Seg fault on closing the xpad

[Sagar Ghuge]

Steps to produce the bug :

1. launch xpad
2. try to close xpad

It will gets closed by throwing seg fault.

[Arthur Borsboom (arthurborsboom)]

Hi Sagar,

Thanks for looking into this and supplying a possible fix.
I haven't tested it, but I do have some questions.

Since the destroy function has been run before, the group->priv->pads object should be destroyed and therefore this unref seems to me not necessary and will never be called, since group->priv->pads is not an object anymore. Would you mind to verify if this added piece of code, will ever be called? Besides that, it is a good habit too set a variable to NULL when not used anymore.

- group->priv->pads = NULL;
+
+ if (G_IS_OBJECT (group->priv->pads))
+ {
+ g_object_unref (group->priv->pads);
+ }

Also by removing the code below, I guess that you introduce a memory leak on application exit. You can verify this with the application gobject-list (https://github.com/danni/gobject-list). On application exit, there should be no references to 'xpad' objects anymore. The command line I use for this is:

LD_PRELOAD=~/home/development/gojbect-list/libgobject-list.so src/xpad | grep xpad

- /* Free the memory used by group. */
- if (G_IS_OBJECT (pad_group))
- g_object_unref (pad_group);
-

My guess of the cause of the segmentation fault is a timing issue (race condition), between different threads while destroying the different objects. However, I don't have a solution for this problem yet.

Can you verify that
- the g_object_unref (group->priv->pads) is ever called?
- there are no memory leaks of xpad objects?

Cheers,
Arthur.

[Arthur Borsboom (arthurborsboom)]

In fact this is the command I use to verify memory leaks of Xpad objects:

LD_PRELOAD=~/Development/tools/gobject-list/libgobject-list.so src/xpad | grep xpad -i

And this is the result, I of Xpad 4.3 in the main branch, when I start and immediately quit the application.

 ++ Created object 0xff0af0, XpadSettings
 ++ Created object 0xfed440, XpadPadGroup
 ++ Created object 0x1055660, XpadUndo
 ++ Created object 0xf72ba0, XpadTextBuffer
 ++ Created object 0x10f8260, XpadTextView
 ++ Created object 0x112c7e0, XpadGripToolItem
 ++ Created object 0x11271d0, XpadToolbar
 ++ Created object 0x10f6450, XpadPad
 ++ Created object 0x111b1e0, XpadUndo
 ++ Created object 0x7f8b240076d0, XpadTextBuffer
 ++ Created object 0x10f8500, XpadTextView
 ++ Created object 0x1154f40, XpadGripToolItem
 ++ Created object 0x1173170, XpadToolbar
 ++ Created object 0x10f6740, XpadPad
 -- Finalized object 0x112c7e0, XpadGripToolItem
 -- Finalized object 0x11271d0, XpadToolbar
 -- Finalized object 0x10f8260, XpadTextView
 -- Finalized object 0x1055660, XpadUndo
 -- Finalized object 0xf72ba0, XpadTextBuffer
 -- Finalized object 0x10f6450, XpadPad
 -- Finalized object 0x1154f40, XpadGripToolItem
 -- Finalized object 0x1173170, XpadToolbar
 -- Finalized object 0x10f8500, XpadTextView
 -- Finalized object 0x111b1e0, XpadUndo
 -- Finalized object 0x7f8b240076d0, XpadTextBuffer
 -- Finalized object 0x10f6740, XpadPad
 -- Finalized object 0xfed440, XpadPadGroup
 -- Finalized object 0xff0af0, XpadSettings
[arthur@AOD270 xpad]$

[Arthur Borsboom (arthurborsboom)]

Okay, I couldn't resist. I just checked an indeed, this does introduce a memory leak.
After the patch, this is the result.

[arthur@AOD270 xpad-4.4]$ LD_PRELOAD=~/Development/tools/gobject-list/libgobject-list.so src/xpad | grep xpad -i
 ++ Created object 0x16c72f0, XpadSettings
 ++ Created object 0x1657e40, XpadPadGroup
 ++ Created object 0x172aa60, XpadUndo
 ++ Created object 0x1649ba0, XpadTextBuffer
 ++ Created object 0x17ce260, XpadTextView
 ++ Created object 0x18037e0, XpadGripToolItem
 ++ Created object 0x17fe1d0, XpadToolbar
 ++ Created object 0x17cc450, XpadPad
 ++ Created object 0x17f21e0, XpadUndo
 ++ Created object 0x7f53980076d0, XpadTextBuffer
 ++ Created object 0x17ce500, XpadTextView
 ++ Created object 0x182af40, XpadGripToolItem
 ++ Created object 0x1849170, XpadToolbar
 ++ Created object 0x17cc740, XpadPad
 -- Finalized object 0x18037e0, XpadGripToolItem
 -- Finalized object 0x17fe1d0, XpadToolbar
 -- Finalized object 0x17ce260, XpadTextView
 -- Finalized object 0x172aa60, XpadUndo
 -- Finalized object 0x1649ba0, XpadTextBuffer
 -- Finalized object 0x17cc450, XpadPad
 -- Finalized object 0x182af40, XpadGripToolItem
 -- Finalized object 0x1849170, XpadToolbar
 -- Finalized object 0x17ce500, XpadTextView
 -- Finalized object 0x17f21e0, XpadUndo
 -- Finalized object 0x7f53980076d0, XpadTextBuffer
 -- Finalized object 0x17cc740, XpadPad
 -- Finalized object 0x16c72f0, XpadSettings
 - 0x1657e40, XpadPadGroup: 1 refs
[arthur@AOD270 xpad-4.4]$