QML: Encode "missing" line number as negated address of stack frame

This way we can identify which entry in a stack frame to amend when
processing an exception in generated code. However, negative line
numbers are also used to signal the position of "Ret" instructions.
Since you cannot throw an exception from a "Ret" instruction, those
cannot collide, but we cannot qAbs() the line number anymore when saving
it in the stack trace. We have to qAbs() it in all the places where it's
read.

Pick-to: 6.5
Fixes: QTBUG-112946
Change-Id: I24dc4008fb7eab38e4d24e70211c22e46f1b72a7
Reviewed-by: Fabian Kosmale <fabian.kosmale@qt.io>

4 files changed, 30 insertions, 2 deletions

diff --git a/tests/auto/qml/debugger/qv4debugger/tst_qv4debugger.cpp b/tests/auto/qml/debugger/qv4debugger/tst_qv4debugger.cpp
index 6f147446f0..f95a7ade9a 100644
--- a/tests/auto/qml/debugger/qv4debugger/tst_qv4debugger.cpp
+++ b/tests/auto/qml/debugger/qv4debugger/tst_qv4debugger.cpp
@@ -274,9 +274,10 @@ public:
     void dumpStackTrace() const
     {
         qDebug() << "Stack depth:" << m_stackTrace.size();
-        foreach (const QV4::StackFrame &frame, m_stackTrace)
+        for (const QV4::StackFrame &frame : m_stackTrace) {
             qDebug("\t%s (%s:%d:%d)", qPrintable(frame.function), qPrintable(frame.source),
-                   frame.line, frame.column);
+                   qAbs(frame.line), frame.column);
+        }
     }
 };
 
diff --git a/tests/auto/qml/qmlcppcodegen/data/CMakeLists.txt b/tests/auto/qml/qmlcppcodegen/data/CMakeLists.txt
index 370ef4ac9c..363c24c648 100644
--- a/tests/auto/qml/qmlcppcodegen/data/CMakeLists.txt
+++ b/tests/auto/qml/qmlcppcodegen/data/CMakeLists.txt
@@ -105,6 +105,7 @@ set(qml_files
     equalityQUrl.qml
     equalityVarAndNonStorable.qml
     equalsUndefined.qml
+    exceptionFromInner.qml
     excessiveParameters.qml
     extendedTypes.qml
     failures.qml
diff --git a/tests/auto/qml/qmlcppcodegen/data/exceptionFromInner.qml b/tests/auto/qml/qmlcppcodegen/data/exceptionFromInner.qml
new file mode 100644
index 0000000000..13855356f2
--- /dev/null
+++ b/tests/auto/qml/qmlcppcodegen/data/exceptionFromInner.qml
@@ -0,0 +1,10 @@
+pragma Strict
+import QtQml
+
+QtObject {
+    property QtObject theNull: null
+
+    function doFail() : string { return theNull.objectName }
+    function delegateFail() : string { doFail() }
+    function disbelieveFail() : string { delegateFail() }
+}
diff --git a/tests/auto/qml/qmlcppcodegen/tst_qmlcppcodegen.cpp b/tests/auto/qml/qmlcppcodegen/tst_qmlcppcodegen.cpp
index 20e6922dc4..f3869e6e40 100644
--- a/tests/auto/qml/qmlcppcodegen/tst_qmlcppcodegen.cpp
+++ b/tests/auto/qml/qmlcppcodegen/tst_qmlcppcodegen.cpp
@@ -74,6 +74,7 @@ private slots:
     void equalityVarAndNonStorable();
     void equalsUndefined();
     void evadingAmbiguity();
+    void exceptionFromInner();
     void excessiveParameters();
     void extendedTypes();
     void failures();
@@ -1415,6 +1416,21 @@ void tst_QmlCppCodegen::evadingAmbiguity()
     QCOMPARE(o2->property("i").toString(), QStringLiteral("Ambiguous2"));
 }
 
+void tst_QmlCppCodegen::exceptionFromInner()
+{
+    QQmlEngine engine;
+    QQmlComponent component(&engine, QUrl(u"qrc:/qt/qml/TestTypes/exceptionFromInner.qml"_s));
+    QVERIFY2(!component.isError(), component.errorString().toUtf8());
+    QScopedPointer<QObject> object(component.create());
+    QVERIFY(!object.isNull());
+
+    QTest::ignoreMessage(
+        QtWarningMsg,
+        "qrc:/qt/qml/TestTypes/exceptionFromInner.qml:7: TypeError: "
+        "Cannot read property 'objectName' of null");
+    QMetaObject::invokeMethod(object.data(), "disbelieveFail");
+}
+
 void tst_QmlCppCodegen::excessiveParameters()
 {
     QQmlEngine engine;