Re: Scope Checking Patch

["Rob Quill" <rob.quill@gmail.com>]

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On 10/06/07, Rob Quill <rob.quill@gmail.com> wrote:
> Hi all,
>
> This is the first patch I have ever submitted to an open source
> project, so I'm a little bit unsure of the process. The patch adds the
> ability to check if a variable is in scope, as descibed here:
>
> http://sourceware.org/ml/gdb/2006-11/msg00149.html
>
> I have attached the diffs for the two files I've changed. However, I
> am seeing some regressions against the current cvs, which I can't
> understand, so I was wondering if a) the regressions happen for anyone
> esle? (which presumably it does), b) if anyone could offer any
> suggestions as to the cause, and c) give thier opinions on the patch.
>
> The patch allows the scope of constants, variables and variables in
> classes/structures, by using $in_scope(variable_name) as an
> expression, with value 1 if variable_name is in scope and 0 if it is
> not.
>
> Any help and thoughts you can offer is much appreciated.

...Diffs attached, sorry.

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103a104,106
> /* Global variable denoting whether we are only interested in scope, not value */
> int check_scope = 0;
> 
203a207,208
> /* $in_scope opperator */
> %left IN_SCOPE
246a252,256
> exp	:	IN_SCOPE
> 			{ check_scope = 1; }
> 		'(' exp ')'
> 	;
> 
586c596,602
< 			    error ("No symbol \"%s\" in specified context.",
---
> 			  {
> 			    /* Case for scope checking. If scope is being checked and
> 				   the symbol is not in scope, return an expresison of
> 				   value 0. */
> 			    if(check_scope == 0)
> 			    {
> 			       error ("No symbol \"%s\" in specified context.",
587a604,614
> 			    }
> 			    else
> 			    {
> 				   YYSTYPE val;
> 			 	   parse_number ("0", 1, 0, &val);
> 			  	   write_exp_elt_opcode (OP_LONG);
> 			  	   write_exp_elt_type (val.typed_val_int.type);
> 			  	   write_exp_elt_longcst ((LONGEST)val.typed_val_int.val);
> 			  	   write_exp_elt_opcode (OP_LONG);
> 			    }
> 			  }
666,667c693,708
< 			      error ("No symbol \"%s\" in current context.", name);
< 			}
---
> 			    {
> 			      if(check_scope == 0)
> 			      {
> 			    	error ("No symbol \"%s\" in current context.", name);
> 			      }
> 			      else
> 			      {
>                      YYSTYPE val;
>                      parse_number ("0", 1, 0, &val);
>                      write_exp_elt_opcode (OP_LONG);
>                      write_exp_elt_type (val.typed_val_int.type);
>                      write_exp_elt_longcst ((LONGEST)val.typed_val_int.val);
>                      write_exp_elt_opcode (OP_LONG);
> 			      }
> 			    }
> }
721,722c762,774
< 				error ("No symbol \"%s\" in current context.",
< 				       copy_name ($1.stoken));
---
> 			      {
> 			        if(check_scope == 0)
> 				       error ("No symbol \"%s\" in current context.", copy_name ($1.stoken));
> 			        else
> 			        {
> 				       YYSTYPE val;
> 			 	       parse_number ("0", 1, 0, &val);
> 			  	       write_exp_elt_opcode (OP_LONG);
> 			  	       write_exp_elt_type (val.typed_val_int.type);
> 			  	       write_exp_elt_longcst ((LONGEST)val.typed_val_int.val);
> 			  	       write_exp_elt_opcode (OP_LONG);
> 				    }
> 			      }
1260a1313,1317
> static const struct token tokentab9[] =
>   {
>     {"$in_scope", IN_SCOPE, BINOP_END}
>   };
> 
1322a1380,1388
>   /* Code for recognising the $in_scope token. */
>   /* See if it is a special token of length 9.  */
>   for (i = 0; i < sizeof tokentab9 / sizeof tokentab9[0]; i++)
>     if (strncmp (tokstart, tokentab9[i].operator, 9) == 0)
>       {
> 	lexptr += 9;
> 	yylval.opcode = tokentab9[i].opcode;
> 	return tokentab9[i].token;
>       }

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48a49,51
> /* Variable denoting is scope is being checked */
> extern int check_scope;
> 
167c170,179
<   return evaluate_subexp (NULL_TYPE, exp, &pc, EVAL_NORMAL);
---
> 
>   /* Modifications so that if we are checking scope we can 
>      reset the value of the variable to 0, so we don't check 
>      scope when we don't want to */
>   struct value *val = evaluate_subexp (NULL_TYPE, exp, &pc, EVAL_NORMAL);
>   
>   if(check_scope == 1)
>     check_scope = 0;
> 
>   return val;
474a487,494
> 	/* Special case, if we are checking scope and a variable is 
>        in scope, return a expression of value 1. */
> 	if(check_scope == 0)
> 	  return value_of_variable (exp->elts[pc + 2].symbol,
> 				    exp->elts[pc + 1].block);
> 	else
> 	  return value_from_longest (builtin_type_int, (LONGEST) 1);
> 
1336c1356,1368
<       arg1 = evaluate_subexp (NULL_TYPE, exp, pos, noside);
---
> 
>       /* Temporalily disable scope checking while we evaluate
>          the subexpression, so that the correct type of value
>          is returned */
>       if(check_scope == 1)
>        {
> 	     check_scope = 0;
>          arg1 = evaluate_subexp (NULL_TYPE, exp, pos, noside);
>          check_scope = 1;
>        }
>       else
>          arg1 = evaluate_subexp (NULL_TYPE, exp, pos, noside);
>