Re: Avoiding empty element when splitting NUL-separated string from command substitution

[Peter Stephenson <Peter.Stephenson@xxxxxxx>]

On Tue, 16 Aug 2011 13:51:38 +0100
Peter Stephenson <Peter.Stephenson@xxxxxxx> wrote:
> On Tue, 16 Aug 2011 14:13:58 +0200
> Nikolai Weibull <now@xxxxxxxx> wrote:
> > % b=(${(0)"$(print -n)"})
> > % echo $#b
> > 1
>
> I think that's a bug.
> 
> The fix might be as simple as the following, but it probably needs a bit
> more investigation as to where the Nularg came from.  If it was a
> nulstring, used in subst.c for reasons I can never remember (and, of
> course, aren't commented) this is fine; if it was something that should
> already have had remnulargs() applied to it the fix is somewhere else.

This is indeed a specially created null string propagating up from
readoutput() via multsub(), so I think the fix is legitimate.  It's not
clear if sepsplit() should be using null strings in its output, however,
since I have no idea what they're for.  That would be a different
pre-existing bug with different effects.

If you have any theories, you can post them to zsh-workers.

Index: Test/D04parameter.ztst
===================================================================
RCS file: /cvsroot/zsh/zsh/Test/D04parameter.ztst,v
retrieving revision 1.59
diff -p -u -r1.59 D04parameter.ztst
--- Test/D04parameter.ztst	3 Jun 2011 22:03:44 -0000	1.59
+++ Test/D04parameter.ztst	16 Aug 2011 14:50:13 -0000
@@ -1453,3 +1453,8 @@
    print ${foo:5:-6}
 1:Regression test for total length < 0 in array
 ?(eval):2: substring expression: 3 < 5
+
+   foo=(${(0)"$(print -n)"})
+   print ${#foo}
+0:Nularg removed from split empty string
+>0


-- 
Peter Stephenson <pws@xxxxxxx>            Software Engineer
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