question on bits32 wraparound check

So there's a minor issue on Takahiro-san fillfactor-on-toast patch,
which is that it does not hand out the last possible "kind" value. This
is a bits32 field, so at least theoretically on some platforms it will
be wider than 32 while on others it will be exactly 32. I'm wondering
if this is the correct way to check for wraparound:

relopt_kind
add_reloption_kind(void)
{
relopt_kind kind;

/* wraparound check */
if (last_assigned_kind > RELOPT_KIND_MAX ||
last_assigned_kind == 0)
ereport(ERROR,
(errcode(ERRCODE_PROGRAM_LIMIT_EXCEEDED),
errmsg("user-defined relation parameter types limit exceeded")));

kind = (relopt_kind) last_assigned_kind;
last_assigned_kind <<= 1;
return kind;
}

Fixing this I'm ready to commit this patch.

--
Alvaro Herrera http://www.CommandPrompt.com/
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