[PATCH 1/5] range-set: fix sort_and_merge_range_set() corner case bug
- From
Eric Sunshine <sunshine@sunshineco.com>
- Date
- Jul 23, 2013, 14:28 UTC
- Message-ID
- <1374589688-27751-2-git-send-email-sunshine@sunshineco.com>
- In-Reply-To
- <1374589688-27751-1-git-send-email-sunshine@sunshineco.com>
When handed an empty range_set (range_set.nr == 0), sort_and_merge_range_set() incorrectly sets range_set.nr to 1 at exit. Subsequent range_set functions then access the bogus range at element zero and crash or throw an assertion failure. Fix this bug.
Signed-off-by: Eric Sunshine <sunshine@sunshineco.com> ---
This bug could have been fixed with a simple conditional rather than changing the for() loop to start at 0. I did it this way, however, because the next fix (range-set: satisfy non-empty ranges invariant) also needs the for() loop starting at 0. Thus, by changing the for() loop here, the subsequent fix becomes much more obvious and easy to read.
line-log.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-)
diff --git a/line-log.c b/line-log.c index 8cc29a0..5234879 100644 --- a/line-log.c +++ b/line-log.c @@ -110,12 +110,12 @@ static void range_set_check_invariants(struct range_set *rs) static void sort_and_merge_range_set(struct range_set *rs) { int i; - int o = 1; /* output cursor */ + int o = 0; /* output cursor */ qsort(rs->ranges, rs->nr, sizeof(struct range), range_cmp); - for (i = 1; i < rs->nr; i++) { - if (rs->ranges[i].start <= rs->ranges[o-1].end) { + for (i = 0; i < rs->nr; i++) { + if (o > 0 && rs->ranges[i].start <= rs->ranges[o-1].end) { if (rs->ranges[o-1].end < rs->ranges[i].end) rs->ranges[o-1].end = rs->ranges[i].end; } else {
-- 1.8.3.4.1120.gc240c48