regex engine: Issue #19168 - Fix variable length lookbehind matches

We were not validating that when (?<=a|ab) matched that the right hand
side of the match lined up with the position of the assertion. Similar
for (?<!a|ab) and related patterns, eg, (*positive_lookbehind:).
Note these problems do NOT affect lookahead.

Part of the difficulty here was that the SUCCEED node was serving too
many purposes, necessitating a new regop LOOKBEHIND_END.

Includes more tests for various lookahead or lookbehind cases.

1 files changed, 1 insertions, 0 deletions

diff --git a/regexp.h b/regexp.h
index e404206133..7bd7162d33 100644
--- a/regexp.h
+++ b/regexp.h
@@ -842,6 +842,7 @@ typedef struct regmatch_state {
             char *start;
             char *end;
             regnode  *me; /* the IFMATCH/SUSPEND/UNLESSM node  */
+            char *prev_match_end;
         } ifmatch; /* and SUSPEND/UNLESSM */
 
         struct {