Re: -var-update and address changes

[Jim Ingham <jingham@apple.com>]

Shouldn't the call to var->root->lang->value_of_root down at the  
bottom of value_of_root take care of fetching the new value?  You  
don't want to discard the old varobj unless you have to, because if  
the varobj represents a structure or pointer to a structure and the  
user has fetched any children, or changed the format, or whatever,  
you will lose that state.

Also, I must be missing something this morning, but I can't see any  
difference between your two examples.

Jim

On May 2, 2006, at 6:40 AM, Vladimir Prus wrote:

> On Tuesday 02 May 2006 17:14, Nick Roberts wrote:
>> Vladimir Prus writes:
>>> On Friday 14 April 2006 23:49, Jim Ingham wrote:
>>>> Note as an aside, that we had to add another varobj type which is
>>>> evaluated in the selected frame, whatever that happens to be.  That
>>>> was useful for a general "variable inspector" window.  People  
>>>> wanted
>>>> to put some expression there, and have it re-evaluated in the  
>>>> topmost
>>>> frame whenever they stopped.  So we added that functionality.  But
>>>> that is clearly distinct from what the "*" varobj type is  
>>>> supposed to
>>>> mean.
>>>
>>> Hi Jim,
>>> is this "variable inspector" the same thing that's called  
>>> "watches" in
>>> other IDEs? Well, I really wish that gdb did support variable  
>>> objects
>>> that are reevaluated in the current frame. As it stands now, I  
>>> have to
>>> re-create variable objects on each step.
>>
>> Assuming some ambiguity with current/selected, have you tried (not
>> documented):
>>
>> "-var-create - @ NAME"
>>
>> which behaves a bit differently to "-var-create - * NAME".
>
> Wow, that's exactly what I'm looking for. Except that it's buggy :-(
> When I have code like this:
>
>   int foo()
>   {
>       long i = 15;
>       printf("foo\n");
>   }
>
>   int main()
>   {
>     int i = 5;
>     printf("hi 1\n");
>     foo();
>   }
>
> and I use
>
>   -var-create I @ i
>
> right before call to 'foo()', then when I enter 'foo', -var-update  
> correctly
> notices the change in value and in type. However, when I have:
>
>   int foo()
>   {
>       long i = 15;
>       printf("foo\n");
>   }
>
>   int main()
>   {
>     int i = 5;
>     printf("hi 1\n");
>     foo();
>   }
>
> then -var-update inside 'foo' does not report anything and
> -var-evaluate-expression still reports the value of 'i' from  
> 'main'. Here's
> the faulty code (varobj.c: value_of_root):
>
>     tmp_var = varobj_create (NULL, var->name, (CORE_ADDR) 0,
> 			       USE_SELECTED_FRAME);
>      if (tmp_var == NULL)
> 	{
> 	  return NULL;
> 	}
>      new_type = varobj_get_type (tmp_var);
>      if (strcmp (old_type, new_type) == 0)
> 	{
> 	  varobj_delete (tmp_var, NULL, 0);
> 	  *type_changed = 0;
> 	}
>      else
>
> In other words, if the type of 'i' in the current frame happens to  
> be the
> same, the newly created varobj is immediately deleted. What about  
> patch along
> the following lines, that will create new varobj even if type is  
> the same?
>
> @@ -1641,28 +1741,14 @@
>  	  return NULL;
>  	}
>        new_type = varobj_get_type (tmp_var);
> -      if (strcmp (old_type, new_type) == 0)
> -	{
> -	  varobj_delete (tmp_var, NULL, 0);
> -	  *type_changed = 0;
> -	}
> -      else
> -	{
> -	  if (*type_changed)
> -	    {
> -	      tmp_var->obj_name =
> -		savestring (var->obj_name, strlen (var->obj_name));
> -	      varobj_delete (var, NULL, 0);
> -	    }
> -	  else
> -	    {
> -	      tmp_var->obj_name = varobj_gen_name ();
> -	    }
> -	  install_variable (tmp_var);
> -	  *var_handle = tmp_var;
> -	  var = *var_handle;
> -	  *type_changed = 1;
> -	}
> +      *type_changed = (strcmp (old_type, new_type) != 0);
> +
> +      tmp_var->obj_name =
> +          savestring (var->obj_name, strlen (var->obj_name));
> +      varobj_delete (var, NULL, 0);
> +      install_variable (tmp_var);
> +      *var_handle = tmp_var;
> +      var = *var_handle;
>      }
>
> - Volodya
>