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// Copyright 2018 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#include "base/no_destructor.h"
#include <memory>
#include <string>
#include <utility>
#include <vector>
#include "base/atomicops.h"
#include "base/barrier_closure.h"
#include "base/bind.h"
#include "base/check.h"
#include "base/system/sys_info.h"
#include "base/threading/platform_thread.h"
#include "base/threading/simple_thread.h"
#include "build/build_config.h"
#include "testing/gtest/include/gtest/gtest.h"
namespace base {
namespace {
struct CheckOnDestroy {
~CheckOnDestroy() { CHECK(false); }
};
TEST(NoDestructorTest, SkipsDestructors) {
NoDestructor<CheckOnDestroy> destructor_should_not_run;
}
struct UncopyableUnmovable {
UncopyableUnmovable() = default;
explicit UncopyableUnmovable(int value) : value(value) {}
UncopyableUnmovable(const UncopyableUnmovable&) = delete;
UncopyableUnmovable& operator=(const UncopyableUnmovable&) = delete;
int value = 1;
};
struct CopyOnly {
CopyOnly() = default;
CopyOnly(const CopyOnly&) = default;
CopyOnly& operator=(const CopyOnly&) = default;
CopyOnly(CopyOnly&&) = delete;
CopyOnly& operator=(CopyOnly&&) = delete;
};
struct MoveOnly {
MoveOnly() = default;
MoveOnly(const MoveOnly&) = delete;
MoveOnly& operator=(const MoveOnly&) = delete;
MoveOnly(MoveOnly&&) = default;
MoveOnly& operator=(MoveOnly&&) = default;
};
struct ForwardingTestStruct {
ForwardingTestStruct(const CopyOnly&, MoveOnly&&) {}
};
TEST(NoDestructorTest, UncopyableUnmovable) {
static NoDestructor<UncopyableUnmovable> default_constructed;
EXPECT_EQ(1, default_constructed->value);
static NoDestructor<UncopyableUnmovable> constructed_with_arg(-1);
EXPECT_EQ(-1, constructed_with_arg->value);
}
TEST(NoDestructorTest, ForwardsArguments) {
CopyOnly copy_only;
MoveOnly move_only;
static NoDestructor<ForwardingTestStruct> test_forwarding(
copy_only, std::move(move_only));
}
TEST(NoDestructorTest, Accessors) {
static NoDestructor<std::string> awesome("awesome");
EXPECT_EQ("awesome", *awesome);
EXPECT_EQ(0, awesome->compare("awesome"));
EXPECT_EQ(0, awesome.get()->compare("awesome"));
}
// Passing initializer list to a NoDestructor like in this test
// is ambiguous in GCC.
// https://gcc.gnu.org/bugzilla/show_bug.cgi?id=84849
#if !defined(COMPILER_GCC) && !defined(__clang__)
TEST(NoDestructorTest, InitializerList) {
static NoDestructor<std::vector<std::string>> vector({"a", "b", "c"});
}
#endif
} // namespace
namespace {
// A class whose constructor busy-loops until it is told to complete
// construction.
class BlockingConstructor {
public:
BlockingConstructor() {
EXPECT_FALSE(WasConstructorCalled());
subtle::NoBarrier_Store(&constructor_called_, 1);
EXPECT_TRUE(WasConstructorCalled());
while (!subtle::NoBarrier_Load(&complete_construction_))
PlatformThread::YieldCurrentThread();
done_construction_ = true;
}
BlockingConstructor(const BlockingConstructor&) = delete;
BlockingConstructor& operator=(const BlockingConstructor&) = delete;
~BlockingConstructor() = delete;
// Returns true if BlockingConstructor() was entered.
static bool WasConstructorCalled() {
return subtle::NoBarrier_Load(&constructor_called_);
}
// Instructs BlockingConstructor() that it may now unblock its construction.
static void CompleteConstructionNow() {
subtle::NoBarrier_Store(&complete_construction_, 1);
}
bool done_construction() const { return done_construction_; }
private:
// Use Atomic32 instead of AtomicFlag for them to be trivially initialized.
static subtle::Atomic32 constructor_called_;
static subtle::Atomic32 complete_construction_;
bool done_construction_ = false;
};
// static
subtle::Atomic32 BlockingConstructor::constructor_called_ = 0;
// static
subtle::Atomic32 BlockingConstructor::complete_construction_ = 0;
// A SimpleThread running at |thread_priority| which invokes |before_get|
// (optional) and then invokes thread-safe
// scoped-static-initializationconstruction on its NoDestructor instance.
class BlockingConstructorThread : public SimpleThread {
public:
BlockingConstructorThread(ThreadPriority thread_priority,
OnceClosure before_get)
: SimpleThread("BlockingConstructorThread", Options(thread_priority)),
before_get_(std::move(before_get)) {}
BlockingConstructorThread(const BlockingConstructorThread&) = delete;
BlockingConstructorThread& operator=(const BlockingConstructorThread&) =
delete;
void Run() override {
if (before_get_)
std::move(before_get_).Run();
static NoDestructor<BlockingConstructor> instance;
EXPECT_TRUE(instance->done_construction());
}
private:
OnceClosure before_get_;
};
} // namespace
// Tests that if the thread assigned to construct the local-static
// initialization of the NoDestructor runs at background priority : the
// foreground threads will yield to it enough for it to eventually complete
// construction. While local-static thread-safe initialization isn't specific to
// NoDestructor, it is tested here as NoDestructor is set to replace
// LazyInstance and this is an important regression test for it
// (https://crbug.com/797129).
TEST(NoDestructorTest, PriorityInversionAtStaticInitializationResolves) {
TimeTicks test_begin = TimeTicks::Now();
// Construct BlockingConstructor from a background thread.
BlockingConstructorThread background_getter(ThreadPriority::BACKGROUND,
OnceClosure());
background_getter.Start();
while (!BlockingConstructor::WasConstructorCalled())
PlatformThread::Sleep(TimeDelta::FromMilliseconds(1));
// Spin 4 foreground thread per core contending to get the already under
// construction NoDestructor. When they are all running and poking at it :
// allow the background thread to complete its work.
const int kNumForegroundThreads = 4 * SysInfo::NumberOfProcessors();
std::vector<std::unique_ptr<SimpleThread>> foreground_threads;
RepeatingClosure foreground_thread_ready_callback =
BarrierClosure(kNumForegroundThreads,
BindOnce(&BlockingConstructor::CompleteConstructionNow));
for (int i = 0; i < kNumForegroundThreads; ++i) {
foreground_threads.push_back(std::make_unique<BlockingConstructorThread>(
ThreadPriority::NORMAL, foreground_thread_ready_callback));
foreground_threads.back()->Start();
}
// This test will hang if the foreground threads become stuck in
// NoDestructor's construction per the background thread never being scheduled
// to complete construction.
for (auto& foreground_thread : foreground_threads)
foreground_thread->Join();
background_getter.Join();
// Fail if this test takes more than 5 seconds (it takes 5-10 seconds on a
// Z840 without r527445 but is expected to be fast (~30ms) with the fix).
EXPECT_LT(TimeTicks::Now() - test_begin, TimeDelta::FromSeconds(5));
}
} // namespace base
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