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Date: Sat, 25 Sep 2004 15:31:33 -0400 (EDT)
From: Igor Pechtchanski <pechtcha AT cs DOT nyu DOT edu>
Reply-To: cygwin AT cygwin DOT com
To: Peter Dons Tychsen <donpedro AT tdcadsl DOT dk>
cc: cygwin AT cygwin DOT com
Subject: Re: Fw: 1.5.11 bug in WEXITSTATUS() macro (wait.h)
In-Reply-To: <00f001c4a32f$d724a570$0200000a@donpedro>
Message-ID: <Pine.GSO.4.61.0409251528570.630@slinky.cs.nyu.edu>
References: <00f001c4a32f$d724a570$0200000a AT donpedro>
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On Sat, 25 Sep 2004, Peter Dons Tychsen wrote:

> Hello.
>
> The WEXITSTATUS is a bit buggy. (wait.h)
>
> The macro extracts information gained from a call to waitpid() (and others).
> The information it extracts is the status of the completed process (8 bit
> signed value).
>
> The problem is that the macro does not cast the value to a signed integer
> (like other systems do), which can cause the value to be incorrectly
> interpreted (breaks some programs).
>
> The following fails:
>
> // Wait for processes to complete
> if(waitpid(pid, &status, 0) == pid)
> {
>   // Check return value for failure (-1)
>   if(WEXITSTATUS(status) == -1)
>   {
>     /* We will never get here, as the macro returns 255 if the process exited with -1 */
>   }
> }
>
> The problem can be fixed by changing the macro from:
>
> #define WEXITSTATUS(w) (((w) >> 8) & 0xff)
>
> To:
>
> #define WEXITSTATUS(w) ((signed char)(((w) >> 8) & 0xff))
>
> It is kind of weird that no one has discovered this boo-boo before :-(
> Hope it is not me who is boo-boo. :-)
>
> /Peter

This was reported back in July.  Google for '"negative exit status"
site:cygwin.com' for the full thread.
	Igor
-- 
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     |,4-  ) )-,_. ,\ (  `'-'		Igor Pechtchanski, Ph.D.
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