Re: safer node casting

Andres Freund <andres(at)anarazel(dot)de> writes:
> On 2016-12-31 12:08:22 -0500, Peter Eisentraut wrote:
>> This is inspired by the dynamic_cast operator in C++, but follows the
>> syntax of the well-known makeNode() macro.

> The analogy to dynamic_cast goes only so far, because we don't actually
> support inheritance. I.e. in c++ we could successfully cast SeqScanState to a
> PlanState, ScanState and SeqScanState - but with our model only
> SeqScanState can be checked.

Yeah, I was thinking about that earlier --- this can only be used to cast
to a concrete node type, not one of the "abstract" types like Plan * or
Expr *. Not sure if that's worth worrying about though; I don't think
I've ever seen actual bugs in PG code from casting the wrong thing in that
direction. For the most part, passing the wrong thing would end up firing
a default: case in a switch, or some such, so we already do have some
defenses for that direction.

regards, tom lane