Re: [PATCH] add tests for tzset(3)

On Mon, May 16, 2022 at 12:06 PM Dimitar Dimitrov <[email protected]> wrote:

> On Sat, May 14, 2022 at 04:39:16PM +0200, jdoubleu wrote:
> > > To summarize, the following cases are errors:
> > > 1. name is too short (less than 3 chars)
> > > 2. name is too long (more than TZNAME_MAX)
> > > 3. name includes arbitrary chars (not <>+-ALPHANUM)
> > > In all of these error cases, the time should be set back to UTC, right?
>

Yes.

>
> > Here's my patch which adds test cases for the above error cases.
>
> Did you forget to attach the actual patch with updated test cases? I
> can't find it.
>
> Regards,
> Dimitar
>
> >
> > It's based on the latest (pending) changes of tzset[1]. Please apply them
> > first.
> >
> > I wasn't able to run the tests, yet. With glibc they're obviously
> failing.
> >
> > Could you please test them?
> >
> >
> >
> > [1]: https://sourceware.org/pipermail/newlib/2022/019581.html
> >
> >
> > Cheers
> > ---
> > 🙎🏻‍♂️ jdoubleu
> > On 4/14/2022 10:59 AM, jdoubleu wrote:
> > > On 2022-04-13 14:33, Jeff Johnston wrote:
> > > > Looking at the glibc tzset code I have locally (not latest/greatest,
> but
> > > > does support angle brackets):
> > >
> > > I can confirm the behavior with glibc[1]. As it turns out, glibc does
> > > not directly impose a character limit on the timezone name, but
> requires
> > > at least 3 characters. From the man page[2]:
> > >
> > > > The std string specifies an abbreviation for the timezone and must be
> > > > three or more alphabetic characters.
> > >
> > > To my misunderstanding, they don't even ignore remaining characters,
> but
> > > keep all of them, as you can see in the output[1] and Jeff Johnston
> > > explained.
> > >
> > > > but you imply that glibc in fact uses the equivalent of the scanf
> > > > "%m[...]" (malloc) > modifier, and I think using that would be
> > > > against the newlib
> > > philosophy to keep things
> > > > limited and under control to support small targets.
> > >
> > > I agree, newlib SHOULD impose a limit. Especially, since the POSIX
> > > standard[3] already introduces an upper limit, though unspecified.
> > >
> > > The current limit is 11 characters, if I'm not mistaken. The longest
> > > name from the tzdb[4] is "<+1030>" i.e. 5 chars (see all extracted
> > > names[5]). All others usually are 3 or 4 chars long.
> > >
> > > That said, I think 11 is reasonably large enough.
> > >
> > > However, it could be helpful to get the limit from user-code, because
> > > there is no error reporting mechanism used. Right now, the limit is
> only
> > > defined in tzset_r.c[6]. So maybe move it to limits.h? One thing to not
> > > forget here is to keep limit in sync with the sscanf format's maximum
> > > field width[7].
> > >
> > >
> > > To summarize, the following cases are errors:
> > > 1. name is too short (less than 3 chars)
> > > 2. name is too long (more than TZNAME_MAX)
> > > 3. name includes arbitrary chars (not <>+-ALPHANUM)
> > > In all of these error cases, the time should be set back to UTC, right?
> > >
> > >
> > > I'm going to prepare some test cases for the test suite to check for
> the
> > > errors as well.
> > >
> > >
> > > [1]: https://godbolt.org/z/o93zo3qxv
> > > [2]: https://www.man7.org/linux/man-pages/man3/tzset.3.html
> > > [3]:
> https://pubs.opengroup.org/onlinepubs/9699919799/basedefs/V1_chap08.html#tag_08_03
> > >
> > > [4]: https://github.com/eggert/tz
> > > [5]:
> > >
> https://raw.githubusercontent.com/nayarsystems/posix_tz_db/master/zones.csv
> > > [6]:
> https://sourceware.org/git/?p=newlib-cygwin.git;a=blob;f=newlib/libc/time/tzset_r.c;h=9cb30b188f989f65ec9eb6417f5d74020f8c72e9;hb=HEAD#l13
> > >
> > > [7]:
> https://sourceware.org/git/?p=newlib-cygwin.git;a=blob;f=newlib/libc/time/tzset_r.c;h=9cb30b188f989f65ec9eb6417f5d74020f8c72e9;hb=HEAD#l57
> > >
> > >
> > >
> > >
> > > Cheers
> > > ---
> > > 🙎🏻‍♂️ jdoubleu
> > > On 4/14/2022 12:19 AM, Brian Inglis wrote:
> > > > On 2022-04-13 14:33, Jeff Johnston wrote:
> > > > > Looking at the glibc tzset code I have locally (not
> latest/greatest, but
> > > > > does support angle brackets):
> > > > >
> > > > > If there any parse failures, UTC is defaulted.
> > > >
> > > > We currently leave the time zone info unchanged.
> > > >
> > > > > Extraneous characters inside brackets or less than 3 characters is
> a
> > > > > parse failure.
> > > > ✔ Check    ✔ Check
> > > >
> > > > > Glibc parses the tz name string char by char and allocates space
> for
> > > > > the name strings so there is no max size.
> > > >
> > > > The suggestion was that glibc ignores the remaining characters, but
> > > > you imply that glibc in fact uses the equivalent of the scanf
> > > > "%m[...]" (malloc) modifier, and I think using that would be against
> > > > the newlib philosophy to keep things limited and under control to
> > > > support small targets.  Larger targets like Cygwin (do our own thing
> > > > including zoneinfo), and perhaps RTEMS, can supply their own
> > > > enhancements.
> > > >
> > > > > the name strings so there is no max size.  I am fine if you want
> > > > > to mandate a maximum, but if you do, then too many chars should
> > > > > be treated as a failure.  If you aren't certain of the limit,
> > > > > make the limit higher than you expect.
> > > > Current limits are 3-10 allowing for e.g. <MESZ+03:30> which is the
> > > > most ever likely to be used. It might be reasonable to bump it up to
> > > > say 15.
> > > >
> > > > > If people run into max limit with reasonable timezone format
> > > > > strings, then
> > > > > we can up the limit.
> > > >
> > > > The conditions are more or less what is implemented, but we could do
> > > > with a couple more tweaks to improve things, like check for more or
> > > > extraneous chars within the bracket quotes, and that no characters
> > > > remain unconsumed at the end of the parse.
>
>