Re: libpq support for NegotiateProtocolVersion

On 03/04/2025 14:55, Ranier Vilela wrote:
> Hi.
>
> Per Coverity.
>
> CID 1596094: (#1 of 1): Structurally dead code (UNREACHABLE)
> unreachable: Since the loop increment i++; is unreachable, the loop body
> will never execute more than once.

That is true, and I think we should just silence it. The loop is is
written that way in anticipation of future changes where libpq would
actually request some protocol extensions, but would be happy to
continue without server supporting them. But since we don't have any
yet, it's always an error if the server responded with any unsupported
protocol extensions.

> The code of the function *pqGetNegotiateProtocolVersion3* is a little
> confusing.
>
> I believe that the Coverity alert is valid.
> The function never returns 0.

It certainly does. It returns 0 when connecting to a pre-v18 server,
with the "max_protocol_version=3.2" option. In that case, the local
variable "num" is 0, the loop never executes, and the function returns 0.

--
Heikki Linnakangas
Neon (https://neon.tech)