Re: [PATCH] Free results of varobj_get_type and type_to_string

[Simon Marchi <simon dot marchi at ericsson dot com>]

On 15-01-29 12:11 AM, Joel Brobecker wrote:
> 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 *"...

Done.

>> @@ -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.

Done and done.

>>  /* 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)
>             {

Done.

Thanks, here's v2.

>From a1f4ce1e15a1ce7806c331a2600b57353331807b Mon Sep 17 00:00:00 2001
From: Simon Marchi <simon.marchi@ericsson.com>
Date: Tue, 27 Jan 2015 11:43:35 -0500
Subject: [PATCH] Free results of varobj_get_type and type_to_string

varobj_get_type and type_to_string return an allocated string, which is
not freed at a couple of places.

New in v2:
 * Rename char * type to type_name.
 * Free in all cases in update_type_if_necessary.

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.
---
 gdb/mi/mi-cmd-var.c | 13 +++++++++++--
 gdb/varobj.c        | 10 ++++++++--
 2 files changed, 19 insertions(+), 4 deletions(-)

diff --git a/gdb/mi/mi-cmd-var.c b/gdb/mi/mi-cmd-var.c
index 01838b1..d873a17 100644
--- a/gdb/mi/mi-cmd-var.c
+++ b/gdb/mi/mi-cmd-var.c
@@ -447,14 +447,18 @@ mi_cmd_var_info_type (char *command, char **argv, int argc)
 {
   struct ui_out *uiout = current_uiout;
   struct varobj *var;
+  char *type_name;

   if (argc != 1)
     error (_("-var-info-type: Usage: NAME."));

   /* Get varobj handle, if a valid var obj name was specified.  */
   var = varobj_get_handle (argv[0]);
+  type_name = varobj_get_type (var);

-  ui_out_field_string (uiout, "type", varobj_get_type (var));
+  ui_out_field_string (uiout, "type", type_name);
+
+  xfree (type_name);
 }

 void
@@ -765,7 +769,12 @@ 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_name = varobj_get_type (r->varobj);
+
+	  ui_out_field_string (uiout, "new_type", type_name);
+	  xfree (type_name);
+	}

       if (r->type_changed || r->children_changed)
 	ui_out_field_int (uiout, "new_num_children",
diff --git a/gdb/varobj.c b/gdb/varobj.c
index a10560f..dad284d 100644
--- a/gdb/varobj.c
+++ b/gdb/varobj.c
@@ -972,7 +972,8 @@ varobj_add_child (struct varobj *var, struct varobj_item *item)
 }

 /* 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.
+   */

 char *
 varobj_get_type (struct varobj *var)
@@ -1289,11 +1290,16 @@ update_type_if_necessary (struct varobj *var, struct value *new_value)
 	{
 	  struct type *new_type;
 	  char *curr_type_str, *new_type_str;
+	  int type_name_changed;

 	  new_type = value_actual_type (new_value, 0, 0);
 	  new_type_str = type_to_string (new_type);
 	  curr_type_str = varobj_get_type (var);
-	  if (strcmp (curr_type_str, new_type_str) != 0)
+	  type_name_changed = strcmp (curr_type_str, new_type_str) != 0;
+	  xfree (curr_type_str);
+	  xfree (new_type_str);
+
+	  if (type_name_changed)
 	    {
 	      var->type = new_type;

-- 
1.9.1