diff mbox series

[PUSHED,1/3] Check past-the-end before dereferencing iterator

Message ID 20260901124929.514896-1-j@lambda.is
State Committed
Commit 5da256175a9f7a5f82afcd475ac71eb5c065fac8
Headers
Series [PUSHED,1/3] Check past-the-end before dereferencing iterator |

Commit Message

Jørgen Kvalsvik Sept. 1, 2026, 12:49 p.m. UTC 
  Guard the dereference in the case where the current cursor in the
needle isn't a tombstone in case we're at the end of the
haystack. Example pair:

  NEEDLE:   6 x x 4 6
  HAYSTACK: 4 6 x x 4

We find the subsequence 6 4, but the needle is not yet at end (missing
6) while the haystack is moved past the end:

  NEEDLE:   6 x x 4 6
                    ^
  HAYSTACK: 4 6 x x 4
                      ^

If the haystack (super) is exhausted before the needle (sub) we know
it isn't a proper subsequence, so this is the correct behaviour.

This example was in the testsuite and caught by ASAN.

	PR gcov-profile/127038

gcc/ChangeLog:

	* gcov.cc (tombstone_subsequence_p): Guard iterator
	dereference.
---
 gcc/gcov.cc | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
diff mbox series

Patch

diff --git a/gcc/gcov.cc b/gcc/gcov.cc
index 87deeadcc75..0ad48eb1b54 100644
--- a/gcc/gcov.cc
+++ b/gcc/gcov.cc
@@ -1015,7 +1015,7 @@  tombstone_subsequence_p (const vector<unsigned>& sub,
 	if (yitr == yend)
 	  return false;
       }
-    else if (*yitr != *xitr)
+    else if (yitr == yend || *yitr != *xitr)
       return false;
 
   yitr = find_if_not (yitr, yend, tombstone_p);