Issue #1173 - Default behavior for catch-all blocks

src/plugin/Exception.h

+/*
+ * This file is part of Adblock Plus <https://adblockplus.org/>,
+ * Copyright (C) 2006-2015 Eyeo GmbH
+ *
+ * Adblock Plus is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 3 as
+ * published by the Free Software Foundation.
+ *
+ * Adblock Plus is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with Adblock Plus.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+/** \file Exception.h -- Default behavior for catch-all exception handlers.
+ */
+
+template<class SubHandlers>
+struct CatchAllVoid
+{
+  static void Handler()
+  {
+    try
+    {
+      std::rethrow_exception(std::current_exception());
+    }
+    catch (std::system_error& ex)
+    {
+      SubHandlers::SystemError(ex);
+    }
+    catch (std::runtime_error& ex)
+    {
+      SubHandlers::RuntimeError(ex);
+    }
+    catch (std::logic_error& ex)
+    {
+      SubHandlers::LogicError(ex);
+    }
+    catch (std::exception& ex)
+    {
+      SubHandlers::Exception(ex);
+    }
+    catch (...)
+    {
+      SubHandlers::Unknown();
+    }
+  }
+};
+
+template<class SubHandlers, class ReturnType=SubHandlers::return_t>
+struct CatchAllReturn
+{
+  static ReturnType Handler()
+  {
+    try
+    {
+      std::rethrow_exception(std::current_exception());
+      // Apparently VS 2012 does not realize that this function always throws.
+      // Unless we have an explicit return statement, we get a spurious warning C4715 "not all control paths return a value".
+      return ReturnType();
+    }
+    catch (std::system_error& ex)
+    {
+      return SubHandlers::SystemError(ex);
+    }
+    catch (std::runtime_error& ex)
+    {
+      return SubHandlers::RuntimeError(ex);
+    }
+    catch (std::logic_error& ex)
+    {
+      return SubHandlers::LogicError(ex);
+    }
+    catch (std::exception& ex)
+    {
+      return SubHandlers::Exception(ex);
+    }
+    catch (...)
+    {
+      return SubHandlers::Unknown();
+    }
+  }
+};
+
+/*
+ * NullHandlers is used at present to define the default exception behavior.
+ * When we get non-trivial default exception behavior, this class can move into the unit tests.
+ */
+struct NullHandlers
+{
+  static void Unknown() {}
+  static void Exception(std::exception& ex) {}
+  static void LogicError(std::logic_error& ex) { Exception(ex); }
+  static void RuntimeError(std::runtime_error& ex) { Exception(ex); }
+  static void SystemError(std::system_error& ex) { RuntimeError(ex); }
+};
+
+void DefaultExceptionBehavior()
+{
+  CatchAllVoid<NullHandlers>::Handler();
+}
+