[bknr-devel] Motivation for not interning symbols when loading a store

[Vladimir Sedach]

That makes sense. I don't think it's a good idea to include the
automatic interning option in, since that will change the semantics of
store loading, plus is probably an indication that the datastore user
is probably making a design mistake in his/her application code
(which, in hindsight, is what prompted my original query).

Thank you,
Vladimir

On Thu, May 21, 2009 at 1:31 PM, Hans Hübner <hans.huebner at gmail.com> wrote:
> On Thu, May 21, 2009 at 20:18, Vladimir Sedach <vsedach at gmail.com> wrote:
>> The patch is trivial, but I'd like to know the reason for the current behavior.
>
> The reason is that we want to be able to read snapshots with new
> software releases without neccessarily interning all symbols found in
> them.
>
>> There's also something fishy about %decode-symbol's :intern keyword
>> parameter. When it's not true, %decode-symbol returns nil. The only
>> time this is possibly the case occurs in snapshot-read-layout:
>> [...]
>> So if find-class-with-interactive-renaming doesn't find a class, all
>> %decode-symbol does is read the stream and throw what it reads away? I
>> don't get whether that's intended behavior or a bug.
>
> That is indeed the intended behavior.  If a snapshot references a
> class that does not exist in the running Lisp image and that is not
> interactively renamed, objects of that class should just be skipped.
> I have used that mechanism when upgrading software releases, finding
> it easier to hack the store so that old snapshots can be read rather
> than having to do in-image upgrades (load old software, load snapshot,
> load new software, dump).
>
> -Hans
>