Symbian: improving diagnostics for QWaitCondition

If a QWaitCondition was deleted while it was waiting, it would crash in
the wait() function while trying to use its internal mutex. This crash
is not particularly obvious in its cause.

QWaitCondition can detect this delete-while-waiting case, issue
appropriate warnings and avoid a crash in its internal state.

In the app crash case where this problem was found, there is a further
crash after this one due to an externally deleted mutex. The app is
clearly at fault. But at least there's now more debug info about
what the app is doing wrong.

Task-number: ou1cimx1#946509 partial fix
Reviewed-by: Shane Kearns

1 files changed, 4 insertions, 1 deletions

diff --git a/src/corelib/thread/qwaitcondition_symbian.cpp b/src/corelib/thread/qwaitcondition_symbian.cpp
index c6414e8..ed1011c 100644
--- a/src/corelib/thread/qwaitcondition_symbian.cpp
+++ b/src/corelib/thread/qwaitcondition_symbian.cpp
@@ -112,7 +112,10 @@ public:
             --wakeups;
         }
 
-        mutex.Signal();
+        // if err is KErrGeneral it signals that the RCondVar is closed along with the mutex and that this has been deleted
+        // we must not access any member variables in this case
+        if (err != KErrGeneral)
+            mutex.Signal();
 
         if (err && err != KErrTimedOut)
             report_error(err, "QWaitCondition::wait()", "cv wait");