Quoted parameter parsing glitch

Quoted parameter parsing glitch

[Bart Schaefer]

schaefer<502> print "${foo:-"}"
dquote braceparam> 

At this point the parser is in an infinite loop.  There's nothing you can
type (except end-of-file or interrupt) that will free you from the PS2
prompt.

-- 
Bart Schaefer                                 Brass Lantern Enterprises
http://www.well.com/user/barts              http://www.brasslantern.com

Zsh: http://www.zsh.org | PHPerl Project: http://phperl.sourceforge.net   

RE: Quoted parameter parsing glitch

[Borsenkow Andrej]

> schaefer<502> print "${foo:-"}"
> dquote braceparam>
> 
> At this point the parser is in an infinite loop.  There's nothing you
can
> type (except end-of-file or interrupt) that will free you from the PS2
> prompt.
> 

Shell should not hang, but please note it is invalid as per POSIX.
Double-quotes and braces must match. So whatever fix is used, it should
not make the above valid construct (i.e. it should not print `"'). 

-andrej

Re: Quoted parameter parsing glitch

[Bart Schaefer]

On Aug 22,  8:21pm, Borsenkow Andrej wrote:
} Subject: RE: Quoted parameter parsing glitch
}
} > schaefer<502> print "${foo:-"}"
} > dquote braceparam>
} > 
} > At this point the parser is in an infinite loop.

I'm wrong, it's either more complicated than that example shows or it's
just me.  It's possible to get out of that one by just:

schaefer<502> print "${foo:-"}"
dquote braceparam> }
dquote> "
}


schaefer<503> 

I'm pretty sure I did manage to get it stuck on a more complicated
substitution, but my attempt to produce a minimal example went astray,
and I haven't reproduced whatever it was I first did.

} Shell should not hang, but please note it is invalid as per POSIX.
} Double-quotes and braces must match.

Zsh 4 (and ksh) is supposed to accept double-quotes inside ${...} inside
double-quotes; the braces act as an extra level of quoting so that the
inner quotes can nest in the outer ones.  I don't know what POSIX says
about that.

-- 
Bart Schaefer                                 Brass Lantern Enterprises
http://www.well.com/user/barts              http://www.brasslantern.com

Zsh: http://www.zsh.org | PHPerl Project: http://phperl.sourceforge.net   

Re: Quoted parameter parsing glitch

[Borsenkow Andrej]

On Wed, 22 Aug 2001, Bart Schaefer wrote:

>
> } Shell should not hang, but please note it is invalid as per POSIX.
> } Double-quotes and braces must match.
>
> Zsh 4 (and ksh) is supposed to accept double-quotes inside ${...} inside
> double-quotes; the braces act as an extra level of quoting so that the
> inner quotes can nest in the outer ones.  I don't know what POSIX says
> about that.
>

As I said - they must match. "${foo:-""}" is valid but "${foo:-"}" - not.
Neither is "${foo:-\"}". You cannot quote braces or double quotes in this
case. They must match (opening - closing).

-andrej

Re: Quoted parameter parsing glitch

[Bart Schaefer]

On Aug 22, 10:25pm, Borsenkow Andrej wrote:
}
} As I said - they must match. "${foo:-""}" is valid but "${foo:-"}" - not.

The question is whether "${foo:-"}"}" is valid.

Also, the PS2 prompt doesn't know about nested double quotes.  This is
probably what had me confused before:

schaefer<502> echo "${foo:-"}
dquote braceparam> 

Note that the prompt indicates that `}"' will end the quoting scope, but
in fact you need `"}"'.  The prompt should say

dquote braceparam dquote>

and does with the patch below.

Index: Src/lex.c
===================================================================
RCS file: /extra/cvsroot/zsh/zsh-4.0/Src/lex.c,v
retrieving revision 1.3
diff -c -r1.3 lex.c
--- Src/lex.c	2001/04/23 15:35:41	1.3
+++ Src/lex.c	2001/08/26 17:22:15
@@ -1395,7 +1395,9 @@
 		break;
 	    if (bct) {
 		add(Dnull);
+		cmdpush(CS_DQUOTE);
 		err = dquote_parse('"', sub);
+		cmdpop();
 		c = Dnull;
 	    } else
 		err = 1;

-- 
Bart Schaefer                                 Brass Lantern Enterprises
http://www.well.com/user/barts              http://www.brasslantern.com

Zsh: http://www.zsh.org | PHPerl Project: http://phperl.sourceforge.net   

Re: Quoted parameter parsing glitch

[Borsenkow Andrej]

Bart Schaefer wrote:
> On Aug 22, 10:25pm, Borsenkow Andrej wrote:
> }
> } As I said - they must match. "${foo:-""}" is valid but "${foo:-"}" - not.
> 
> The question is whether "${foo:-"}"}" is valid.
> 

No. Pairs of quotes and braces must match.

-andrej

Re: Quoted parameter parsing glitch

[Bart Schaefer]

On Aug 26,  9:59pm, Borsenkow Andrej wrote:
}
} Bart Schaefer wrote:
} > 
} > The question is whether "${foo:-"}"}" is valid.
} 
} No. Pairs of quotes and braces must match.

And is there no way to quote a brace within braces?

In any case, zsh accepts the above, nested like so:

    "           "
     ${        }
       foo:-" "
             }

I don't see any reason to change that in zsh, even if it's not accepted
under the POSIX rules, unless it conflicts with whatever means POSIX
provides for quoting the inner right brace.

-- 
Bart Schaefer                                 Brass Lantern Enterprises
http://www.well.com/user/barts              http://www.brasslantern.com

Zsh: http://www.zsh.org | PHPerl Project: http://phperl.sourceforge.net