Re: bad edge created in CFG ?

["Seongbae Park" <seongbae dot park at gmail dot com>]

On 3/14/07, Sunzir Deepur <sunzird@gmail.com> wrote:
> Hello,
>
> I have used -da and -dv to produce vcg files of the CFG of this simple program:
>
> int main(int argc, char**argv)
> {
>         if(argc)
>                 printf("positive\n");
>         else
>                 printf("zero\n");
>
>         return 0;
> }
>
> I have expected to get a CFG as follows:
>
>                  -----------
>                  | BB 0 |
>                  -----------
>               /              \
>    -----------                 -----------
>    | BB 1 |                  | BB 2 |
>    -----------                 -----------
>               \              /
>                  -----------
>                  | END |
>                  -----------
>
> But instead, I was surprised to get this CFG:
>
>                  -----------
>                  | BB 0 |
>                  -----------
>               /              \
>    -----------                 -----------
>    | BB 1 |  ------------> | BB 2 |
>    -----------                 -----------
>               \              /
>                  -----------
>                  | END |
>                  -----------
>
> as if one case of the "if" can lead to the other !
>
> Can someone please explain to me why it is so ?
>
> I am attaching the VCG representation, the VCG text file, and the original
> test program..
>
> Thank You
> sunzir

I don't know what kind of vcg viewer/converter you're using,
but set it to ignore class 3 edges - you'll get what you expected.

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