On 2016-02-10 16:19, Tom Lane wrote:
> I wrote:
>> Artur Zakirov <a.zakirov@postgrespro.ru> writes:
>>> I think this is not a bug. It is a normal behavior. In Mac OS
>>> sscanf()
>>> with the %s format reads the string one character at a time. The size
>>> of
>>> letter 'х' is 2. And sscanf() separate it into two wrong characters.
>
>> That argument might be convincing if OSX behaved that way for all
>> multibyte characters, but it doesn't seem to be doing that. Why is
>> only 'х' affected?
>
> I looked into the OS X sources, and found that indeed you are right:
> *scanf processes the input a byte at a time, and applies isspace() to
> each byte separately, even when the locale is such that that's a
> clearly
> insane thing to do. Since this code was derived from FreeBSD, FreeBSD
> has or once had the same issue. (A look at the freebsd project on
> github
> says it still does, assuming that's the authoritative repo.) Not sure
> about other BSDen.
>
> I also verified that in UTF8-based locales, isspace() thinks that 0x85
> and
> 0xA0, and no other high-bit-set values, are spaces. Not sure exactly
> why
> it thinks that, but that explains why 'х' fails when adjacent code
> points
> don't.
>
> So apparently the coding rule we have to adopt is "don't use *scanf()
> on data that might contain multibyte characters". (There might be
> corner
> cases where it'd work all right for conversion specifiers other than
> %s,
> but probably you might as well just use strtol and friends in such
> cases.)
> Ugh.
>
> regards, tom lane
Definitive FreeBSD Sources:
https://svnweb.freebsd.org/base/
--
Larry Rosenman http://www.lerctr.org/~ler
Phone: +1 214-642-9640 E-Mail: ler@lerctr.org
US Mail: 7011 W Parmer Ln, Apt 1115, Austin, TX 78729-6961