Re: %destructor can leak the lookahead

[Akim Demaille]

Le 4 sept. 04, à 00:29, Paul Eggert a écrit :
> > how can you type it...
>
> With a %token declaration, presumably.  You are allowed to say "%token
> error 37".  So I guess you'd say "%token <string> error 37".  It might
> be useful to have this as an extension, e.g., a variant of YYERROR
> that lets you pass a semantic value back.  (But for now let's not
> worry about this.  :-)

I didn't mean how you could do that in practice, but really "what could
it really mean, and how could a single typing fit a token such as error
which is used with many different types".  This is what I meant by
"overloaded token".

> > --- data/yacc.c 2 Sep 2004 14:27:02 -0000 1.65
> > +++ data/yacc.c 3 Sep 2004 08:57:48 -0000
> > @@ -1209,6 +1209,9 @@
> >  | yyabortlab -- YYABORT comes here.  |
> >  `-----------------------------------*/
> >  yyabortlab:
> > +  YY_SYMBOL_PRINT ("Error: discarding lookahead", yytoken, &yylval, 
> > &yylloc);
> > +  yydestruct (yytoken, &yylval]b4_location_if([, &yylloc])[);
> > +  yychar = YYEMPTY;
> >    yyresult = 1;
> >    goto yyreturn;
>
> How do we know that yytoken is valid here, and can be destroyed?
> Might it not be the case that yychar == YYEMPTY as we pass yyabortlab?
> Similarly for the other parsers.

I don't remember so.  But anyway, extending yydestruct to the other
situations will require to make it robust to this case.

> Other than that, I didn't see any problem (except that the other
> memory leaks mention above still remain -- do you have time to look
> into them as well?).

Yep, I'll address these too.  Next week I guess.