Seeking very simple ANTLR error handling example when generating C code

I want to generate C code. I will not be reading from an input file, one line at a time (as, for instance, a compiler might). Rather, I will be parsing user input as it arrives, one line at a time.

I would prefer to detect and handle bad input in the lexer/parser, e.g

/* lexer tokens */
foo : "FOO";
bar : "BAR";
baz : "BAZ";
/* grammar*/
grammar : foo "=" BAZ 
        | foo "=" BAR 
        | <some non-existent Antrl-else> :  {printf(stderr, "bad input\n");}
        ;

OK, if I can't catch it in the lexer/parser, it seems like I need to use displayRecognitionError() but how??

Can anyone point me at a very simple example which generates C code and shows some error han开发者_如何转开发dling of invalid input?

Thanks!

Ok, bounty, yippee!

But only for a real, working answer, with real, working code. No "use method X()" without an wxample.

What you are most likely looking for is the displayRecognitionError() function. This function is called in the cases that you are interested in, and is part of the C runtime.

If you want to see an example of how to use this function, look at this mailing list post. Although this code mixes C and C++, you should be able to work out what you need from it.

Handling a recognition exception in Java would go like this:

grammar X;

// ...

@rulecatch{
  catch(RecognitionException rex) {
    // do something
  }
}

// parser rules

// lexer rules 

In other words, simply add some custom C code inside the @rulecatch{ ... } block.