Re: mb_metacharlenconv vs. tokens

[Peter Stephenson <pws@csr.com>]

Andrey Borzenkov wrote:
> Apparently mb_metacharlenconv gets passed tokenized string (how is it called
> properly in zsh lingua?) It means that the fact length(any-token-char) == 1
> is actually side effect of mbrtowc failing miserably and mb_metacharlenconv
> returning fallback 1 (at least using UTF-8).
> 
> Should not it untokenize character first? If yes, I will provide a fix as
>  part of larger patch; if no, I fail to see how it works then.

It's a bug if it's getting a tokenized character.  It should have been
untokenized at some point in the sequence leading to the call, since
mb_metacharlenconv() should already be dealing with a printable
string---by implication, we're looking at its width or length in
characters because we're about to do something to it which is
appropriate to a printable string.  However, this being zsh, the exact
point at which untokenization should be done is not necessarily obvious.
This is particularly true if we're using the string as a pattern.

I had a case like this in substitution recently:

2006-09-12  Peter Stephenson  <pws@csr.com>

	* 22689: Src/subst.c, Test/D04parameter.ztst: untokenize
	strings for substitution in cases like
	${${~:-*}//(#m)*/$MATCH=$MATCH}.  The pattern code tried
	to metafy the tokens, which caused chaos.

We're a victim of the fact that metafied strings are used both to
protect tokens and to protect embedded NULs; it tends to hide the logic
indicating that tokens are still around when they shouldn't be.

-- 
Peter Stephenson <pws@csr.com>                  Software Engineer
CSR PLC, Churchill House, Cambridge Business Park, Cowley Road
Cambridge, CB4 0WZ, UK                          Tel: +44 (0)1223 692070


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