Refactor context handling

Fix the push/pop context instructions to not modify the JS
stack anymore, as that can cause conflicts with the VME
(and was an ugly hack in any case). Instead, these instructions
not return the old context, that is then stored in a temporary.

Get rid of Engine::current and Engine::currentContext. The
StackFrame structures do now contain the only and authoritive
data. This finally gives us a nice setup where we create and
destroy frames on the stack when entering/leaving functions.

Change-Id: If161e3e941f59865c47ecfe1e094faf62b52bfa0
Reviewed-by: Simon Hausmann <simon.hausmann@qt.io>

1 files changed, 8 insertions, 11 deletions

diff --git a/src/plugins/qmltooling/qmldbg_nativedebugger/qqmlnativedebugservice.cpp b/src/plugins/qmltooling/qmldbg_nativedebugger/qqmlnativedebugservice.cpp
index 7f11cea9ab..32c67b3986 100644
--- a/src/plugins/qmltooling/qmldbg_nativedebugger/qqmlnativedebugservice.cpp
+++ b/src/plugins/qmltooling/qmldbg_nativedebugger/qqmlnativedebugservice.cpp
@@ -229,7 +229,7 @@ private:
 
     QV4::ExecutionEngine *m_engine;
     QQmlNativeDebugServiceImpl *m_service;
-    QV4::PersistentValue m_currentContext;
+    QV4::EngineBase::StackFrame *m_currentFrame = 0;
     Speed m_stepping;
     bool m_pauseRequested;
     bool m_runningJob;
@@ -249,10 +249,7 @@ QV4::ReturnedValue NativeDebugger::evaluateExpression(const QString &expression)
     QV4::Scope scope(m_engine);
     m_runningJob = true;
 
-    QV4::ExecutionContextSaver saver(m_engine);
-
-    QV4::ExecutionContext *ctx = m_engine->currentContext;
-    m_engine->pushContext(ctx);
+    QV4::ExecutionContext *ctx = m_engine->currentContext();
 
     QV4::Script script(ctx, expression);
     script.strictMode = ctx->d()->v4Function->isStrict();
@@ -594,7 +591,7 @@ void NativeDebugger::handleContinue(QJsonObject *response, Speed speed)
     if (!m_returnedValue.isUndefined())
         m_returnedValue.set(m_engine, QV4::Encode::undefined());
 
-    m_currentContext.set(m_engine, *m_engine->currentContext);
+    m_currentFrame = m_engine->currentStackFrame;
     m_stepping = speed;
 }
 
@@ -604,7 +601,7 @@ void NativeDebugger::maybeBreakAtInstruction()
         return;
 
     if (m_stepping == StepOver) {
-        if (m_currentContext.asManaged()->d() == m_engine->current)
+        if (m_currentFrame == m_engine->currentStackFrame)
             pauseAndWait();
         return;
     }
@@ -635,7 +632,7 @@ void NativeDebugger::enteringFunction()
         return;
 
     if (m_stepping == StepIn) {
-        m_currentContext.set(m_engine, *m_engine->currentContext);
+        m_currentFrame = m_engine->currentStackFrame;
     }
 }
 
@@ -644,8 +641,8 @@ void NativeDebugger::leavingFunction(const QV4::ReturnedValue &retVal)
     if (m_runningJob)
         return;
 
-    if (m_stepping != NotStepping && m_currentContext.asManaged()->d() == m_engine->current) {
-        m_currentContext.set(m_engine, *m_engine->parentContext(m_engine->currentContext));
+    if (m_stepping != NotStepping && m_currentFrame == m_engine->currentStackFrame) {
+        m_currentFrame = m_currentFrame->parent;
         m_stepping = StepOver;
         m_returnedValue.set(m_engine, retVal);
     }
@@ -667,7 +664,7 @@ void NativeDebugger::aboutToThrow()
 
 QV4::Function *NativeDebugger::getFunction() const
 {
-    QV4::ExecutionContext *context = m_engine->currentContext;
+    QV4::ExecutionContext *context = m_engine->currentContext();
     if (QV4::Function *function = context->getFunction())
         return function;
     else