Fix crash in tst_Spellchecking::spellcheck

The test tst_Spellchecking::spellcheck crashes when run with

    QT_LOGGING_RULES=qt.accessibility.cache.debug=true

which triggers debug output from

    QAccessible::registerAccessibleInterface and
    QAccessible::deleteAccessibleInterface

These functions are called during the construction/destruction of
BrowserAccessibilityQt. The problem is that BrowserAccessibilityQt is not
necessarily in a valid state at these times: BrowserAccessibilityQt relies on
it's manager to be *fully* initialized yet BrowserAccessibilityQt may be
constructed/destructed *during* the managers construction/destruction.

The solution is to override QAccessibleInterface::isValid to return true only if
the manager is in a valid state too. This disables the debug output and avoids
the crash.

Fixes: QTBUG-72878
Change-Id: Icffe4e503145133c24535fb094bbcb606568e57c
Reviewed-by: Allan Sandfeld Jensen <allan.jensen@qt.io>
Reviewed-by: Peter Varga <pvarga@inf.u-szeged.hu>

1 files changed, 3 insertions, 0 deletions

diff --git a/src/core/browser_accessibility_manager_qt.h b/src/core/browser_accessibility_manager_qt.h
index a2d6db458..87c8875ba 100644
--- a/src/core/browser_accessibility_manager_qt.h
+++ b/src/core/browser_accessibility_manager_qt.h
@@ -57,14 +57,17 @@ public:
                                   const ui::AXTreeUpdate& initialTree,
                                   BrowserAccessibilityDelegate* delegate,
                                   BrowserAccessibilityFactory* factory = new BrowserAccessibilityFactory());
+    ~BrowserAccessibilityManagerQt() override;
     void FireBlinkEvent(ax::mojom::Event event_type,
                         BrowserAccessibility* node) override;
 
     QAccessibleInterface *rootParentAccessible();
+    bool isValid() const { return m_valid; }
 
 private:
     Q_DISABLE_COPY(BrowserAccessibilityManagerQt)
     QObject *m_parentObject;
+    bool m_valid = false;
 };
 
 }