Gregory Stark <stark@enterprisedb.com> writes:
> We could always tighten this up a bit by listing the alignment of a
> handful of built-in data types but I suppose there will always be
> holes in this area anyways.
In theory yeah, but the note in pg_control.h still applies to every
platform I've heard of:
* This data is used to check for hardware-architecture compatibility of * the database and the backend
executable. We need not check endianness * explicitly, since the pg_control version will surely look wrong to a *
machineof different endianness, but we do need to worry about MAXALIGN * and floating-point format. (Note: storage
layoutnominally also * depends on SHORTALIGN and INTALIGN, but in practice these are the same * on all
architecturesof interest.)
The main risk we are taking is in the assumption that int64 and float8
have the same alignment requirement, ie DOUBLEALIGN. Which is probably
a fairly safe thing in reality. Also, we've so far avoided using either
type in the system catalogs, which takes away one of the possible
failure modes (that the C compiler's alignment of struct fields might
vary from what we think the type needs).
regards, tom lane
