Re: Ariane 5 failure (Was: Size code Ada and C)

[pfk@schnecke.offl.uni-jena.de (Frank Klemm)]

On 10 Jul 1998 08:20:16 GMT, John McCabe <john@assen.demon.co.uk> wrote:
>Dale Stanbrough <dale@goanna.cs.rmit.edu.au> wrote:
>>"You can always disable range checking in Ada, but was this the idea of
>>Ada ???"
>
>>The idea in Ada is that it gives you _more_ freedom than C. You have the 
>>freedom to check or not to check.
>
>>The only option you have with C is to accept array index overflows, and
>>try and find them in the debugger.
>
>And then what? Put in checks manually that you could have done in the 
>first place? As this would be an alternative option, your suggestion 
>being the only option is not quite true.
>
Manually checks are *NO* checks. For those who can read C:

double x[1000];

void sinusize(double *p, size_t len)
  {
    while (len--)
      *p = sin (*p), p++;
  }


main(...)
  {
    sinusize(x, sizeof(x));
    
    return 0;
  }

Array address and length are stored independendly, i.e. it is *very* easy to make
errors in the range checking. An array must be more than a pointer to enable range checking,
C can't do this.

-- 
Frank Klemm

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