gregex: Do not try access the undefined match offsets if we have no match

In case we're getting NO-MATCH "errors", we were still recomputing the
match offsets and taking decisions based on that, that might lead to
undefined behavior.

Avoid this by just returning early a FALSE result (but with no error) in
case there's no result to proceed on.

Fixes: #2741

1 files changed, 6 insertions, 0 deletions

diff --git a/glib/gregex.c b/glib/gregex.c
index 219d9cee3..f2a5b5fd1 100644
--- a/glib/gregex.c
+++ b/glib/gregex.c
@@ -1073,6 +1073,12 @@ g_match_info_next (GMatchInfo  *match_info,
                    match_info->regex->pattern, match_error (match_info->matches));
       return FALSE;
     }
+  else if (match_info->matches == PCRE2_ERROR_NOMATCH)
+    {
+      /* We're done with this match info */
+      match_info->pos = -1;
+      return FALSE;
+    }
   else
     if (!recalc_match_offsets (match_info, error))
       return FALSE;