Re: Locations in bison itself are wrong

[Paul Eggert]

Akim Demaille <address@hidden> writes:

> @@ -1069,6 +1073,7 @@
>    yyssp = yyss;
>    yyvsp = yyvs;
>    yylsp = yyls;
> +  *yylsp = b4_location_initial;
>    goto yysetstate;
>
>  /*------------------------------------------------------------.
>
> with a bit more m4_ifdef so that only people specifying it will
> trigger the code (any K&R portability issue with struct assignments?).

glr.c has this:

static YYLTYPE yyloc_default;

and uses it unconditionally, without letting the user override it as
far as I can see.  Is that the sort of thing you wanted to see?

Hmm, how about something like this instead?  It would allow overriding.

#ifndef YYLOC_START_OF_INPUT
# define YYLOC_START_OF_INPUT(loc) ((loc).last_line = 1, (loc).last_column = 0)
#endif

    ...
    yylsp = yyls;
    YYLOC_START_OF_INPUT (*yylsp);
    goto yysetstate;

That way, a user who overrides YYLLOC_DEFAULT can also override
YYLOC_START_OF_INPUT consistently with YYLLOC_DEFAULT.

> An alternative would consist in using the location of the lookahead,

I agree that this won't work, for the reasons that you gave.