[Python-3000] Immutable bytes type and bsddb or other IO

[Gregory P. Smith]

> Adding data locking shouldn't be too complicated, but is it necessary?
> The bytes object does support locking the buffer in place; isn't that
> enough? It means someone evil could still produce a phase error by
> changing the contents while you're looking at it (basically sabotaging
> their own application) but I don't see how they could cause a segfault
> that way.

I'm sure the BerkeleyDB library is not expecting the data passed in as
a lookup key to change mid database traversal.  No idea if it'll
handle that gracefully or not but I wouldn't expect it to and bet its
possible to cause a segfault and/or irrepairable database damage that
way.  The same goes for any other C APIs that you may pass data to
that release the GIL.

> Even if you really need the LOCKDATA feature, perhaps you can check in
> a slight mod of your code that uses SIMPLE for now -- use a macro for
> the flags that's defined as PyBUF_SIMPLE and add a comment that you'd
> like it to be LOCKDATA once bytes support that.
>
> That way we have less code in the tracker and more in subversion --
> always a good thing IMO.

yeah i have it almost working in SIMPLE mode for now, i'll check it in
soon.  its no worse in behavior than the existing bytes object using
code currently checked in.