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gh-97786: Fix compiler warnings in pytime.c #101826

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Merged
gpshead merged 3 commits into from
Feb 20, 2023
Merged

gh-97786: Fix compiler warnings in pytime.c #101826

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622ec0a
Fix compiler warnings in pytime.c
mdickinson Feb 11, 2023
32aee25
Add news
mdickinson Feb 11, 2023
c381e4c
Add note on nans; remove unnecessary asserts
mdickinson Feb 12, 2023
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Fix compiler warnings in pytime.c
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@mdickinson
mdickinson committed Feb 11, 2023
commit 622ec0afd1a6f1a607a542a861fdd21237a16fb7
35 changes: 29 additions & 6 deletions Python/pytime.c
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Original file line number Diff line number Diff line change
@@ -1,5 +1,4 @@
#include "Python.h"
#include "pycore_pymath.h" // _Py_InIntegralTypeRange()
#ifdef MS_WINDOWS
# include <winsock2.h> // struct timeval
#endif
Expand Down Expand Up @@ -41,6 +40,14 @@
# error "unsupported time_t size"
#endif

#if PY_TIME_T_MAX + PY_TIME_T_MIN != -1
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# error "time_t is not a two's complement integer type"
#endif

#if _PyTime_MIN + _PyTime_MAX != -1
# error "_PyTime_t is not a two's complement integer type"
#endif


static void
pytime_time_t_overflow(void)
Expand Down Expand Up @@ -294,7 +301,19 @@ pytime_double_to_denominator(double d, time_t *sec, long *numerator,
}
assert(0.0 <= floatpart && floatpart < denominator);

if (!_Py_InIntegralTypeRange(time_t, intpart)) {
/*
Conversion of an out-of-range value to time_t gives undefined behaviour
(C99 §6.3.1.4p1), so we must guard against it. However, checking that
`intpart` is in range is delicate: the obvious expression `intpart <=
PY_TIME_T_MAX` will first convert the value `PY_TIME_T_MAX` to a double,
potentially changing its value and leading to us failing to catch some
UB-inducing values. The code below works correctly under the mild
assumption that time_t is a two's complement integer type with no trap
representation, and that `PY_TIME_T_MIN` is within the representable
range of a C double.
*/
assert(fmod(intpart, 1.0) == 0.0);
if (!((double)PY_TIME_T_MIN <= intpart && intpart < -(double)PY_TIME_T_MIN)) {
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pytime_time_t_overflow();
return -1;
}
Expand Down Expand Up @@ -349,7 +368,9 @@ _PyTime_ObjectToTime_t(PyObject *obj, time_t *sec, _PyTime_round_t round)
d = pytime_round(d, round);
(void)modf(d, &intpart);

if (!_Py_InIntegralTypeRange(time_t, intpart)) {
/* See comments in pytime_double_to_denominator */
assert(fmod(intpart, 1.0) == 0.0);
if (!((double)PY_TIME_T_MIN <= intpart && intpart < -(double)PY_TIME_T_MIN)) {
pytime_time_t_overflow();
return -1;
}
Expand Down Expand Up @@ -515,8 +536,10 @@ pytime_from_double(_PyTime_t *tp, double value, _PyTime_round_t round,
d *= (double)unit_to_ns;
d = pytime_round(d, round);

if (!_Py_InIntegralTypeRange(_PyTime_t, d)) {
pytime_overflow();
/* See comments in pytime_double_to_denominator */
assert(fmod(d, 1.0) == 0.0);
if (!((double)_PyTime_MIN <= d && d < -(double)_PyTime_MIN)) {
pytime_time_t_overflow();
return -1;
}
_PyTime_t ns = (_PyTime_t)d;
Expand Down Expand Up @@ -910,7 +933,7 @@ py_get_system_clock(_PyTime_t *tp, _Py_clock_info_t *info, int raise_exc)
info->monotonic = 0;
info->adjustable = 1;
if (clock_getres(CLOCK_REALTIME, &res) == 0) {
info->resolution = res.tv_sec + res.tv_nsec * 1e-9;
info->resolution = (double)res.tv_sec + (double)res.tv_nsec * 1e-9;
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}
else {
info->resolution = 1e-9;
Expand Down