[antlr-interest] null pointer to ADAPTOR->setTokenBoundaries

[John B. Brodie]

Pardon me for butting in.

And I have never used the C code generator, but.....

On Wed, 2010-05-19 at 14:06 -0700, Alan Condit wrote:

> which I assume, based on the comment, is generated from this rule:
> line	:	line_number? segment+ K_NEWLINE
> 		-> ^(STMT segment+)
> 	|	line_number? K_NEWLINE
> 		->
> 	|	oword_stmt
> 		-> ^(STMT oword_stmt)
> 	;
> 
> The grammar is for parsing an existing language not one of my invention,
> and grammatically the newlines delineate a semantic block therefore must
> be known by the parser, but empty lines are discarded and therefore
> should not be in the tree.

having an empty RHS of the -> rewrite operator feels well unusual.

i am not sure that ANTLR permits a rule which produces no tree when
output=AST is present....

Maybe try (untested):

line : line_number? ( segment+ -> ^(STMT segment+) )? K_NEWLINE
     | oword_stmt -> ^(STMT oword_stmt)
     ;

but i do not know what would happen when no segment is present for the
above rule....

have you considered building a dummy tree node for the empty case and
then your tree walker can just ignore it?

not sure that i have really helped any, sorry.
   -jbb