Exclude M4 with buggy strstr when configuring Autoconf. (was: configure oddity)

[Ralf Wildenhues]

[ dropping lots of cc, adding autoconf-patches ]

Hi Eric,

* Eric Blake wrote on Sat, Feb 26, 2011 at 03:02:25PM CET:
> I like the concept, although I can make it shorter.
> 
> Autoconf's m4/m4.m4 needs a similar test.

Thanks.  Like this?

I should note that it won't exclude a buggy m4 that the user has
explicitly set by setting the M4 environment variable.

It seems like a bug in AC_MSG_ERROR that I cannot use a comma in
the message, with the current amount of quoting.

Thanks,
Ralf

2011-02-26  Ralf Wildenhues  <address@hidden>
            Eric Blake  <address@hidden>

        Exclude M4 with buggy strstr when configuring Autoconf.
        * m4/m4.m4 (AC_PROG_GNU_M4): When searching PATH, do not accept
        an m4 that has the gnulib strstr bug.

diff --git a/m4/m4.m4 b/m4/m4.m4
index a11fe0d..5aef986 100644
--- a/m4/m4.m4
+++ b/m4/m4.m4
@@ -1,4 +1,4 @@
-# m4.m4 serial 11
+# m4.m4 serial 12
 
 # Copyright (C) 2000, 2006-2011 Free Software Foundation, Inc.
 
@@ -25,15 +25,18 @@ AS_UNSET([POSIXLY_CORRECT])
 AC_PATH_PROGS_FEATURE_CHECK([M4], [m4 gm4 gnum4],
       [dnl Creative quoting here to avoid raw dnl and ifdef in configure.
       # Root out GNU M4 1.4.5, as well as non-GNU m4 that ignore -t, -F.
+      # Root out GNU M4 1.4.13 and 1.4.14 with buggy replacement strstr.
       ac_snippet=change'quote(<,>)in''dir(<if''def>,mac,bug)'
       ac_snippet=${ac_snippet}pat'subst(a,\(b\)\|\(a\),\1)d'nl
+      
ac_snippet=${ac_snippet}${as_nl}if'else(in''dex(..wi.d.,.d.),-1,strstr-bug)'
       test -z "`$ac_path_M4 -F conftest.m4f </dev/null 2>&1`" \
       && test -z "`AS_ECHO([$ac_snippet]) | $ac_path_M4 --trace=mac 2>&1`" \
       && test -f conftest.m4f \
       && ac_cv_path_M4=$ac_path_M4 ac_path_M4_found=:
       rm -f conftest.m4f],
       [AC_MSG_ERROR([no acceptable m4 could be found in \$PATH.
-GNU M4 1.4.6 or later is required; 1.4.14 is recommended])])])
+GNU M4 1.4.6 or later is required; 1.4.13 or 1.4.16+ are recommended.
+GNU M4 1.4.14 and 1.4.15 use a buggy strstr on some systems])])])
   M4=$ac_cv_path_M4
   AC_CACHE_CHECK([whether $ac_cv_path_M4 accepts --gnu],
     [ac_cv_prog_gnu_m4_gnu],