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mktime: fix non-EOVERFLOW errno handling
[BZ#23789] mktime was not properly reporting failures when the underlying localtime_r fails with errno != EOVERFLOW; it incorrectly treated them like EOVERFLOW failures, and set errno to EOVERFLOW. The problem could happen on non-glibc platforms, with Gnulib. * time/mktime.c (guess_time_tm): Remove, replacing with ... (tm_diff): ... this simpler function, which does not change errno. All callers changed to deal with errno themselves. (ranged_convert, __mktime_internal): Return failure immediately if the underlying function reports any failure other than EOVERFLOW. (__mktime_internal): Set errno to EOVERFLOW if the spring-forward gap code fails.
This commit is contained in:
Paul Eggert
Albert ARIBAUD (3ADEV)
parent
f6b3331bba
commit
86aece3bfb
14
ChangeLog
14
ChangeLog
@ -1,5 +1,19 @@
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2018-11-15 Paul Eggert <eggert@cs.ucla.edu>
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mktime: fix non-EOVERFLOW errno handling
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[BZ#23789]
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mktime was not properly reporting failures when the underlying
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localtime_r fails with errno != EOVERFLOW; it incorrectly treated
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them like EOVERFLOW failures, and set errno to EOVERFLOW.
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The problem could happen on non-glibc platforms, with Gnulib.
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* time/mktime.c (guess_time_tm): Remove, replacing with ...
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(tm_diff): ... this simpler function, which does not change errno.
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All callers changed to deal with errno themselves.
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(ranged_convert, __mktime_internal): Return failure immediately if
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the underlying function reports any failure other than EOVERFLOW.
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(__mktime_internal): Set errno to EOVERFLOW if the spring-forward
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gap code fails.
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mktime: fix bug with Y2038 DST transition
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[BZ#23789]
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* time/mktime.c (ranged_convert): On 32-bit platforms, don’t
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197
time/mktime.c
197
time/mktime.c
@ -250,45 +250,25 @@ long_int_avg (long_int a, long_int b)
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return shr (a, 1) + shr (b, 1) + ((a | b) & 1);
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}
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/* Return a time_t value corresponding to (YEAR-YDAY HOUR:MIN:SEC),
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assuming that T corresponds to *TP and that no clock adjustments
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occurred between *TP and the desired time.
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Although T and the returned value are of type long_int,
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they represent time_t values and must be in time_t range.
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If TP is null, return a value not equal to T; this avoids false matches.
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/* Return a long_int value corresponding to (YEAR-YDAY HOUR:MIN:SEC)
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minus *TP seconds, assuming no clock adjustments occurred between
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the two timestamps.
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YEAR and YDAY must not be so large that multiplying them by three times the
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number of seconds in a year (or day, respectively) would overflow long_int.
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If TP is non-null and the returned value would be out of range, set
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errno to EOVERFLOW and yield a minimal or maximal in-range value
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that is not equal to T. */
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*TP should be in the usual range. */
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static long_int
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guess_time_tm (long_int year, long_int yday, int hour, int min, int sec,
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long_int t, const struct tm *tp)
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tm_diff (long_int year, long_int yday, int hour, int min, int sec,
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struct tm const *tp)
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{
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if (tp)
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{
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long_int result;
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long_int d = ydhms_diff (year, yday, hour, min, sec,
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tp->tm_year, tp->tm_yday,
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tp->tm_hour, tp->tm_min, tp->tm_sec);
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if (! INT_ADD_WRAPV (t, d, &result))
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return result;
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__set_errno (EOVERFLOW);
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}
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/* An error occurred, probably overflow. Return the nearest result
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that is actually in range, except don't report a zero difference
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if the actual difference is nonzero, as that would cause a false
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match; and don't oscillate between two values, as that would
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confuse the spring-forward gap detector. */
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return (t < long_int_avg (mktime_min, mktime_max)
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? (t <= mktime_min + 1 ? t + 1 : mktime_min)
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: (mktime_max - 1 <= t ? t - 1 : mktime_max));
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return ydhms_diff (year, yday, hour, min, sec,
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tp->tm_year, tp->tm_yday,
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tp->tm_hour, tp->tm_min, tp->tm_sec);
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}
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/* Use CONVERT to convert T to a struct tm value in *TM. T must be in
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range for time_t. Return TM if successful, NULL if T is out of
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range for CONVERT. */
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range for time_t. Return TM if successful, NULL (setting errno) on
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failure. */
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static struct tm *
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convert_time (struct tm *(*convert) (const time_t *, struct tm *),
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long_int t, struct tm *tm)
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@ -300,49 +280,48 @@ convert_time (struct tm *(*convert) (const time_t *, struct tm *),
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/* Use CONVERT to convert *T to a broken down time in *TP.
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If *T is out of range for conversion, adjust it so that
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it is the nearest in-range value and then convert that.
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A value is in range if it fits in both time_t and long_int. */
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A value is in range if it fits in both time_t and long_int.
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Return TP on success, NULL (setting errno) on failure. */
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static struct tm *
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ranged_convert (struct tm *(*convert) (const time_t *, struct tm *),
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long_int *t, struct tm *tp)
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{
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struct tm *r;
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if (*t < mktime_min)
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*t = mktime_min;
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else if (mktime_max < *t)
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*t = mktime_max;
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r = convert_time (convert, *t, tp);
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if (!r && *t)
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long_int t1 = (*t < mktime_min ? mktime_min
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: *t <= mktime_max ? *t : mktime_max);
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struct tm *r = convert_time (convert, t1, tp);
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if (r)
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{
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long_int bad = *t;
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long_int ok = 0;
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*t = t1;
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return r;
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}
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if (errno != EOVERFLOW)
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return NULL;
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/* BAD is a known unconvertible value, and OK is a known good one.
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Use binary search to narrow the range between BAD and OK until
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they differ by 1. */
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while (true)
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{
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long_int mid = long_int_avg (ok, bad);
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if (mid == ok || mid == bad)
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break;
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r = convert_time (convert, mid, tp);
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if (r)
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ok = mid;
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else
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bad = mid;
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}
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long_int bad = t1;
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long_int ok = 0;
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struct tm oktm; oktm.tm_sec = -1;
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*t = ok;
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if (!r && ok)
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{
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/* The last conversion attempt failed;
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revert to the most recent successful attempt. */
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r = convert_time (convert, ok, tp);
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}
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/* BAD is a known out-of-range value, and OK is a known in-range one.
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Use binary search to narrow the range between BAD and OK until
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they differ by 1. */
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while (true)
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{
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long_int mid = long_int_avg (ok, bad);
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if (mid == ok || mid == bad)
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break;
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if (convert_time (convert, mid, tp))
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ok = mid, oktm = *tp;
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else if (errno != EOVERFLOW)
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return NULL;
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else
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bad = mid;
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}
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return r;
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if (oktm.tm_sec < 0)
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return NULL;
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*t = ok;
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*tp = oktm;
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return tp;
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}
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@ -359,7 +338,6 @@ __mktime_internal (struct tm *tp,
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struct tm *(*convert) (const time_t *, struct tm *),
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mktime_offset_t *offset)
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{
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long_int t, gt, t0, t1, t2;
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struct tm tm;
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/* The maximum number of probes (calls to CONVERT) should be enough
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@ -379,7 +357,7 @@ __mktime_internal (struct tm *tp,
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int isdst = tp->tm_isdst;
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/* 1 if the previous probe was DST. */
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int dst2;
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int dst2 = 0;
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/* Ensure that mon is in range, and set year accordingly. */
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int mon_remainder = mon % 12;
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@ -418,36 +396,46 @@ __mktime_internal (struct tm *tp,
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time. */
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INT_SUBTRACT_WRAPV (0, off, &negative_offset_guess);
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t0 = ydhms_diff (year, yday, hour, min, sec,
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EPOCH_YEAR - TM_YEAR_BASE, 0, 0, 0, negative_offset_guess);
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long_int t0 = ydhms_diff (year, yday, hour, min, sec,
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EPOCH_YEAR - TM_YEAR_BASE, 0, 0, 0,
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negative_offset_guess);
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long_int t = t0, t1 = t0, t2 = t0;
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/* Repeatedly use the error to improve the guess. */
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for (t = t1 = t2 = t0, dst2 = 0;
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(gt = guess_time_tm (year, yday, hour, min, sec, t,
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ranged_convert (convert, &t, &tm)),
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t != gt);
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t1 = t2, t2 = t, t = gt, dst2 = tm.tm_isdst != 0)
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if (t == t1 && t != t2
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&& (tm.tm_isdst < 0
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|| (isdst < 0
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? dst2 <= (tm.tm_isdst != 0)
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: (isdst != 0) != (tm.tm_isdst != 0))))
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/* We can't possibly find a match, as we are oscillating
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between two values. The requested time probably falls
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within a spring-forward gap of size GT - T. Follow the common
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practice in this case, which is to return a time that is GT - T
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away from the requested time, preferring a time whose
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tm_isdst differs from the requested value. (If no tm_isdst
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was requested and only one of the two values has a nonzero
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tm_isdst, prefer that value.) In practice, this is more
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useful than returning -1. */
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goto offset_found;
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else if (--remaining_probes == 0)
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{
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__set_errno (EOVERFLOW);
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while (true)
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{
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if (! ranged_convert (convert, &t, &tm))
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return -1;
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}
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long_int dt = tm_diff (year, yday, hour, min, sec, &tm);
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if (dt == 0)
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break;
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if (t == t1 && t != t2
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&& (tm.tm_isdst < 0
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|| (isdst < 0
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? dst2 <= (tm.tm_isdst != 0)
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: (isdst != 0) != (tm.tm_isdst != 0))))
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/* We can't possibly find a match, as we are oscillating
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between two values. The requested time probably falls
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within a spring-forward gap of size DT. Follow the common
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practice in this case, which is to return a time that is DT
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away from the requested time, preferring a time whose
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tm_isdst differs from the requested value. (If no tm_isdst
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was requested and only one of the two values has a nonzero
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tm_isdst, prefer that value.) In practice, this is more
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useful than returning -1. */
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goto offset_found;
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remaining_probes--;
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if (remaining_probes == 0)
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{
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__set_errno (EOVERFLOW);
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return -1;
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}
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t1 = t2, t2 = t, t += dt, dst2 = tm.tm_isdst != 0;
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}
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/* We have a match. Check whether tm.tm_isdst has the requested
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value, if any. */
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@ -489,17 +477,30 @@ __mktime_internal (struct tm *tp,
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if (! INT_ADD_WRAPV (t, delta * direction, &ot))
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{
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struct tm otm;
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ranged_convert (convert, &ot, &otm);
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if (! ranged_convert (convert, &ot, &otm))
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return -1;
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if (! isdst_differ (isdst, otm.tm_isdst))
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{
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/* We found the desired tm_isdst.
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Extrapolate back to the desired time. */
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t = guess_time_tm (year, yday, hour, min, sec, ot, &otm);
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ranged_convert (convert, &t, &tm);
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goto offset_found;
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long_int gt = ot + tm_diff (year, yday, hour, min, sec,
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&otm);
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if (mktime_min <= gt && gt <= mktime_max)
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{
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if (convert_time (convert, gt, &tm))
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{
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t = gt;
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goto offset_found;
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}
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if (errno != EOVERFLOW)
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return -1;
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}
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}
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}
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}
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__set_errno (EOVERFLOW);
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return -1;
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}
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offset_found:
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