diff options
| author | Derrick Stolee <dstolee@microsoft.com> | 2017-10-08 21:29:37 +0300 |
|---|---|---|
| committer | Junio C Hamano <gitster@pobox.com> | 2017-10-10 02:57:24 +0300 |
| commit | 19716b21a4255ecc7148b54ab2c78039c59f25bf (patch) | |
| tree | 5f1cecbffc543c64e7c4c4f371d204424e1ce1bb /builtin | |
| parent | 217f2767cbcb562872437eed4dec62e00846d90c (diff) | |
cleanup: fix possible overflow errors in binary search
A common mistake when writing binary search is to allow possible
integer overflow by using the simple average:
mid = (min + max) / 2;
Instead, use the overflow-safe version:
mid = min + (max - min) / 2;
This translation is safe since the operation occurs inside a loop
conditioned on "min < max". The included changes were found using
the following git grep:
git grep '/ *2;' '*.c'
Making this cleanup will prevent future review friction when a new
binary search is contructed based on existing code.
Signed-off-by: Derrick Stolee <dstolee@microsoft.com>
Reviewed-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Diffstat (limited to 'builtin')
| -rw-r--r-- | builtin/index-pack.c | 4 | ||||
| -rw-r--r-- | builtin/pack-objects.c | 2 | ||||
| -rw-r--r-- | builtin/unpack-objects.c | 2 |
3 files changed, 4 insertions, 4 deletions
diff --git a/builtin/index-pack.c b/builtin/index-pack.c index f2be145e128..8ec459f5225 100644 --- a/builtin/index-pack.c +++ b/builtin/index-pack.c @@ -633,7 +633,7 @@ static int find_ofs_delta(const off_t offset, enum object_type type) int first = 0, last = nr_ofs_deltas; while (first < last) { - int next = (first + last) / 2; + int next = first + (last - first) / 2; struct ofs_delta_entry *delta = &ofs_deltas[next]; int cmp; @@ -687,7 +687,7 @@ static int find_ref_delta(const unsigned char *sha1, enum object_type type) int first = 0, last = nr_ref_deltas; while (first < last) { - int next = (first + last) / 2; + int next = first + (last - first) / 2; struct ref_delta_entry *delta = &ref_deltas[next]; int cmp; diff --git a/builtin/pack-objects.c b/builtin/pack-objects.c index 5ee2c48ffb8..6e77dfd4443 100644 --- a/builtin/pack-objects.c +++ b/builtin/pack-objects.c @@ -1277,7 +1277,7 @@ static int done_pbase_path_pos(unsigned hash) int lo = 0; int hi = done_pbase_paths_num; while (lo < hi) { - int mi = (hi + lo) / 2; + int mi = lo + (hi - lo) / 2; if (done_pbase_paths[mi] == hash) return mi; if (done_pbase_paths[mi] < hash) diff --git a/builtin/unpack-objects.c b/builtin/unpack-objects.c index 689a29fac1a..62ea264c467 100644 --- a/builtin/unpack-objects.c +++ b/builtin/unpack-objects.c @@ -394,7 +394,7 @@ static void unpack_delta_entry(enum object_type type, unsigned long delta_size, lo = 0; hi = nr; while (lo < hi) { - mid = (lo + hi)/2; + mid = lo + (hi - lo) / 2; if (base_offset < obj_list[mid].offset) { hi = mid; } else if (base_offset > obj_list[mid].offset) { |