Re: warning: unused value: $3

[Hans Aberg]

On 25 Oct 2006, at 17:05, address@hidden wrote:

> Hi Bison list,
>
> using bison version 2.2.
> Message from bison:
> pl1-parser.y:873.17-63: warning: unused value: $3
>
> This warning I find a bit confusing...
>
>
> Line 873 contains: |    procoptionlist ',' {$$=$1;} procoption {$$=$1;}
> $3 refers to the embedded action after the comma.
>
> My grammar set a number of attributes in an allocated structure  
> using $0 to
> reference the structure on the stack. The full rules are as follow
>
> procoptionlist:
>   { $<pol>$ = newProcOptionList(); }
>           procoption
>   { $$ = $<pol>1; }
> |       procoptionlist procoption {$$=$1;}
> |       procoptionlist ',' {$$=$1;} procoption {$$=$1;}
>         ;
>
> procoption:
>         MAIN { if(setTristateAttribute(&($<pol>0)->main,1)<0)  
> YYERROR; }
> ;
>
>
> unless I am missing something $3 in line 873 is by the rule  
> procoption.
> Is there anyway to supress this IMO, unnecessary warning.

I think you should take away the use of $0, because it may no longer  
be guaranteed, in view of that Bison is switching to other types of  
containers than an underlying array. Then you mid-rule action becomes  
unnecessary.

  Hans Aberg