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Date: Mon, 17 May 2004 10:48:42 -0500
From: Brian Ford <ford AT vss DOT fsi DOT com>
Reply-To: cygwin AT cygwin DOT com
To: John William <jw2357 AT hotmail DOT com>
cc: cygwin AT cygwin DOT com
Subject: Re: CYGWIN 1.5.9-1 - Is vprintf() not thread safe?
In-Reply-To: <BAY1-F125a9hoUHAQfN00018dc6@hotmail.com>
Message-ID: <Pine.CYG.4.58.0405171045270.2712@fordpc.vss.fsi.com>
References: <BAY1-F125a9hoUHAQfN00018dc6 AT hotmail DOT com>
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On Sun, 16 May 2004, John William wrote:

> I'm having problems with a program that uses vprintf() to show error
> messages. The program works fine when run as a single-threaded program. When
> compiled as a multi-threaded program, the console output of vprintf() is
> "interleaved" with output from the various threads mixed together. With a
> large number of threads, the program often drops core.
>
> Adding a pthread_mutex_lock() and ..._unlock() pair around the vprintf()
> makes it work correctly and it no longer drops core.
>
> From reading the GNU docs, I had the impression that functions such as
> vprintf() were supposed to be thread safe. I have noticed that printf() also
> appears to not be thread-safe, but I haven't methodically checked all the
> related functions.

Um..., Cygwin uses newlib for its C library, so what GNU docs were you
reading?

IIRC, several thread safe stdio issues have been fixed recently, both in
Cygwin and in newlib.  Please try a recent Cygwin DLL snapshot:

http://cygwin.com/snapshots/

and report back.  Thanks.

-- 
Brian Ford
Senior Realtime Software Engineer
VITAL - Visual Simulation Systems
FlightSafety International
the best safety device in any aircraft is a well-trained pilot...

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