[fpc-devel] Const optimization is a serious bug

[Martin]

On 05/07/2011 18:27, José Mejuto wrote:
> This changes should be detected ?
>
> var
>    a: ansistring;
>
> procedure DoSomehting(const v: ansistring);
> begin
>    a[1]:='a';
> end;
>
> begin
>    a:='b';
>    DoSomething(a);
> end.

It would probably best to detect this  changes too.
But since it would be more of a performance penality, i would like to 
see it as an option of it's own. (even if only used in 
debug/development, the penalty could be severe enough to hinter development)

Why detect those?
Well at current such a trick could actually be used intentionally. and 
it could work well, if done correctly.

But I expect this behaviour is not defined/documented.
If the optimizer improves, the optimizer could do thinks that would make 
any code fail, if it uses such tricks. So better to let people know now, 
that it isn't safe.