Question

I’m using ANTLR3 with the C runtime.

I’d like to do some custom error handling. What I’m really after is that if there is an antlr matching exception of any kind in a sub rule I’d like to tell ANTLR to skip trying to handle it and let it percolate up to a more global rule.

At that rule I’ll log it and then try to resume.

I’ve set the rule catch method like so, so that all rules won’t try to recover.

@rulecatch 
{
    if (HASEXCEPTION())
    {
    PREPORTERROR();
    }
}

This allows me to insert catch handlers on the rules that i want.

At my rule of interest i can then use the catch syntax like so:

catch [ANTLR3_RECOGNITION_EXCEPTION]
{
    PREPORTERROR();
    RECOGNIZER->consumeUntil(RECOGNIZER,RCURLY);
    CONSUME();
    PSRSTATE->error = ANTLR3_FALSE;
    PSRSTATE->failed = ANTLR3_FALSE;
     }

The problem is that this syntax seems to only allow me to catch one type of exception. I’d like to be able to catch all exception types.

Is there a way to do this?

I thought I could overload all the recovery functions but then some code generates exceptions like so:

                    CONSTRUCTEX();
                    EXCEPTION->type         = ANTLR3_NO_VIABLE_ALT_EXCEPTION;
                    EXCEPTION->message      = (void *)"";
                    EXCEPTION->decisionNum  = 23;
                    EXCEPTION->state        = 0;


                    goto rulewhenEx;

which means I’ll need to catch all possible exceptions.

Any thoughts??

Answer 1

I’ve ended up trying two solutions for this.

Approach 1)

Overloading the rulecatch setting to set the exception type to one specific type

@rulecatch 
{
    if (HASEXCEPTION())
    {

    // This is ugly.  We set the exception type to ANTLR3_RECOGNITION_EXCEPTION so we can always
    // catch them.
    PREPORTERROR();
    EXCEPTION->type = ANTLR3_RECOGNITION_EXCEPTION;
    }
}

This allows me to use one catch block as all exceptions will be of that type.

Approach 2)

I just use multiple catch blocks and they all dispatch to a common function to handle the error

catch [ANTLR3_RECOGNITION_EXCEPTION]
{
    handleException();
}
catch [ANTLR3_MISMATCHED_TOKEN_EXCEPTION]
{
    handleException();
}
....