I have written a grammar for a small subset of C and my parser does not work
reliably, that is sometimes it reports syntax errors and sometimes it
doesn't. For example, my grammar insists on variable initialization:
bool x; // This is not allowed.
bool y = true; // This is allowed
My problem is that the parser emits an error message for the program above.
But if I simply switch the lines like so:
bool y = true; // This is allowed
bool x; // This is not allowed.
the parser happily creates an AST for the first statement and simply ignores
the second one without noticing me about the syntax error.
What am I doing wrong? My grammar looks as follows:
grammar MyGrammar;
options {
language = CSharp3;
output = AST;
ASTLabelType = MyAST;
}
tokens {
VAR_DECL;
ARG_DECL;
METHOD_DECL;
ASSIGN = '=';
EXPR;
ELIST;
BLOCK;
CALL;
UNARY_MINUS;
UNARY_NOT;
}
@lexer::namespace{MyGrammar}
@parser::namespace{MyGrammar}
/******************************************************************************
* Parser section
*****************************************************************************/
public
compilationUnit
: (methodDeclaration | variableDeclaration)+
;
methodDeclaration
: returnType IDENTIFIER '(' (formalParameter (',' formalParameter)*)?
')' block -> ^(METHOD_DECL returnType IDENTIFIER formalParameter* block)
;
formalParameter
: type IDENTIFIER -> ^(ARG_DECL type IDENTIFIER)
;
variableDeclaration
: type IDENTIFIER '=' expression ';' -> ^(VAR_DECL type IDENTIFIER
expression)
;
block
: '{' (statement)* '}' -> ^(BLOCK statement*)
;
statement
options { backtrack=true; }
: block
| variableDeclaration
| lhs '=' expression ';' -> ^('=' lhs expression)
| 'return' expression? ';' -> ^('return' expression?)
| 'if' '(' expression ')' b1=block
('else' b2=block -> ^('if' expression $b1 $b2)
| -> ^('if' expression $b1)
)
| postfixExpression ';' -> ^(EXPR postfixExpression)
| ';'!
;
lhs : postfixExpression -> ^(EXPR postfixExpression)
;
expressionList
: expr (',' expr)* -> ^(ELIST expr+)
| -> ELIST
;
expression
: expr -> ^(EXPR expr)
;
expr: logicalOrExpression
;
logicalOrExpression
: logicalAndExpression ('or'^ logicalAndExpression)*
;
logicalAndExpression
: equalityExpression ('and'^ equalityExpression)*
;
equalityExpression
: relationalExpression (('!='^ | '=='^) relationalExpression)*
;
relationalExpression
: additiveExpression (('<'^ | '>'^ | '<='^ | '>='^ )
additiveExpression)*
;
additiveExpression
: multiplicativeExpression (('+'^ | '-'^) multiplicativeExpression)*
;
multiplicativeExpression
: unaryExpression (('*'^ | '/'^) unaryExpression)*
;
unaryExpression
: '-' unaryExpression -> ^(UNARY_MINUS unaryExpression)
| '+' unaryExpression -> unaryExpression
| '!' unaryExpression -> ^(UNARY_NOT unaryExpression)
| postfixExpression
;
postfixExpression
: (atom -> atom)
(
'(' expressionList ')' -> ^(CALL["CALL"] $postfixExpression
expressionList)
)*
;
atom: IDENTIFIER
| literal
| '(' expr ')' -> expr
;
literal
: INTLITERAL
| LONGLITERAL
| DOUBLELITERAL
| STRINGLITERAL
| 'true'
| 'false'
;
returnType
: type
| 'void'
;
type
: primitiveType
;
primitiveType
: 'int'
| 'long'
| 'double'
| 'string'
| 'bool'
;
/******************************************************************************
* Lexer section
*****************************************************************************/
TRUE
: 'true'
;
FALSE
: 'false'
;
LONGLITERAL
: IntegerNumber LongSuffix
;
INTLITERAL
: IntegerNumber
;
fragment
IntegerNumber
: '0'
| '1'..'9' ('0'..'9')*
| '0' ('0'..'7')+
| HexPrefix HexDigit+
;
fragment
HexPrefix
: '0x' | '0X'
;
fragment
HexDigit
: ('0'..'9'|'a'..'f'|'A'..'F')
;
fragment
LongSuffix
: 'l' | 'L'
;
fragment
NonIntegerNumber
: ('0' .. '9')+ '.' ('0' .. '9')* Exponent?
| '.' ( '0' .. '9' )+ Exponent?
| ('0' .. '9')+ Exponent
| ('0' .. '9')+
|
HexPrefix (HexDigit )*
( ()
| ('.' (HexDigit )* )
)
( 'p' | 'P' )
( '+' | '-' )?
( '0' .. '9' )+
;
fragment
Exponent
: ( 'e' | 'E' ) ( '+' | '-' )? ( '0' .. '9' )+
;
fragment
DoubleSuffix
: 'd' | 'D'
;
DOUBLELITERAL
: NonIntegerNumber DoubleSuffix?
;
STRINGLITERAL
: '"' (EscapeSequence | ~( '\\' | '"' | '\r' | '\n' ) )* '"'
;
fragment
EscapeSequence
: '\\' (
'b'
| 't'
| 'n'
| 'f'
| 'r'
| '\"'
| '\''
| '\\'
| ('0'..'3') ('0'..'7') ('0'..'7')
| ('0'..'7') ('0'..'7')
| ('0'..'7')
)
;
IDENTIFIER : ('a'..'z' |'A'..'Z' |'_' ) ('a'..'z' |'A'..'Z' |'_'
|'0'..'9'
)* ;
WS : (' ' | '\t' | '\n' | '\r')+ { $channel = 99; } ;
COMMENT
: '/*' (options {greedy=false;} : . )* '*/' { $channel = 99; }
;
LINE_COMMENT
: '//' ~('\n'|'\r')* ('\r\n' | '\r' | '\n') { $channel = 99; }
| '//' ~('\n'|'\r')* { $channel = 99; } // A line comment could
appear at the end of the file without CR/LF
;
ANYCHAR : . ;
Maik
--
View this message in context:
http://antlr.1301665.n2.nabble.com/Recognizing-syntax-errors-with-C-tp6831210p6831210.html
Sent from the ANTLR mailing list archive at Nabble.com.
List: http://www.antlr.org/mailman/listinfo/antlr-interest
Unsubscribe:
http://www.antlr.org/mailman/options/antlr-interest/your-email-address
--
You received this message because you are subscribed to the Google Groups
"il-antlr-interest" group.
To post to this group, send email to [email protected].
To unsubscribe from this group, send email to
[email protected].
For more options, visit this group at
http://groups.google.com/group/il-antlr-interest?hl=en.
