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Re: too many warnings from Bison CVS for Pike
From: |
Joel E. Denny |
Subject: |
Re: too many warnings from Bison CVS for Pike |
Date: |
Sun, 29 Jan 2006 14:11:16 -0500 (EST) |
On Sun, 29 Jan 2006, Hans Aberg wrote:
> On 29 Jan 2006, at 18:28, Joel E. Denny wrote:
>
> > Beyond the C++ issue you raise, it seems that an action containing nothing
> > but $$ = $2 ought to warn about an unused (typed) $1.
>
> Unused token values are pretty common: just take
> "if" A "then" B
> Here, the token values of "if" and "then" will be unused in the rule action.
> If this should work, I guess you are calling for a special token type, say
> "void", and the warning should come if some non-void $k isn't used.
We already have this "void" type: just don't declare a type.
> Now, with a code placement in hand, one wants to be able to put code at
> various place, including just ahead of the switch statement; call the macro
> say 'pre-switch'. Then a fix under C for those that want $$ = $1 would a
> grammar '.y' file containing:
> %define pre-switch { if (yylen >= 1) $$ = $1; }
This isn't yacc compatible. If the Open Group says we need implicit $$ =
$1 for explicit actions, bison needs to support it for pure yacc
specifications.
Maybe there's still the question of what exactly they mean by:
By default, the value of a rule is the value of the first element in it.
I feel pretty sure that Paul is right: `By default' does *not* mean `When
the user doesn't specify the action'; it means `When the user doesn't
specify the value of the rule'. In other words, in all cases, $1 is the
default value of $$. So, this is a yacc issue.
Joel
- too many warnings from Bison CVS for Pike, Paul Eggert, 2006/01/28
- Re: too many warnings from Bison CVS for Pike, Hans Aberg, 2006/01/29
- Re: too many warnings from Bison CVS for Pike, Joel E. Denny, 2006/01/29
- Re: too many warnings from Bison CVS for Pike, Hans Aberg, 2006/01/29
- Re: too many warnings from Bison CVS for Pike,
Joel E. Denny <=
- Re: too many warnings from Bison CVS for Pike, Hans Aberg, 2006/01/29
- Re: too many warnings from Bison CVS for Pike, Joel E. Denny, 2006/01/29
- Re: too many warnings from Bison CVS for Pike, Hans Aberg, 2006/01/29
- Re: too many warnings from Bison CVS for Pike, Joel E. Denny, 2006/01/29
- Re: too many warnings from Bison CVS for Pike, Hans Aberg, 2006/01/29
- Re: too many warnings from Bison CVS for Pike, Joel E. Denny, 2006/01/29
- Re: too many warnings from Bison CVS for Pike, Hans Aberg, 2006/01/30
- Re: too many warnings from Bison CVS for Pike, Joel E. Denny, 2006/01/30
- Re: too many warnings from Bison CVS for Pike, Hans Aberg, 2006/01/30
- Re: too many warnings from Bison CVS for Pike, Joel E. Denny, 2006/01/30