Re: [PATCH] Free results of varobj_get_type and type_to_string

[Joel Brobecker <brobecker at adacore dot com>]

Hi Simon,

On Tue, Jan 27, 2015 at 01:33:38PM -0500, Simon Marchi wrote:
> varobj_get_type and type_to_string return an allocated string, which is
> not freed at a couple of places.
> 
> gdb/ChangeLog:
> 
> 	* mi/mi-cmd-var.c (mi_cmd_var_info_type): Free result of
> 	varobj_get_type.
> 	(varobj_update_one): Same.
> 	* varobj.c (update_type_if_necessary): Free curr_type_str and
> 	new_type_str.
> 	(varobj_get_type): Specify in comment that the result needs to be
> 	freed by the caller.

Thanks looking into this. Comments below.

>    struct ui_out *uiout = current_uiout;
>    struct varobj *var;
> +  char *type;

Would you mind renaming this variable "type_name" instead of type.
I don't know about the others, but "type" is now wired into my brain
as to be a "struct type *"...

> @@ -765,7 +769,11 @@ varobj_update_one (struct varobj *var, enum print_values print_values,
>  	}
>  
>        if (r->type_changed)
> -	ui_out_field_string (uiout, "new_type", varobj_get_type (r->varobj));
> +	{
> +	  char *type = varobj_get_type (r->varobj);
> +	  ui_out_field_string (uiout, "new_type", type);
> +	  xfree (type);
> +	}

Same here, please.

Also, can you add an empty line after the local declarations?
This is part of GDB's Coding Style.

>  /* Obtain the type of an object Variable as a string similar to the one gdb
> -   prints on the console.  */
> +   prints on the console.  The caller is responsible for freeing the string.
> +   */

Thanks for updating functions' documentation. I really appreciate that.

>  char *
>  varobj_get_type (struct varobj *var)
> @@ -1303,6 +1304,8 @@ update_type_if_necessary (struct varobj *var, struct value *new_value)
>  	      var->num_children = -1;
>  	      return 1;
>  	    }
> +	  xfree (curr_type_str);
> +	  xfree (new_type_str);

In this case, you're still missing the case where the function returns,
I believe.

One way to handle the situation, I think in a way that makes the
allocation + deallocation localized would be to introduce a variable
containing the result of the strcmp? For instance:

          new_type_str = type_to_string (new_type);
          curr_type_str = varobj_get_type (var);
          type_name_has_changed = strcmp (curr_type_str, new_type_str) != 0;
          xfree (new_type_str);
          xfree (curr_type_str);

          if (type_name_has_changed)
            {

-- 
Joel