Guard QScxmlStateMachineInfo::stateChildren()

Make sure we return something useful when querying the children of the
root state.

Add tests

Change-Id: I39f41403dce6f67fc5aeb93cee98950368f7e14b
Reviewed-by: Ulf Hermann <ulf.hermann@qt.io>

1 files changed, 9 insertions, 3 deletions

diff --git a/src/scxml/qscxmlstatemachineinfo.cpp b/src/scxml/qscxmlstatemachineinfo.cpp
index 7b52f8a..154cea1 100644
--- a/src/scxml/qscxmlstatemachineinfo.cpp
+++ b/src/scxml/qscxmlstatemachineinfo.cpp
@@ -140,12 +140,18 @@ QVector<QScxmlStateMachineInfo::StateId> QScxmlStateMachineInfo::stateChildren(S
 {
     Q_D(const QScxmlStateMachineInfo);
 
+    int childStates = QScxmlExecutableContent::StateTable::InvalidIndex;
+    if (stateId == InvalidStateId)
+        childStates = d->stateTable()->childStates;
+    if (stateId >= 0 && stateId < d->stateTable()->stateCount)
+        childStates = d->stateTable()->state(stateId).childStates;
+
     QVector<QScxmlStateMachineInfo::StateId> all;
-    auto state = d->stateTable()->state(stateId);
-    if (state.childStates == QScxmlExecutableContent::StateTable::InvalidIndex)
+    if (childStates == QScxmlExecutableContent::StateTable::InvalidIndex)
         return all;
 
-    auto kids = d->stateTable()->array(state.childStates);
+    const auto kids = d->stateTable()->array(childStates);
+    all.reserve(kids.size());
     for (auto childId : kids) {
         all.append(childId);
     }