QCocoaWindow::setVisible accesses destroyed QCocoaGLContext via m_glContext member variable

With Qt 5.2.1, our application started getting random crashes, usually after closing a dialog that had a QGLWidget in it.

I found QTBUG-35600 and discovered that the sample application provided also crashes or reports one of the following errors:
"QObject: shared QObject was deleted directly. The program is malformed and may crash."
or
"malloc: *** error for object 0x1114e56c0: pointer being freed was not allocated"

After looking through the code, and at changes in 5.2, I found the changes for QTBUG-35363. Removing the changes resolved the issue. So then I tried to figure out why that was the case.

When a QGLWidget is deleted, it first deletes the openGL context, then the QWidget destructor is called and eventually calls QCocoaWindow::setVisible(false). At this point, m_glContext has been deleted but not cleared, so the call "m_glContext->windowWasHidden()" corrupts memory, leading to later random crashes.

A solution that is working for me is to call doneCurrent() on the context in the QGLWidget destructor:

QGLWidget::~QGLWidget()
{
    Q_D(QGLWidget);
    if (d->glcx) // ADDED BLOCK. This clears the member m_glContext in QCocoaWindow before we delete it below.
    {
        d->glcx->doneCurrent();
    }
    delete d->glcx;
    d->glcx = 0;
    d->cleanupColormaps();
}