[PATCH] add tests for tzset(3)

Wed Apr 13 22:21:12 GMT 2022

See [PATCH v2 ...] thread for JJ response and my reply!

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?
> 
> 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

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