[perl #49061] [BUG] parsing hangs forever, fixed with custom token ws

[Will Coleda via RT]

On Sat Dec 29 00:24:28 2007, pmichaud wrote:
> On Sun, Dec 23, 2007 at 06:01:22PM -0800, Stephen Weeks wrote:
> > Working on getting parrot to parse the lojban grammar, I found that 
it
> > would hang forever with --target=parse.  Tracked it down to a <ws> 
rule.
> > When I define a custom token ws in the grammar, it parses without
> > problem.
> > 
> > Built a stripped-down test case.
> > 
> > http://nopaste.snit.ch:8001/paste has the grammar.
> > http://pleasedieinafire.net/~tene/jp.tar.bz2 has the grammar, a 
slightly
> > modified version of abc's .pir and Makefile.
> > 
> > Can anyone else confirm this?  Am I doing something wrong?
> 
> The default <ws> rule (as defined by Synopsis 5) only requires 
whitespace
> between two word characters.  Thus the grammar as written (without a 
custom
> <ws> rule) looks for an infinite number of <space_char> matches, and 
since
> <ws> can match an empty string when not between two word characters, 
PGE
> gets caught in an infinite loop.
> 
> Thus this ticket should likely be merged with or treated as a 
duplicate
> of RT#37745 (handle repeated zero-length captures in PGE).  At any 
rate,
> until #37745 is fixed it's probably worthwhile to make sure grammars 
don't
> end up with repeated zero-length subrules or subpatterns.
> 
> Pm

37745 is now being tracked at https://trac.parrot.org/parrot/ticket/721

Closing this ticket as a duplicate of that per Patrick's suggestion.

If you'd like to preserve this as a separate issue, please open a new 
ticket at https://trac.parrot.org/

Regards.


-- 
Will "Coke" Coleda