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From: "Dan Haynes" <haynes AT anchorgaming DOT com>
To: "Brian J Ball" <bjball AT sep DOT com>, <cygwin AT sourceware DOT cygnus DOT com>
Subject: RE: B 20: Post incrementers in arrays as function arguments
Date: Thu, 17 Aug 2000 16:25:30 -0600
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Try using PC Lint to find the bugs in your code.

(hint - array[i++]=i depends on order of evaluation and is totally bogus C
code)

:-)

  Dan


> -----Original Message-----
> From: cygwin-owner AT sources DOT redhat DOT com
> [mailto:cygwin-owner AT sources DOT redhat DOT com]On Behalf Of Brian J Ball
> Sent: Thursday, August 17, 2000 4:07 PM
> To: cygwin AT sourceware DOT cygnus DOT com
> Subject: B 20: Post incrementers in arrays as function arguments
>
>
> 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
>
>
> --
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>


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