On 10/20/19 14:47, Tom Lane wrote: > Chapman Flack <c...@anastigmatix.net> writes: >> data type. The allowed values equate to alignment on 1, 2, 4, or 8 byte >> boundaries." >> ... while the documentation for pg_type has: >> "c = char alignment, i.e., no alignment needed. >> s = short alignment (2 bytes on most machines). >> i = int alignment (4 bytes on most machines). >> d = double alignment (8 bytes on many machines, but by no means all)." > > 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. 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? Regards, -Chap