On Wed, 2 Sep 2015 15:34:43 +0200 Alan McKinnon <alan.mckin...@gmail.com> wrote:
> On 02/09/2015 15:04, Neil Bothwick wrote: > > On Wed, 2 Sep 2015 05:24:33 -0700, walt wrote: > > > >> If the devs can't explain slots to their > >> users then they don't understand it themselves. (Hm. That phrase > >> sounds familiar. Where did I get that?) > > > > I think it is an Einstein quote that says something like "if you > > can't explain it in simple terms, you don't understand it". He was > > probably having a pop at Niels Bohr and quantum theory at the time. > > > > Bohr said something like "if thinking about quantum theory doesn't > > give you a headache, you don't understand it". > > > > > > And Feynmann said something along the lines of "Anyone who claims to > understand quantum mechanics, doesn't". > > Back to subslots and not replying to Neil directly: They aren't that > hard to grasp, they look like this: > > cat/pkg/pkg-1.2:3/4 > > The SLOT is 3 and the subslot is 4. As usual, different versions of > the same package in different SLOTs can co-exist. Subslots are a > different matter, and it's an unfortunate choice of name, as they are > *not* a subset of a SLOT. Look at ncurses: > > [I] sys-libs/ncurses > Available versions: > (0) 5.9-r3 (~)5.9-r4 5.9-r5(0/5) (~)6.0-r1(0/6) > (5) 5.9-r99(5/5) (~)5.9-r101(5/5) (~)6.0(5/6) > > There's 2 SLOTs (0 and 5), and both have versions of subslot 5 and 6. > Subslots are most useful for things like api/abi versions where > upstream breaks these but don't increment the major version, this is > why we had endless issues in the past where emerge world broke stuff > horribly and it only got fixed much later when we could run > revdep-rebuild. Nowadays we have better tools, if the subslot changes > for a consumed library, then all consuming packages need to be > rebuilt. > > Describing and defining subslots is not hard, neither are the > operators. The problem with subslots is the usual one - you have to > deal with real life, and in real life upstreams sometimes do peculiar > things to their code that doesn't exactly match the effect of a > subslot operation. > > Or put another way: subslot docs describe the effect you should end up > with, it's not always the same thing as what you *do* end up with. > Finding that out means testing every possible circumstances and seeing > the results, but there's an infinite variety of those. I just updated my virtualbox ~amd64 guest and all went well when I ran emerge ncurses:5/5, so I'm encouraged but not fearless about doing the same on my real machine. I'm going to be quickpkged to the max before I try it. BTW, emerge world on the vbox guest did not offer to touch ncurses in any way. I had to do it manually as I just said. Leveraging Neil's quote: thinking about slots (and their misnamed subslots) gives me a 4-dimensional headache. Anyway, thanks for the helpful explanation.
