Change exception handling API

This patch changes the exception handling API in the engine slightly, encapsulating
any use of direct throw statements and catch blocks with concrete types. In the future
we need to be able to change the way these are implemented, in order to ensure that
the correct stack unwinding code is triggered for throw and re-throw.

This patch separates the C++ exception object thrown from the V4 exception
(that includes value, throwing context pointer) and stores the latter inside
the engine.

In order for that to compile, ExecutionEngine::StackTrace and StackFrame had to
move into the QV4 namespace directly.

In addition the syntax for catching exceptions changes from

try {
    ...
} catch (QV4::Exception &ex) {
    ex.accept(context);
    QV4::ScopedValue exceptionValue(scope, ex.value());
}

to

try {
    ...
} catch (...) {
    QV4::ScopedValue exception(scope, context->catchException());
}

Context::catchException() checks if there's a "current" exception in the engine,
and if not assumes that we caught an unrelated exception and consequently re-throws.

partiallyUnwind() is also gone and replaced with rethrowException(), in order to
encapsulate the re-throw.

Lastly, in the future nesting try/catch blocks isn't going to be possible due to
limitations in the common C++ ABI with regards to foreign exceptions.

Change-Id: Ic81c75b057a2147e3176d8e0b4d326c14278b47d
Reviewed-by: Lars Knoll <lars.knoll@digia.com>

3 files changed, 26 insertions, 32 deletions

diff --git a/src/qml/jsapi/qjsengine.cpp b/src/qml/jsapi/qjsengine.cpp
index 57647a49d3..d42cabd81c 100644
--- a/src/qml/jsapi/qjsengine.cpp
+++ b/src/qml/jsapi/qjsengine.cpp
@@ -269,9 +269,8 @@ QJSValue QJSEngine::evaluate(const QString& program, const QString& fileName, in
         script.inheritContext = true;
         script.parse();
         result = script.run();
-    } catch (QV4::Exception& ex) {
-        ex.accept(ctx);
-        result = ex.value();
+    } catch (...) {
+        result = ctx->catchException();
     }
     return new QJSValuePrivate(d->m_v4Engine, result);
 }
diff --git a/src/qml/jsapi/qjsvalue.cpp b/src/qml/jsapi/qjsvalue.cpp
index 8bcdccc507..ba94afadc6 100644
--- a/src/qml/jsapi/qjsvalue.cpp
+++ b/src/qml/jsapi/qjsvalue.cpp
@@ -380,8 +380,8 @@ double QJSValue::toNumber() const
     QV4::ExecutionContext *ctx = d->engine ? d->engine->current : 0;
     try {
         return d->value.toNumber();
-    } catch (Exception &e) {
-        e.accept(ctx);
+    } catch (...) {
+        ctx->catchException();
         return 0;
     }
 }
@@ -403,8 +403,8 @@ bool QJSValue::toBool() const
     QV4::ExecutionContext *ctx = d->engine ? d->engine->current : 0;
     try {
         return d->value.toBoolean();
-    } catch (Exception &e) {
-        e.accept(ctx);
+    } catch (...) {
+        ctx->catchException();
         return false;
     }
 }
@@ -426,8 +426,8 @@ qint32 QJSValue::toInt() const
     QV4::ExecutionContext *ctx = d->engine ? d->engine->current : 0;
     try {
         return d->value.toInt32();
-    } catch (Exception &e) {
-        e.accept(ctx);
+    } catch (...) {
+        ctx->catchException();
         return 0;
     }
 }
@@ -449,8 +449,8 @@ quint32 QJSValue::toUInt() const
     QV4::ExecutionContext *ctx = d->engine ? d->engine->current : 0;
     try {
         return d->value.toUInt32();
-    } catch (Exception &e) {
-        e.accept(ctx);
+    } catch (...) {
+        ctx->catchException();
         return 0;
     }
 }
@@ -521,9 +521,8 @@ QJSValue QJSValue::call(const QJSValueList &args)
     QV4::ExecutionContext *ctx = engine->current;
     try {
         result = f->call(callData);
-    } catch (Exception &e) {
-        e.accept(ctx);
-        result = e.value();
+    } catch (...) {
+        result = ctx->catchException();
     }
 
     return new QJSValuePrivate(engine, result);
@@ -578,9 +577,8 @@ QJSValue QJSValue::callWithInstance(const QJSValue &instance, const QJSValueList
     QV4::ExecutionContext *ctx = engine->current;
     try {
         result = f->call(callData);
-    } catch (Exception &e) {
-        e.accept(ctx);
-        result = e.value();
+    } catch (...) {
+        result = ctx->catchException();
     }
 
     return new QJSValuePrivate(engine, result);
@@ -627,9 +625,8 @@ QJSValue QJSValue::callAsConstructor(const QJSValueList &args)
     QV4::ExecutionContext *ctx = engine->current;
     try {
         result = f->construct(callData);
-    } catch (Exception &e) {
-        e.accept(ctx);
-        result = e.value();
+    } catch (...) {
+        result = ctx->catchException();
     }
 
     return new QJSValuePrivate(engine, result);
@@ -819,9 +816,8 @@ QJSValue QJSValue::property(const QString& name) const
     QV4::ScopedValue result(scope);
     try {
         result = o->get(s);
-    } catch (QV4::Exception &e) {
-        e.accept(ctx);
-        result = e.value();
+    } catch (...) {
+        result = ctx->catchException();
     }
     return new QJSValuePrivate(engine, result);
 }
@@ -853,9 +849,8 @@ QJSValue QJSValue::property(quint32 arrayIndex) const
     QV4::ScopedValue result(scope);
     try {
         result = arrayIndex == UINT_MAX ? o->get(engine->id_uintMax) : o->getIndexed(arrayIndex);
-    } catch (QV4::Exception &e) {
-        e.accept(ctx);
-        result = e.value();
+    } catch (...) {
+        result = ctx->catchException();
     }
     return new QJSValuePrivate(engine, result);
 }
@@ -899,8 +894,8 @@ void QJSValue::setProperty(const QString& name, const QJSValue& value)
     try {
         QV4::ScopedValue v(scope, value.d->getValue(engine));
         o->put(s, v);
-    } catch (QV4::Exception &e) {
-        e.accept(ctx);
+    } catch (...) {
+        ctx->catchException();
     }
 }
 
@@ -934,8 +929,8 @@ void QJSValue::setProperty(quint32 arrayIndex, const QJSValue& value)
             o->putIndexed(arrayIndex, v);
         else
             o->put(engine->id_uintMax, v);
-    } catch (QV4::Exception &e) {
-        e.accept(ctx);
+    } catch (...) {
+        ctx->catchException();
     }
 }
 
diff --git a/src/qml/jsapi/qjsvalueiterator.cpp b/src/qml/jsapi/qjsvalueiterator.cpp
index e1786f06cd..fd5f709e14 100644
--- a/src/qml/jsapi/qjsvalueiterator.cpp
+++ b/src/qml/jsapi/qjsvalueiterator.cpp
@@ -211,8 +211,8 @@ QJSValue QJSValueIterator::value() const
             return QJSValue();
         }
         return new QJSValuePrivate(engine, v);
-    } catch (QV4::Exception &e) {
-        e.accept(ctx);
+    } catch (...) {
+        ctx->catchException();
         return QJSValue();
     }
 }