Re: pg_controldata doesn't report 64/32bit?

Gregory Stark <stark(at)enterprisedb(dot)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
* machine of different endianness, but we do need to worry about MAXALIGN
* and floating-point format. (Note: storage layout nominally also
* depends on SHORTALIGN and INTALIGN, but in practice these are the same
* on all architectures of 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