Re: [dev] [PATCH] [st] Fix issues with wcwidth() returning -1 for

From: Dmitrij D. Czarkoff <>
Date: Mon, 27 Oct 2014 19:11:53 +0100

FRIGN said:
> >> The wcwidth() function returns the number of columns needed to
> >> represent the wide character c. If c is a printable wide
> >> character, the value is at least 0. If c
> >> is null wide character (L'\0'), the value is 0. Otherwise -1 is
> >> returned.
> That's how POSIX-2001 defines it.
> So yeah, using abs() to "catch" the invalid case is fine, but could be
> refined even more.

I don't follow your logic here. Glibc currently yelds incorrect result
for a set of valid Unicode 7.0 codepoints that were invalid previously.
This time they are 1 column width (I didn't verify that, so don't take
my word for it), but in future wide characters may be added as well, and
wcwidth() will return -1 for them as well, so the "abs()" hack won't

IMO ideally st should either not print characters whose codepoints are
unknown to libc, or should silently replace them with U+FFFD. At any
rate, assumptions about codepoints' properties are not st's business.

Dmitrij D. Czarkoff
Received on Mon Oct 27 2014 - 19:11:53 CET

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