On Sat, 7 Nov 2009, Constantine Sapuntzakis wrote:

>> If a getaddrinfo() or a gethostbyname_r() implementation anywhere is
>> unsafe, we already should have problems since libcurl is claimed to be
>> thread-safe already when using those functions and it has used them for
>> many years without problems.
>
> That's assuming the client program is threaded. Perhaps on Unix, people
> mostly use curl in a single thread per process (curl executable, Apache).

I think single-threaded is the most common case, yes, but a large number of
users use libcurl multi-threaded in various ways. If the standard name
resolving ways we use wouldn't be thread-safe, our users would have suffered
and we have *never* seen it happen.

But it could also be a sign that users of multi-threaded libcurl are on
operating systems that do these things right.

> A gethostbyname_r() that's thread unsafe would be a horrible hack. I would
> hope such setups are exceedingly rare.

I'd claim that getaddrinfo() done thread unsafe is a horrible hack as well.
And in fact
http://www.opengroup.org/onlinepubs/009695399/functions/getaddrinfo.html
clearly states that:

   "The freeaddrinfo() and getaddrinfo() functions shall be thread-safe."

At least that means that such implementations aren't followin the spec - but
yeah I know, that doesn't help us much...

>> Can anyone mention a getaddrinfo() or a gethostbyname_r() implementation
>> that isn't thread-safe?
>
> In many of the BSDs getaddrinfo() was not thread safe.

Ugh! Hm. Wasn't that back in the old days when they also basically had no
multi-threading? (Assuming they even have decent threading today, which I'm
not sure of.) I found docs online claiming that FreeBSD for example had this
problem fixed back in 2004.

I also found documents about ecos not having a thread-safe getaddrinfo().

So it looks our configure script should check getaddrinfo() for
thread-safeness no matter what. How annoying.

-- 
  / daniel.haxx.se
-------------------------------------------------------------------
List admin: http://cool.haxx.se/list/listinfo/curl-library
Etiquette:  http://curl.haxx.se/mail/etiquette.html