Andres Freund <andres@2ndquadrant.com> writes:
>>> It does *not* combine elog_start and elog_finish into one function if
>>> varargs are available although that brings a rather measurable
>>> size/performance benefit.
>> Since you've apparently already done the measurement: how much?
>> It would be a bit tedious to support two different infrastructures for
>> elog(), but if it's a big enough win maybe we should.
> Imo its pretty definitely a big enough win. So big I have a hard time
> believing it can be true without negative effects somewhere else.
Well, actually there's a pretty serious negative effect here, which is
that when it's implemented this way it's impossible to save errno for %m
before the elog argument list is evaluated. So I think this is a no-go.
We've always had the contract that functions in the argument list could
stomp on errno without care.
If we switch to a do-while macro expansion it'd be possible to do
something like
do { int save_errno = errno; int elevel = whatever;
elog_internal( save_errno, elevel, fmt, __VA__ARGS__ );} while (0);
but this would almost certainly result in more code bloat not less,
since call sites would now be responsible for fetching errno.
regards, tom lane