On Sat, Feb 19, 2011 at 12:26:47PM -0500, Joel E. Denny wrote:
> On Sat, 12 Feb 2011, Bill Allombert wrote:
>
> > I have a grammar that handles errors.
>
> Do you mean you're using Bison's error token?
Yes.
> Or do you mean that you've written grammar rules that match syntactically
> incorrect input?
More or less.
The grammar specification has a notion of the 'largest valid subexpression'.
I use the error token to implement that: the error token mark the end of the
expression.
At this point I call yyerrok and continue. This works fine unless one of the
largest
valid subexpression is empty because bison will discard token instead fo
reporting a syntax
error.
Basically I do:
list: expr
| list error {if (!once) { yyerrok; } once=1;} expr {once=0;}
;
the variable once preventing two error to coalesce into one.
> > However, in this contest, discarding
> > tokens is highly undesirable, much more so than aborting.
>
> Do you mean that you've declared destructors with %destructor?
No.
However Chris verBurg suggested to me to add a destructor
%destructor { ++number_discarded_symbols; }
and to check at the end of parsing if number_discarded_symbols > 1 in which case
the program abort with a syntax error. So far this has been successful.
Cheers,
Bill.
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