Hi,
On 2022-08-24 00:32:53 -0400, Tom Lane wrote:
> Andres Freund <andres@anarazel.de> writes:
> > On 2022-08-24 00:18:27 -0400, Tom Lane wrote:
> >> But if the regression tests are triggering use of uninitialized values, how
> >> could we have failed to detect that? Either valgrind or unstable behavior
> >> should have found this ages ago.
>
> > I think it's just different criteria for when to report issues. Valgrind
> > reports uninitialized memory only when there's a conditional branch depending
> > on it or such. Whereas this seems to trigger when passing an uninitialized
> > value to a function by value, even if it's then not relied upon.
>
> If the value is not actually relied on, then it's a false positive.
My understanding is that formally speaking passing an undefined value by value
to a function is "relying on it" and undefined behaviour. Hard to believe
it'll cause any compiler go haywire and eat the computer, but ...
> I don't say we shouldn't fix it, because we routinely jump through
> hoops to silence various sorts of functionally-harmless warnings.
> But let's be clear about whether there's a real bug here.
Yea.
Greetings,
Andres Freund