Hi all,
I am quite amateur when it comes to development, but I really want to keep
GNUMail alive as my primary email client.
So bear with me if this analysis is a bit thin.
While debugging why the closing the Compose window (by hitting X or clicking
'Send') generates a SIGSEGV, I found the following and I would like to know
your opinions whether this is a bug in GNUstep gui classes or in GNUMail.
First some structures:
EditWindow is a subclass of NSWindow
EditWindowController is a subclass of NSWindowController.
The controller is has the following initializer, and it is not using NIBs on
Linux so the method argument is not important right now:
- (id) initWithWindowNibName: (NSString *) windowNibName
It creates a window with:
theEditWindow = [[EditWindow alloc] initWithContentRect:
NSMakeRect(50,75,750,520)
styleMask: (NSClosableWindowMask|NSTitledWindowMask|
NSMiniaturizableWindowMask|NSResizableWindowMask)
backing: NSBackingStoreRetained
defer: NO];
self = [super initWithWindow: theEditWindow];
It then sets itself to be the delegate:
[theEditWindow setDelegate: self];
the controller is adding a Toolbar with the following setup and attaches it
to the window
// We initialize our toolbar
aToolbar = [[NSToolbar alloc] initWithIdentifier: @"EditWindowToolbar"];
[aToolbar setDelegate: self];
..
[[self window] setToolbar: aToolbar];
RELEASE(aToolbar);
With this known we know that:
* the EditWindow's delegate is the EditWindowController
* the toolbar in the EditWindow has the EditWindowController as delegate.
Now the problem:
When you hit 'Send' or close the window the following deallocation sequence
is happening (ordered):
-dealloc in EditWindowController is called. (This goes fine)
-dealloc in EditWindow is called and crashes.
The crash is happening when [super dealloc] is called and the following
deallocation sequence is happening:
In NSWindow.m:734 -dealloc first thing that is called is [self setToolbar:
nil];
It will try to remove the last toolbar view with (a GSWindowDecorationView
*_wv;) with removeToolbarView: [_toolbar _toolbarView].
The last method call in removeToolbarView is this:
[self changeWindowHeight: -toolbarViewHeight];
This is calling the follwing to adjust the frame in the NSWindow:
[window setFrame: windowFrame display: YES];
Here is the problem in the setFrame:display method that causes the sigsegv:
2067 if (NSEqualSizes(frameRect.size, _frame.size) == NO)
2068 {
2069 if ([_delegate respondsToSelector:
@selector(windowWillResize:toSize:)])
2070 {
2071 frameRect.size = [_delegate windowWillResize: self
2072 toSize:
frameRect.size];
2073 }
2074 }
Note, at this point _delegate will be 0xdeadface because the
EditWindowController has been deallocated and therefore respondsToSelector
will crash.
Now, my question is - is this a GNUMail bug (i.e. the NSToolbar should have
been deallocated earlier) or is it a problem with the GSWindowDecorationView
removeToolbarView? Perhaps there should be a check if the delegate still is
valid before calling setFrame?
The workaround is to set NSZombieEnabled to YES, but that will just hide the
problem.
Any ideas?
Best regards,
Tim
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