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Date: Mon, 10 Feb 2003 21:51:57 -0500
From: Christopher Faylor <cgf AT redhat DOT com>
To: cygwin AT cygwin DOT com
Subject: Re: gethostbyname thread-safe?
Message-ID: <20030211025157.GA14792@redhat.com>
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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

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