From: Brian Inglis <Brian.Inglis@SystematicSw.ab.ca>
To: Newlib <newlib@sourceware.org>
Subject: Re: [PATCH] add tests for tzset(3)
Date: Wed, 13 Apr 2022 11:53:27 -0600 [thread overview]
Message-ID: <9603e3aa-bd7d-6740-c710-27ace1d80397@SystematicSw.ab.ca> (raw)
In-Reply-To: <20220407233425.2012-1-Brian.Inglis@SystematicSW.ab.ca>
On 2022-04-12 12:33, Brian Inglis wrote:
> On 2022-04-12 05:19, jdoubleu wrote:
>> On 4/11/2022 7:27 PM, Dimitar Dimitrov wrote:
>>> On Mon, Apr 11, 2022 at 01:17:16PM +0200, jdoubleu wrote:
>>>> looks like I'm running the testsuite against glibc and not newlib
>>>> (for target x86_64-pc-linux-gnu). I'm not even sure whether
>>>> there's a backend for linux.
>>>> I'm currently trying to run only the tzset code against the test
>>>> vectors (like Brian Inglis did[1]).
>>>> At least it show, that the newlib implementation differs from glibc.
>>>> Maybe the test case is flawed and it should indeed fail.
>
>>>>> 6:20:12 is the timezone string of the previous test case, whose tzset
>>>>> call was successful. Looking at the current code, this is expected
>>>>> behaviour.
>
>>>> Okay. Looks like the condition[2] fails. The question is, which
>>>> part of it does?
>>> I believe it is the ('>' != tzenv[n]) check that fails, because the
>>> maximum parsed string limit of 10 has been reached and n=10.
>
>>>> I've appended a patch, which prints all variables when the condition
>>>> fails.
>>>> Could you please apply the patch and then recompile and re-run the
>>>> tests
>>>> again?
>
>>> Here is the result for arm-none-eabi:
>>> parsing name: tzenv="+0123456789ABCDEF>3:33:33", res=1, n=10,
>>> tzenv[n] = 9
>>> Assertion failed! Expected 1647906533 to equal 1647916532. winter
>>> time, timezone = "<+0123456789ABCDEF>3:33:33"
>>> I assume you no longer need assembly output from compiler?
>
>>>> I've previously noticed something with the sscanf format[3].
>>>>> Perhaps TZ should be reset to UTC before the bail out?
>
>>>> I don't think the implementation should fall back to UTC
>>>> whenever parsing failed. It apparently doesn't in glibc. I'm not
>>>> sure if the behavior is specified somewhere.
>
>>> The tzset manual page says that UTC is used if TZ cannot be parsed:
>>> https://man7.org/linux/man-pages/man3/tzset.3.html
>
>>>> Maybe resetting it before each test case is a good idea, though.
>>>> That makes it clearer, why the test case failed.
>>>>> With that chunk removed, as shown below:
>>>>> {"3:33:33", IN_SECONDS(3, 33, 33),
>>>>> NO_TIME}, // truncates the name (17 + 1)
>>>>> I still get:
>>>>> Assertion failed! Expected 1647906533 to equal 1647916532.
>>>>> winter time, timezone = "3:33:33"
>
>>>> My bad; "3:33:33" isn't a valid timezone string. It has to be
>>>> prefixed by a
>>>> name e.g. "MESZ" or "<+00>", as you tried. That explains why it is also
>>>> failing.
>
>>>> [1]: https://sourceware.org/pipermail/newlib/2022/019529.html
>>>> [2]:
>>>> https://sourceware.org/git/?p=newlib-cygwin.git;a=blob;f=newlib/libc/time/tzset_r.c;h=9cb30b188f989f65ec9eb6417f5d74020f8c72e9;hb=HEAD#l57
>>>>
>>>> [3]: https://sourceware.org/pipermail/newlib/2022/019535.html
>
>>> I believe it is the ('>' != tzenv[n]) check that fails, because the
>>> maximum parsed string limit of 10 has been reached and n=10.
>
>> Okay, so the newlib implementation actually fails, when the name is
>> too long.
>> The POSIX standard leaves it up to the implementation how to handle
>> names[1]:
>
>>> The interpretation of these fields is unspecified if either field is
>>> less than three bytes (except for the case when dst is missing), more
>>> than {TZNAME_MAX} bytes, or if they contain characters other than
>>> those specified.
>
>> I'm not sure where to go with this. In both cases, the current
>> implementation needs a fix. Looping in Brian Inglis, the writer of the
>> current implementation and Jeff Johnston, a maintainer.
>> As I see it, there are two solutions:
>> 1. Treat long names as an error case. The failed condition[2] needs to
>> apply UTC as current time, like Dimitar Dimitrov previously suggested.
>> The test needs to be changed to check that it actually fails.
>> 2. Mimic glibc's behavior and ignore the remaining characters from the
>> name. In that case, the condition[2] and following code needs to be
>> updated as well.
>> I am happy to provide a patch, when we agreed on one solution.
>
>>> I assume you no longer need assembly output from compiler?
>
>> No, thanks. We already found the issue. It would only be helpful, if
>> different configurations generate different code (through macros,
>> optimization, etc.).
>> [1]:https://pubs.opengroup.org/onlinepubs/9699919799/basedefs/V1_chap08.html#tag_08_03
>> [2]:https://sourceware.org/git/?p=newlib-cygwin.git;a=blob;f=newlib/libc/time/tzset_r.c;hb=HEAD#l57
> Does anyone know what glibc or the BSDs do on short < 3 char
> abbreviations, or the BSDs do on > LIMIT abbreviations?
> What do they do on errors - nothing or revert to UTC?
>
> Should tzset_r allow 1...2 char abbreviations or treat them as errors?
>
> Should tzset_r allow > 10 char abbreviations, ignore and skip extra
> chars, or treat them as errors?
Should tzset_r accept characters within quotes not in the allowed
character set, ignore and skip them, or reject such abbreviations?
> If it ignores and skips extra or accepts too few characters, then
> presumably it should process the remaining fields if present?
>
> POSIX tzset_r says only that it overrides the default time zone, so is
> there a spec for the default time zone, or is it implementation defined
> (e.g. /etc/timezone /etc/localtime)?
>
> Should tzset_r revert to UTC on errors, or just not change the TZ, and
> leave it up to the application to handle the error?
--
Take care. Thanks, Brian Inglis, Calgary, Alberta, Canada
This email may be disturbing to some readers as it contains
too much technical detail. Reader discretion is advised.
[Data in binary units and prefixes, physical quantities in SI.]
next prev parent reply other threads:[~2022-04-13 17:53 UTC|newest]
Thread overview: 35+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-04-07 15:58 jdoubleu
2022-04-08 21:21 ` Jeff Johnston
2022-04-10 8:43 ` Dimitar Dimitrov
2022-04-10 17:55 ` jdoubleu
2022-04-10 21:00 ` Dimitar Dimitrov
2022-04-11 11:17 ` jdoubleu
2022-04-11 17:27 ` Dimitar Dimitrov
2022-04-12 11:19 ` jdoubleu
2022-04-12 18:33 ` Brian Inglis
2022-04-07 23:34 ` [PATCH v2 0/2] add tzset/_r POSIX angle bracket <> support in TZ env var Brian Inglis
2022-04-07 23:34 ` [PATCH v2 1/2] newlib/libc/time/tzset.c: doc update POSIX angle bracket <> support Brian Inglis
2022-04-07 23:34 ` [PATCH v2 2/2] newlib/libc/time/tzset_r.c(_tzset_unlocked_r): " Brian Inglis
2022-04-08 19:11 ` [PATCH v2 0/2] add tzset/_r POSIX angle bracket <> support in TZ env var Jeff Johnston
2022-04-13 17:53 ` Brian Inglis [this message]
2022-04-13 20:33 ` [PATCH] add tests for tzset(3) Jeff Johnston
2022-04-13 22:19 ` Brian Inglis
2022-04-14 8:59 ` jdoubleu
2022-04-14 16:31 ` Brian Inglis
2022-04-14 19:23 ` Jeff Johnston
2022-04-15 10:10 ` jdoubleu
2022-04-27 19:30 ` Jeff Johnston
2022-05-14 14:39 ` jdoubleu
2022-05-16 16:05 ` Dimitar Dimitrov
2022-05-16 17:38 ` Jeff Johnston
2022-05-17 8:45 ` [PATCH] update tzset tests jdoubleu
2022-05-18 18:48 ` Dimitar Dimitrov
2022-05-18 20:56 ` Keith Packard
2022-05-19 8:47 ` jdoubleu
2022-05-22 9:51 ` [PATCH v2] " jdoubleu
2022-05-22 21:02 ` Dimitar Dimitrov
2022-05-27 15:46 ` Jeff Johnston
2022-04-13 22:21 ` [PATCH] add tests for tzset(3) Brian Inglis
2022-04-29 15:46 Jeff Johnston
2022-05-12 18:35 ` jdoubleu
2022-05-16 17:49 ` Jeff Johnston
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