[antlr-interest] Tell ANTLR to ignore parsing errors?

[Jim Idle]

When putting things in the parser, you have not enough control over the tokens both in terms of what they are named in code generation time (hence error messages are difficult, and producing a tree parser is difficult), and you cannot see the potential ambiguities in your lexer. It just makes things more difficult for no(IMO) advantage.

If you have told the input stream to be case insensitive, then I am afraid that the problem is going to be with your grammar. You will have to single step though the code to find out why.

Jim

> -----Original Message-----
> From: Andi Clemens [mailto:Andi.Clemens at gmx.net]
> Sent: Thursday, September 09, 2010 7:32 AM
> To: Jim Idle; antlr-interest at antlr.org
> Subject: Re: [antlr-interest] Tell ANTLR to ignore parsing errors?
> 
> Yes it is case insensitive. What is the difference if I add "CREATE" or similar to
> the lexer?
> Is it more reliable in detecting the right tokens?
> 
> Andi
> 
> -------- Original-Nachricht --------
> > Datum: Thu, 9 Sep 2010 07:21:45 -0700
> > Von: "Jim Idle" <jimi at temporal-wave.com>
> > An: antlr-interest at antlr.org
> > Betreff: Re: [antlr-interest] Tell ANTLR to ignore parsing errors?
> 
> > If you are getting errors it is because your grammar is incorrect.
> > Oracle SQL is a huge grammar to undertake and you cannot 'hack' it.
> > Your token in the parser (which you should move to the lexer anyway and
> not use 'LITERAL'
> > in your parser code) is CREATEE but your input is create. Did you tell
> > the runtime to be case insensitive?
> >
> > Read the API or use antlr.markmail.org to see how to override
> > displayRecognitionError(). You cannot just ignore errors though
> > because somehow you have to recover. You could just make them silent
> > and when the parser returns if the error count is >0 then ignore that source
> or something.
> >
> > I will have a commercial version of Oracle SQOL and PLSQL available
> > before too long too.
> >
> > Jim
> >
> >
> >
> > > -----Original Message-----
> > > From: antlr-interest-bounces at antlr.org [mailto:antlr-interest-
> > > bounces at antlr.org] On Behalf Of Andi Clemens
> > > Sent: Thursday, September 09, 2010 5:45 AM
> > > To: antlr-interest at antlr.org
> > > Subject: [antlr-interest] Tell ANTLR to ignore parsing errors?
> > >
> > > Hi,
> > >
> > > I use this ANTLR grammar file to parse Oracle PL/SQL statements:
> > > http://pastebin.com/uy0wZTax
> > >
> > > But some of the statements produce errors when I try to parse them,
> > > for
> > > example:
> > >
> > > "create user u1 identified by p1 account unlock;"
> > >
> > > I get the following error message:
> > >
> > > ==============================
> > > statementString(1)  : error 3 : , at offset -1
> > >     near [Index: 0 (Start: 141054912-Stop: 141054917) ='create',
> > type<50> Line:
> > > 1 LinePos:-1]
> > >      : cannot match to any predicted input...
> > > ==============================
> > >
> > > But why? The rule looks like this:
> > > ==============================
> > > create_user_statement
> > > 	:	'CREATE' 'USER' identifier 'INDENTIFIED' .*
> > > 	;
> > > ==============================
> > >
> > > Could the wildcard character be the problem?
> > > Actually I just want to parse known Statements with my grammar, all
> > > unknown statements (parsing errors) could be ignored.
> > >
> > > Can I tell ANTLR (for the C target) to ignore those error messages
> > > and
> > just
> > > return FALSE or something like that, so that I can decide wether to
> > > take
> > an
> > > appropiate action?
> > >
> > > I get a lot of those error messages, and to be honest, the error
> > messages are
> > > not helping me here. I can not see problems with the grammar.
> > > Unfortunately I'm not able to debug the grammar with ANTLRworks.
> > >
> > > Can someone show me the error or tell me a way to disable those
> > > error messages in the ANTLR C target?
> > >
> > > Andi
> > >
> > > --
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