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Re: The empty string and other empty strings

From: Mark H Weaver
Subject: Re: The empty string and other empty strings
Date: Tue, 10 Jan 2012 08:03:06 -0500
User-agent: Gnus/5.13 (Gnus v5.13) Emacs/24.0.92 (gnu/linux)

Mike Gran <address@hidden> writes:
> Right now it seems that zero-length shared substring of a wide string is
> wide.  A zero-length substring still shares the stringbuf of the
> original string.
> What do you think about that?  Do zero-length substrings need to
> still share stringbufs with their parent strings?

I think the answer is: no they don't, and avoiding that might be a
worthwhile optimization, mainly to avoid needlessly holding a reference
to a potentially large stringbuf.

> In any case, a string-copy of a narrow substring of an otherwise wide string
> should be a new narrow string.  This should apply to zero-length
> substrings as well.  This isn't happening, because we're missing
> a scm_i_try_narrow_string in string-copy, which is a bug.

I just fixed this.

> Looks like for zero-length input strings, u32_conv_from_encoding can
> return NULL.

Interesting!  Anyway, we now avoid calling `u32_conv_from_encoding' for
empty strings.


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