Annotate stack traces when frames are elided through tail calls

Task-number: QTBUG-72407
Change-Id: I98b96852309fc783a945797185f666196513d24b
Reviewed-by: Ulf Hermann <ulf.hermann@qt.io>

4 files changed, 24 insertions, 0 deletions

diff --git a/src/qml/jsruntime/qv4engine.cpp b/src/qml/jsruntime/qv4engine.cpp
index 57a364b205..f00578aa70 100644
--- a/src/qml/jsruntime/qv4engine.cpp
+++ b/src/qml/jsruntime/qv4engine.cpp
@@ -1011,6 +1011,11 @@ StackTrace ExecutionEngine::stackTrace(int frameLimit) const
         frame.line = qAbs(f->lineNumber());
         frame.column = -1;
         stack.append(frame);
+        if (f->isTailCalling) {
+            QV4::StackFrame frame;
+            frame.function = QStringLiteral("[elided tail calls]");
+            stack.append(frame);
+        }
         --frameLimit;
         f = f->parent;
     }
diff --git a/src/qml/jsruntime/qv4functionobject.cpp b/src/qml/jsruntime/qv4functionobject.cpp
index dfe9d35194..41a21ba379 100644
--- a/src/qml/jsruntime/qv4functionobject.cpp
+++ b/src/qml/jsruntime/qv4functionobject.cpp
@@ -518,6 +518,7 @@ ReturnedValue ArrowFunction::virtualCall(const FunctionObject *fo, const Value *
     do {
         frame.pendingTailCall = false;
         result = Moth::VME::exec(&frame, engine);
+        frame.isTailCalling = true;
     } while (frame.pendingTailCall);
 
     frame.pop();
diff --git a/src/qml/jsruntime/qv4stackframe_p.h b/src/qml/jsruntime/qv4stackframe_p.h
index a97ae0e7c9..44cfef9173 100644
--- a/src/qml/jsruntime/qv4stackframe_p.h
+++ b/src/qml/jsruntime/qv4stackframe_p.h
@@ -125,6 +125,7 @@ struct Q_QML_EXPORT CppStackFrame {
     bool yieldIsIterator;
     bool callerCanHandleTailCall;
     bool pendingTailCall;
+    bool isTailCalling;
 
     void init(EngineBase *engine, Function *v4Function, const Value *argv, int argc, bool callerCanHandleTailCall = false) {
         this->engine = engine;
@@ -140,6 +141,7 @@ struct Q_QML_EXPORT CppStackFrame {
         yieldIsIterator = false;
         this->callerCanHandleTailCall = callerCanHandleTailCall;
         pendingTailCall = false;
+        isTailCalling = false;
     }
 
     void push() {
diff --git a/tests/auto/qml/qjsengine/tst_qjsengine.cpp b/tests/auto/qml/qjsengine/tst_qjsengine.cpp
index 00c631141b..cf7b9c7224 100644
--- a/tests/auto/qml/qjsengine/tst_qjsengine.cpp
+++ b/tests/auto/qml/qjsengine/tst_qjsengine.cpp
@@ -1759,6 +1759,22 @@ void tst_QJSEngine::stacktrace()
     QJSValue result2 = eng.evaluate(script2, fileName);
     QVERIFY(!result2.isError());
     QVERIFY(result2.isString());
+
+    {
+        QString script3 = QString::fromLatin1(
+                    "'use strict'\n"
+                    "function throwUp() { throw new Error('up') }\n"
+                    "function indirectlyThrow() { return throwUp() }\n"
+                    "indirectlyThrow()\n"
+                    );
+        QJSValue result3 = eng.evaluate(script3);
+        QVERIFY(result3.isError());
+        QJSValue stack = result3.property("stack");
+        QVERIFY(stack.isString());
+        QString stackTrace = stack.toString();
+        QVERIFY(!stackTrace.contains(QStringLiteral("indirectlyThrow")));
+        QVERIFY(stackTrace.contains(QStringLiteral("elide")));
+    }
 }
 
 void tst_QJSEngine::numberParsing_data()