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

[Nick Roberts <nickrob at snap dot net dot nz>]

 > > 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.
 > 
 > Sounds good.  I generally agree with Vladimir about reusing
 > c_value_of_variable, however.
 > 
 > I believe it is as simple as:
 >   - Passing a struct value *.
 >   - Always returning NULL if there is no value, instead of doing
 >     the struct and array special cases first.
 >   - Using value_type to get the type code and the number of children.
 >   - Probably calling value_fetch_lazy first when passing it the new
 >     value, to avoid the assertions.

I've probably done it the other way round to how you're asking (used
value_get_print_value in c_value_of_variable) but, likewise, it involves
re-use. 

 > Let me know if you want me to try that myself.

If you approve what I've done that's fine, if not, perhaps you could show me
what you want.

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


2007-01-03  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. 
	(c_value_of_variable): Use value_get_print_value.


*** varobj.c	04 Jan 2007 16:22:25 +1300	1.68
--- varobj.c	04 Jan 2007 17:00:45 +1300	
*************** struct varobj
*** 102,107 ****
--- 102,108 ----
    /* 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
*** 127,132 ****
--- 128,136 ----
  
    /* 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
*** 234,239 ****
--- 238,246 ----
  
  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
*************** c_value_of_variable (struct varobj *var)
*** 2153,2171 ****
  	  }
  	else
  	  {
- 	    long dummy;
- 	    struct ui_file *stb = mem_fileopen ();
- 	    struct cleanup *old_chain = make_cleanup_ui_file_delete (stb);
- 	    char *thevalue;
- 
  	    gdb_assert (type_changeable (var));
  	    gdb_assert (!value_lazy (var->value));
! 	    common_val_print (var->value, stb,
! 			      format_code[(int) var->format], 1, 0, 0);
! 	    thevalue = ui_file_xstrdup (stb, &dummy);
! 	    do_cleanups (old_chain);
! 	return thevalue;
!       }
        }
      }
  }
--- 2186,2195 ----
  	  }
  	else
  	  {
  	    gdb_assert (type_changeable (var));
  	    gdb_assert (!value_lazy (var->value));
! 	    return value_get_print_value (var->value, var->format);
! 	  }
        }
      }
  }