Re: Portability concerns over pq_sendbyte?

From: Andres Freund <andres(at)anarazel(dot)de>
To: Andrew Gierth <andrew(at)tao11(dot)riddles(dot)org(dot)uk>
Cc: pgsql-hackers(at)postgresql(dot)org
Subject: Re: Portability concerns over pq_sendbyte?
Date: 2018-06-13 18:50:11
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On 2018-05-24 18:13:23 +0100, Andrew Gierth wrote:
> In PG11, pq_sendbyte got changed from taking an int parameter to taking
> an int8.
> While that seems to work in general, it does mean that there are now
> several places in the code that do the equivalent of:
> unsigned char x = 128;
> pq_sendbyte(&buf, x);
> which I believe is not well-defined since pq_sendbyte takes an int8, and
> conversions of unrepresentable values to _signed_ integer types are
> (iirc) implementation-dependent.

It's not implementation defined in postgres' dialect of C - we rely on
accurate signed->unsigned conversions in a number of places. But I
doin't think we should increase that reliance, so I think you're right
we should do something about this.

> There are also some cases where pq_sendint16 is being called for an
> unsigned value or a value that might exceed 32767.

Hm, which case were you thinking of here? The calls usually are exactly
the types that the wire protocol expects, no?

> Would it be better for these to take unsigned values, or have unsigned
> variants?

I wonder if we should just take 'int' out of the name. Say,
pg_send{8,16,32,64}(unsigned ...).


Andres Freund

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