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Re: gethostbyname thread-safe?
- From: Igor Pechtchanski <pechtcha at cs dot nyu dot edu>
- To: cygwin at cygwin dot com
- Date: Mon, 10 Feb 2003 22:50:04 -0500 (EST)
- Subject: Re: gethostbyname thread-safe?
- Reply-to: cygwin at cygwin dot com
On Mon, 10 Feb 2003, Christopher Faylor wrote:
> On Mon, Feb 10, 2003 at 09:36:53PM -0500, Igor Pechtchanski wrote:
> >On Mon, 10 Feb 2003, Ajay Nerurkar wrote:
> >
> >> Is Cygwin's gethostbyname thread-safe? From a web search I got the
> >> impression that it wasn't and also that Cygwin does not have its
> >> reentrant version gethostbyname_r. So, what does one do?
> >>
> >> Ajay
> >
> >Ajay,
> >
> >Looking at the code (src/winsup/cygwin/net.cc),
> >
> >964:#ifdef _MT_SAFE
> >965:#define hostent_buf _reent_winsup ()->_hostent_buf
> >966:#else
> >967:static struct hostent *hostent_buf = NULL;
> >968:#endif
> >969:
> >970:/* exported as gethostbyname: standards? */
> >971:extern "C" struct hostent *
> >972:cygwin_gethostbyname (const char *name)
> >
> >you can see that there is a provision for reentrancy. However,
> >src/winsup/cygwin/acconfig.h #undef's _MT_SAFE. OpenGroup's specification
> >(<http://www.opengroup.org/onlinepubs/007904975/functions/gethostbyaddr.html>)
> >says that "The gethostbyname() function need not be reentrant."
> >See <http://wcug.wwu.edu/lists/ipng/199710/msg00002.html> for a good
> >discussion of gethostbyname() thread-safety issues.
>
> _MT_SAFE is always set to 1 in config.h unless the dll is built with
> --disable-threadsafe. I don't know that this option even works, though.
>
> So gethostbyname should be threadsafe.
>
> cgf
Yeah, I started a build with a full intention of searching the result for
any overrides of _MT_SAFE, but got too impatient and sent the message
before the build finished. Apologies for the misinformation.
Igor
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