bug#11073: 24.0.94; BIDI-related crash in redisplay with certain byte sequences

[Stefan Monnier <monnier@iro.umontreal.ca>]

>> But isn't this (unify-charset 'big5 "MyBig5.map") performed in the .emacs?
> Usually yes.  But, in that case, if .emacs is encoded in
> Big5 and it contains some Big5 PUA chars, they are not
> unified while loading .emacs.

Hmm... that doesn't sound like it would be a very common problem, but
it's not completely hypothetical either.  Would this problem also come
up in a BIG5 locale?  If not, then I think we can ignore this problem.

>> Is it really important to support adding unification rules
>> after decoding took place?  If so, why?
> As I wrote, I can't tell how important it is.  It may be very
> important for those (but I guess very few) who need the above
> operation, but not important for the majority.
> I'm ok to remove such a feature if the maintainers decide that.

The problem with it is that it costs all the time for everyone, and it
makes the behavior of some macros subtly more complex/different and
hence adds a nasty complexity.
So if at all possible, I'd rather find a way to remove it (not for
24.1, obviously).

>> And also, what about removing unification rules after decoding?
> When one tells Emacs to unify some chars, and then reads a file
> containing those chars, there's no way to dis-unify them.

But I guess this problem is even much less common.


        Stefan