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Date: Thu, 17 Aug 2000 18:16:10 -0400
To: "Brian J Ball" <bjball AT sep DOT com>,
        "cygwin AT sourceware DOT cygnus DOT com" <cygwin AT hotpop DOT com>
From: "Larry Hall (RFK Partners, Inc)" <lhall AT rfk DOT com>
Subject: Re: B 20: Post incrementers in arrays as function arguments
In-Reply-To: <NEBBINHAMKDDGPELHGEPAEBNCAAA.bjball@sep.com>
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At 06:06 PM 8/17/2000, Brian J Ball wrote:
>This code has produced 3 different results on 4 systems.
>The second result was on the Cygwin B20 system
>
>#include <stdio.h>
>int i;
>void do_increment(int array[]){
>    for(i;i<10;){
>       array[i++]=i;
>    }
>}
>void print_array(int a, int b, int c){
>   printf("%i\t%i\t%i\n",a,b,c);
>}
>
>main(void){
>    int array[10];
>    i=0;
>    do_increment(array);
>    i=0;
>    /*  This use of var++ in a function call is
>         unpredictable */
>    print_array(array[i++],array[i++],array[i++]);
>}
>
>B20 (gcc 2.91.57) on NT 4 output:
>2       1       0
>
>The only workarround is to know how your system behaves or define temp
>variables.  a similar function call was used by a client, and our tests
>showed it failing, since our tester was using VStudio.  The client was using
>the Tasking complier.
>However, this works on some platforms and could become an error in porting
>software.  As to patching...  I haven't tried the latest gcc, and I'm not
>versed in compiler theory.
>
>I was not able to find information about this on GNATS or in the cygnus
>mailing list archives.
>
>gcc 2.8.0 on solaris (expected answer)
>0       1       2
>
>Microsoft Visual Studio 6
>0       0       0
>
>Our fourth platform was a Tasking compiler for a Seimens micro
>It behaved as we expected (no stdio though).
>
>--
>Brian Ball
>Software Engineer - SEP
>mailto:bjball AT sep DOT com



And what's the reason that you expect that the results would be predictable
here?



Larry Hall                              lhall AT rfk DOT com
RFK Partners, Inc.                      http://www.rfk.com
118 Washington Street                   (508) 893-9779 - RFK Office
Holliston, MA 01746                     (508) 893-9889 - FAX



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