(re_search_internal): Limit search to the beginning of the buffer if the initial states are empty for contexts that do not include CONTEXT_BEGBUF or, if !preg->newline_anchor, that do not include any one of CONTEXT_BEGBUF and CONTEXT_NEWLINE.

1 files changed, 18 insertions, 5 deletions

diff --git a/posix/regexec.c b/posix/regexec.c
index 0c2f7bf3ff..72b26f112b 100644
--- a/posix/regexec.c
+++ b/posix/regexec.c
@@ -597,6 +597,24 @@ re_search_internal (preg, string, length, start, range, stop, nmatch, pmatch,
 	  || dfa->init_state_begbuf == NULL, 0))
     return REG_NOMATCH;
 
+#ifdef DEBUG
+  /* We assume front-end functions already check them.  */
+  assert (start + range >= 0 && start + range <= length);
+#endif
+
+  /* If initial states with non-begbuf contexts have no elements,
+     the regex must be anchored.  If preg->newline_anchor is set,
+     we'll never use init_state_nl, so do not check it.  */
+  if (dfa->init_state->nodes.nelem == 0
+      && dfa->init_state_word->nodes.nelem == 0
+      && (dfa->init_state_nl->nodes.nelem == 0
+	  || !preg->newline_anchor))
+    {
+      if (start != 0 && start + range != 0)
+        return REG_NOMATCH;
+      start = range = 0;
+    }
+
   re_node_set_init_empty (&empty_set);
   memset (&mctx, '\0', sizeof (re_match_context_t));
 
@@ -630,11 +648,6 @@ re_search_internal (preg, string, length, start, range, stop, nmatch, pmatch,
   else
     mctx.state_log = NULL;
 
-#ifdef DEBUG
-  /* We assume front-end functions already check them.  */
-  assert (start + range >= 0 && start + range <= length);
-#endif
-
   match_first = start;
   input.tip_context = ((eflags & REG_NOTBOL) ? CONTEXT_BEGBUF
 		       : CONTEXT_NEWLINE | CONTEXT_BEGBUF);