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Re: Compiler warning cleanup - unitilized const variables, pointer type mismatch

From: Zdenek Kotala <Zdenek(dot)Kotala(at)Sun(dot)COM>
To: Michael Meskes <meskes(at)postgresql(dot)org>
Cc: "pgsql-hackers(at)postgresql(dot)org" <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: Compiler warning cleanup - unitilized const variables, pointer type mismatch
Date: 2009-05-28 14:34:38
Message-ID: 1243521278.22457.13.camel@localhost (view raw or flat)
Thread:
Lists: pgsql-hackers
Michael Meskes píše v čt 28. 05. 2009 v 14:47 +0200:
> On Thu, May 28, 2009 at 01:51:07PM +0200, Zdenek Kotala wrote:
> > Problem is with YYLLOC_DEFAULT. When I look on macro definition 
> > 
> > #define YYLLOC_DEFAULT(Current, Rhs, N)          \
> >   Current.first_line   = Rhs[1].first_line;      \
> >   Current.first_column = Rhs[1].first_column;    \
> >   Current.last_line    = Rhs[N].last_line;       \
> >   Current.last_column  = Rhs[N].last_column;
> > 
> > It seems to me that it is OK, because 1 is used as a index which finally
> > point on yyerror_range[0]. 
> 
> Wait, this is the bison definition. Well to be more precise the bison
> definition in your bison version. Mine is different:

I took it from documentation. I have same as you in generated code.

> # define YYLLOC_DEFAULT(Current, Rhs, N)                                \
>     do                                                                  \
>       if (YYID (N))                                                    \
>         {                                                               \
>           (Current).first_line   = YYRHSLOC (Rhs, 1).first_line;        \
>           (Current).first_column = YYRHSLOC (Rhs, 1).first_column;      \
>           (Current).last_line    = YYRHSLOC (Rhs, N).last_line;         \
>           (Current).last_column  = YYRHSLOC (Rhs, N).last_column;       \
>         }                                                               \
>       else                                                              \
>         {                                                               \
>           (Current).first_line   = (Current).last_line   =              \
>             YYRHSLOC (Rhs, 0).last_line;                                \
>           (Current).first_column = (Current).last_column =              \
>             YYRHSLOC (Rhs, 0).last_column;                              \
>        }                                                               \
>     while (YYID (0))
> 
> Having said that, it doesn't really matter as we redefine the macro:
> 
> #define YYLLOC_DEFAULT(Current, Rhs, N) \
>         do { \
>                 if (N) \
>                         (Current) = (Rhs)[1]; \
>                 else \
>                         (Current) = (Rhs)[0]; \
>         } while (0)
> 
> I have to admit that those version look strikingly unsimilar to me. There is no
> reference to Rhs[N] in our macro at all. But then I have no idea whether this
> is needed.

Current is only int. See gramparse.h. I think we could rewrite it this
way:

#define YYLLOC_DEFAULT(Current, Rhs, N) \
	do { \
		if (N) \
			(Current) = (Rhs)[1]; \
		else \
			(Current) = (Rhs)[N]; \
	} while (0)

It is same result and compiler is quite.

		Zdenek






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