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

From: Stefan Monnier <[email-masked]>
Date: Tue, 03 Apr 2012 09:02:52 -0400

>> > Please note that not all characters in the code-space of a
>> > CJK charset are unified.  For instance, Big5 has it's own
>> > PUA (private use area), and characters in PUA are not
>> > unified by default.  So, if Emacs reads a Big5 file that
>> > contains PUA chars, those chars stay in high-area.   Then,
>> > one can provide his own unification map that also maps PUA
>> > chars to some Unicode chars as this:
>> >   (unify-charset 'big5 "MyBig5.map")
>> > After this, I thought that previously read PUA chars staying
>> > in the high-area should be treated as the corresponding
>> > Unicode chars (in displaying, search, etc).
> No.  In the above scenario, PUA chars read before the call
> of unify-charset are not unified.  The unification should
> take place after the call of unify-charset.

But isn't this (unify-charset 'big5 "MyBig5.map") performed in the
.emacs?  Is it really important to support adding unification rules
after decoding took place?  If so, why?  And also, what about
removing unification rules after decoding?

        Stefan