issue with pointer to user defiled types in C grammar

[sreeb...@gmail.com]

Hi Experts,

I see an issue in C grammar. We can define pointer to user defined typedef structures. Antlr considering it as multiplicative operation. It works fine for pointer to default data types. Could you suggest me on how to correct this?

Non working case:

(translator) ubuntu@ip-172-31-94-97:~/antlrc$ antlr4-parse C.g4 translationUnit -tree
int main() {
nginx *d;
}
(translationUnit:1 (externalDeclaration:1 (functionDefinition:1 (declarationSpecifiers:1 (declarationSpecifier:2 (typeSpecifier:4 int))) (declarator:2 (directDeclarator:8 (directDeclarator:1 main) ( ))) (compoundStatement:1 { (blockItemList:1 (blockItem:1 (statement:3 (expressionStatement:1 (expression:1 (assignmentExpression:1 (conditionalExpression:1 (logicalOrExpression:1 (logicalAndExpression:1 (inclusiveOrExpression:1 (exclusiveOrExpression:1 (andExpression:1 (equalityExpression:1 (relationalExpression:1 (shiftExpression:1 (additiveExpression:1 (multiplicativeExpression:1 (castExpression:2 (unaryExpression:1 (postfixExpression:1 (primaryExpression:1 nginx)))) * (castExpression:2 (unaryExpression:1 (postfixExpression:1 (primaryExpression:1 d))))))))))))))))) ;)))) }))))

working case:

(translator) ubuntu@ip-172-31-94-97:~/antlrc$ antlr4-parse C.g4 translationUnit -tree
int main() {
int *b;
}
(translationUnit:1 (externalDeclaration:1 (functionDefinition:1 (declarationSpecifiers:1 (declarationSpecifier:2 (typeSpecifier:4 int))) (declarator:2 (directDeclarator:8 (directDeclarator:1 main) ( ))) (compoundStatement:1 { (blockItemList:1 (blockItem:2 (declaration:1 (declarationSpecifiers:1 (declarationSpecifier:2 (typeSpecifier:4 int))) (initDeclaratorList:1 (initDeclarator:1 (declarator:1 (pointer:1 *) (directDeclarator:1 b)))) ;))) }))))
(translator) ubuntu@ip-172-31-94-97:~/antlrc$

Thanks

Bharat

[Ken Domino]

The cause of the problem is because the grammar is ambiguous between `statement` and `declaration`. The "good" example avoids the ambiguity because basic types are hardwired into the grammar. Really, the grammar should have a basic symbol table. There are other possible hacks, but they will have varying unsavory assumptions.

$ trparse --ambig bad.c | trtree -a
CSharp 0 bad.c success 0.0608332
bad.c.d=116.a=1: (compilationUnit (translationUnit (externalDeclaration (functionDefinition (declarationSpecifiers (declarationSpecifier (typeSpecifier (Int "int")))) (declarator (directDeclarator (directDeclarator (Identifier "bad")) (LeftParen "(") (RightParen ")"))) (compoundStatement (LeftBrace "{") (blockItemList (blockItem (statement (expressionStatement (expression (assignmentExpression (conditionalExpression (logicalOrExpression (logicalAndExpression (inclusiveOrExpression (exclusiveOrExpression (andExpression (equalityExpression (relationalExpression (shiftExpression (additiveExpression (multiplicativeExpression (castExpression (unaryExpression (postfixExpression (primaryExpression (Identifier "nginx"))))) (Star "*") (castExpression (unaryExpression (postfixExpression (primaryExpression (Identifier "d")))))))))))))))))) (Semi ";"))))) (RightBrace "}"))))) (EOF ""))
bad.c.d=116.a=2: (compilationUnit (translationUnit (externalDeclaration (functionDefinition (declarationSpecifiers (declarationSpecifier (typeSpecifier (Int "int")))) (declarator (directDeclarator (directDeclarator (Identifier "bad")) (LeftParen "(") (RightParen ")"))) (compoundStatement (LeftBrace "{") (blockItemList (blockItem (declaration (declarationSpecifiers (declarationSpecifier (typeSpecifier (typedefName (Identifier "nginx"))))) (initDeclaratorList (initDeclarator (declarator (pointer (Star "*")) (directDeclarator (Identifier "d"))))) (Semi ";")))) (RightBrace "}"))))) (EOF ""))

[sreeb...@gmail.com]

Thanks for details. I will find a workaround.