Avoid side effects when en exception has been thrown.

We don't want to check for exceptions after every single
line on our runtime methods. A better way to handle this
is to add the check in all methods that have direct side
effects (as e.g. writing to a property of the JS stack).

We also need to return whereever we throw an exception.
To simplify the code, ExecutionContext::throwXxx methods now
return a ReturnedValue (always undefined) for convenience.

Change-Id: Ide6c804f819c731a3f14c6c43121d08029c9fb90
Reviewed-by: Simon Hausmann <simon.hausmann@digia.com>

1 files changed, 14 insertions, 4 deletions

diff --git a/src/imports/localstorage/plugin.cpp b/src/imports/localstorage/plugin.cpp
index 2b3ef34d4c..3202acc82b 100644
--- a/src/imports/localstorage/plugin.cpp
+++ b/src/imports/localstorage/plugin.cpp
@@ -68,11 +68,21 @@ using namespace QV4;
     QV4::Scoped<Object> ex(scope, ctx->engine->newErrorObject(v)); \
     ex->put(QV4::ScopedString(scope, ctx->engine->newIdentifier(QStringLiteral("code"))), QV4::ScopedValue(scope, Primitive::fromInt32(error))); \
     ctx->throwError(ex); \
+    return Encode::undefined(); \
+}
+
+#define V4THROW_SQL2(error, desc) { \
+    QV4::Scoped<String> v(scope, ctx->engine->newString(desc)); \
+    QV4::Scoped<Object> ex(scope, ctx->engine->newErrorObject(v)); \
+    ex->put(QV4::ScopedString(scope, ctx->engine->newIdentifier(QStringLiteral("code"))), QV4::ScopedValue(scope, Primitive::fromInt32(error))); \
+    args->setReturnValue(ctx->throwError(ex)); \
+    return; \
 }
 
 #define V4THROW_REFERENCE(string) { \
     QV4::Scoped<String> v(scope, ctx->engine->newString(string)); \
     ctx->throwReferenceError(v); \
+    return Encode::undefined(); \
 }
 
 
@@ -168,7 +178,7 @@ static ReturnedValue qmlsqldatabase_rows_setForwardOnly(SimpleCallContext *ctx)
     if (!r || r->type != QQmlSqlDatabaseWrapper::Rows)
         V4THROW_REFERENCE("Not a SQLDatabase::Rows object");
     if (ctx->callData->argc < 1)
-        ctx->throwTypeError();
+        return ctx->throwTypeError();
 
     r->sqlQuery.setForwardOnly(ctx->callData->args[0].toBoolean());
     return Encode::undefined();
@@ -652,7 +662,7 @@ void QQuickLocalStorage::openDatabaseSync(QQmlV4Function *args)
     QV4::ExecutionContext *ctx = args->v4engine()->current;
     QV4::Scope scope(ctx);
     if (engine->engine()->offlineStoragePath().isEmpty())
-        V4THROW_SQL(SQLEXCEPTION_DATABASE_ERR, QQmlEngine::tr("SQL: can't create database, offline storage is disabled."));
+        V4THROW_SQL2(SQLEXCEPTION_DATABASE_ERR, QQmlEngine::tr("SQL: can't create database, offline storage is disabled."));
 
     qmlsqldatabase_initDatabasesPath(engine);
 
@@ -680,7 +690,7 @@ void QQuickLocalStorage::openDatabaseSync(QQmlV4Function *args)
             database = QSqlDatabase::database(dbid);
             version = ini.value(QLatin1String("Version")).toString();
             if (version != dbversion && !dbversion.isEmpty() && !version.isEmpty())
-                V4THROW_SQL(SQLEXCEPTION_VERSION_ERR, QQmlEngine::tr("SQL: database version mismatch"));
+                V4THROW_SQL2(SQLEXCEPTION_VERSION_ERR, QQmlEngine::tr("SQL: database version mismatch"));
         } else {
             created = !QFile::exists(basename+QLatin1String(".sqlite"));
             database = QSqlDatabase::addDatabase(QLatin1String("QSQLITE"), dbid);
@@ -695,7 +705,7 @@ void QQuickLocalStorage::openDatabaseSync(QQmlV4Function *args)
             } else {
                 if (!dbversion.isEmpty() && ini.value(QLatin1String("Version")) != dbversion) {
                     // Incompatible
-                    V4THROW_SQL(SQLEXCEPTION_VERSION_ERR,QQmlEngine::tr("SQL: database version mismatch"));
+                    V4THROW_SQL2(SQLEXCEPTION_VERSION_ERR,QQmlEngine::tr("SQL: database version mismatch"));
                 }
                 version = ini.value(QLatin1String("Version")).toString();
             }