On 2020-Sep-03, Tom Lane wrote:
> Alvaro Herrera <alvherre@2ndquadrant.com> writes:
> > Well, the intention there is to cast the first operand (which is uint32)
> > so that it turns into signed 64-bits; the subtraction then occurs in 64
> > bit arithmetic normally. If I let the subtraction occur in 32-bit width
> > unsigned, the result might overflow 32 bits.
>
> Uh ... is it really possible for gotlen to be more than total_len?
> (I've not looked at the surrounding code here, but that seems weird.)
Well, as I understand, total_len comes from one page, and gotlen comes
from the continuation record(s) in the next page(s) of WAL. So if
things are messed up, it could happen. (This *is* the code that
validates the record, so it can't make too many assumptions.)
--
Álvaro Herrera https://www.2ndQuadrant.com/
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