Re: gai_strerror() is not thread-safe on Windows

At Thu, 7 Dec 2023 09:43:37 +1300, Thomas Munro <thomas.munro@gmail.com> wrote in 
> On Tue, Dec 5, 2023 at 3:43 PM Kyotaro Horiguchi
> <horikyota.ntt@gmail.com> wrote:
> > Windows' gai_strerror outputs messages that correspond to the language
> > environment. Similarly, I think that the messages that the messages
> > returned by our version should be translatable.
> 
> Hmm, that is a good point.  Wow, POSIX has given us a terrible
> interface here, in terms of resource management.  Let's see what glibc
> does:
>
> https://github.com/lattera/glibc/blob/master/sysdeps/posix/gai_strerror.c
> https://github.com/lattera/glibc/blob/master/sysdeps/posix/gai_strerror-strs.h

It is quite a sight for sore eyes...

> It doesn't look like it knows about locales at all.  And a test
> program seems to confirm:
..
>     setlocale(LC_MESSAGES, "ja_JP.UTF-8");
>     printf("%s\n", gai_strerror(EAI_MEMORY));
> 
> That prints:
> 
> Memory allocation failure
> 
> FreeBSD tries harder, and prints:
> 
> メモリ割り当て失敗
> 
> We can see that it has a thread-local variable that holds a copy of
> that localised string until the next call to gai_strerror() in the
> same thread:
> 
> https://github.com/freebsd/freebsd-src/blob/main/lib/libc/net/gai_strerror.c
> https://github.com/freebsd/freebsd-src/blob/main/lib/libc/nls/ja_JP.UTF-8.msg
> 
> FreeBSD's message catalogues would provide a read-made source of
> translations, bu... hmm, if glibc doesn't bother and the POSIX
> interface is unhelpful and Windows' own implementation is so willfully
> unusable, I don't really feel inclined to build a whole thread-local
> cache thing on our side just to support this mess.

I agree, I wouldn't want to do it either.

> So I think we should just hard-code the error messages in English and
> move on.  However, English is my language so perhaps I should abstain
> and leave it to others to decide how important that is.

I also think that would be a good way.

> > These messages may add extra line-end periods to the parent (or
> > cotaining) messages when appended. This looks as follows.
> >
> > (auth.c:517 : errdetail_log() : sub (detail) message)
> > > Could not translate client host name "hoge" to IP address: An address incompatible with the requested protocol
wasused..
 
> >
> > (hba.c:1562 : errmsg() : main message)
> > > invalid IP address "192.0.2.1": This is usually a temporary error during hostname resolution and means that the
localserver did not receive a response from an authoritative server.
 
> >
> > When I first saw the first version, I thought it would be better to
> > use Windows' own messages, just like you did. However, considering the
> > content of the message above, wouldn't it be better to adhere to
> > Linux-style messages overall?
> 
> Yeah, I agree that either the glibc or the FreeBSD messages would be
> better than those now that I've seen them.  They are short and sweet.
> 
> > A slightly subtler point is that the second example seems to have a
> > misalignment between the descriptions before and after the colon, but
> > do you think it's not something to be concerned about to this extent?
> 
> I didn't understand what you meant here.

If it was just a temporary error that couldn't be resolved, it doesn't
mean that the IP address is invalid. If such a cause is possible, then
probabyly an error message saying "failed to resolve" would be more
appropriate. However, I wrote it meaning that there is no need to go
to great length to ensure consistency with this message.

regards.

-- 
Kyotaro Horiguchi
NTT Open Source Software Center