Patchwork Free results of varobj_get_type and type_to_string

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Submitter Simon Marchi
Date Jan. 27, 2015, 6:33 p.m.
Message ID <1422383618-8215-1-git-send-email-simon.marchi@ericsson.com>
Download mbox | patch
Permalink /patch/4830/
State New
Headers show

Comments

Simon Marchi - Jan. 27, 2015, 6:33 p.m.
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.
---
 gdb/mi/mi-cmd-var.c | 12 ++++++++++--
 gdb/varobj.c        |  5 ++++-
 2 files changed, 14 insertions(+), 3 deletions(-)
Joel Brobecker - Jan. 29, 2015, 5:11 a.m.
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)
            {

Patch

diff --git a/gdb/mi/mi-cmd-var.c b/gdb/mi/mi-cmd-var.c
index 01838b1..4aabb57 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;
 
   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 = varobj_get_type (var);
+
+  ui_out_field_string (uiout, "type", type);
 
-  ui_out_field_string (uiout, "type", varobj_get_type (var));
+  xfree (type);
 }
 
 void
@@ -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);
+	}
 
       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..9735958 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)
@@ -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);
 	}
     }