Re: how to get left hand side symbol in action

[Akim Demaille]

Hi Christian,

CC'd to help-bison FTR.

> Le 7 juin 2020 à 18:17, Christian Schoenebeck <schoenebeck@crudebyte.com> a 
> écrit :
> 
> Hi Akim,
> 
> I just realized that you removed YYTERROR from Bison.

YYTERROR was not a documented feature.  I'm curious: how did you use it?

Bison 3.6 introduce symbol kinds, e.g., for Bison itself:

enum yysymbol_kind_t
{
  YYSYMBOL_YYEMPTY = -2,
  YYSYMBOL_YYEOF = 0,                      /* "end of file"  */
  YYSYMBOL_YYerror = 1,                    /* error  */
  YYSYMBOL_YYUNDEF = 2,                    /* "invalid token"  */
  YYSYMBOL_STRING = 3,                     /* "string"  */
  YYSYMBOL_TSTRING = 4,                    /* "translatable string"  */
  YYSYMBOL_PERCENT_TOKEN = 5,              /* "%token"  */
  YYSYMBOL_PERCENT_NTERM = 6,              /* "%nterm"  */
  YYSYMBOL_PERCENT_TYPE = 7,               /* "%type"  */


so something like this should help supporting both:

#ifndef YYTERROR
# define YYTERROR YYSYMBOL_YYerror
#endif

Unfortunately it sends the present into the past instead of the converse.  
Alternatively

#ifdef YYTERROR
# define YYSYMBOL_YYerror YYTERROR
#endif

or something like that, should allow you to use the public interface with 
earlier versions of Bison.

> As I have to preserve backward compatibility to older Bison versions, that 
> hard change is exactly Bison >= 3.6.0, correct?

Yup.  What is your current requirement?

Cheers!