Implement ReadableNative*::mapException without dynamic_cast

Summary:
Changing fbjni's mapException interface to use `std::exception_ptr`, this enables us to use `std::rethrow_exception` and `catch` statements to check for specific exception types, rather than using dynamic_casts and having an explicit dependency on RTTI.

While generally, we should always be enabling RTTI and exception support simultaneously, we have a number of targets where we don't, or where avoiding RTTI provides significant binary size gains.

Changelog: [Internal]

Reviewed By: mhorowitz

Differential Revision: D34379950

fbshipit-source-id: 446d105f9fb50ada3526f242f98e163215abd0ab

cxx/fbjni/detail/Hybrid.h

@@ -258,14 +258,12 @@ class HybridClass : public detail::HybridTraits<Base>::CxxBase {
     return JavaPart::newInstance(std::move(args)...);
   }
 
-  // If a hybrid class throws an exception which derives from
-  // std::exception, it will be passed to mapException on the hybrid
-  // class, or nearest ancestor.  This allows boilerplate exception
-  // translation code (for example, calling throwNewJavaException on a
-  // particular java class) to be hoisted to a common function.  If
-  // mapException returns, then the std::exception will be translated
-  // to Java.
-  static void mapException(const std::exception& ex) {
+  // If a hybrid class throws an exception, it will be passed to mapException
+  // on the hybrid class, or nearest ancestor. This allows boilerplate exception
+  // translation code (for example, calling throwNewJavaException on a particular
+  // java class) to be hoisted to a common function.  If mapException returns,
+  // then the std::exception will be translated to Java.
+  static void mapException(std::exception_ptr ex) {
     (void)ex;
   }
 };

cxx/fbjni/detail/Registration-inl.h

@@ -119,8 +119,8 @@ struct MethodWrapper {
       // this will get the right type for the registered method.
       auto cobj = static_cast<C*>(ref->cthis());
       return (cobj->*method)(std::forward<Args>(args)...);
-    } catch (const std::exception& ex) {
-      C::mapException(ex);
+    } catch (...) {
+      C::mapException(std::current_exception());
       throw;
     }
   }

test/jni/hybrid_tests.cpp

@@ -123,8 +123,11 @@ class TestHybridClass : public facebook::jni::HybridClass<TestHybridClass> {
    return newObjectCxxArgs(3, "three", true);
   }
 
-  static void mapException(const std::exception& ex) {
-    if (dynamic_cast<const TestException*>(&ex) != 0) {
+  static void mapException(std::exception_ptr ex) {
+    try {
+      std::rethrow_exception(ex);
+    }
+    catch (const TestException &ex) {
       throwNewJavaException("java/lang/ArrayStoreException", "");
     }
   }