Change event posting to use a QVector.

This provides a ~10% improvement to the newly introduced QCoreApplication
event_posting_benchmark (a simple synthetic benchmark of creating a bunch of
events, posting them, and sending the queue).

before:
********* Start testing of QCoreApplicationBenchmark *********
Config: Using QTest library 5.0.0, Qt 5.0.0
PASS   : QCoreApplicationBenchmark::initTestCase()
RESULT : QCoreApplicationBenchmark::signal_slot_benchmark():"1000":
     0.82 msecs per iteration (total: 53, iterations: 64)
RESULT : QCoreApplicationBenchmark::signal_slot_benchmark():"10000":
     8.6 msecs per iteration (total: 69, iterations: 8)
RESULT : QCoreApplicationBenchmark::signal_slot_benchmark():"100000":
     84 msecs per iteration (total: 84, iterations: 1)
RESULT : QCoreApplicationBenchmark::signal_slot_benchmark():"1000000":
     874 msecs per iteration (total: 874, iterations: 1)
PASS   : QCoreApplicationBenchmark::signal_slot_benchmark()
PASS   : QCoreApplicationBenchmark::cleanupTestCase()
Totals: 3 passed, 0 failed, 0 skipped
********* Finished testing of QCoreApplicationBenchmark *********

after:
********* Start testing of QCoreApplicationBenchmark *********
Config: Using QTest library 5.0.0, Qt 5.0.0
PASS   : QCoreApplicationBenchmark::initTestCase()
RESULT : QCoreApplicationBenchmark::event_posting_benchmark():"1000 events":
     0.781 msecs per iteration (total: 100, iterations: 128)
RESULT : QCoreApplicationBenchmark::event_posting_benchmark():"10000 events":
     7.8 msecs per iteration (total: 63, iterations: 8)
RESULT : QCoreApplicationBenchmark::event_posting_benchmark():"100000 events":
     75 msecs per iteration (total: 75, iterations: 1)
RESULT : QCoreApplicationBenchmark::event_posting_benchmark():"1000000 events":
     774 msecs per iteration (total: 774, iterations: 1)
PASS   : QCoreApplicationBenchmark::event_posting_benchmark()
PASS   : QCoreApplicationBenchmark::cleanupTestCase()
Totals: 3 passed, 0 failed, 0 skipped
********* Finished testing of QCoreApplicationBenchmark *********

Change-Id: Ibf56d9526b0a8cbaf171008da4104bb457628172
Reviewed-by: Sergio Ahumada <sergio.ahumada@nokia.com>

1 files changed, 12 insertions, 3 deletions

diff --git a/src/corelib/kernel/qcoreapplication.cpp b/src/corelib/kernel/qcoreapplication.cpp
index 6f26be2928..e105100e3e 100644
--- a/src/corelib/kernel/qcoreapplication.cpp
+++ b/src/corelib/kernel/qcoreapplication.cpp
@@ -1405,9 +1405,18 @@ void QCoreApplicationPrivate::sendPostedEvents(QObject *receiver, int event_type
             if (!allowDeferredDelete) {
                 // cannot send deferred delete
                 if (!event_type && !receiver) {
-                    // don't lose the event
-                    data->postEventList.addEvent(pe);
+                    // we must copy it first; we want to re-post the event
+                    // with the event pointer intact, but we can't delay
+                    // nulling the event ptr until after re-posting, as
+                    // addEvent may invalidate pe.
+                    QPostEvent pe_copy = pe;
+
+                    // null out the event so if sendPostedEvents recurses, it
+                    // will ignore this one, as it's been re-posted.
                     const_cast<QPostEvent &>(pe).event = 0;
+
+                    // re-post the copied event so it isn't lost
+                    data->postEventList.addEvent(pe_copy);
                 }
                 continue;
             }
@@ -1509,7 +1518,7 @@ void QCoreApplication::removePostedEvents(QObject *receiver, int eventType)
             const_cast<QPostEvent &>(pe).event = 0;
         } else if (!data->postEventList.recursion) {
             if (i != j)
-                data->postEventList.swap(i, j);
+                qSwap(data->postEventList[i], data->postEventList[j]);
             ++j;
         }
     }