Re: -funsafe-loop-optimizations

[Robert Dewar <dewar at adacore dot com>]

I apologize for breaking the thread in my last message, I guess I
was up too late last night and slipped up on my procedures. So here
is the message from me again, with proper threading:

Daniel Jacobowitz wrote:

> (because it is infinite if n is ~0).  So they aren't a "presumed
> mistake".  I think the warning would only be useful for people who were
> considering turning on the matching optimization.

But how useful? I would guess that virtually 100% of such warnings would
be false positives, in the sense that they are not warning of situations
in which the standard semantics would be fine. Let's take the example:

> void foo (unsigned int n)
> {
>   for (i = 0; i <= n; i++)
>     bar ();
> }

I simply don't believe that anyone would write this code, expecting that
in the case where n was the max value, an infinite loop would occur, and
that's just what the programmer wants.

I can easily believe that this program might have a bug, in that the function
misbehaves if n is the max value, but in that case, the warning is useful
in any case, regardless of the proposed "optimization".