Re: [RFA] Change to parse error reporting

[Michael Snyder <msnyder at redhat dot com>]

Michael Snyder wrote:
> 
> Folks,
> 
> I've never liked the way in which "parse error" messages in gdb
> always point to the token _after_ the error, instead of at the
> token _causing_ the error.
> 
> This change (implemented for the c/c++ parser only) will make it
> point at the error token instead of the following token.
> Extending the change to the other languages will be trivial,
> if you agree with this.
> 
> OK to commit?

Does anybody have any opinion about this?
If not I'll check it in next week.

> 
> 2002-04-12  Michael Snyder  <msnyder@redhat.com>
> 
>         * parser-defs.h (prev_lexptr): New external variable.
>         * parse.c (parse_exp_1): Set prev_lexptr to null before
>         calling the language-specific parser.
>         * c-exp.y (yylex): Set prev_lexptr to start of current token.
>         (yyerror): Use prev_lexptr in error reporting.
> 
> Index: parse.c
> ===================================================================
> RCS file: /cvs/src/src/gdb/parse.c,v
> retrieving revision 1.22
> diff -p -r1.22 parse.c
> *** parse.c     9 Apr 2002 22:14:39 -0000       1.22
> --- parse.c     12 Apr 2002 19:40:35 -0000
> *************** int arglist_len;
> *** 76,81 ****
> --- 76,82 ----
>   union type_stack_elt *type_stack;
>   int type_stack_depth, type_stack_size;
>   char *lexptr;
> + char *prev_lexptr;
>   char *namecopy;
>   int paren_depth;
>   int comma_terminates;
> *************** parse_exp_1 (char **stringptr, struct bl
> *** 1126,1131 ****
> --- 1127,1133 ----
>     struct cleanup *old_chain;
> 
>     lexptr = *stringptr;
> +   prev_lexptr = NULL;
> 
>     paren_depth = 0;
>     type_stack_depth = 0;
> Index: parser-defs.h
> ===================================================================
> RCS file: /cvs/src/src/gdb/parser-defs.h,v
> retrieving revision 1.7
> diff -p -r1.7 parser-defs.h
> *** parser-defs.h       9 Apr 2002 22:14:39 -0000       1.7
> --- parser-defs.h       12 Apr 2002 19:40:35 -0000
> *************** extern struct type *follow_types (struct
> *** 150,155 ****
> --- 150,159 ----
> 
>   extern char *lexptr;
> 
> + /* After a token has been recognized, this variable points to it.
> +    Currently used only for error reporting.  */
> + extern char *prev_lexptr;
> +
>   /* Tokens that refer to names do so with explicit pointer and length,
>      so they can share the storage that lexptr is parsing.
> 
> Index: c-exp.y
> ===================================================================
> RCS file: /cvs/src/src/gdb/c-exp.y,v
> retrieving revision 1.7
> diff -p -r1.7 c-exp.y
> *** c-exp.y     15 Nov 2001 01:55:59 -0000      1.7
> --- c-exp.y     12 Apr 2002 19:40:35 -0000
> *************** yylex ()
> *** 1218,1223 ****
> --- 1218,1224 ----
> 
>    retry:
> 
> +   prev_lexptr = lexptr;
>     unquoted_expr = 1;
> 
>     tokstart = lexptr;
> *************** void
> *** 1738,1742 ****
> --- 1739,1746 ----
>   yyerror (msg)
>        char *msg;
>   {
> +   if (prev_lexptr)
> +     lexptr = prev_lexptr;
> +
>     error ("A %s in expression, near `%s'.", (msg ? msg : "error"), lexptr);
>   }