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authorDerrick Stolee <dstolee@microsoft.com>2017-10-08 14:29:37 -0400
committerJunio C Hamano <gitster@pobox.com>2017-10-10 08:57:24 +0900
commit19716b21a4255ecc7148b54ab2c78039c59f25bf (patch)
tree5f1cecbffc543c64e7c4c4f371d204424e1ce1bb /compat
parent217f2767cbcb562872437eed4dec62e00846d90c (diff)
downloadgit-19716b21a4255ecc7148b54ab2c78039c59f25bf.tar.gz
cleanup: fix possible overflow errors in binary searchds/avoid-overflow-in-midpoint-computation
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 'compat')
-rw-r--r--compat/regex/regex_internal.c4
-rw-r--r--compat/regex/regexec.c2
2 files changed, 3 insertions, 3 deletions
diff --git a/compat/regex/regex_internal.c b/compat/regex/regex_internal.c
index d4121f2f4f..98342b8316 100644
--- a/compat/regex/regex_internal.c
+++ b/compat/regex/regex_internal.c
@@ -613,7 +613,7 @@ re_string_reconstruct (re_string_t *pstr, int idx, int eflags)
int low = 0, high = pstr->valid_len, mid;
do
{
- mid = (high + low) / 2;
+ mid = low + (high - low) / 2;
if (pstr->offsets[mid] > offset)
high = mid;
else if (pstr->offsets[mid] < offset)
@@ -1394,7 +1394,7 @@ re_node_set_contains (const re_node_set *set, int elem)
right = set->nelem - 1;
while (idx < right)
{
- mid = (idx + right) / 2;
+ mid = idx + (right - idx) / 2;
if (set->elems[mid] < elem)
idx = mid + 1;
else
diff --git a/compat/regex/regexec.c b/compat/regex/regexec.c
index 0a745d9c3b..6f2b48a78b 100644
--- a/compat/regex/regexec.c
+++ b/compat/regex/regexec.c
@@ -4284,7 +4284,7 @@ search_cur_bkref_entry (const re_match_context_t *mctx, int str_idx)
last = right = mctx->nbkref_ents;
for (left = 0; left < right;)
{
- mid = (left + right) / 2;
+ mid = left + (right - left) / 2;
if (mctx->bkref_ents[mid].str_idx < str_idx)
left = mid + 1;
else