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Changes type avoiding undefined behaviour shifting left negative value in CFTimeZone #2812

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Merged
merged 2 commits into from
Jun 21, 2020
Merged

Changes type avoiding undefined behaviour shifting left negative value in CFTimeZone #2812

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b1a9d92
Changes type to avoid undefined behaviour of shifting left negative v…
valeriyvan Jun 4, 2020
3457298
Adds comment and explicit cast.
valeriyvan Jun 19, 2020
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5 changes: 3 additions & 2 deletions CoreFoundation/NumberDate.subproj/CFTimeZone.c
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Original file line number Diff line number Diff line change
Expand Up @@ -485,12 +485,13 @@ static CFIndex __CFBSearchTZPeriods(CFTimeZoneRef tz, CFAbsoluteTime at) {


CF_INLINE int32_t __CFDetzcode(const unsigned char *bufp) {
int32_t result = (bufp[0] & 0x80) ? ~0L : 0L;
// `result` is uint32_t to avoid undefined behaviour of shifting left negative values
uint32_t result = (bufp[0] & 0x80) ? ~0L : 0L;
result = (result << 8) | (bufp[0] & 0xff);
result = (result << 8) | (bufp[1] & 0xff);
result = (result << 8) | (bufp[2] & 0xff);
result = (result << 8) | (bufp[3] & 0xff);
return result;
return (int32_t)result;
}

CF_INLINE void __CFEntzcode(int32_t value, unsigned char *bufp) {
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