Remove macro guards against GCC 4.9 code (#1096)

Summary:
- Since folly requires GCC 5+ compiler, remove several macros which were
  guarding against when we supported GCC 4.9.
Pull Request resolved: https://github.com/facebook/folly/pull/1096

Reviewed By: LeeHowes

Differential Revision: D14681043

Pulled By: LeeHowes

fbshipit-source-id: fcc2cd25e00c512f7154a1568003e7c2f0df9c54

folly/FixedString.h

@@ -100,13 +100,6 @@ constexpr const Char (&checkNullTerminated(const Char (&a)[N]) noexcept)[N] {
       : (assertNotNullTerminated(), decltype(a)(a));
 }
 
-// Rather annoyingly, GCC's -Warray-bounds warning issues false positives for
-// this code. See https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61971
-#if defined(__GNUC__) && !defined(__clang__) && __GNUC__ <= 5
-#pragma GCC diagnostic push
-#pragma GCC diagnostic ignored "-Warray-bounds"
-#endif
-
 template <class Left, class Right>
 constexpr ordering compare_(
     const Left& left,
@@ -302,10 +295,6 @@ struct Helper {
   }
 };
 
-#if defined(__GNUC__) && !defined(__clang__) && __GNUC__ <= 4
-#pragma GCC diagnostic pop
-#endif
-
 template <class T>
 constexpr void constexpr_swap(T& a, T& b) noexcept(
     noexcept(a = T(std::move(a)))) {

folly/Poly.cpp

-/*
- * Copyright 2017-present 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.
- */
-
-#if defined(__GNUC__) && !defined(__clang__) && __GNUC__ < 5
-#pragma message "Folly.Poly requires gcc-5 or greater"
-#else
-
-#include <folly/Poly.h>
-
-namespace folly {
-namespace detail {
-
-// empty
-
-} // namespace detail
-} // namespace folly
-
-#endif

folly/Poly.h

@@ -25,10 +25,6 @@
 
 #pragma once
 
-#if defined(__GNUC__) && !defined(__clang__) && __GNUC__ < 5
-#error Folly.Poly requires gcc-5 or greater
-#endif
-
 #include <cassert>
 #include <new>
 #include <type_traits>

folly/Portability.h

@@ -202,11 +202,6 @@ constexpr bool kIsSanitize = false;
 #define FOLLY_GCC_DISABLE_NEW_SHADOW_WARNINGS /* empty */
 #endif
 
-// Globally disable -Wshadow for gcc < 5.
-#if __GNUC__ == 4 && !__clang__
-FOLLY_GCC_DISABLE_NEW_SHADOW_WARNINGS
-#endif
-
 /* Platform specific TLS support
  * gcc implements __thread
  * msvc implements __declspec(thread)

folly/Traits.h

@@ -308,9 +308,6 @@ using aligned_storage_for_t =
 #if defined(__clang__) && !defined(_LIBCPP_VERSION)
 template <class T>
 struct is_trivially_copyable : bool_constant<__is_trivially_copyable(T)> {};
-#elif defined(__GNUC__) && !defined(__clang__) && __GNUC__ < 5
-template <class T>
-struct is_trivially_copyable : std::is_trivial<T> {};
 #else
 template <class T>
 using is_trivially_copyable = std::is_trivially_copyable<T>;

folly/portability/test/ConstexprTest.cpp

@@ -27,8 +27,6 @@ TEST(ConstexprTest, constexpr_strlen_cstr) {
   EXPECT_TRUE((std::is_same<const size_t, decltype(a)>::value));
 }
 
-// gcc-4.9 cannot compile the following constexpr code correctly
-#if !(defined(__GNUC__) && !defined(__clang__) && __GNUC__ < 5)
 TEST(ConstexprTest, constexpr_strlen_ints) {
   constexpr int v[] = {5, 3, 4, 0, 7};
   constexpr auto a = folly::constexpr_strlen(v);
@@ -42,7 +40,6 @@ TEST(ConstexprTest, constexpr_strcmp_ints) {
   static_assert(constexpr_strcmp(v1, v) > 0, "constexpr_strcmp is broken");
   static_assert(constexpr_strcmp(v, v) == 0, "constexpr_strcmp is broken");
 }
-#endif
 
 static_assert(
     constexpr_strcmp("abc", "abc") == 0,

folly/test/ExpectedTest.cpp

@@ -668,7 +668,7 @@ struct WithConstructor {
 
 // libstdc++ with GCC 4.x doesn't have std::is_trivially_copyable
 #if (defined(__clang__) && !defined(_LIBCPP_VERSION)) || \
-    !(defined(__GNUC__) && !defined(__clang__) && __GNUC__ < 5)
+    !(defined(__GNUC__) && !defined(__clang__))
 TEST(Expected, TriviallyCopyable) {
   // These could all be static_asserts but EXPECT_* give much nicer output on
   // failure.

folly/test/FixedStringTest.cpp

@@ -648,30 +648,6 @@ TEST(FixedStringReverseIteratorTest, ConstexprReverseIteration) {
   static_assert((alpha.rend() - 2) == (alpha.rbegin() + 24), "");
 }
 
-namespace GCC61971 {
-// FixedString runs afoul of GCC #61971 (spurious -Warray-bounds)
-// in optimized builds. The following test case triggers it for gcc-4.x.
-// Test that FixedString suppresses the warning correctly.
-// https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61971
-constexpr auto xyz = folly::makeFixedString("xyz");
-constexpr auto dot = folly::makeFixedString(".");
-
-template <typename T1>
-constexpr auto concatStuff(const T1& component) noexcept {
-  return xyz + dot + component;
-}
-constexpr auto co = folly::makeFixedString("co");
-
-struct S {
-  std::string s{concatStuff(co)};
-};
-} // namespace GCC61971
-
-TEST(FixedStringGCC61971, GCC61971) {
-  GCC61971::S s;
-  (void)s;
-}
-
 #include <folly/Range.h>
 
 TEST(FixedStringConversionTest, ConversionToFollyRange) {

folly/test/PolyTest.cpp

@@ -13,9 +13,7 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-#if defined(__GNUC__) && !defined(__clang__) && __GNUC__ < 5
-#pragma message "Folly.Poly requires gcc-5 or greater"
-#else
+
 #include <folly/Poly.h>
 
 #include <folly/Conv.h>
@@ -835,4 +833,3 @@ TEST(Poly, PolyRefAsArg) {
   // should not throw:
   frob.frobnicate(folly::Poly<folly::poly::IRegular&>(x));
 }
-#endif