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From: "Jeff C," <nolongersafeto@userealemailsniff.com>
Newsgroups: comp.arch.embedded,comp.lang.ada
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Subject: Re: Certified C compilers for safety-critical embedded systems
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"Georg Bauhaus" <sb463ba@l1-hrz.uni-duisburg.de> wrote in message
news:bskd67$6me$1@a1-hrz.uni-duisburg.de...
> In comp.lang.ada Ian Bell <ian@ruffrecordsdotworldonline.co.uk> wrote:
> :James Rogers> foo : My_Array_Type;
> :>
> :> for num in 0..99 loop
> :>    foo(num) := num;
> :> end loop;
> :>
> :> All Ada compilers will correctly identify the error in the for loop.
> :> [...]
> :
> : I know nothing about ada so this is a genuine query rather than a
ctiticism.
> : The above example is fine as long as literals are used - even a C
compiler
> : could be devised to make this check - but what happens when the array
index
> : is computed?
>
> Wouldn't that become a famous compiler that finds out, at compile
> time, which value a certain variable is going to have? :-)
>
> If you want a hole in your foot, you can make one, though it might
> not be easy:


Again, tools like this do exist. One can argue over how well they work but
they do exist.
Tools like Polyspace Verifier can at times tell you statically that you have
a problem in your code.

For example the following psuedo code fragment would likely be flagged as a
potential error by polyspace

A, b : float;
C : integer;
D : array(1 .. 10) of float;

begin
 A := random_float;
 B := cos(a);
 C := integer(C * 9.0) + 1;
  D(C) := 0;
end;


while code like


A, b : float;
C : integer;
D : array(1 .. 10) of float;

begin
 A := random_float;
 B := cos(a);
 C := integer(C * 9.0) + 1;
  if C >= D'first and C <= D'last then
    D(C) := 0;
  end if;
end;


Would not generate an error during static analysis. (at least not for the
obvious error I intended to introduce in the first case ... :)

These tools exist now and have existed for some years.