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X-Authentication-Warning: slinky.cs.nyu.edu: pechtcha owned process doing -bs
Date: Mon, 29 Sep 2003 09:32:08 -0400 (EDT)
From: Igor Pechtchanski <pechtcha AT cs DOT nyu DOT edu>
Reply-To: cygwin AT cygwin DOT com
To: Gerry Reno <grenoml AT yahoo DOT com>
cc: cygwin AT cygwin DOT com
Subject: Re: gcc 3.3.1 problem
In-Reply-To: <20030929073422.95559.qmail@web14404.mail.yahoo.com>
Message-ID: <Pine.GSO.4.56.0309290929560.3193@slinky.cs.nyu.edu>
References: <20030929073422 DOT 95559 DOT qmail AT web14404 DOT mail DOT yahoo DOT com>
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On Mon, 29 Sep 2003, Gerry Reno wrote:

>   I'm having a problem with gcc 3.3.1.  Here is a sample program that
> demos the problem:
>
> // test.c
> #include <stdio.h>
> #include <windows.h>
>
> typedef struct abc {
>   HANDLE h1;
>   HANDLE h2;
> } XYZ;
>
> XYZ * somefunc () {
>   XYZ xyz;
>   XYZ *ptr = &xyz;
>
>   ptr->h1 = (HANDLE) 99;
>   ptr->h2 = (HANDLE) 88;
>
> printf("somefunc: ptr->h1 = %d\n",ptr->h1);
> printf("somefunc: ptr->h2 = %d\n",ptr->h2);
>
>   return (ptr);
> }
>
> int main(void) {
>   XYZ *ptr2;
>
>   ptr2 = somefunc ();
> printf("main: ptr2->h1 = %d\n",ptr2->h1);
> printf("main: ptr2->h2 = %d\n",ptr2->h2);
>
> }
> ------------------------------
>
> -- results --
> somefunc: ptr->h1 = 99
> somefunc: ptr->h2 = 88
> main: ptr2->h1 = 99
> main: ptr2->h2 = 99
>
>
>   And sometimes it will give me really large values for main: ptr2-h2
> like 4043574.
>
> ----------------------
> Env:
> Cygwin 1.5.5
> gcc 3.3.1
>
> =====
> Gerry Reno

Tsk, tsk, tsk, Gerry, you should really know better than to return a
pointer to an automatic variable (a struct, in this case).  That's one of
the things K&R explicitly warns against.  You're lucky it worked at all in
the previous versions of gcc.  If you want to return a pointer to
something from a function, either make it global, or static, or allocate
it dynamically.
	Igor
-- 
				http://cs.nyu.edu/~pechtcha/
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     |,4-  ) )-,_. ,\ (  `'-'		Igor Pechtchanski, Ph.D.
    '---''(_/--'  `-'\_) fL	a.k.a JaguaR-R-R-r-r-r-.-.-.  Meow!

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