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-rw-r--r--posix/regcomp.c5
-rw-r--r--posix/rxspencer/tests1
2 files changed, 6 insertions, 0 deletions
diff --git a/posix/regcomp.c b/posix/regcomp.c
index 1a5f795..a7112cf 100644
--- a/posix/regcomp.c
+++ b/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;
diff --git a/posix/rxspencer/tests b/posix/rxspencer/tests
index a8b6e4b..b84a270 100644
--- a/posix/rxspencer/tests
+++ b/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.