[PATCH 2/2] newlib/libc/time/tzset_r.c(_tzset_unlocked_r): POSIX angle bracket <> support
Brian Inglis
Brian.Inglis@SystematicSw.ab.ca
Tue Mar 22 17:35:29 GMT 2022
On 2022-03-21 10:07, jdoubleu wrote:
> Hi,
>
> On 2/25/2022 5:39 PM, Brian Inglis wrote:
>>
>> define POSIX specified minimum TZ abbr size 3 TZNAME_MIN
>> use limits.h TZNAME_MAX, _POSIX_TZNAME_MAX, unistd.h
>> sysconf(_SC_TZNAME_MAX)
>> issue error if no symbols defined (document fallback value in case
>> required)
>> allow POSIX angle bracket < > quoted signed alphanumeric tz abbr e.g.
>> <MESZ+0330>
>> allow POSIX unquoted alphabetic tz abbr e.g. MESZ
>> apply same changes for DST tz abbr
>> ---
>> newlib/libc/time/tzset_r.c | 74 ++++++++++++++++++++++++++++++++------
>> 1 file changed, 64 insertions(+), 10 deletions(-)
>>
>
>> + /* quit if no items, too few or too many chars, or no close
>> quote '>' */
>> + if (sscanf (tzenv, "%10[-+0-9A-Za-z]%n", __tzname_std, &n) <= 0
>> + || n < TZNAME_MIN || TZNAME_MAX < n || '>' != tzenv[n])
>> + return;
>
> Is it safe to use the minus (-) as first char in the sscanf format set:
> "%10[-+0-9A-Za-z]%n"?
The first and last positions are the only generally safe places to
specify the hyphen/minus as part of the set and not part of a range.
> Newlib's sscanf docs states
> (https://sourceware.org/newlib/libc.html#sscanf):
>> There is also a range facility which you can use as a shortcut. %[0-9]
>> matches all decimal digits. The hyphen must not be the first or last
>> character in the set.
I read that as saying that the first or last character within the
brackets can not be the hyphen a la [--@] or [!--], as it then stands
alone, and is not treated as part of a range, allowing the hyphen/minus
to be one of the characters matched, as is also the case when the first
and last characters are not lexically ordered e.g. [z-a] == z|-|a.
I presume this is a lexer limitation to allow safe and efficient range
and set scanning.
--
Take care. Thanks, Brian Inglis, Calgary, Alberta, Canada
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