Re: error: ‘else’ without a previous ‘ if’

[Joel E. Denny]

Hi Tys,

On Wed, 13 Jan 2010, tys lefering wrote:

> when updating today bison, gnulib and autoconf from git repo
> and installing bison the generated yacc parser does not compile
> with this error when using gcc or g++:
> 
> y.tab.c: In function ?yyparse?:
> y.tab.c:5998: error: ?else? without a previous ?if?

> source code part of the parser is here

>           if (yysyntax_error_status == 0)
>             yyerror (yymsg);
>           else  /* <-- y.tab.c:5998: error: ?else? without a previous ?if?*/
>             yyerror (YY_("syntax error"));

> when changing parser code to this adding '{' and '}' gcc / g++ does accept
> it:
> 
> if (yysyntax_error_status == 0) {
>   yyerror (yymsg);
> } else {
>   yyerror (YY_("syntax error"));
> }
> 
> any solution ? maybe add the '{' '}' in the yacc parser code ?

yyerror is supposed to be a function according to the Bison manual, but 
your grammar file defines it as braced code:

> #ifndef yyerror
> #define yyerror(x) { \
>         SPRINTF(message,"unexpected %s \"%s\" (%s)", \
>                  ((yychar<0)?"(?)":yytokname[YYTRANSLATE(yychar)]),     \
>                  (strlen(yytext)<48?yytext:"(?)"),x); \
>         syntaxerror(line_nr,pos_nr,message);\
>     }
> #endif

Thus, the Bison-generated trailing semicolon looks like a separate 
statement after your yyerror's closing brace.  That ends the `if' 
construct.

I have another patch coming that will just happen to change this passage 
of code in such a way that this won't be a problem anymore.  However, I'm 
not sure when I'll get around to proposing it.

Regardless, it would be best if you changed yyerror to a function or at 
least a function invocation.