base/no_destructor_unittest.cc

   1 // Copyright 2018 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #include "base/no_destructor.h"
   6
   7 #include <memory>
   8 #include <string>
   9 #include <utility>
  10 #include <vector>
  11
  12 #include "base/atomicops.h"
  13 #include "base/barrier_closure.h"
  14 #include "base/bind.h"
  15 #include "base/check.h"
  16 #include "base/system/sys_info.h"
  17 #include "base/threading/platform_thread.h"
  18 #include "base/threading/simple_thread.h"
  19 #include "build/build_config.h"
  20 #include "testing/gtest/include/gtest/gtest.h"
  21
  22 namespace base {
  23
  24 namespace {
  25
  26 struct CheckOnDestroy {
  27   ~CheckOnDestroy() { CHECK(false); }
  28 };
  29
  30 TEST(NoDestructorTest, SkipsDestructors) {
  31   NoDestructor<CheckOnDestroy> destructor_should_not_run;
  32 }
  33
  34 struct UncopyableUnmovable {
  35   UncopyableUnmovable() = default;
  36   explicit UncopyableUnmovable(int value) : value(value) {}
  37
  38   UncopyableUnmovable(const UncopyableUnmovable&) = delete;
  39   UncopyableUnmovable& operator=(const UncopyableUnmovable&) = delete;
  40
  41   int value = 1;
  42   std::string something_with_a_nontrivial_destructor;
  43 };
  44
  45 struct CopyOnly {
  46   CopyOnly() = default;
  47
  48   CopyOnly(const CopyOnly&) = default;
  49   CopyOnly& operator=(const CopyOnly&) = default;
  50
  51   CopyOnly(CopyOnly&&) = delete;
  52   CopyOnly& operator=(CopyOnly&&) = delete;
  53 };
  54
  55 struct MoveOnly {
  56   MoveOnly() = default;
  57
  58   MoveOnly(const MoveOnly&) = delete;
  59   MoveOnly& operator=(const MoveOnly&) = delete;
  60
  61   MoveOnly(MoveOnly&&) = default;
  62   MoveOnly& operator=(MoveOnly&&) = default;
  63 };
  64
  65 struct ForwardingTestStruct {
  66   ForwardingTestStruct(const CopyOnly&, MoveOnly&&) {}
  67
  68   std::string something_with_a_nontrivial_destructor;
  69 };
  70
  71 TEST(NoDestructorTest, UncopyableUnmovable) {
  72   static NoDestructor<UncopyableUnmovable> default_constructed;
  73   EXPECT_EQ(1, default_constructed->value);
  74
  75   static NoDestructor<UncopyableUnmovable> constructed_with_arg(-1);
  76   EXPECT_EQ(-1, constructed_with_arg->value);
  77 }
  78
  79 TEST(NoDestructorTest, ForwardsArguments) {
  80   CopyOnly copy_only;
  81   MoveOnly move_only;
  82
  83   static NoDestructor<ForwardingTestStruct> test_forwarding(
  84       copy_only, std::move(move_only));
  85 }
  86
  87 TEST(NoDestructorTest, Accessors) {
  88   static NoDestructor<std::string> awesome("awesome");
  89
  90   EXPECT_EQ("awesome", *awesome);
  91   EXPECT_EQ(0, awesome->compare("awesome"));
  92   EXPECT_EQ(0, awesome.get()->compare("awesome"));
  93 }
  94
  95 TEST(NoDestructorTest, AllowForTriviallyDestructibleType) {
  96   static NoDestructor<bool, AllowForTriviallyDestructibleType>
  97       trivially_destructible_type;
  98 }
  99
 100 // Passing initializer list to a NoDestructor like in this test
 101 // is ambiguous in GCC.
 102 // https://gcc.gnu.org/bugzilla/show_bug.cgi?id=84849
 103 #if !defined(COMPILER_GCC) && !defined(__clang__)
 104 TEST(NoDestructorTest, InitializerList) {
 105   static NoDestructor<std::vector<std::string>> vector({"a", "b", "c"});
 106 }
 107 #endif
 108 }  // namespace
 109
 110 namespace {
 111
 112 // A class whose constructor busy-loops until it is told to complete
 113 // construction.
 114 class BlockingConstructor {
 115  public:
 116   BlockingConstructor() {
 117     EXPECT_FALSE(WasConstructorCalled());
 118     subtle::NoBarrier_Store(&constructor_called_, 1);
 119     EXPECT_TRUE(WasConstructorCalled());
 120     while (!subtle::NoBarrier_Load(&complete_construction_))
 121       PlatformThread::YieldCurrentThread();
 122     done_construction_ = true;
 123   }
 124   BlockingConstructor(const BlockingConstructor&) = delete;
 125   BlockingConstructor& operator=(const BlockingConstructor&) = delete;
 126   ~BlockingConstructor() = delete;
 127
 128   // Returns true if BlockingConstructor() was entered.
 129   static bool WasConstructorCalled() {
 130     return subtle::NoBarrier_Load(&constructor_called_);
 131   }
 132
 133   // Instructs BlockingConstructor() that it may now unblock its construction.
 134   static void CompleteConstructionNow() {
 135     subtle::NoBarrier_Store(&complete_construction_, 1);
 136   }
 137
 138   bool done_construction() const { return done_construction_; }
 139
 140  private:
 141   // Use Atomic32 instead of AtomicFlag for them to be trivially initialized.
 142   static subtle::Atomic32 constructor_called_;
 143   static subtle::Atomic32 complete_construction_;
 144
 145   bool done_construction_ = false;
 146 };
 147
 148 // static
 149 subtle::Atomic32 BlockingConstructor::constructor_called_ = 0;
 150 // static
 151 subtle::Atomic32 BlockingConstructor::complete_construction_ = 0;
 152
 153 // A SimpleThread running at |thread_priority| which invokes |before_get|
 154 // (optional) and then invokes thread-safe
 155 // scoped-static-initializationconstruction on its NoDestructor instance.
 156 class BlockingConstructorThread : public SimpleThread {
 157  public:
 158   BlockingConstructorThread(ThreadPriority thread_priority,
 159                             OnceClosure before_get)
 160       : SimpleThread("BlockingConstructorThread", Options(thread_priority)),
 161         before_get_(std::move(before_get)) {}
 162   BlockingConstructorThread(const BlockingConstructorThread&) = delete;
 163   BlockingConstructorThread& operator=(const BlockingConstructorThread&) =
 164       delete;
 165
 166   void Run() override {
 167     if (before_get_)
 168       std::move(before_get_).Run();
 169
 170     static NoDestructor<BlockingConstructor> instance;
 171     EXPECT_TRUE(instance->done_construction());
 172   }
 173
 174  private:
 175   OnceClosure before_get_;
 176 };
 177
 178 }  // namespace
 179
 180 // Tests that if the thread assigned to construct the local-static
 181 // initialization of the NoDestructor runs at background priority : the
 182 // foreground threads will yield to it enough for it to eventually complete
 183 // construction. While local-static thread-safe initialization isn't specific to
 184 // NoDestructor, it is tested here as NoDestructor is set to replace
 185 // LazyInstance and this is an important regression test for it
 186 // (https://crbug.com/797129).
 187 TEST(NoDestructorTest, PriorityInversionAtStaticInitializationResolves) {
 188   TimeTicks test_begin = TimeTicks::Now();
 189
 190   // Construct BlockingConstructor from a background thread.
 191   BlockingConstructorThread background_getter(ThreadPriority::BACKGROUND,
 192                                               OnceClosure());
 193   background_getter.Start();
 194
 195   while (!BlockingConstructor::WasConstructorCalled())
 196     PlatformThread::Sleep(TimeDelta::FromMilliseconds(1));
 197
 198   // Spin 4 foreground thread per core contending to get the already under
 199   // construction NoDestructor. When they are all running and poking at it :
 200   // allow the background thread to complete its work.
 201   const int kNumForegroundThreads = 4 * SysInfo::NumberOfProcessors();
 202   std::vector<std::unique_ptr<SimpleThread>> foreground_threads;
 203   RepeatingClosure foreground_thread_ready_callback =
 204       BarrierClosure(kNumForegroundThreads,
 205                      BindOnce(&BlockingConstructor::CompleteConstructionNow));
 206   for (int i = 0; i < kNumForegroundThreads; ++i) {
 207     foreground_threads.push_back(std::make_unique<BlockingConstructorThread>(
 208         ThreadPriority::NORMAL, foreground_thread_ready_callback));
 209     foreground_threads.back()->Start();
 210   }
 211
 212   // This test will hang if the foreground threads become stuck in
 213   // NoDestructor's construction per the background thread never being scheduled
 214   // to complete construction.
 215   for (auto& foreground_thread : foreground_threads)
 216     foreground_thread->Join();
 217   background_getter.Join();
 218
 219   // Fail if this test takes more than 5 seconds (it takes 5-10 seconds on a
 220   // Z840 without r527445 but is expected to be fast (~30ms) with the fix).
 221   EXPECT_LT(TimeTicks::Now() - test_begin, TimeDelta::FromSeconds(5));
 222 }
 223
 224 }  // namespace base