From: Eric Blake <ebb9@byu.net>
Date: Sat, 8 Sep 2007 14:48:49 +0000 (+0000)
Subject: Improve M4 path searching during configure.
X-Git-Tag: v2.62~276
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=f3aee13bfac4e3fdaf79d2a94158594210e62e02;p=thirdparty%2Fautoconf.git

Improve M4 path searching during configure.
* lib/autoconf/programs.m4 (AC_PATH_PROGS_FEATURE_CHECK): New
macro.
(_AC_PATH_PROG_FEATURE_CHECK): Rename...
(_AC_PATH_PROGS_FEATURE_CHECK): ...to this, add defaulted action
parameter, and kill side effects.
(_AC_PROG_GREP, AC_PROG_SED): Adjust callers.
(_AC_FEATURE_CHECK_LENGTH): Kill extra whitespace.
* m4/m4.m4 (AC_PROG_GNU_M4): Don't stop searching until working m4
is found.
(AC_PATH_PROGS_FEATURE_CHECK): Add backwards compatibility hack to
allow bootstrapping with autoconf 2.61.
* configure.ac (M4): AC_PROG_GNU_M4 now exits on failure.
* configure: Regenerate.
* doc/autoconf.texi (Generic Programs): Document new macro.
* tests/mktests.sh (au_exclude_script): Exclude auto-testing new
macro.
* tests/semantics.at (AC_PATH_PROGS_FEATURE_CHECK): New test.
* NEWS: Document the change.
* THANKS: Update.
Reported by Hans Aberg.
---

diff --git a/ChangeLog b/ChangeLog
index 891654e3..fb41f2a7 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,27 @@
 2007-09-08  Eric Blake  <ebb9@byu.net>
 
+	Improve M4 path searching during configure.
+	* lib/autoconf/programs.m4 (AC_PATH_PROGS_FEATURE_CHECK): New
+	macro.
+	(_AC_PATH_PROG_FEATURE_CHECK): Rename...
+	(_AC_PATH_PROGS_FEATURE_CHECK): ...to this, add defaulted action
+	parameter, and kill side effects.
+	(_AC_PROG_GREP, AC_PROG_SED): Adjust callers.
+	(_AC_FEATURE_CHECK_LENGTH): Kill extra whitespace.
+	* m4/m4.m4 (AC_PROG_GNU_M4): Don't stop searching until working m4
+	is found.
+	(AC_PATH_PROGS_FEATURE_CHECK): Add backwards compatibility hack to
+	allow bootstrapping with autoconf 2.61.
+	* configure.ac (M4): AC_PROG_GNU_M4 now exits on failure.
+	* configure: Regenerate.
+	* doc/autoconf.texi (Generic Programs): Document new macro.
+	* tests/mktests.sh (au_exclude_script): Exclude auto-testing new
+	macro.
+	* tests/semantics.at (AC_PATH_PROGS_FEATURE_CHECK): New test.
+	* NEWS: Document the change.
+	* THANKS: Update.
+	Reported by Hans Aberg.
+
 	* doc/autoconf.texi (Generic Programs): Fix typo.
 
 2007-09-06  Eric Blake  <ebb9@byu.net>
diff --git a/NEWS b/NEWS
index c21997e0..74027037 100644
--- a/NEWS
+++ b/NEWS
@@ -1,3 +1,5 @@
+GNU Autoconf NEWS - User visible changes.
+
 * Major changes in Autoconf 2.61b (????-??-??)
 
 ** Autoconf is now licensed under the General Public License version 3
@@ -6,7 +8,7 @@
    generated by autoconf under the license of your own program.
  FIXME - revisit this line once exception clause is finalized.
 
-** New macro AC_OPENMP.
+** New macros AC_OPENMP, AC_PATH_PROGS_FEATURE_CHECK.
 
 ** AC_C_BIGENDIAN now supports universal binaries a la Mac OS X.
 
@@ -40,7 +42,8 @@
 
 ** Autoconf now requires GNU M4 1.4.5 or later.  Earlier versions of M4 have
    a bug in macro tracing that interferes with the interaction between
-   Autoconf and Automake.  GNU M4 1.4.8 or later is recommended.
+   Autoconf and Automake.  GNU M4 1.4.8 or later is recommended.  The
+   configure search for a working M4 is improved.
 
 ** Warnings are now generated by default when an installer invokes
    'configure' with an unknown --enable-* or --with-* option.
diff --git a/THANKS b/THANKS
index 3c0af397..c896a1fa 100644
--- a/THANKS
+++ b/THANKS
@@ -124,6 +124,7 @@ Guido Draheim               Guido.Draheim@gmx.de
 Guido Flohr                 gufl0000@stud.uni-sb.de
 Guido van Rossum            ?
 Guillermo Gomez             gomez@mi.uni-erlangen.de
+Hans Aberg                  haberg@math.su.se
 Hans Olsson                 Hans.Olsson@dna.lth.se
 Harlan Stenn                stenn@whimsy.udel.edu
 Henk Krus                   h.krus@cyclone.nl
diff --git a/configure b/configure
index c5a4b753..a97a5517 100755
--- a/configure
+++ b/configure
@@ -692,6 +692,7 @@ with_lispdir
       ac_precious_vars='build_alias
 host_alias
 target_alias
+M4
 EMACS
 EMACSLOADPATH'
 
@@ -1315,6 +1316,8 @@ Optional Packages:
   --with-lispdir          override the default lisp directory
 
 Some influential environment variables:
+  M4          Location of GNU M4 1.4.5 or later. Defaults to the first program
+              of `m4', `gm4', or `gnum4' on PATH that meets Autoconf needs.
   EMACS       the Emacs editor command
   EMACSLOADPATH
               the Emacs library search path
@@ -1634,18 +1637,21 @@ _ACEOF
 
 
 # Let the site file select an alternate cache file if it wants to.
-# Prefer explicitly selected file to automatically selected ones.
+# Prefer an explicitly selected file to automatically selected ones.
+ac_site_file1=NONE
+ac_site_file2=NONE
 if test -n "$CONFIG_SITE"; then
-  set x "$CONFIG_SITE"
+  ac_site_file1=$CONFIG_SITE
 elif test "x$prefix" != xNONE; then
-  set x "$prefix/share/config.site" "$prefix/etc/config.site"
+  ac_site_file1=$prefix/share/config.site
+  ac_site_file2=$prefix/etc/config.site
 else
-  set x "$ac_default_prefix/share/config.site" \
-	"$ac_default_prefix/etc/config.site"
+  ac_site_file1=$ac_default_prefix/share/config.site
+  ac_site_file2=$ac_default_prefix/etc/config.site
 fi
-shift
-for ac_site_file
+for ac_site_file in "$ac_site_file1" "$ac_site_file2"
 do
+  test "x$ac_site_file" = xNONE && continue
   if test -r "$ac_site_file"; then
     { $as_echo "$as_me:$LINENO: loading site script $ac_site_file" >&5
 $as_echo "$as_me: loading site script $ac_site_file" >&6;}
@@ -2336,89 +2342,63 @@ fi
 
 # We use an absolute name for GNU m4 so even if users have another m4 first in
 # their path, the installer can configure with a path that has GNU m4
-# first and get that path embedded in the installed autoconf and
+# on it and get that path embedded in the installed autoconf and
 # autoheader scripts.
-for ac_prog in gm4 gnum4 m4
-do
-  # Extract the first word of "$ac_prog", so it can be a program name with args.
-set dummy $ac_prog; ac_word=$2
-{ $as_echo "$as_me:$LINENO: checking for $ac_word" >&5
-$as_echo_n "checking for $ac_word... " >&6; }
+
+  { $as_echo "$as_me:$LINENO: checking for GNU M4 that supports accurate traces" >&5
+$as_echo_n "checking for GNU M4 that supports accurate traces... " >&6; }
 if test "${ac_cv_path_M4+set}" = set; then
   $as_echo_n "(cached) " >&6
 else
-  case $M4 in
-  [\\/]* | ?:[\\/]*)
-  ac_cv_path_M4="$M4" # Let the user override the test with a path.
-  ;;
-  *)
+  if test -z "$M4"; then
+  ac_path_M4_found=false
+  # Loop through the user's path and test for each of PROGNAME-LIST
   as_save_IFS=$IFS; IFS=$PATH_SEPARATOR
 for as_dir in $PATH
 do
   IFS=$as_save_IFS
   test -z "$as_dir" && as_dir=.
-  for ac_exec_ext in '' $ac_executable_extensions; do
-  if { test -f "$as_dir/$ac_word$ac_exec_ext" && $as_test_x "$as_dir/$ac_word$ac_exec_ext"; }; then
-    ac_cv_path_M4="$as_dir/$ac_word$ac_exec_ext"
-    $as_echo "$as_me:$LINENO: found $as_dir/$ac_word$ac_exec_ext" >&5
-    break 2
-  fi
-done
+  for ac_prog in m4 gm4 gnum4; do
+    for ac_exec_ext in '' $ac_executable_extensions; do
+      ac_path_M4="$as_dir/$ac_prog$ac_exec_ext"
+      { test -f "$ac_path_M4" && $as_test_x "$ac_path_M4"; } || continue
+      test -z "`echo if'def(mac,bug)d'nl | $ac_path_M4 --trace=mac 2>&1`" \
+      && ac_cv_path_M4=$ac_path_M4 ac_path_M4_found=:
+      $ac_path_M4_found && break 3
+    done
+  done
 done
 IFS=$as_save_IFS
-
-  ;;
-esac
-fi
-M4=$ac_cv_path_M4
-if test -n "$M4"; then
-  { $as_echo "$as_me:$LINENO: result: $M4" >&5
-$as_echo "$M4" >&6; }
+  if test -z "$ac_cv_path_M4"; then
+    { { $as_echo "$as_me:$LINENO: error: no acceptable m4 could be found in \$PATH.
+GNU M4 1.4.5 or later is required; 1.4.8 is recommended" >&5
+$as_echo "$as_me: error: no acceptable m4 could be found in \$PATH.
+GNU M4 1.4.5 or later is required; 1.4.8 is recommended" >&2;}
+   { (exit 1); exit 1; }; }
+  fi
 else
-  { $as_echo "$as_me:$LINENO: result: no" >&5
-$as_echo "no" >&6; }
+  ac_cv_path_M4=$M4
 fi
 
-
-  test -n "$M4" && break
-done
-test -n "$M4" || M4="m4"
-
-{ $as_echo "$as_me:$LINENO: checking whether m4 supports accurate traces" >&5
-$as_echo_n "checking whether m4 supports accurate traces... " >&6; }
-if test "${ac_cv_prog_gnu_m4+set}" = set; then
-  $as_echo_n "(cached) " >&6
-else
-  ac_cv_prog_gnu_m4=no
-if test x"$M4" != x \
-    && test -z "`echo if'def(mac,bug)d'nl | $M4 --trace=mac 2>&1`" ; then
-  ac_cv_prog_gnu_m4=yes
-fi
 fi
-{ $as_echo "$as_me:$LINENO: result: $ac_cv_prog_gnu_m4" >&5
-$as_echo "$ac_cv_prog_gnu_m4" >&6; }
-if test $ac_cv_prog_gnu_m4 = yes ; then
+{ $as_echo "$as_me:$LINENO: result: $ac_cv_path_M4" >&5
+$as_echo "$ac_cv_path_M4" >&6; }
+  M4=$ac_cv_path_M4
   { $as_echo "$as_me:$LINENO: checking how m4 supports trace files" >&5
 $as_echo_n "checking how m4 supports trace files... " >&6; }
 if test "${ac_cv_prog_gnu_m4_debugfile+set}" = set; then
   $as_echo_n "(cached) " >&6
 else
   case `$M4 --help < /dev/null 2>&1` in
-    *debugfile*) ac_cv_prog_gnu_m4_debugfile=--debugfile ;;
-    *) ac_cv_prog_gnu_m4_debugfile=--error-output ;;
-  esac
+      *debugfile*) ac_cv_prog_gnu_m4_debugfile=--debugfile ;;
+      *) ac_cv_prog_gnu_m4_debugfile=--error-output ;;
+    esac
 fi
 { $as_echo "$as_me:$LINENO: result: $ac_cv_prog_gnu_m4_debugfile" >&5
 $as_echo "$ac_cv_prog_gnu_m4_debugfile" >&6; }
   M4_DEBUGFILE=$ac_cv_prog_gnu_m4_debugfile
 
-fi
 
-if test x"$ac_cv_prog_gnu_m4" != xyes; then
-  { { $as_echo "$as_me:$LINENO: error: GNU M4 1.4.5 or later is required; 1.4.8 is recommended" >&5
-$as_echo "$as_me: error: GNU M4 1.4.5 or later is required; 1.4.8 is recommended" >&2;}
-   { (exit 1); exit 1; }; }
-fi
 
 ## ----------- ##
 ## Man pages.  ##
@@ -2685,24 +2665,19 @@ $as_echo_n "checking for grep that handles long lines and -e... " >&6; }
 if test "${ac_cv_path_GREP+set}" = set; then
   $as_echo_n "(cached) " >&6
 else
-  # Extract the first word of "grep ggrep" to use in msg output
-if test -z "$GREP"; then
-set dummy grep ggrep; ac_prog_name=$2
-if test "${ac_cv_path_GREP+set}" = set; then
-  $as_echo_n "(cached) " >&6
-else
+  if test -z "$GREP"; then
   ac_path_GREP_found=false
-# Loop through the user's path and test for each of PROGNAME-LIST
-as_save_IFS=$IFS; IFS=$PATH_SEPARATOR
+  # Loop through the user's path and test for each of PROGNAME-LIST
+  as_save_IFS=$IFS; IFS=$PATH_SEPARATOR
 for as_dir in $PATH$PATH_SEPARATOR/usr/xpg4/bin
 do
   IFS=$as_save_IFS
   test -z "$as_dir" && as_dir=.
   for ac_prog in grep ggrep; do
-  for ac_exec_ext in '' $ac_executable_extensions; do
-    ac_path_GREP="$as_dir/$ac_prog$ac_exec_ext"
-    { test -f "$ac_path_GREP" && $as_test_x "$ac_path_GREP"; } || continue
-    # Check for GNU ac_path_GREP and select it if it is found.
+    for ac_exec_ext in '' $ac_executable_extensions; do
+      ac_path_GREP="$as_dir/$ac_prog$ac_exec_ext"
+      { test -f "$ac_path_GREP" && $as_test_x "$ac_path_GREP"; } || continue
+# Check for GNU ac_path_GREP and select it if it is found.
   # Check for GNU $ac_path_GREP
 case `"$ac_path_GREP" --version 2>&1` in
 *GNU*)
@@ -2730,29 +2705,20 @@ case `"$ac_path_GREP" --version 2>&1` in
   rm -f conftest.in conftest.tmp conftest.nl conftest.out;;
 esac
 
-
-    $ac_path_GREP_found && break 3
+      $ac_path_GREP_found && break 3
+    done
   done
 done
-
-done
 IFS=$as_save_IFS
-
-
-fi
-
-GREP="$ac_cv_path_GREP"
-if test -z "$GREP"; then
-  { { $as_echo "$as_me:$LINENO: error: no acceptable $ac_prog_name could be found in $PATH$PATH_SEPARATOR/usr/xpg4/bin" >&5
-$as_echo "$as_me: error: no acceptable $ac_prog_name could be found in $PATH$PATH_SEPARATOR/usr/xpg4/bin" >&2;}
+  if test -z "$ac_cv_path_GREP"; then
+    { { $as_echo "$as_me:$LINENO: error: no acceptable grep could be found in $PATH$PATH_SEPARATOR/usr/xpg4/bin" >&5
+$as_echo "$as_me: error: no acceptable grep could be found in $PATH$PATH_SEPARATOR/usr/xpg4/bin" >&2;}
    { (exit 1); exit 1; }; }
-fi
-
+  fi
 else
   ac_cv_path_GREP=$GREP
 fi
 
-
 fi
 { $as_echo "$as_me:$LINENO: result: $ac_cv_path_GREP" >&5
 $as_echo "$ac_cv_path_GREP" >&6; }
@@ -2767,24 +2733,19 @@ else
   if echo a | $GREP -E '(a|b)' >/dev/null 2>&1
    then ac_cv_path_EGREP="$GREP -E"
    else
-     # Extract the first word of "egrep" to use in msg output
-if test -z "$EGREP"; then
-set dummy egrep; ac_prog_name=$2
-if test "${ac_cv_path_EGREP+set}" = set; then
-  $as_echo_n "(cached) " >&6
-else
+     if test -z "$EGREP"; then
   ac_path_EGREP_found=false
-# Loop through the user's path and test for each of PROGNAME-LIST
-as_save_IFS=$IFS; IFS=$PATH_SEPARATOR
+  # Loop through the user's path and test for each of PROGNAME-LIST
+  as_save_IFS=$IFS; IFS=$PATH_SEPARATOR
 for as_dir in $PATH$PATH_SEPARATOR/usr/xpg4/bin
 do
   IFS=$as_save_IFS
   test -z "$as_dir" && as_dir=.
   for ac_prog in egrep; do
-  for ac_exec_ext in '' $ac_executable_extensions; do
-    ac_path_EGREP="$as_dir/$ac_prog$ac_exec_ext"
-    { test -f "$ac_path_EGREP" && $as_test_x "$ac_path_EGREP"; } || continue
-    # Check for GNU ac_path_EGREP and select it if it is found.
+    for ac_exec_ext in '' $ac_executable_extensions; do
+      ac_path_EGREP="$as_dir/$ac_prog$ac_exec_ext"
+      { test -f "$ac_path_EGREP" && $as_test_x "$ac_path_EGREP"; } || continue
+# Check for GNU ac_path_EGREP and select it if it is found.
   # Check for GNU $ac_path_EGREP
 case `"$ac_path_EGREP" --version 2>&1` in
 *GNU*)
@@ -2812,29 +2773,20 @@ case `"$ac_path_EGREP" --version 2>&1` in
   rm -f conftest.in conftest.tmp conftest.nl conftest.out;;
 esac
 
-
-    $ac_path_EGREP_found && break 3
+      $ac_path_EGREP_found && break 3
+    done
   done
 done
-
-done
 IFS=$as_save_IFS
-
-
-fi
-
-EGREP="$ac_cv_path_EGREP"
-if test -z "$EGREP"; then
-  { { $as_echo "$as_me:$LINENO: error: no acceptable $ac_prog_name could be found in $PATH$PATH_SEPARATOR/usr/xpg4/bin" >&5
-$as_echo "$as_me: error: no acceptable $ac_prog_name could be found in $PATH$PATH_SEPARATOR/usr/xpg4/bin" >&2;}
+  if test -z "$ac_cv_path_EGREP"; then
+    { { $as_echo "$as_me:$LINENO: error: no acceptable egrep could be found in $PATH$PATH_SEPARATOR/usr/xpg4/bin" >&5
+$as_echo "$as_me: error: no acceptable egrep could be found in $PATH$PATH_SEPARATOR/usr/xpg4/bin" >&2;}
    { (exit 1); exit 1; }; }
-fi
-
+  fi
 else
   ac_cv_path_EGREP=$EGREP
 fi
 
-
    fi
 fi
 { $as_echo "$as_me:$LINENO: result: $ac_cv_path_EGREP" >&5
@@ -2853,24 +2805,19 @@ else
      done
      echo "$ac_script" 2>/dev/null | sed 99q >conftest.sed
      $as_unset ac_script || ac_script=
-     # Extract the first word of "sed gsed" to use in msg output
-if test -z "$SED"; then
-set dummy sed gsed; ac_prog_name=$2
-if test "${ac_cv_path_SED+set}" = set; then
-  $as_echo_n "(cached) " >&6
-else
+     if test -z "$SED"; then
   ac_path_SED_found=false
-# Loop through the user's path and test for each of PROGNAME-LIST
-as_save_IFS=$IFS; IFS=$PATH_SEPARATOR
+  # Loop through the user's path and test for each of PROGNAME-LIST
+  as_save_IFS=$IFS; IFS=$PATH_SEPARATOR
 for as_dir in $PATH
 do
   IFS=$as_save_IFS
   test -z "$as_dir" && as_dir=.
   for ac_prog in sed gsed; do
-  for ac_exec_ext in '' $ac_executable_extensions; do
-    ac_path_SED="$as_dir/$ac_prog$ac_exec_ext"
-    { test -f "$ac_path_SED" && $as_test_x "$ac_path_SED"; } || continue
-    # Check for GNU ac_path_SED and select it if it is found.
+    for ac_exec_ext in '' $ac_executable_extensions; do
+      ac_path_SED="$as_dir/$ac_prog$ac_exec_ext"
+      { test -f "$ac_path_SED" && $as_test_x "$ac_path_SED"; } || continue
+# Check for GNU ac_path_SED and select it if it is found.
   # Check for GNU $ac_path_SED
 case `"$ac_path_SED" --version 2>&1` in
 *GNU*)
@@ -2898,24 +2845,16 @@ case `"$ac_path_SED" --version 2>&1` in
   rm -f conftest.in conftest.tmp conftest.nl conftest.out;;
 esac
 
-
-    $ac_path_SED_found && break 3
+      $ac_path_SED_found && break 3
+    done
   done
 done
-
-done
 IFS=$as_save_IFS
-
-
-fi
-
-SED="$ac_cv_path_SED"
-if test -z "$SED"; then
-  { { $as_echo "$as_me:$LINENO: error: no acceptable $ac_prog_name could be found in \$PATH" >&5
-$as_echo "$as_me: error: no acceptable $ac_prog_name could be found in \$PATH" >&2;}
+  if test -z "$ac_cv_path_SED"; then
+    { { $as_echo "$as_me:$LINENO: error: no acceptable sed could be found in \$PATH" >&5
+$as_echo "$as_me: error: no acceptable sed could be found in \$PATH" >&2;}
    { (exit 1); exit 1; }; }
-fi
-
+  fi
 else
   ac_cv_path_SED=$SED
 fi
diff --git a/configure.ac b/configure.ac
index 84170f77..bbb3e87f 100644
--- a/configure.ac
+++ b/configure.ac
@@ -79,12 +79,9 @@ AC_PATH_PROG([EXPR], [expr])
 
 # We use an absolute name for GNU m4 so even if users have another m4 first in
 # their path, the installer can configure with a path that has GNU m4
-# first and get that path embedded in the installed autoconf and
+# on it and get that path embedded in the installed autoconf and
 # autoheader scripts.
 AC_PROG_GNU_M4
-if test x"$ac_cv_prog_gnu_m4" != xyes; then
-  AC_MSG_ERROR([GNU M4 1.4.5 or later is required; 1.4.8 is recommended])
-fi
 
 ## ----------- ##
 ## Man pages.  ##
diff --git a/doc/autoconf.texi b/doc/autoconf.texi
index 19374863..9f7c77ae 100644
--- a/doc/autoconf.texi
+++ b/doc/autoconf.texi
@@ -3960,6 +3960,49 @@ are found, set @var{variable} to the absolute name of the program
 found.
 @end defmac
 
+@defmac AC_PATH_PROGS_FEATURE_CHECK (@var{variable}, @
+  @var{progs-to-check-for}, @var{feature-test}, @
+  @ovar{action-if-not-found}, @dvar{path, $PATH})
+@acindex{PATH_PROGS_FEATURE_CHECK}
+This macro was introduced in Autoconf 2.62.  If @var{variable} is not
+empty, then set the cache variable @code{$ac_cv_path_@var{variable}} to
+its value.  Otherwise, check for each program in the blank-separated
+list @var{progs-to-check-for} existing in @var{path}.  For each program
+found, execute @var{feature-test} with @code{$ac_path_@var{variable}}
+set to the absolute name of the candidate program.  If no invocation of
+@var{feature-test} sets the shell variable
+@code{$ac_cv_path_@var{variable}}, then @var{action-if-not-found} is
+executed.  @var{feature-test} will be run even when
+@code{ac_cv_path_@var{variable}} is set, to provide the ability to
+choose a better candidate found later in @var{path}; to accept the
+current setting and bypass all futher checks, @var{feature-test} can
+execute @code{ac_path_@var{variable}_found=:}.
+
+Note that this macro has some subtle differences from
+@code{AC_CHECK_PROGS}.  It is designed to be run inside
+@code{AC_CACHE_VAL}, therefore, it should have no side effects.  In
+particular, @var{variable} is not set to the final value of
+@code{ac_cv_path_@var{variable}}, nor is @code{AC_SUBST} automatically
+run.  Also, on failure, any action can be performed, whereas
+@code{AC_CHECK_PROGS} only performs
+@code{@var{variable}=@var{value-if-not-found}}.
+
+Here is an example, similar to what Autoconf uses in its own configure
+script.  It will search for an implementation of @command{m4} that
+supports the @code{indir} builtin, even if it goes by the name
+@command{gm4} or is not the first implementation on @env{PATH}.
+
+@example
+AC_CACHE_CHECK([for m4 that supports indir], [ac_cv_path_M4],
+  [AC_PATH_PROGS_FEATURE_CHECK([M4], [m4 gm4],
+    [[m4out=`echo 'changequote([,])indir([divnum])' | $ac_path_M4`
+      test "x$m4out" = x0 \
+      && ac_cv_path_M4=$ac_path_M4 ac_path_M4_found=:]],
+    [AC_MSG_ERROR([could not find m4 that supports indir])])])
+AC_SUBST([M4], [$ac_cv_path_M4])
+@end example
+@end defmac
+
 @defmac AC_PATH_TARGET_TOOL (@var{variable}, @var{prog-to-check-for}, @
   @ovar{value-if-not-found}, @dvar{path, $PATH})
 @acindex{PATH_TARGET_TOOL}
diff --git a/lib/autoconf/programs.m4 b/lib/autoconf/programs.m4
index ba8468a2..9ebdf039 100644
--- a/lib/autoconf/programs.m4
+++ b/lib/autoconf/programs.m4
@@ -2,7 +2,7 @@
 # Checking for programs.
 
 # Copyright (C) 1992, 1993, 1994, 1995, 1996, 1998, 1999, 2000, 2001,
-# 2002, 2003, 2004, 2005, 2006 Free Software Foundation, Inc.
+# 2002, 2003, 2004, 2005, 2006, 2007 Free Software Foundation, Inc.
 
 # This program is free software: you can redistribute it and/or modify
 # it under the terms of the GNU General Public License as published by
@@ -422,54 +422,73 @@ AC_DEFUN([AC_PROG_GREP],
 # AIX silently truncates long lines before matching.
 # NeXT understands only one -e and truncates long lines.
 m4_define([_AC_PROG_GREP],
-[_AC_PATH_PROG_FEATURE_CHECK([$1], [$2],
+[_AC_PATH_PROGS_FEATURE_CHECK([$1], [$2],
 	[_AC_FEATURE_CHECK_LENGTH([ac_path_$1], [ac_cv_path_$1],
-		["$ac_path_$1" $3], [$1])], [$PATH$PATH_SEPARATOR/usr/xpg4/bin])
+		["$ac_path_$1" $3], [$1])], [],
+	[$PATH$PATH_SEPARATOR/usr/xpg4/bin])dnl
 ])
 
 
-# _AC_PATH_PROG_FEATURE_CHECK(VARIABLE, PROGNAME-LIST, FEATURE-TEST, [PATH])
-# --------------------------------------------------------------------------
+# _AC_PATH_PROGS_FEATURE_CHECK(VARIABLE, PROGNAME-LIST, FEATURE-TEST,
+#                              [ACTION-IF-NOT-FOUND], [PATH=$PATH])
+# -------------------------------------------------------------------
 # FEATURE-TEST is called repeatedly with $ac_path_VARIABLE set to the
 # name of a program in PROGNAME-LIST found in PATH.  FEATURE-TEST must set
 # $ac_cv_path_VARIABLE to the path of an acceptable program, or else
-# _AC_PATH_PROG_FEATURE_CHECK will report that no acceptable program
-# was found, and abort.  If a suitable $ac_path_VARIABLE is found in the
-# FEATURE-TEST macro, it can set $ac_path_VARIABLE_found=':' to accept
-# that value without any further checks.
-m4_define([_AC_PATH_PROG_FEATURE_CHECK],
-[# Extract the first word of "$2" to use in msg output
-if test -z "$$1"; then
-set dummy $2; ac_prog_name=$[2]
-AC_CACHE_VAL([ac_cv_path_$1],
-[ac_path_$1_found=false
-# Loop through the user's path and test for each of PROGNAME-LIST
-_AS_PATH_WALK([$4],
-[for ac_prog in $2; do
-  for ac_exec_ext in '' $ac_executable_extensions; do
-    ac_path_$1="$as_dir/$ac_prog$ac_exec_ext"
-    AS_EXECUTABLE_P(["$ac_path_$1"]) || continue
-    $3
-    $ac_path_$1_found && break 3
-  done
-done
-])
-])
-$1="$ac_cv_path_$1"
-if test -z "$$1"; then
-  AC_MSG_ERROR([no acceptable $ac_prog_name could be found in dnl
-m4_default([$4], [\$PATH])])
-fi
-AC_SUBST([$1])
+# ACTION-IF-NOT-FOUND is executed; the default action (for internal use
+# only) issues a fatal error message.  If a suitable $ac_path_VARIABLE is
+# found in the FEATURE-TEST macro, it can set $ac_path_VARIABLE_found=':'
+# to accept that value without any further checks.
+m4_define([_AC_PATH_PROGS_FEATURE_CHECK],
+[if test -z "$$1"; then
+  ac_path_$1_found=false
+  # Loop through the user's path and test for each of PROGNAME-LIST
+  _AS_PATH_WALK([$5],
+  [for ac_prog in $2; do
+    for ac_exec_ext in '' $ac_executable_extensions; do
+      ac_path_$1="$as_dir/$ac_prog$ac_exec_ext"
+      AS_EXECUTABLE_P(["$ac_path_$1"]) || continue
+$3
+      $ac_path_$1_found && break 3
+    done
+  done])dnl
+  if test -z "$ac_cv_path_$1"; then
+    m4_default([$4],
+      [AC_MSG_ERROR([no acceptable m4_bpatsubst([$2], [ .*]) could be dnl
+found in m4_default([$5], [\$PATH])])])
+  fi
 else
   ac_cv_path_$1=$$1
 fi
 ])
 
 
+# AC_PATH_PROGS_FEATURE_CHECK(VARIABLE, PROGNAME-LIST,
+#                             FEATURE-TEST, [ACTION-IF-NOT-FOUND=:],
+#                             [PATH=$PATH])
+# ----------------------------------------------------------------
+# Designed to be used inside AC_CACHE_VAL.  It is recommended,
+# but not required, that the user also use AC_ARG_VAR([VARIABLE]).
+# If VARIABLE is not empty, set the cache variable
+# $ac_cv_path_VARIABLE to VARIABLE without any further tests.
+# Otherwise, call FEATURE_TEST repeatedly with $ac_path_VARIABLE
+# set to the name of a program in PROGNAME-LIST found in PATH.  If
+# no invocation of FEATURE-TEST sets $ac_cv_path_VARIABLE to the
+# path of an acceptable program, ACTION-IF-NOT-FOUND is executed.
+# FEATURE-TEST is invoked even when $ac_cv_path_VARIABLE is set,
+# in case a better candidate occurs later in PATH; to accept the
+# current setting and bypass further checks, FEATURE-TEST can set
+# $ac_path_VARIABLE_found=':'.  Note that, unlike AC_CHECK_PROGS,
+# this macro does not have any side effect on the current value
+# of VARIABLE.
+m4_define([AC_PATH_PROGS_FEATURE_CHECK],
+[_$0([$1], [$2], [$3], m4_default([$4], [:]), [$5])dnl
+])
+
+
 # _AC_FEATURE_CHECK_LENGTH(PROGPATH, CACHE-VAR, CHECK-CMD, [MATCH-STRING])
 # ------------------------------------------------------------------------
-# For use as the FEATURE-TEST argument to _AC_PATH_PROG_FEATURE_TEST.
+# For use as the FEATURE-TEST argument to _AC_PATH_PROGS_FEATURE_TEST.
 # On each iteration run CHECK-CMD on an input file, storing the value
 # of PROGPATH in CACHE-VAR if the CHECK-CMD succeeds.  The input file
 # is always one line, starting with only 10 characters, and doubling
@@ -503,7 +522,7 @@ dnl   # for best performing tool in a list breaks down.
     # 10*(2^10) chars as input seems more than enough
     test $ac_count -gt 10 && break
   done
-  rm -f conftest.in conftest.tmp conftest.nl conftest.out])
+  rm -f conftest.in conftest.tmp conftest.nl conftest.out])dnl
 ])
 
 
@@ -863,7 +882,7 @@ AC_DEFUN([AC_PROG_SED],
      done
      echo "$ac_script" 2>/dev/null | sed 99q >conftest.sed
      $as_unset ac_script || ac_script=
-     _AC_PATH_PROG_FEATURE_CHECK(SED, [sed gsed],
+     _AC_PATH_PROGS_FEATURE_CHECK(SED, [sed gsed],
 	[_AC_FEATURE_CHECK_LENGTH([ac_path_SED], [ac_cv_path_SED],
 		["$ac_path_SED" -f conftest.sed])])])
  SED="$ac_cv_path_SED"
diff --git a/m4/m4.m4 b/m4/m4.m4
index 70b99f89..70f30767 100644
--- a/m4/m4.m4
+++ b/m4/m4.m4
@@ -1,4 +1,4 @@
-# m4.m4 serial 3
+# m4.m4 serial 4
 dnl Copyright (C) 2000, 2006, 2007 Free Software Foundation, Inc.
 dnl This file is free software; the Free Software Foundation
 dnl gives unlimited permission to copy and/or distribute it,
@@ -12,20 +12,29 @@ dnl with or without modifications, as long as this notice is preserved.
 # Also, check whether --error-output (through 1.4.x) or --debugfile (2.0)
 # is supported, and AC_SUBST M4_DEBUGFILE accordingly.
 AC_DEFUN([AC_PROG_GNU_M4],
-[AC_PATH_PROGS([M4], [gm4 gnum4 m4], [m4])
-AC_CACHE_CHECK([whether m4 supports accurate traces], [ac_cv_prog_gnu_m4],
-[ac_cv_prog_gnu_m4=no
-dnl Creative quoting here to avoid raw dnl and ifdef in configure.
-if test x"$M4" != x \
-    && test -z "`echo if'def(mac,bug)d'nl | $M4 --trace=mac 2>&1`" ; then
-  ac_cv_prog_gnu_m4=yes
-fi])
-if test $ac_cv_prog_gnu_m4 = yes ; then
+  [AC_ARG_VAR([M4], [Location of GNU M4 1.4.5 or later.  Defaults to the first
+    program of `m4', `gm4', or `gnum4' on PATH that meets Autoconf needs.])
+  AC_CACHE_CHECK([for GNU M4 that supports accurate traces], [ac_cv_path_M4],
+    [AC_PATH_PROGS_FEATURE_CHECK([M4], [m4 gm4 gnum4],
+      [dnl Creative quoting here to avoid raw dnl and ifdef in configure.
+      test -z "`echo if'def(mac,bug)d'nl | $ac_path_M4 --trace=mac 2>&1`" \
+      && ac_cv_path_M4=$ac_path_M4 ac_path_M4_found=:],
+      [AC_MSG_ERROR([no acceptable m4 could be found in \$PATH.
+GNU M4 1.4.5 or later is required; 1.4.8 is recommended])])])
+  M4=$ac_cv_path_M4
   AC_CACHE_CHECK([how m4 supports trace files], [ac_cv_prog_gnu_m4_debugfile],
-  [case `$M4 --help < /dev/null 2>&1` in
-    *debugfile*) ac_cv_prog_gnu_m4_debugfile=--debugfile ;;
-    *) ac_cv_prog_gnu_m4_debugfile=--error-output ;;
-  esac])
-  AC_SUBST([M4_DEBUGFILE], $ac_cv_prog_gnu_m4_debugfile)
-fi
+    [case `$M4 --help < /dev/null 2>&1` in
+      *debugfile*) ac_cv_prog_gnu_m4_debugfile=--debugfile ;;
+      *) ac_cv_prog_gnu_m4_debugfile=--error-output ;;
+    esac])
+  AC_SUBST([M4_DEBUGFILE], [$ac_cv_prog_gnu_m4_debugfile])
 ])
+
+# Compatibility for bootstrapping with Autoconf 2.61.
+dnl FIXME - replace this with AC_PREREQ([2.62]) after the release.
+# AC_PATH_PROGS_FEATURE_CHECK was added the same time the slightly broken,
+# undocumented _AC_PATH_PROG_FEATURE_CHECK was deleted.
+m4_ifndef([AC_PATH_PROGS_FEATURE_CHECK],
+  [m4_define([AC_PATH_PROGS_FEATURE_CHECK],
+    [_AC_PATH_PROG_FEATURE_CHECK([$1], [$2], [$3], [$5])
+])])
diff --git a/tests/mktests.sh b/tests/mktests.sh
index f804056a..a7145e99 100755
--- a/tests/mktests.sh
+++ b/tests/mktests.sh
@@ -2,7 +2,7 @@
 
 # Build some of the Autoconf test files.
 
-# Copyright (C) 2000, 2001, 2002, 2003, 2004, 2005, 2006 Free Software
+# Copyright (C) 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007 Free Software
 # Foundation, Inc.
 
 # This program is free software; you can redistribute it and/or modify
@@ -91,6 +91,7 @@ ac_exclude_list='
 
 	# Performed in the semantics tests.
 	/^AC_CHECK_(ALIGNOF|DECL|FILE|FUNC|HEADER|LIB|MEMBER|PROG|SIZEOF|(TARGET_)?TOOL|TYPE)S?$/ {next}
+	/^AC_PATH_PROGS_FEATURE_CHECK$/ {next}
 
 	# Fail when the source does not exist.
 	/^AC_CONFIG/ {next}
@@ -202,7 +203,8 @@ do
     ## Do not edit by hand.  ##
     ## --------------------- ##
 
-    # Copyright (C) 2000, 2001, 2003, 2004, 2005, 2006 Free Software Foundation, Inc.
+    # Copyright (C) 2000, 2001, 2003, 2004, 2005, 2006, 2007 Free Software
+    # Foundation, Inc.
 
     AT_BANNER([Testing autoconf/$base macros.])
 
diff --git a/tests/semantics.at b/tests/semantics.at
index 4c294a88..68553650 100644
--- a/tests/semantics.at
+++ b/tests/semantics.at
@@ -548,6 +548,79 @@ AT_CLEANUP
 
 
 
+# ----------------------------- #
+# AC_PATH_PROGS_FEATURE_CHECK.  #
+# ----------------------------- #
+
+AT_SETUP([AC_PATH_PROGS_FEATURE_CHECK])
+
+AT_CHECK_PROGS_PREPARE
+
+AT_DATA([configure.ac],
+[[AC_INIT
+pwd=`pwd`
+p="1${PATH_SEPARATOR}2${PATH_SEPARATOR}3${PATH_SEPARATOR}4${PATH_SEPARATOR}5${PATH_SEPARATOR}6"
+path=`echo $p | sed -e 's,\([[0-9]]\),'"$pwd"'/path/\1,g'`
+fail=false
+
+# Find first candidate and stop search
+AC_PATH_PROGS_FEATURE_CHECK(TOOL1, [tool better],
+  [$ac_path_TOOL1 && ac_cv_path_TOOL1=$ac_path_TOOL1 ac_path_TOOL1_found=:],
+  fail=:, $path)
+test -z "$TOOL1" || fail=:
+test "$ac_cv_path_TOOL1" = "$pwd/path/1/tool" || fail=:
+
+# Keep searching each candidate
+AC_PATH_PROGS_FEATURE_CHECK(TOOL2, [tool better],
+  [$ac_path_TOOL2 && ac_cv_path_TOOL2=$ac_path_TOOL2],
+  fail=:, $path)
+test "$ac_cv_path_TOOL2" = "$pwd/path/6/better" || fail=:
+
+# Only accept better candidate
+AC_PATH_PROGS_FEATURE_CHECK(TOOL3, [tool better],
+  [case "$ac_path_TOOL3" in #(
+    *better) ac_cv_path_TOOL3=$ac_path_TOOL3;;
+  esac],
+  fail=:, $path)
+test "$ac_cv_path_TOOL3" = "$pwd/path/6/better" || fail=:
+
+# When a tool is not found, and no action is given for not-found,
+# the variable is left empty.
+AC_PATH_PROGS_FEATURE_CHECK(TOOL4, missing,
+  [ac_cv_path_TOOL4=$ac_path_TOOL4], [], $path)
+test -z "$ac_cv_path_TOOL4" || fail=:
+
+# Test action when tool is not found
+AC_PATH_PROGS_FEATURE_CHECK(TOOL5, missing, [],
+  [ac_cv_path_TOOL5='not found'], $path)
+test "$ac_cv_path_TOOL5" = "not found" || fail=:
+
+# Test that pre-set tool bypasses feature test
+TOOL6=$pwd/path/6/better
+AC_PATH_PROGS_FEATURE_CHECK(TOOL6, tool, fail=:, fail=:, $path)
+test "$ac_cv_path_TOOL6" = "$pwd/path/6/better" || fail=:
+
+# A blank pre-set does not bypass feature test
+TOOL7=
+AC_PATH_PROGS_FEATURE_CHECK(TOOL7, [tool better],
+  [$ac_path_TOOL7 && ac_cv_path_TOOL7=$ac_path_TOOL7 ac_path_TOOL7_found=:],
+  fail=:, $path)
+test -z "$TOOL7" || fail=:
+test "$ac_cv_path_TOOL7" = "$pwd/path/1/tool" || fail=:
+
+# No AC-OUTPUT, we don't need config.status.
+$fail &&
+  AC_MSG_ERROR([[PATH_PROG failed]])
+AS_EXIT(0)
+]])
+
+AT_CHECK_AUTOCONF
+AT_CHECK_CONFIGURE
+
+AT_CLEANUP
+
+
+
 
 ## -------------- ##
 ## AC_PATH_XTRA.  ##