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Date: Wed, 5 May 2004 18:40:13 -0400 (EDT)
From: Steve Thompson <smt AT vgersoft DOT com>
Reply-To: smt AT vgersoft DOT com
To: cygwin AT cygwin DOT com
Subject: Re: pthreads and sockets - Cannot register window class error
In-Reply-To: <20040505210340.GB321@coe.bosbc.com>
Message-ID: <Pine.LNX.4.58.0405051838240.6708@honker.vgersoft.com>
References: <4098760F DOT CDB4F630 AT hot DOT pl> <4098E04B DOT 34D2866B AT dessent DOT net> <20040505210340 DOT GB321 AT coe DOT bosbc DOT com>
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On Wed, 5 May 2004, Christopher Faylor wrote:

> On Wed, May 05, 2004 at 05:38:35AM -0700, Brian Dessent wrote:
> >Jacek Trzmiel wrote:
> >
> >> void test()
> >> {
> >>     /* go find out about the desired host machine */
> >>     struct hostent *he = gethostbyname(HOST);
> >>     if (he == 0) {
> >>         perror("gethostbyname");
> >>         exit(1);
> >>     }
> >
> >Just a wild guess, but gethostbyname() is probably not reentrant and
> >can't be called from threads like that.
>
> Unless HOST is a numeric IP address, gethostbyname should be properly
> reentrant.  The only time gethostbyname is not thread safe is when it is
> resolving a numeric IP.

I believe that gethostbyname(), since it is returning a pointer to a
statically allocated structure, cannot be thread safe under any
circumstances. I always wrap it with a mutex until I'm done with the
hostent structure.

Steve

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