bug#4751: 23.1; `read-char' inserts accented chars when you use `M-' modifier

[Stefan Monnier]

> I'm also confused about `characterp' and the notion of a character.
> `(elisp)Character Type' says that only integers/chars from 0 to
> 4194303 can be in strings or buffers.
> But ?\M-t is 134217844,

Yes.

> yet "\M-t" is a string with that char (`o' circumflex),

\M-t in strings is a special case inherited from ASCII days where the
meta modifier was used to represent the upper 8th bit.  We still support
it because it's very commonly (mis)used in .emacsen for key bindings,
but I'd strongly recommend to stay very far away from it.

And whenever \M-t is turned into ô (or vice-versa), this is a pretty
much a bug (tho there are a few cases where fixing this bug may be
difficult).  The only case I know where it's a "feature" is for C-q M-t.

> and (insert-char ?\M-t 1) inserts it in a buffer.

I believe the patch I installed earlier to fix read_char also fixed this one.

> a string or buffer. What is that subset (it seems to be chars <
> 4194304)? 

Yes, currently this is the subset.  In Emacs-22 it was different, and
who knows what the future may bring.

> Wrt `read-char' what is/are the intention(s) - use cases?

I really wish I knew.


        Stefan