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cleanup: fix possible overflow errors in binary search

Browse Source 
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>
This commit is contained in:
Derrick Stolee
2017-10-08 14:29:37 -04:00
committed by Junio C Hamano
parent 217f2767cb
commit 19716b21a4
12 changed files with 15 additions and 15 deletions
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4
compat/regex/regex_internal.c
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@ -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