[antlr-interest] implementing C-style #define macros in ANTLR

[Andy Tripp]

Bruce Bauman wrote:
> I am trying to convert 4 million lines of Pascal code from the MetaWare Pascal compiler to Free Pascal. (yes, really). Unfortunately, MetaWare Pascal supports many non-standard extensions to Pascal, including C-style macros. Our existing Pascal code base uses the macro feature extensively..
>  
> Any suggestions on how to implement this? Any examples in existing ANTL grammars?
>  
> Thanks.
> 
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> 

Maybe you could just run the C preprocessor on the pascal file.
IIRC, cpp works on any code, not just C/C++.

Or, you could add the rules below in your grammar to recognize the preprocessor directives.
The problems here are:
a) There's no one "correct" place in your grammar to put the "ppDirective" rule - 
cpp directives can go *anywhere* in your code.
b) Your parser may not be able to parse certain code, even with these rules added.

Andy

Parser rule:
ppDirective
	: PPspace 
	| PPdefine 
	| PPif 
	| PPelse
	| PPelif
	| PPendif
	| PPinclude
	| PPifdef
	| PPifndef
	| PPundef
	| PPpragma
	| PPerror
	| PPline
	;


Lexer rules:


// atripp: added support for preprocessor
protected RestOfPP :
( 
	'\\'! Newline!		// atripp: note the "!"s to delete escaped newlines
	| Comment
	| CharLiteral							// 6/11/04: avoid matching '"' as StringLiteral
	| StringLiteral							// atripp:without this, "//" inside string gets processed
	| {LA(2) != '*' && LA(2) != '/'}? '/'
	| '#'			// "stringification"
	| ~('\r' | '\n' | '/')
)+ 
;

// PPSpaceRule will convert "# define" to "#define", etc.
PPspace		: "#" (Whitespace)+ RestOfPP
;
PPdefine	: "#define" (Whitespace)+ RestOfPP
;
PPif		: "#if" (Whitespace)+ RestOfPP
;
PPelse		: "#else" 
;
PPelif		: "#elif" (Whitespace)+ RestOfPP
;
PPendif		: "#endif"
;
// Note the "*" instead of "+" here, to handle "#include<whatever.h>"
PPinclude	: "#include" (Whitespace)* RestOfPP
;
PPifdef		: "#ifdef" (Whitespace)+ RestOfPP
;
PPifndef	: "#ifndef" (Whitespace)+ RestOfPP
;
PPundef		: "#undef" (Whitespace)+ RestOfPP
;
PPpragma	: "#pragma" RestOfPP
;
PPerror		: "#error" (RestOfPP)?
;
PPline		: "#line" RestOfPP
;