Re: [PATCH 04/16] Add embedded list interface (header only)

On Friday, June 22, 2012 04:18:35 PM Tom Lane wrote:
> Andres Freund <andres(at)2ndquadrant(dot)com> writes:
> > On Friday, June 22, 2012 12:23:57 AM Peter Geoghegan wrote:
> >> Why are you using the stdlib's <assert.h>? Why have you used the
> >> NDEBUG macro rather than USE_ASSERT_CHECKING? This might make sense if
> >> the header was intended to live in port, but it isn't, right?
> >
> > That should probably be removed, yes. I did it that way that it could be
> > tested independently of casserts because the list checking code turns
> > some linear algorithms into quadratic ones which is noticeable even when
> > --enable- cassert is defined.
>
> As far as that goes, I wonder whether the list-checking code hasn't
> long since served its purpose. Neil Conway put it in when he redid the
> List API to help catch places that were using no-longer-supported hacks;
> but it's been years since I've seen it catch anything. I suggest that
> we might want to either remove it, or enable it via something other than
> USE_ASSERT_CHECKING (and not enable it by default).
Oh, I and Peter weren't talking about the pg_list.h stuff, it was about my
'embedded list' implementation which started this subthread. The
pg_list.h/list.c stuff isn't problematic as far as I have seen in profiles;
its checks are pretty simple so I do not find that surprising. We might want
to disable it by default anyway.

In my code the list checking stuff iterates over the complete list after
modifications and checks that all prev/next pointers are correct so its linear
in itself...

Andres
--
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