Re: [PATCH] Redudant initilization

Em sáb., 5 de set. de 2020 às 14:29, Tom Lane <tgl@sss.pgh.pa.us> escreveu:

> Ranier Vilela <ranier.vf@gmail.com> writes:
> > Attached is a patch I made in March/2020, but due to problems,
> > it was sent but did not make the list.
> > Would you mind taking a look?
>
> I applied some of this, but other parts had been overtaken by
> events, and there were other changes that I didn't agree with.
>
I fully agree with your judgment.


> A general comment on the sort of "dead store" that I don't think
> we should remove is where a function is trying to maintain an
> internal invariant, such as "this pointer points past the last
> data written to a buffer" or "these two variables are in sync".
> If the update happens to be the last one in the function, the
> compiler may be able to see that the store is dead ... but IMO
> it should just optimize such a store away and not get in the
> programmer's face about it.  If we manually remove the dead
> store then what we've done is broken the invariant, and we'll
> pay for that in future bugs and maintenance costs.  Somebody
> may someday want to add more code after the step in question,
> and if they fail to undo the manual optimization then they've
> got a bug.  Besides which, it's confusing when a function
> does something the same way N-1 times and then differently the

N'th time.
>
Good point.
The last store is a little strange, but the compiler will certainly
optimize.
Maintenance is expensive, and the current code should be the best example.

regards,
Ranier Vilela