* posix/regcomp.c (lower_subexp): Do not optimize empty

subexpressions even with REG_NOSUB.
	* posix/rxspencer/tests: Add a previously failing testcase.

ChangeLog

@@ -1,3 +1,9 @@
+2005-02-10  Paolo Bonzini  <bonzini@gnu.org>
+
+	* posix/regcomp.c (lower_subexp): Do not optimize empty
+	subexpressions even with REG_NOSUB.
+	* posix/rxspencer/tests: Add a previously failing testcase.
+
 2005-02-21  Alan Modra <amodra@bigpond.net.au>
 
 	* elf/dl-reloc.c (_dl_nothread_init_static_tls): Assert that dtv

posix/regcomp.c

@@ -1321,6 +1321,11 @@ lower_subexp (err, preg, node)
   bin_tree_t *op, *cls, *tree1, *tree;
 
   if (preg->no_sub
+      /* We do not optimize empty subexpressions, because otherwise we may
+	 have bad CONCAT nodes with NULL children.  This is obviously not
+	 very common, so we do not lose much.  An example that triggers
+	 this case is the sed "script" /\(\)/x.  */
+      && node->left != NULL
       && (node->token.opr.idx >= 8 * sizeof (dfa->used_bkref_map)
 	  || !(dfa->used_bkref_map & (1 << node->token.opr.idx))))
     return node->left;

posix/rxspencer/tests

@@ -376,6 +376,7 @@ a(b?c)+d	-	accd	accd
 a[bc]d		-	xyzaaabcaababdacd	abd
 a[ab]c		-	aaabc	abc
 abc		s	abc	abc
+()		s	abc	@abc
 a*		&	b	@b
 
 # Let's have some fun -- try to match a C comment.