Re: documentation inconsistent re: alignment

Chapman Flack <chap@anastigmatix.net> writes:
> On 10/20/19 14:47, Tom Lane wrote:
>> Probably the statement in CREATE TYPE is too strong.  There are, I
>> believe, still machines in the buildfarm where maxalign is just 4.

> So just closing the circle on this, the low-down seems to be that
> the alignments called s, i, and d (by pg_type), and int2, int4, and
> double (by CREATE TYPE) refer to the machine values configure picks
> for ALIGNOF_SHORT, ALIGNOF_INT, and ALIGNOF_DOUBLE, respectively.

Right.

> And while configure also defines an ALIGNOF_LONG, and there are
> LONGALIGN macros in c.h that use it, that one isn't a choice when
> creating a type, presumably because it's never been usefully different
> on any interesting platform?

The problem with "long int" is that it's 32 bits on some platforms
and 64 bits on others, so it's not terribly useful as a basis for
a user-visible SQL type.  That's why it's not accounted for in the
typalign options.  I think ALIGNOF_LONG is just there for completeness'
sake --- it doesn't look to me like we actually use that, or LONGALIGN,
anyplace.

            regards, tom lane