On 2018-01-02 20:40:50 -0500, Tom Lane wrote: > Andres Freund <and...@anarazel.de> writes: > > On 2018-01-03 14:29:15 +1300, Thomas Munro wrote: > >> On Wed, Jan 3, 2018 at 2:20 PM, Tom Lane <t...@sss.pgh.pa.us> wrote: > >>> Andres Freund <and...@anarazel.de> writes: > >>> But note that dsa_pointer can be wider than a regular pointer on > >>> platforms without atomics support. > > >>> Hm. I did not get that impression from the comments in dsa.h, > >>> but if it's true then this approach won't work --- and indeed the > >>> hash code would be actively broken in such a case, so it's a problem > >>> we must fix. > > >> Maybe Andres is thinking of dsa_pointer_atomic? dsa_pointer is > >> normally the size of a pointer (well, really, the size of size_t), > >> though it could be *narrower* if you don't have atomics or ask for it > >> with USE_SMALL_DSA_POINTER > > > Yep, I was. > > OK, then there's not a live bug, but I'm a bit tempted to get rid of > the data[] member anyway. It's not clear to me now that keeping it > results in net cleaner code. Thoughts?
I like that plan. I don't think the data field buys us anything, and I personally in most cases find "fully manual" alignment code easier to reason about than fiddling with padding fields. Greetings, Andres Freund
