[antlr-interest] [BUG FIX] Generates bad empty lookahead test expression in C++

[mzukowski at yci.com]

This is fixed in the 2.7.2 alpha code which you can download from
www.antlr.org

Monty

> -----Original Message-----
> From: ods94538 [mailto:ods94538 at yahoo.com]
> Sent: Monday, September 23, 2002 9:49 AM
> To: antlr-interest at yahoogroups.com
> Subject: [antlr-interest] [BUG FIX] Generates bad empty lookahead test
> expression in C++
> 
> 
> Greetings,
> 
> Found the following bug but am unsure how to submit it. Here's the
> skinny; if anyone knows a better place for me to send such stuff,
> please let me know!
> 
> The problem occurs with the following (stripped-down) grammar:
> 
> -- begin test.g --
> 
> options {
>     language="Cpp";
> }
> 
> class TestLexer extends Lexer;
> 
> options {
>     k=2;
>     charVocabulary='\3'..'\377';
> }
> 
> COMMENT
>     : "/*"
>       ( '*' ~'/' 
>       | NEWLINE
>       | ~('*'|'/'|'\n'|'\r') )*
>       "*/"
>     ;
> 
> NEWLINE: '\r' ('\n')? | '\n' { newline(); };
> 
> -- end test.g --
> 
> There is a nondeterminism in NEWLINE which generates the following
> lookahead tests in the corresponding lexer method, mNEWLINE.  The
> problem is that the "if (true)" is missing parentheses, so the file
> doesn't compile.
> 
> -- begin TestLexer.cpp:134-149 --
> 
> case static_cast<unsigned char>('\r'):
> 	{
> 		match(static_cast<unsigned char>('\r'));
> 		{
> 		if ((LA(1)==static_cast<unsigned char>('\n')) 
> && (true)) {
> 			match(static_cast<unsigned char>('\n'));
> 		}
> 		else if true {     // <-- should be (true)
> 		}
> 		else {
> 			throw ...
> 		}
> 		}
> 		break;
> 	}
> 
> -- end TestLexer.cpp --
> 
> I propose the following patch:
> 
> CppCodeGenerator.java:3584
> < return "true";
> > return "(true)";
> 
> as this seems to generate the correct C++ code.
> 
> -- Owen
> 
> 
> 
>  
> 
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