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pytime: add _PyTime_check_mul_overflow() macro to avoid undefined behaviour

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Overflow test in test_FromSecondsObject() fails on FreeBSD 10.0 buildbot which
uses clang. clang implements more aggressive optimization which gives
different result than GCC on undefined behaviours.

Check if a multiplication will overflow, instead of checking if a
multiplicatin had overflowed, to avoid undefined behaviour.

Add also debug information if the test on overflow fails.
This commit is contained in:
Victor Stinner 2015-09-10 15:55:07 +02:00
parent ff0ed3e71c
commit c60542b12b
2 changed files with 26 additions and 12 deletions
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35
Python/pytime.c
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@ -7,6 +7,11 @@
#include <mach/mach_time.h> /* mach_absolute_time(), mach_timebase_info() */
#endif
#define _PyTime_check_mul_overflow(a, b) \
(assert(b > 0), \
(_PyTime_t)(a) < _PyTime_MIN / (_PyTime_t)(b) \
|| _PyTime_MAX / (_PyTime_t)(b) < (_PyTime_t)(a))
/* To millisecond (10^-3) */
#define SEC_TO_MS 1000
@ -226,12 +231,15 @@ _PyTime_FromTimespec(_PyTime_t *tp, struct timespec *ts, int raise)
_PyTime_t t;
int res = 0;
t = (_PyTime_t)ts->tv_sec * SEC_TO_NS;
if (t / SEC_TO_NS != ts->tv_sec) {
assert(sizeof(ts->tv_sec) <= sizeof(_PyTime_t));
t = (_PyTime_t)ts->tv_sec;
if (_PyTime_check_mul_overflow(t, SEC_TO_NS)) {
if (raise)
_PyTime_overflow();
res = -1;
}
t = t * SEC_TO_NS;
t += ts->tv_nsec;
@ -245,12 +253,15 @@ _PyTime_FromTimeval(_PyTime_t *tp, struct timeval *tv, int raise)
_PyTime_t t;
int res = 0;
t = (_PyTime_t)tv->tv_sec * SEC_TO_NS;
if (t / SEC_TO_NS != tv->tv_sec) {
assert(sizeof(ts->tv_sec) <= sizeof(_PyTime_t));
t = (_PyTime_t)tv->tv_sec;
if (_PyTime_check_mul_overflow(t, SEC_TO_NS)) {
if (raise)
_PyTime_overflow();
res = -1;
}
t = t * SEC_TO_NS;
t += (_PyTime_t)tv->tv_usec * US_TO_NS;
@ -308,11 +319,11 @@ _PyTime_FromObject(_PyTime_t *t, PyObject *obj, _PyTime_round_t round,
return -1;
}
*t = sec * unit_to_ns;
if (*t / unit_to_ns != sec) {
if (_PyTime_check_mul_overflow(sec, unit_to_ns)) {
_PyTime_overflow();
return -1;
}
*t = sec * unit_to_ns;
return 0;
}
}
@ -587,19 +598,20 @@ _PyTime_GetSystemClockWithInfo(_PyTime_t *t, _Py_clock_info_t *info)
return pygettimeofday_new(t, info, 1);
}
static int
pymonotonic(_PyTime_t *tp, _Py_clock_info_t *info, int raise)
{
#if defined(MS_WINDOWS)
ULONGLONG result;
ULONGLONG ticks;
_PyTime_t t;
assert(info == NULL || raise);
result = GetTickCount64();
ticks = GetTickCount64();
assert(sizeof(result) <= sizeof(_PyTime_t));
t = (_PyTime_t)ticks;
*tp = result * MS_TO_NS;
if (*tp / MS_TO_NS != result) {
if (_PyTime_check_mul_overflow(t, MS_TO_NS)) {
if (raise) {
_PyTime_overflow();
return -1;
@ -607,6 +619,7 @@ pymonotonic(_PyTime_t *tp, _Py_clock_info_t *info, int raise)
/* Hello, time traveler! */
assert(0);
}
*tp = t * MS_TO_NS;
if (info) {
DWORD timeAdjustment, timeIncrement;