Re: [PATCH] apply: Avoid ambiguous pointer provenance for CHERI/Arm's Morello

> 
> On Wed, Jan 05, 2022 at 01:23:10PM +0000, Jessica Clarke wrote:
>> [...] In most cases this is clear, as normally at least one operand is
>> provably a plain integer, but if both operands are uintptr_t and have
>> no indication they're just plain integers then it is ambiguous, and
>> the current implementation will arbitrarily, but deterministically,
>> pick the left-hand side, due to empirical evidence that it is more
>> likely to be correct.
> 
> Wouldn't a simpler, less invasive fix be to instead write the expression
> so that the left-hand operand is a pointer? IOW, shouldn't the following
> work (with no other changes):
> 
>    ent->util = (void *)((uintptr_t)what | ent->util);
> 
> ?
> 
> (I dropped the explicit cast on the right-hand side, since ent->util is
> already a uintptr_t, and the left-hand side has an explicit cast, so
> there isn't any type promotion going on here).