From 42c429142cd46d35bf0599dcfff3b3160001b483 Mon Sep 17 00:00:00 2001
From: Ashwin Bharambe <ashwin@fb.com>
Date: Thu, 11 May 2017 13:29:41 -0700
Subject: [PATCH] Outline `Optional::require_value()`

Summary:
We would like to use `folly/Optional` in settings where exceptions
are disabled. An example is ObjC++ codebases where supporting exceptions
doesn't quite help (since objc_msgSend() can throw) and yet we need to pay the
additional binary size cost for the unwind tables.

This patch makes a small change to outline the "assert" utility included
inside Optional.h

Reviewed By: yfeldblum, mzlee

Differential Revision: D5030172

fbshipit-source-id: 7def3c6eda22c41c8cab2037444978e0a4c50abf
---
 folly/Makefile.am  |  1 +
 folly/Optional.cpp | 27 +++++++++++++++++++++++++++
 folly/Optional.h   | 11 +++++++++--
 3 files changed, 37 insertions(+), 2 deletions(-)
 create mode 100644 folly/Optional.cpp

diff --git a/folly/Makefile.am b/folly/Makefile.am
index 01045105..1ffd7304 100644
--- a/folly/Makefile.am
+++ b/folly/Makefile.am
@@ -525,6 +525,7 @@ libfolly_la_SOURCES = \
 	SharedMutex.cpp \
 	Shell.cpp \
 	MicroLock.cpp \
+	Optional.cpp \
 	Singleton.cpp \
 	SocketAddress.cpp \
 	SpookyHashV1.cpp \
diff --git a/folly/Optional.cpp b/folly/Optional.cpp
new file mode 100644
index 00000000..4c173b14
--- /dev/null
+++ b/folly/Optional.cpp
@@ -0,0 +1,27 @@
+/*
+ * Copyright 2017 Facebook, Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include <folly/Optional.h>
+
+namespace folly {
+namespace detail {
+
+void throw_optional_empty_exception() {
+  throw OptionalEmptyException();
+}
+
+} // namespace detail
+} // namespace folly
diff --git a/folly/Optional.h b/folly/Optional.h
index 5350b2ee..6b49f1ab 100644
--- a/folly/Optional.h
+++ b/folly/Optional.h
@@ -64,7 +64,14 @@
 
 namespace folly {
 
-namespace detail { struct NoneHelper {}; }
+namespace detail {
+struct NoneHelper {};
+
+// Allow each translation unit to control its own -fexceptions setting.
+// If exceptions are disabled, std::terminate() will be called instead of
+// throwing OptionalEmptyException when the condition fails.
+[[noreturn]] void throw_optional_empty_exception();
+}
 
 typedef int detail::NoneHelper::*None;
 
@@ -252,7 +259,7 @@ class Optional {
  private:
   void require_value() const {
     if (!storage_.hasValue) {
-      throw OptionalEmptyException();
+      detail::throw_optional_empty_exception();
     }
   }
 
-- 
2.34.1