Re: [PATCH] PR 78534 Change character length from int to size_t

[Andre Vehreschild <vehre at gmx dot de>]

> Here p is the character variable, and _p is the charlen. My guess is
> that the problem is that with -O1 it sees that the second memmove
> would overflow p, but it doesn't realize that branch is never taken.
> Cranking up the optimization level to -O2 and beyond makes it realize
> it, and thus the warning disappears.
> 
> Perhaps one could rewrite that to something like
> 
> __builtin_memmove ((void *) *p, (void *) &"12345679"[1]{lb: 1 sz: 1},
> MIN_EXPR<(unsigned long) D.3598,8>);
> if ((unsigned long) D.3598 > 8)
>   {
>   __builtin_memset ((void*) *p + 8, 32, D.3599);
>   }

That looks interesting. It assumes though, that D.3598 will *never* be
negative. Because when it is negative 8 characters (cast to unsigned makes the
negative number huge) will be copied, while in the former code memmove will
reject the coping of a negative number of bytes. Therefore I propose to omit
the cast in the MIN_EXPR and make the constant 8 signed, too. That should
comply and mimick the former behavior more closely. What do you think? Who's
going to try?

-- 
Andre Vehreschild * Email: vehre ad gmx dot de