ANTLR Not Emitting Error Messages on Invalid Input

Question

I have begun learning ANTLR in order to implement a domain-specific language (DSL) in the future. I have purchased The Definitive ANTLR Reference and have begun working my way through it in order to familiarize myself with the program and the concepts of languages/compiler design. I have successfully gotten everything working within my environment (Visual Studio 2010 and C#), and I have successfully been able to create some basic grammars, as described throughout the book. Source code for java can be found here: http://pragprog.com/titles/tpantlr/source_code

However, while working through Chapter 3, I have come across a problem involving the classes not emitting errors to the console, as it shows in the book. I am using the same grammar that is used in the book, so I am assuming it has something to do with the C# runtimes. I am currently using ANTLRWorks to generate the lexer/parser, and I am using the 3.4 ANTLR distribution runtimes for CSharp3 (Antlr3.Runtime.dll and Antlr4.StringTemplate.dll).

Is this a known issue? If not, should I try using an older version of the runtimes or ANTLRWorks?

The grammar I am using:

grammar Expr;

options
{
   language = CSharp3;
}

prog    :   stat+ ;

stat    :   expr NEWLINE
|   ID '=' expr NEWLINE
|       NEWLINE
;

expr    :   multExpr (('+'|'-') multExpr)*
;

multExpr 
:   atom('*' atom)*
;

atom    :   INT
|   ID
|   '(' expr ')'
;

ID  :   ('a'..'z'|'A'..'Z')+ ;
INT :   '0'..'9'+ ;
NEWLINE :   '\r'? '\n';
WS  :   (' '|'\t')+ {Skip();};

I will post the C# classes if anyone needs to see them, but they are very long, so I will hold off until someone requests them. Thank you.

I am not getting errors for any invalid input. I have tried things like "3+@", with no error. "(3" also results in no error. It appears that it isn't a specific type of exception that is causing it. — almostProgramming

pseudonym pseudonym · Accepted Answer · 2012-02-24T02:31:57

After some debugging on 3.4.1.9004 source code, I found that the traceDestination property was null. So, I set the property as shown below in Main() and messages started showing up on the console.

parser.TraceDestination = Console.Out;

ANTLR Not Emitting Error Messages on Invalid Input

2 Answers