Index: autoconf.in
===================================================================
RCS file: /cvs/autoconf/autoconf.in,v
retrieving revision 1.124
diff -u -u -r1.124 autoconf.in
--- autoconf.in 2001/06/23 22:58:54 1.124
+++ autoconf.in 2001/07/06 12:11:28
@@ -115,11 +115,20 @@
   ;;
 esac

+
+# Find a good AWK.
+: address@hidden@}
+if echo foo | $AWK '/foo|^bar$/ { print }' | grep foo >/dev/null; then :; else
+  echo "$me: the regex engine of $AWK is too broken to be used" >&2
+  echo "$me: you might want to install GNU AWK" >&2
+  exit 1
+fi
+
+
 # Variables.
 : address@hidden@}}
 test -z "$AC_ACLOCALDIR" &&
   AC_ACLOCALDIR=`(aclocal --print-ac-dir) 2>/dev/null`
-: address@hidden@}
 debug=false
 # Trace Autoconf's initialization?
 initialization=false
Index: configure.in
===================================================================
RCS file: /cvs/autoconf/configure.in,v
retrieving revision 1.52
diff -u -u -r1.52 configure.in
--- configure.in 2001/06/28 15:53:38 1.52
+++ configure.in 2001/07/06 12:11:29
@@ -21,8 +21,13 @@
 # a AC-SUBST inside AC-PROG-GNU-M4.  Grmph!
 AC_SUBST(M4)

-# `autoconf' and `ifnames' use AWK.
+# `autoconf' and `ifnames' use AWK.  And we need decent RE support.
 AC_PROG_AWK
+# Some AWK fail
+if echo foo | $AWK '/foo|^bar$/ { print }' | grep foo >/dev/null; then :; else
+  AC_MSG_ERROR([the regex engine of $AWK is too broken to be used
+                you might want to install GNU AWK])
+fi

 # Generating man pages.
 AM_MISSING_PROG(HELP2MAN, help2man)
Index: doc/autoconf.texi
===================================================================
RCS file: /cvs/autoconf/doc/autoconf.texi,v
retrieving revision 1.483
diff -u -u -r1.483 autoconf.texi
--- doc/autoconf.texi 2001/07/05 01:23:20 1.483
+++ doc/autoconf.texi 2001/07/06 12:11:34
@@ -8303,6 +8303,23 @@
 foo
 @end example

+Some AWK, such as HPUX 11.0's native one, have regex engines fragile to
+inner anchors:
+
address@hidden
+$ echo foo | $AWK '/foo|^bar/ { print }'
+$ echo bar | $AWK '/foo|^bar/ { print }'
+bar
+$ echo foo | $AWK '/^bar|foo/ { print }'
+foo
+$ echo bar | $AWK '/^bar|foo/ { print }'
+bar
address@hidden example
+
address@hidden
+Either do not depend on such patterns (i.e., use @samp{/^(.*foo|bar)/},
+or use a simple test to reject such AWK.
+

 @item @command{cat}
 @c ----------------