Re: RFC: MI - Detecting change of string contents with variable objects

[Nick Roberts <nickrob@snap.net.nz>]

 >  Should a varobj always report changed if the way GDB
 > would display the value has changed, in which case the special casing
 > isn't necessary?

That's a vary good idea.  Here's a revised patch that isn't language dependent.
In addition to detecting string contents changes it detects when the output
format has changed with -var-set-format.  I don't see this as a bad thing
and it means that my patch earlier in the year for including the value
in the output of -var-set-format probably isn't needed.

It also means that value_contents_equal is not needed any longer, although I
guess there's no harm in keeping it.


-- 
Nick                                           http://www.inet.net.nz/~nickrob


2006-12-19  Nick Roberts  <nickrob@snap.net.nz>

	* varobj.c (struct varobj): New member print_value.
	(install_new_value): Compare last printed value with current one
	instead of contents.
	(new_variable): Initialize var->print_value to NULL.
	(free_variable): Free var->print_value.
	(value_get_print_value): New function derived from
	c_value_of_variable.


*** varobj.c	11 Dec 2006 08:13:03 +1300	1.65
--- varobj.c	19 Dec 2006 10:27:50 +1300	
*************** struct varobj
*** 101,106 ****
--- 101,107 ----
    /* The type of this variable. This may NEVER be NULL. */
    struct type *type;
  
+ 
    /* The value of this expression or subexpression.  This may be NULL. 
       Invariant: if type_changeable (this) is non-zero, the value is either
       NULL, or not lazy.  */
*************** struct varobj
*** 126,131 ****
--- 127,135 ----
  
    /* Was this variable updated via a varobj_set_value operation */
    int updated;
+ 
+   /* Last print value */
+   char *print_value;
  };
  
  /* Every variable keeps a linked list of its children, described
*************** static int variable_editable (struct var
*** 233,238 ****
--- 237,245 ----
  
  static char *my_value_of_variable (struct varobj *var);
  
+ static char *value_get_print_value (struct value *value,
+ 				    enum varobj_display_formats format);
+ 
  static int type_changeable (struct varobj *var);
  
  /* C implementation */
*************** install_new_value (struct varobj *var, s
*** 979,1003 ****
  	  else
  	    {
  	      gdb_assert (!value_lazy (var->value));
- 	      gdb_assert (!value_lazy (value));
  	      
! 	      if (!value_contents_equal (var->value, value))
! 		changed = 1;
  	    }
  	}
      }
!     
    /* We must always keep the new value, since children depend on it.  */
    if (var->value != NULL)
      value_free (var->value);
    var->value = value;
    var->updated = 0;
!   
    gdb_assert (!var->value || value_type (var->value));
  
    return changed;
  }
-   
  
  /* Update the values for a variable and its children.  This is a
     two-pronged attack.  First, re-parse the value for the root's
--- 986,1020 ----
  	  else
  	    {
  	      gdb_assert (!value_lazy (var->value));
  	      
! 	      if (var->print_value)
! 		{
! 		  if (strcmp (var->print_value,
! 			      value_get_print_value (value, var->format)))
! 		    {
! 		      xfree (var->print_value);
! 		      var->print_value =
! 			xstrdup (value_get_print_value (value, var->format));
! 		      changed = 1;
! 		    }
! 		}
! 	      else
! 		var->print_value =
! 		  xstrdup (value_get_print_value (value, var->format));
  	    }
  	}
      }
! 
    /* We must always keep the new value, since children depend on it.  */
    if (var->value != NULL)
      value_free (var->value);
    var->value = value;
    var->updated = 0;
! 
    gdb_assert (!var->value || value_type (var->value));
  
    return changed;
  }
  
  /* Update the values for a variable and its children.  This is a
     two-pronged attack.  First, re-parse the value for the root's
*************** new_variable (void)
*** 1470,1475 ****
--- 1487,1493 ----
    var->format = 0;
    var->root = NULL;
    var->updated = 0;
+   var->print_value = NULL;
  
    return var;
  }
*************** free_variable (struct varobj *var)
*** 1503,1508 ****
--- 1521,1527 ----
  
    xfree (var->name);
    xfree (var->obj_name);
+   xfree (var->print_value);
    xfree (var);
  }
  
*************** my_value_of_variable (struct varobj *var
*** 1785,1790 ****
--- 1804,1823 ----
    return (*var->root->lang->value_of_variable) (var);
  }
  
+ static char *
+ value_get_print_value (struct value *value, enum varobj_display_formats format)
+ {
+   long dummy;
+   struct ui_file *stb = mem_fileopen ();
+   struct cleanup *old_chain = make_cleanup_ui_file_delete (stb);
+   char *thevalue;
+ 	    
+   common_val_print (value, stb, format_code[(int) format], 1, 0, 0);
+   thevalue = ui_file_xstrdup (stb, &dummy);
+   do_cleanups (old_chain);
+   return thevalue;
+ }
+ 
  /* Return non-zero if changes in value of VAR
     must be detected and reported by -var-update.
     Return zero is -var-update should never report