[v2] tst: Provide test for difftime
Commit Message
This change adds new test to assess difftime's functionality by
adding some arbitrary offsets to current time_t value (read via
time).
If 64 bit time_t is supported, the same procedure is applied around
the threshold of Y2038 time overflow.
---
Changes for v2:
- Remove FAIL_UNSUPPORTED() when sizeof (time_t) <= 4
---
time/Makefile | 2 +-
time/tst-difftime.c | 55 +++++++++++++++++++++++++++++++++++++++++++++
2 files changed, 56 insertions(+), 1 deletion(-)
create mode 100644 time/tst-difftime.c
Comments
On 1/27/21 4:42 AM, Lukasz Majewski wrote:
> This change adds new test to assess difftime's functionality by
> adding some arbitrary offsets to current time_t value (read via
> time).
That would make tests irreproducible. Why is that helpful for difftime?
I suggest using only reproducible tests; this should make the code
simpler anyway.
> +static void
> +test_difftime_helper (time_t start, time_t t1, time_t t0, double exp_val)
The signature should be simpler:
static void
test_difftime_helper (long long t1, long long t0, double exp_val)
And test_difftime_helper can test whether its arguments fit into time_t
with code like this:
time_t u1;
if (__builtin_add_overflow (t1, 0, &u1))
return;
That way, you can omit the 'sizeof (time_t) > 4' test, which is a bit
dubious anyway as it wouldn't work on hypothetical hosts where char is
wider than 8 bits. You can do this sort of thing in all the time_t
tests, to omit all uses of sizeof (time_t).
On Jan 27 2021, Paul Eggert wrote:
> dubious anyway as it wouldn't work on hypothetical hosts where char is
> wider than 8 bits.
This is irrelevant.
Andreas.
Hi Andreas, Paul,
> On Jan 27 2021, Paul Eggert wrote:
>
> > dubious anyway as it wouldn't work on hypothetical hosts where char
> > is wider than 8 bits.
>
> This is irrelevant.
I also think that sizeof (time_t) > 4 is more readable and simpler.
Moreover, similar condition was used in ./time/tst-y2039.c test.
>
> Andreas.
>
Best regards,
Lukasz Majewski
--
DENX Software Engineering GmbH, Managing Director: Wolfgang Denk
HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany
Phone: (+49)-8142-66989-59 Fax: (+49)-8142-66989-80 Email: lukma@denx.de
On 1/27/21 1:46 PM, Lukasz Majewski wrote:
> I also think that sizeof (time_t) > 4 is more readable and simpler.
> Moreover, similar condition was used in ./time/tst-y2039.c test.
It would be simpler, except for the warnings from GCC. Using
__builtin_add_overflow would mean we wouldn't have to worry about those
warnings.
Hi Paul,
> On 1/27/21 1:46 PM, Lukasz Majewski wrote:
> > I also think that sizeof (time_t) > 4 is more readable and simpler.
> > Moreover, similar condition was used in ./time/tst-y2039.c test.
>
> It would be simpler, except for the warnings from GCC. Using
> __builtin_add_overflow would mean we wouldn't have to worry about
> those warnings.
I don't mind to use it, when other developers agree.
Best regards,
Lukasz Majewski
--
DENX Software Engineering GmbH, Managing Director: Wolfgang Denk
HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany
Phone: (+49)-8142-66989-59 Fax: (+49)-8142-66989-80 Email: lukma@denx.de
Dear Community,
> Hi Paul,
>
> > On 1/27/21 1:46 PM, Lukasz Majewski wrote:
> > > I also think that sizeof (time_t) > 4 is more readable and
> > > simpler. Moreover, similar condition was used in
> > > ./time/tst-y2039.c test.
> >
> > It would be simpler, except for the warnings from GCC. Using
> > __builtin_add_overflow would mean we wouldn't have to worry about
> > those warnings.
>
> I don't mind to use it, when other developers agree.
>
Any feedback on this idea?
>
>
>
> Best regards,
>
> Lukasz Majewski
>
> --
>
> DENX Software Engineering GmbH, Managing Director: Wolfgang Denk
> HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany
> Phone: (+49)-8142-66989-59 Fax: (+49)-8142-66989-80 Email:
> lukma@denx.de
Best regards,
Lukasz Majewski
--
DENX Software Engineering GmbH, Managing Director: Wolfgang Denk
HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany
Phone: (+49)-8142-66989-59 Fax: (+49)-8142-66989-80 Email: lukma@denx.de
Dear Community,
> Dear Community,
>
> > Hi Paul,
> >
> > > On 1/27/21 1:46 PM, Lukasz Majewski wrote:
> > > > I also think that sizeof (time_t) > 4 is more readable and
> > > > simpler. Moreover, similar condition was used in
> > > > ./time/tst-y2039.c test.
> > >
> > > It would be simpler, except for the warnings from GCC. Using
> > > __builtin_add_overflow would mean we wouldn't have to worry about
> > > those warnings.
> >
> > I don't mind to use it, when other developers agree.
> >
>
> Any feedback on this idea?
Would it be OK, if I follow the idea proposed by Paul to check if the
overflow in time_t is present (with __builtin_add_overflow()) in tests,
which require it?
>
> >
> >
> >
> > Best regards,
> >
> > Lukasz Majewski
> >
> > --
> >
> > DENX Software Engineering GmbH, Managing Director: Wolfgang
> > Denk HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell,
> > Germany Phone: (+49)-8142-66989-59 Fax: (+49)-8142-66989-80 Email:
> > lukma@denx.de
>
>
>
>
> Best regards,
>
> Lukasz Majewski
>
> --
>
> DENX Software Engineering GmbH, Managing Director: Wolfgang Denk
> HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany
> Phone: (+49)-8142-66989-59 Fax: (+49)-8142-66989-80 Email:
> lukma@denx.de
Best regards,
Lukasz Majewski
--
DENX Software Engineering GmbH, Managing Director: Wolfgang Denk
HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany
Phone: (+49)-8142-66989-59 Fax: (+49)-8142-66989-80 Email: lukma@denx.de
On 2/3/21 4:40 AM, Lukasz Majewski wrote:
> Would it be OK, if I follow the idea proposed by Paul to check if the
> overflow in time_t is present (with __builtin_add_overflow()) in tests,
> which require it?
I'd say yes (of course :-). I don't think anyone else cares, so I'd go
ahead.
@@ -51,7 +51,7 @@ tests := test_time clocktest tst-posixtz tst-strptime tst_wcsftime \
tst-clock tst-clock2 tst-clock_nanosleep tst-cpuclock1 \
tst-adjtime tst-clock-y2038 tst-clock2-y2038 \
tst-cpuclock1-y2038 tst-clock_nanosleep-y2038 tst-clock_settime \
- tst-clock_adjtime tst-ctime
+ tst-clock_adjtime tst-ctime tst-difftime
include ../Rules
new file mode 100644
@@ -0,0 +1,55 @@
+/* Test for difftime
+ Copyright (C) 2021 Free Software Foundation, Inc.
+ This file is part of the GNU C Library.
+
+ The GNU C Library is free software; you can redistribute it and/or
+ modify it under the terms of the GNU Lesser General Public
+ License as published by the Free Software Foundation; either
+ version 2.1 of the License, or (at your option) any later version.
+
+ The GNU C Library is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ Lesser General Public License for more details.
+
+ You should have received a copy of the GNU Lesser General Public
+ License along with the GNU C Library; if not, see
+ <https://www.gnu.org/licenses/>. */
+
+#include <time.h>
+#include <support/check.h>
+
+static void
+test_difftime_helper (time_t start, time_t t1, time_t t0, double exp_val)
+{
+ time_t time1, time0;
+
+ time1 = time0 = start;
+ time1 += t1;
+ time0 += t0;
+
+ double sub = difftime (time1, time0);
+ if (sub != exp_val)
+ FAIL_EXIT1 ("*** Difftime returned %f (expected %f)\n", sub, exp_val);
+}
+
+static int
+do_test (void)
+{
+ /* Check if difftime works with current time. */
+ test_difftime_helper (time (NULL), +1800, -1800, 3600.0);
+ test_difftime_helper (time (NULL), -1800, +1800, -3600.0);
+
+ /* Check if difftime works correctly near 32 bit time_t overflow. */
+ if (sizeof (time_t) > 4)
+ {
+ test_difftime_helper (0x7FFFFFFF, +1800, -1800, 3600.0);
+ test_difftime_helper (0x80000000, +1800, -1800, 3600.0);
+ test_difftime_helper (0x80000000, -1800, +1800, -3600.0);
+ test_difftime_helper (0x7FFFFFFF, -1800, +1800, -3600.0);
+ }
+
+ return 0;
+}
+
+#include <support/test-driver.c>