   %
+  \definedummyword\subentry
+  %
   % We want to disable all macros so that they are not expanded by \write.
   \macrolist
   \let\value\dummyvalue
@@ -5224,10 +5226,10 @@
 }
 
 \def\indexwriteseealso#1{
-  \gdef\pagenumbertext{@seealso{#1}}%
+  \gdef\pagenumbertext{\string\seealso{#1}}%
 }
 \def\indexwriteseeentry#1{
-  \gdef\pagenumbertext{@seeentry{#1}}%
+  \gdef\pagenumbertext{\string\seeentry{#1}}%
 }
 
 % The default definitions
@@ -5315,6 +5317,15 @@
 % the current value of \escapechar.
 \def\escapeisbackslash{\escapechar=`\\}
 
+% Use \ in index files by default.  texi2dvi didn't support @ as as the escape 
+% character (as it checked for "\entry" in the files, and not "@entry").  When 
+% the new version of texi2dvi has had a chance to become more prevalent, then 
+% the escape character can change back to @ again.  This should be an easy 
+% change to make now because both @ and \ are only used as escape characters in 
+% index files, never standing for themselves. 
+%
+\set txiindexescapeisbackslash
+
 % Write the entry in \indextext to the index file.
 %
 \def\doindwrite{%
diff --git a/lib/flexmember.h b/lib/flexmember.h
index 0d65f6da60..af17b41d29 100644
--- a/lib/flexmember.h
+++ b/lib/flexmember.h
@@ -33,11 +33,26 @@
 # define FLEXALIGNOF(type) _Alignof (type)
 #endif
 
-/* Upper bound on the size of a struct of type TYPE with a flexible
-   array member named MEMBER that is followed by N bytes of other data.
-   This is not simply sizeof (TYPE) + N, since it may require
-   alignment on unusually picky C11 platforms, and
-   FLEXIBLE_ARRAY_MEMBER may be 1 on pre-C11 platforms.
+/* Yield a properly aligned upper bound on the size of a struct of
+   type TYPE with a flexible array member named MEMBER that is
+   followed by N bytes of other data.  The result is suitable as an
+   argument to malloc.  For example:
+
+     struct s { int n; char d[FLEXIBLE_ARRAY_MEMBER]; };
+     struct s *p = malloc (FLEXSIZEOF (struct s, d, n * sizeof (char)));
+
+   FLEXSIZEOF (TYPE, MEMBER, N) is not simply (sizeof (TYPE) + N),
+   since FLEXIBLE_ARRAY_MEMBER may be 1 on pre-C11 platforms.  Nor is
+   it simply (offsetof (TYPE, MEMBER) + N), as that might yield a size
+   that causes malloc to yield a pointer that is not properly aligned
+   for TYPE; for example, if sizeof (int) == alignof (int) == 4,
+   malloc (offsetof (struct s, d) + 3 * sizeof (char)) is equivalent
+   to malloc (7) and might yield a pointer that is not a multiple of 4
+   (which means the pointer is not properly aligned for struct s),
+   whereas malloc (FLEXSIZEOF (struct s, d, 3 * sizeof (char))) is
+   equivalent to malloc (8) and must yield a pointer that is a
+   multiple of 4.
+
    Yield a value less than N if and only if arithmetic overflow occurs.  */
 
 #define FLEXSIZEOF(type, member, n) \
diff --git a/lib/verify.h b/lib/verify.h
index 6930645a35..f8e4eff026 100644
--- a/lib/verify.h
+++ b/lib/verify.h
@@ -21,29 +21,37 @@
 #define _GL_VERIFY_H
 
 
-/* Define _GL_HAVE__STATIC_ASSERT to 1 if _Static_assert works as per C11.
-   This is supported by GCC 4.6.0 and later, in C mode, and its use
-   here generates easier-to-read diagnostics when verify (R) fails.
-
-   Define _GL_HAVE_STATIC_ASSERT to 1 if static_assert works as per C++11.
-   This is supported by GCC 6.1.0 and later, in C++ mode.
-
-   Use this only with GCC.  If we were willing to slow 'configure'
-   down we could also use it with other compilers, but since this
-   affects only the quality of diagnostics, why bother?  */
-#if (4 < __GNUC__ + (6 <= __GNUC_MINOR__) \
-     && (201112L <= __STDC_VERSION__  || !defined __STRICT_ANSI__) \
-     && !defined __cplusplus)
-# define _GL_HAVE__STATIC_ASSERT 1
-#endif
-#if (6 <= __GNUC__) && defined __cplusplus
-# define _GL_HAVE_STATIC_ASSERT 1
+/* Define _GL_HAVE__STATIC_ASSERT to 1 if _Static_assert (R, DIAGNOSTIC)
+   works as per C11.  This is supported by GCC 4.6.0 and later, in C
+   mode.
+
+   Define _GL_HAVE__STATIC_ASSERT1 to 1 if _Static_assert (R) works as
+   per C2X, and define _GL_HAVE_STATIC_ASSERT1 if static_assert (R)
+   works as per C++17.  This is supported by GCC 9.1 and later.
+
+   Support compilers claiming conformance to the relevant standard,
+   and also support GCC when not pedantic.  If we were willing to slow
+   'configure' down we could also use it with other compilers, but
+   since this affects only the quality of diagnostics, why bother?  */
+#ifndef __cplusplus
+# if (201112L <= __STDC_VERSION__ \
+      || (!defined __STRICT_ANSI__ && 4 < __GNUC__ + (6 <= __GNUC_MINOR__)))
+#  define _GL_HAVE__STATIC_ASSERT 1
+# endif
+# if (202000L <= __STDC_VERSION__ \
+      || (!defined __STRICT_ANSI__ && 9 <= __GNUC__))
+#  define _GL_HAVE__STATIC_ASSERT1 1
+# endif
+#else
+# if 201703L <= __cplusplus || 9 <= __GNUC__
+#  define _GL_HAVE_STATIC_ASSERT1 1
+# endif
 #endif
 
 /* FreeBSD 9.1 <sys/cdefs.h>, included by <stddef.h> and lots of other
    system headers, defines a conflicting _Static_assert that is no
    better than ours; override it.  */
-#ifndef _GL_HAVE_STATIC_ASSERT
+#ifndef _GL_HAVE__STATIC_ASSERT
 # include <stddef.h>
 # undef _Static_assert
 #endif
@@ -141,9 +149,9 @@ #define _GL_VERIFY_H
      which do not support _Static_assert, also do not warn about the
      last declaration mentioned above.
 
-   * GCC warns if -Wnested-externs is enabled and verify() is used
+   * GCC warns if -Wnested-externs is enabled and 'verify' is used
      within a function body; but inside a function, you can always
-     arrange to use verify_expr() instead.
+     arrange to use verify_expr instead.
 
    * In C++, any struct definition inside sizeof is invalid.
      Use a template type to work around the problem.  */
@@ -167,11 +175,9 @@ #define _GL_CONCAT0(x, y) x##y
 #define _GL_GENSYM(prefix) _GL_CONCAT (prefix, _GL_COUNTER)
 
 /* Verify requirement R at compile-time, as an integer constant expression
-   that returns 1.  If R is false, fail at compile-time, preferably
-   with a diagnostic that includes the string-literal DIAGNOSTIC.  */
+   that returns 1.  If R is false, fail at compile-time.  */
 
-#define _GL_VERIFY_TRUE(R, DIAGNOSTIC) \
-   (!!sizeof (_GL_VERIFY_TYPE (R, DIAGNOSTIC)))
+#define _GL_VERIFY_TRUE(R) (!!sizeof (_GL_VERIFY_TYPE (R)))
 
 #ifdef __cplusplus
 # if !GNULIB_defined_struct__gl_verify_type
@@ -181,40 +187,43 @@ #define _GL_VERIFY_TRUE(R, DIAGNOSTIC) \
   };
 #  define GNULIB_defined_struct__gl_verify_type 1
 # endif
-# define _GL_VERIFY_TYPE(R, DIAGNOSTIC) \
-    _gl_verify_type<(R) ? 1 : -1>
-#elif defined _GL_HAVE__STATIC_ASSERT
-# define _GL_VERIFY_TYPE(R, DIAGNOSTIC) \
+# define _GL_VERIFY_TYPE(R) _gl_verify_type<(R) ? 1 : -1>
+#elif defined _GL_HAVE__STATIC_ASSERT1
+# define _GL_VERIFY_TYPE(R) \
     struct {                                   \
-      _Static_assert (R, DIAGNOSTIC);          \
+      _Static_assert (R); \
       int _gl_dummy;                          \
     }
 #else
-# define _GL_VERIFY_TYPE(R, DIAGNOSTIC) \
+# define _GL_VERIFY_TYPE(R)                                             \
     struct { unsigned int _gl_verify_error_if_negative: (R) ? 1 : -1; }
 #endif
 
 /* Verify requirement R at compile-time, as a declaration without a
-   trailing ';'.  If R is false, fail at compile-time, preferably
-   with a diagnostic that includes the string-literal DIAGNOSTIC.
+   trailing ';'.  If R is false, fail at compile-time.
+
+   This macro requires three or more arguments but uses at most the first
+   two, so that the _Static_assert macro optionally defined below supports
+   both the C11 two-argument syntax and the C2X one-argument syntax.
 
    Unfortunately, unlike C11, this implementation must appear as an
    ordinary declaration, and cannot appear inside struct { ... }.  */
 
-#ifdef _GL_HAVE__STATIC_ASSERT
-# define _GL_VERIFY _Static_assert
+#if defined _GL_HAVE__STATIC_ASSERT
+# define _GL_VERIFY(R, DIAGNOSTIC, ...) _Static_assert (R, DIAGNOSTIC)
 #else
-# define _GL_VERIFY(R, DIAGNOSTIC)				       \
+# define _GL_VERIFY(R, DIAGNOSTIC, ...)                                \
     extern int (*_GL_GENSYM (_gl_verify_function) (void))	       \
-      [_GL_VERIFY_TRUE (R, DIAGNOSTIC)]
+      [_GL_VERIFY_TRUE (R)]
 #endif
 
 /* _GL_STATIC_ASSERT_H is defined if this code is copied into assert.h.  */
 #ifdef _GL_STATIC_ASSERT_H
-# if !defined _GL_HAVE__STATIC_ASSERT && !defined _Static_assert
-#  define _Static_assert(R, DIAGNOSTIC) _GL_VERIFY (R, DIAGNOSTIC)
+# if !defined _GL_HAVE__STATIC_ASSERT1 && !defined _Static_assert
+#  define _Static_assert(...) \
+     _GL_VERIFY (__VA_ARGS__, "static assertion failed", -)
 # endif
-# if !defined _GL_HAVE_STATIC_ASSERT && !defined static_assert
+# if !defined _GL_HAVE_STATIC_ASSERT1 && !defined static_assert
 #  define static_assert _Static_assert /* C11 requires this #define.  */
 # endif
 #endif
@@ -226,31 +235,24 @@ #define _GL_VERIFY_TRUE(R, DIAGNOSTIC) \
    assert (R), there is no run-time overhead.
 
    There are two macros, since no single macro can be used in all
-   contexts in C.  verify_true (R) is for scalar contexts, including
+   contexts in C.  verify_expr (R, E) is for scalar contexts, including
    integer constant expression contexts.  verify (R) is for declaration
    contexts, e.g., the top level.  */
 
-/* Verify requirement R at compile-time, as an integer constant expression.
-   Return 1.  This is equivalent to verify_expr (R, 1).
-
-   verify_true is obsolescent; please use verify_expr instead.  */
-
-#define verify_true(R) _GL_VERIFY_TRUE (R, "verify_true (" #R ")")
-
 /* Verify requirement R at compile-time.  Return the value of the
    expression E.  */
 
-#define verify_expr(R, E) \
-   (_GL_VERIFY_TRUE (R, "verify_expr (" #R ", " #E ")") ? (E) : (E))
+#define verify_expr(R, E) (_GL_VERIFY_TRUE (R) ? (E) : (E))
 
 /* Verify requirement R at compile-time, as a declaration without a
-   trailing ';'.  */
+   trailing ';'.  verify (R) acts like static_assert (R) except that
+   it is portable to C11/C++14 and earlier, and its name is shorter
+   and may be more convenient.  */
 
-#ifdef __GNUC__
-# define verify(R) _GL_VERIFY (R, "verify (" #R ")")
+#ifdef _GL_HAVE__STATIC_ASSERT1
+# define verify(R) _Static_assert (R)
 #else
-/* PGI barfs if R is long.  Play it safe.  */
-# define verify(R) _GL_VERIFY (R, "verify (...)")
+# define verify(R) _GL_VERIFY (R, "verify (...)", -)
 #endif
 
 #ifndef __has_builtin
diff --git a/m4/flexmember.m4 b/m4/flexmember.m4
index 1347068fe3..c245ab025f 100644
--- a/m4/flexmember.m4
+++ b/m4/flexmember.m4
@@ -34,12 +34,10 @@ AC_DEFUN
     AC_DEFINE([FLEXIBLE_ARRAY_MEMBER], [],
       [Define to nothing if C supports flexible array members, and to
        1 if it does not.  That way, with a declaration like 'struct s
-       { int n; double d@<:@FLEXIBLE_ARRAY_MEMBER@:>@; };', the struct hack
+       { int n; short d@<:@FLEXIBLE_ARRAY_MEMBER@:>@; };', the struct hack
        can be used with pre-C99 compilers.
-       When computing the size of such an object, don't use 'sizeof (struct s)'
-       as it overestimates the size.  Use 'offsetof (struct s, d)' instead.
-       Don't use 'offsetof (struct s, d@<:@0@:>@)', as this doesn't work with
-       MSVC and with C++ compilers.])
+       Use 'FLEXSIZEOF (struct s, d, N * sizeof (short))' to calculate
+       the size in bytes of such a struct containing an N-element array.])
   else
     AC_DEFINE([FLEXIBLE_ARRAY_MEMBER], [1])
   fi
diff --git a/m4/gnulib-comp.m4 b/m4/gnulib-comp.m4
index f648b7a495..0a7a30e5ae 100644
--- a/m4/gnulib-comp.m4
+++ b/m4/gnulib-comp.m4
@@ -200,7 +200,6 @@ AC_DEFUN
   gl_BYTESWAP
   AC_CHECK_FUNCS_ONCE([readlinkat])
   gl_CLOCK_TIME
-  gl_CLOSE_STREAM
   gl_MODULE_INDICATOR([close-stream])
   gl_COUNT_LEADING_ZEROS
   gl_COUNT_ONE_BITS
@@ -996,7 +995,6 @@ AC_DEFUN
   m4/builtin-expect.m4
   m4/byteswap.m4
   m4/clock_time.m4
-  m4/close-stream.m4
   m4/count-leading-zeros.m4
   m4/count-one-bits.m4
   m4/count-trailing-zeros.m4
diff --git a/m4/pthread_sigmask.m4 b/m4/pthread_sigmask.m4
index cadc239a3c..648edf911f 100644
--- a/m4/pthread_sigmask.m4
+++ b/m4/pthread_sigmask.m4
@@ -1,4 +1,4 @@
-# pthread_sigmask.m4 serial 16
+# pthread_sigmask.m4 serial 17
 dnl Copyright (C) 2011-2019 Free Software Foundation, Inc.
 dnl This file is free software; the Free Software Foundation
 dnl gives unlimited permission to copy and/or distribute it,
@@ -9,103 +9,101 @@ AC_DEFUN
   AC_REQUIRE([gl_SIGNAL_H_DEFAULTS])
 
   AC_CHECK_FUNCS_ONCE([pthread_sigmask])
+
+  dnl On MinGW pthread_sigmask is just a macro which always returns 0.
+  dnl It does not exist as a real function, which is required by POSIX.
+  AC_CACHE_CHECK([whether pthread_sigmask is a macro],
+    [gl_cv_func_pthread_sigmask_macro],
+    [AC_EGREP_CPP([headers_define_pthread_sigmask], [
+#include <pthread.h>
+#include <signal.h>
+#ifdef pthread_sigmask
+ headers_define_pthread_sigmask
+#endif],
+       [gl_cv_func_pthread_sigmask_macro=yes],
+       [gl_cv_func_pthread_sigmask_macro=no])
+    ])
+
   LIB_PTHREAD_SIGMASK=
 
-  dnl Test whether the gnulib module 'threadlib' is in use.
-  dnl Some packages like Emacs use --avoid=threadlib.
-  dnl Write the symbol in such a way that it does not cause 'aclocal' to pick
-  dnl the threadlib.m4 file that is installed in $PREFIX/share/aclocal/.
-  m4_ifdef([gl_][THREADLIB], [
-    AC_REQUIRE([gl_][THREADLIB])
+  if test $gl_cv_func_pthread_sigmask_macro = yes; then
+    dnl pthread_sigmask is a dummy macro.
+    HAVE_PTHREAD_SIGMASK=0
+    dnl Make sure to '#undef pthread_sigmask' before defining it.
+    REPLACE_PTHREAD_SIGMASK=1
+  else
+    dnl Test whether the gnulib module 'threadlib' is in use.
+    dnl Some packages like Emacs use --avoid=threadlib.
+    dnl Write the symbol in such a way that it does not cause 'aclocal' to pick
+    dnl the threadlib.m4 file that is installed in $PREFIX/share/aclocal/.
+    m4_ifdef([gl_][THREADLIB], [
+      AC_REQUIRE([gl_][THREADLIB])
 
-    if test "$gl_threads_api" = posix; then
-      if test $ac_cv_func_pthread_sigmask = yes; then
-        dnl pthread_sigmask is available without -lpthread.
-        :
-      else
-        if test -n "$LIBMULTITHREAD"; then
-          AC_CACHE_CHECK([for pthread_sigmask in $LIBMULTITHREAD],
-            [gl_cv_func_pthread_sigmask_in_LIBMULTITHREAD],
-            [gl_save_LIBS="$LIBS"
-             LIBS="$LIBS $LIBMULTITHREAD"
-             AC_LINK_IFELSE(
-               [AC_LANG_PROGRAM(
-                  [[#include <pthread.h>
-                    #include <signal.h>
-                  ]],
-                  [[return pthread_sigmask (0, (sigset_t *) 0, (sigset_t *) 0);]])
-               ],
-               [gl_cv_func_pthread_sigmask_in_LIBMULTITHREAD=yes],
-               [gl_cv_func_pthread_sigmask_in_LIBMULTITHREAD=no])
-             LIBS="$gl_save_LIBS"
-            ])
-          if test $gl_cv_func_pthread_sigmask_in_LIBMULTITHREAD = yes; then
-            AC_CACHE_CHECK([whether pthread_sigmask is only a macro],
-              [gl_cv_func_pthread_sigmask_is_macro],
+      if test "$gl_threads_api" = posix; then
+        if test $ac_cv_func_pthread_sigmask = yes; then
+          dnl pthread_sigmask is available without -lpthread.
+          :
+        else
+          if test -n "$LIBMULTITHREAD"; then
+            AC_CACHE_CHECK([for pthread_sigmask in $LIBMULTITHREAD],
+              [gl_cv_func_pthread_sigmask_in_LIBMULTITHREAD],
               [gl_save_LIBS="$LIBS"
                LIBS="$LIBS $LIBMULTITHREAD"
                AC_LINK_IFELSE(
                  [AC_LANG_PROGRAM(
                     [[#include <pthread.h>
                       #include <signal.h>
-                      #undef pthread_sigmask
                     ]],
                     [[return pthread_sigmask (0, (sigset_t *) 0, (sigset_t *) 0);]])
                  ],
-                 [gl_cv_func_pthread_sigmask_is_macro=no],
-                 [gl_cv_func_pthread_sigmask_is_macro=yes])
+                 [gl_cv_func_pthread_sigmask_in_LIBMULTITHREAD=yes],
+                 [gl_cv_func_pthread_sigmask_in_LIBMULTITHREAD=no])
                LIBS="$gl_save_LIBS"
               ])
-            if test $gl_cv_func_pthread_sigmask_is_macro = yes; then
-              dnl On MinGW pthread_sigmask is just a macro which always returns 0.
-              dnl It does not exist as a real function, which is required by POSIX.
-              REPLACE_PTHREAD_SIGMASK=1
-              gl_cv_func_pthread_sigmask_in_LIBMULTITHREAD=no
+            if test $gl_cv_func_pthread_sigmask_in_LIBMULTITHREAD = yes; then
+              dnl pthread_sigmask is available with -pthread or -lpthread.
+              LIB_PTHREAD_SIGMASK="$LIBMULTITHREAD"
+            else
+              dnl pthread_sigmask is not available at all.
+              HAVE_PTHREAD_SIGMASK=0
             fi
-          fi
-          if test $gl_cv_func_pthread_sigmask_in_LIBMULTITHREAD = yes; then
-            dnl pthread_sigmask is available with -pthread or -lpthread.
-            LIB_PTHREAD_SIGMASK="$LIBMULTITHREAD"
           else
             dnl pthread_sigmask is not available at all.
             HAVE_PTHREAD_SIGMASK=0
           fi
+        fi
+      else
+        dnl pthread_sigmask may exist but does not interoperate with the chosen
+        dnl multithreading facility.
+        dnl If "$gl_threads_api" = pth, we could use the function pth_sigmask,
+        dnl but it is equivalent to sigprocmask, so we choose to emulate
+        dnl pthread_sigmask with sigprocmask also in this case. This yields
+        dnl fewer link dependencies.
+        if test $ac_cv_func_pthread_sigmask = yes; then
+          REPLACE_PTHREAD_SIGMASK=1
         else
-          dnl pthread_sigmask is not available at all.
           HAVE_PTHREAD_SIGMASK=0
         fi
       fi
-    else
-      dnl pthread_sigmask may exist but does not interoperate with the chosen
-      dnl multithreading facility.
-      dnl If "$gl_threads_api" = pth, we could use the function pth_sigmask,
-      dnl but it is equivalent to sigprocmask, so we choose to emulate
-      dnl pthread_sigmask with sigprocmask also in this case. This yields fewer
-      dnl link dependencies.
+    ], [
+      dnl The module 'threadlib' is not in use, due to --avoid=threadlib being
+      dnl specified.
+      dnl The package either has prepared CPPFLAGS and LIBS for use of
+      dnl POSIX:2008 threads, or wants to build single-threaded programs.
       if test $ac_cv_func_pthread_sigmask = yes; then
-        REPLACE_PTHREAD_SIGMASK=1
+        dnl pthread_sigmask exists and does not require extra libraries.
+        dnl Assume that it is declared.
+        :
       else
+        dnl pthread_sigmask either does not exist or needs extra libraries.
         HAVE_PTHREAD_SIGMASK=0
+        dnl Define the symbol rpl_pthread_sigmask, not pthread_sigmask,
+        dnl so as to not accidentally override the system's pthread_sigmask
+        dnl symbol from libpthread. This is necessary on IRIX 6.5.
+        REPLACE_PTHREAD_SIGMASK=1
       fi
-    fi
-  ], [
-    dnl The module 'threadlib' is not in use, due to --avoid=threadlib being
-    dnl specified.
-    dnl The package either has prepared CPPFLAGS and LIBS for use of POSIX:2008
-    dnl threads, or wants to build single-threaded programs.
-    if test $ac_cv_func_pthread_sigmask = yes; then
-      dnl pthread_sigmask exists and does not require extra libraries.
-      dnl Assume that it is declared.
-      :
-    else
-      dnl pthread_sigmask either does not exist or needs extra libraries.
-      HAVE_PTHREAD_SIGMASK=0
-      dnl Define the symbol rpl_pthread_sigmask, not pthread_sigmask,
-      dnl so as to not accidentally override the system's pthread_sigmask
-      dnl symbol from libpthread. This is necessary on IRIX 6.5.
-      REPLACE_PTHREAD_SIGMASK=1
-    fi
-  ])
+    ])
+  fi
 
   AC_SUBST([LIB_PTHREAD_SIGMASK])
   dnl We don't need a variable LTLIB_PTHREAD_SIGMASK, because when
-- 
2.21.0