Re: Pushback buffer overflow exception

["Franz Beil" <franz.beil@temis-group.com>]

Thanks a lot, Etienne!
You are right, I used the one-argument constructor of PushbackReader, so my
buffer didn't have the right size and went out of range.

Franz

----- Original Message -----
From: "Prof. Etienne M. Gagnon" <etienne.gagnon@uqam.ca>
To: "Franz Beil" <franz.beil@temis-group.com>
Cc: "SableCC-List" <sablecc-list@sable.mcgill.ca>
Sent: Friday, March 28, 2003 7:40 PM
Subject: Re: Pushback buffer overflow exception


> Hi Franz,
>
> I have tested your grammar with SableCC 2.18.0, and it simply works.
Maybe you
> forgot to give a large enough buffer to your PushbackReader.
>
> I have attached to this message the Main.java that I ued to test your
grammar.
>
> [It works with both definitions of class_char].
>
> Maybe I mised something?
>
> Etienne
>
> Franz Beil wrote:
> > Hi,
> >
> > I get an "IOException: Pushback buffer overflow" with the SableCC
grammar
> > appended below.
> >
> > Test 1:    "[+-]"
> > Parsing this string leads to pushback buffer overflow. The problem seems
to
> > arise from the competition between T.range and T.class_char.
> >
> > Test 2:    "[\a]"
> > When I use the commented alternative to T.class_char (i.e. "{
charclass }
> > class_char = class_char ;"), I get a pushback buffer overflow exception
on
> > any backslash escaped character occurring within brackets.
> > I guess this is a SableCC bug, since the expected exception should be a
> > LexerException.
> >
> > Any help is greatly appreciated!
> > Franz
> >
> >
> > PS: I have a JUnit test for the above cases. I'll be happy to send a
zip.
> >
> > PPS: Can anyone point me to a SableCC grammar for regular expressions?
> >
> >
> > /**********  GRAMMAR **********/
> > Package quoted_char;
> >
> > Helpers
> >
> >   all            = [ 0 .. 0xffff ] ;
> >
> > //   metacharacters
> >   esc            = '\' ;  //'
> >   hyphen         = '-' ;
> >   l_bracket      = '[' ;
> >   r_bracket      = ']' ;
> >
> > //   general
> >   plain_ch              = all ;
> >   quoted_ch             = esc plain_ch ;
> >   class_char            = [ plain_ch - r_bracket ];
> >
> >
> > States
> > //   The first state is the initial state
> >   normal ,
> >   charclass ;
> >
> >
> > Tokens
> >
> >   { normal->charclass }  l_bracket = l_bracket ;
> >
> >   { charclass->normal }  r_bracket = r_bracket ;
> >
> >   { charclass }  range  = (class_char|quoted_ch) hyphen
> > (class_char|quoted_ch);
> > //  { charclass }  class_char = class_char ;
> >   { charclass }  class_char = (class_char|quoted_ch) ;
> >
> >   { normal }  plain_ch   =  plain_ch ;
> >   { normal }  quoted_ch  =  quoted_ch ;
> >
> >
> > Productions
> >
> >   char =
> >         {plain}         T.plain_ch              |
> >         {quoted}        T.quoted_ch             |
> >         {class}         ch_class                ;
> >
> >   // character class
> >   ch_class =
> >         T.l_bracket  ch_class_unit+  T.r_bracket ;
> >
> >   ch_class_unit =
> >         {single}        T.class_char            |
> >         {range}         T.range                 ;
> >
> >
> >
>
>