From e5fc0341fcb0e1514daa2d347d832d1525142b33 Mon Sep 17 00:00:00 2001
From: Hidehiko Abe <hidehiko@chromium.org>
Date: Fri, 23 Feb 2018 09:50:41 +0000
Subject: [PATCH 03/10] Workaround for g++7 is_trivially_copy_constructible
 failure.

cf) https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80654
Please see also crbug.com/784732#27 for details.

BUG=784732
TEST=Some with GCC.

Change-Id: I0a6d28d9c26ac9ed026d137e17fddbe86586f1e1
Reviewed-on: https://chromium-review.googlesource.com/927942
Commit-Queue: Hidehiko Abe <hidehiko@chromium.org>
Reviewed-by: danakj <danakj@chromium.org>
Cr-Commit-Position: refs/heads/master@{#538740}
---
 base/optional.h                |  3 ++-
 base/template_util.h           | 18 ++++++++++++++++++
 base/template_util_unittest.cc |  9 +++++++++
 3 files changed, 29 insertions(+), 1 deletion(-)

diff --git a/base/optional.h b/base/optional.h
index f6619a575815..c763acf824ee 100644
--- a/base/optional.h
+++ b/base/optional.h
@@ -9,6 +9,7 @@
 #include <utility>
 
 #include "base/logging.h"
+#include "base/template_util.h"
 
 namespace base {
 
@@ -106,7 +107,7 @@ struct OptionalStorageBase<T, true /* trivially destructible */> {
 // compiler generated constexpr {copy,move} constructors). Note that
 // placement-new is prohibited in constexpr.
 template <typename T,
-          bool = std::is_trivially_copy_constructible<T>::value,
+          bool = is_trivially_copy_constructible<T>::value,
           bool = std::is_trivially_move_constructible<T>::value>
 struct OptionalStorage : OptionalStorageBase<T> {
   // This is no trivially {copy,move} constructible case. Other cases are
diff --git a/base/template_util.h b/base/template_util.h
index f76003d8237b..8544aa294597 100644
--- a/base/template_util.h
+++ b/base/template_util.h
@@ -10,6 +10,7 @@
 #include <iterator>
 #include <type_traits>
 #include <utility>
+#include <vector>
 
 #include "build/build_config.h"
 
@@ -127,6 +128,23 @@ template <class T>
 using is_trivially_copyable = std::is_trivially_copyable<T>;
 #endif
 
+#if defined(__GNUC__) && !defined(__clang__) && __GNUC__ <= 7
+// Workaround for g++7 and earlier family.
+// Due to https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80654, without this
+// Optional<std::vector<T>> where T is non-copyable causes a compile error.
+// As we know it is not trivially copy constructible, explicitly declare so.
+template <typename T>
+struct is_trivially_copy_constructible
+    : std::is_trivially_copy_constructible<T> {};
+
+template <typename... T>
+struct is_trivially_copy_constructible<std::vector<T...>> : std::false_type {};
+#else
+// Otherwise use std::is_trivially_copy_constructible as is.
+template <typename T>
+using is_trivially_copy_constructible = std::is_trivially_copy_constructible<T>;
+#endif
+
 }  // namespace base
 
 #undef CR_USE_FALLBACKS_FOR_GCC_WITH_LIBCXX
diff --git a/base/template_util_unittest.cc b/base/template_util_unittest.cc
index 12e5d362dd25..2c42445f785d 100644
--- a/base/template_util_unittest.cc
+++ b/base/template_util_unittest.cc
@@ -92,6 +92,15 @@ static_assert(!base::is_trivially_copyable<TrivialCopyButWithDestructor>::value,
               "TrivialCopyButWithDestructor should not be detected as "
               "trivially copyable");
 
+class NoCopy {
+ public:
+  NoCopy(const NoCopy&) = delete;
+};
+
+static_assert(
+    !base::is_trivially_copy_constructible<std::vector<NoCopy>>::value,
+    "is_trivially_copy_constructible<std::vector<T>> must be compiled.");
+
 }  // namespace
 
 }  // namespace base
-- 
2.16.2