[antlr-interest] @rulecatch in a C environment

[Jim Idle]

We need to add better support so that targets can tell you whether the section you are using is supported. @after currently isn't officially supported though I have been playing around with it.

Rather than try to do this through things like rule catch, just override the displayRecognitionError routine, or routines tath are called before that is called if you find a need.

At that point you can find out everything you would normally need to know, including what rule/alt the parser was in and the expected token set (if this can be worked out) and so on.

>From the C API docs:

Unless you wish to create your own tree structures using the built in ANTLR AST rewriting
notation, you will rarely need to override the default implementation of runtime methods. The
exception to this will be the syntax err reporting method, which is essentially a stub function
that you will usually want to provide your own implementation for. You should consider the built in function
displayRecognitionError() as an example of where to start as there can be no really useful
generic error message display.


In your grammar you can do this:

@parser::apifuncs
{
	// Override the standard error display and install my own.
      // Look at the runtime library code to see what the default one
      // does to find things out, then do what I want in my version.
      ..
	ctx->displayrecognitionError = myDisplayrecognitionError;
}

Jim

> -----Original Message-----
> From: antlr-interest-bounces at antlr.org [mailto:antlr-interest-
> bounces at antlr.org] On Behalf Of Pierre Attar
> Sent: Tuesday, April 08, 2008 6:14 AM
> To: antlr-interest at antlr.org
> Subject: [antlr-interest] @rulecatch in a C environment
> 
> Hi,
> 
> I want to catch recognition errors on my parsing. In order to achieve
> this, I've creating the following rulecatch:
> 
> @rulecatch {
>     pANTLR3_EXCEPTION exe = EXCEPTION;
>     if(NULL != exe) {
>         char    buffer[100];
>         sprintf(buffer, "\%s", exe->name);
>         cout << "Got an exception in parsing recognition: " << buffer;;
>     }
> }
> 
> This works fine except that when nothing is provided, the generation is
> :
>     if (HASEXCEPTION())
>     {PREPORTERROR();
>         PRECOVER(); }
>     else
>     {{resultTree= doc;}}
> 
> ... where the line is an @after clause.
> 
> 
> My problem ? As soon as I put my rulecatcher, the after clause is no
> more generated.
> 
> I would be very glad to understand what I've done wrong here and also,
> if someone have a sample I may clone, it would help me.
> 
> Thanks a lot, Pierre
> 
> 
>