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Message-ID: <bd33e92c-e57f-40b3-a069-560526996036@iki.fi>
Date: Mon, 30 Mar 2026 22:34:07 +0300
From: Hannu Nyman <hannu.nyman@....fi>
To: Rich Felker <dalias@...c.org>, musl@...ts.openwall.com
Cc: Shiji Yang <yangshiji66@...look.com>
Subject: Re: strptime in 1.2.6 - is tzname[0/1] guaranteed to be set?
Rich Felker kirjoitti 30.3.2026 klo 22.27:
> On Mon, Mar 30, 2026 at 10:05:33PM +0300, Hannu Nyman wrote:
>> Rich Felker kirjoitti 23.3.2026 klo 19.38:
>>> On Mon, Mar 23, 2026 at 06:38:07PM +0200, Hannu Nyman wrote:
>>>> Is a new patch version still coming, or was the last one ("the attached is
>>>> good") already fine?
>>> Here's a fixed one,
>>>
>> Hello Rich,
>>
>> the current patch version seems to be still somewhat problematic regarding
>> the fallback 'else' part.
>>
>> + } else {
>> + /* FIXME: is this supposed to be an error? */
>> + while ((**s|32)-'a' <= 'z'-'a') ++*s;
>> + }
>>
>> To my understanding the part is supposed to consume the alpha chars of the
>> passed timezone name string and then enable further parsing of the total
>> date stamp with other possible %-modifiers. Apparently the current check
>> fails to stop at null \0 and may continue further, causing segmentation
>> error at some point.
> Oh, it's a signedness error. Changing it to
>
> while ((**s|32)-'a' < 26U) ++*s;
>
> would fix it. But isalpha might be a nicer approach, yes, especially
> since we have the macro that does exactly that anyway.
>
> Rich
After further thought, "isalpha" might actually be wrong, as the quoted
POSIX timezone format like <-02>2 are also valid.
(Reference to our discussion in 2016 ;-)
https://www.openwall.com/lists/musl/2016/03/31/9
http://pubs.opengroup.org/onlinepubs/9699919799/basedefs/V1_chap08.html#tag_08_03
In the quoted form, the first character shall be the <less-than-sign> ( '<' )
character and the last character shall be the <greater-than-sign> ( '>' )
character. All characters between these quoting characters shall be
alphanumeric characters from the portable character set in the current
locale, the <plus-sign> ( '+' ) character, or the <hyphen-minus> ( '-' )
character. The /std/ and /dst/ fields in this case shall not include the
quoting characters.
Then the STD string might be "-02" and DST would be empty. So, isalpha would
wrongly fail on "-02" which could quite legitimately exist there.
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