Re: %destructor feedback

[Joel E. Denny]

On Tue, 27 Dec 2005, Akim Demaille wrote:

> Le 22 d?c. 05 ? 19:49, Joel E. Denny a ?crit :
> 
> > Would it be worthwhile to warn about unmentioned typed $$ as well?
[snip]
> I installed the following.  Note that the warning is somewhat annoying
> with rules running YYERROR etc.

After seeing your test case patch, I seriously reconsidered whether $$ 
warnings were reasonable.  However, the function analogy for semantic 
actions helped me think this through.  Typed RHS symbols are like 
parameters.  As we well know, a good compiler or lint implementation will 
warn you if you forget to use one.  Typed LHS symbols are like non-void 
return types.  A good compiler will also warn you if you forget to return 
something.  However, I've not seen a compiler that suppresses this warning 
just because you invoke abort() somewhere.

The following seems misleading to me because it seems to imply that the 0 
actually has some significance even though the parser discards $$.  You 
did something similar in your test case patch:

  {
    $$ = 0;
    YYABORT;
  }

This seems clearer:

  {
    YYABORT;
    $$ = 0;
  }

similar to:

  int function() {
    abort();
    return 0;
  }

This seems even clearer:

  {
    YYABORT;
    YYUSE_VAL ($$);
  }

What do you think?

Joel