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

[ods94538]

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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