base/containers/stack_container_unittest.cc

// Copyright (c) 2012 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/containers/stack_container.h"

#include <stddef.h>

#include <algorithm>

#include "base/memory/ref_counted.h"
#include "build_config.h"
#include "testing/gtest/include/gtest/gtest.h"

namespace base {

namespace {

class Dummy : public base::RefCounted<Dummy> {
 public:
  explicit Dummy(int* alive) : alive_(alive) {
    ++*alive_;
  }

 private:
  friend class base::RefCounted<Dummy>;

  ~Dummy() {
    --*alive_;
  }

  int* const alive_;
};

}  // namespace

TEST(StackContainer, Vector) {
  const int stack_size = 3;
  StackVector<int, stack_size> vect;
  const int* stack_buffer = &vect.stack_data().stack_buffer()[0];

  // The initial |stack_size| elements should appear in the stack buffer.
  EXPECT_EQ(static_cast<size_t>(stack_size), vect.container().capacity());
  for (int i = 0; i < stack_size; i++) {
    vect.container().push_back(i);
    EXPECT_EQ(stack_buffer, &vect.container()[0]);
    EXPECT_TRUE(vect.stack_data().used_stack_buffer_);
  }

  // Adding more elements should push the array onto the heap.
  for (int i = 0; i < stack_size; i++) {
    vect.container().push_back(i + stack_size);
    EXPECT_NE(stack_buffer, &vect.container()[0]);
    EXPECT_FALSE(vect.stack_data().used_stack_buffer_);
  }

  // The array should still be in order.
  for (int i = 0; i < stack_size * 2; i++)
    EXPECT_EQ(i, vect.container()[i]);

  // Resize to smaller. Our STL implementation won't reallocate in this case,
  // otherwise it might use our stack buffer. We reserve right after the resize
  // to guarantee it isn't using the stack buffer, even though it doesn't have
  // much data.
  vect.container().resize(stack_size);
  vect.container().reserve(stack_size * 2);
  EXPECT_FALSE(vect.stack_data().used_stack_buffer_);

  // Copying the small vector to another should use the same allocator and use
  // the now-unused stack buffer. GENERALLY CALLERS SHOULD NOT DO THIS since
  // they have to get the template types just right and it can cause errors.
  std::vector<int, StackAllocator<int, stack_size> > other(vect.container());
  EXPECT_EQ(stack_buffer, &other.front());
  EXPECT_TRUE(vect.stack_data().used_stack_buffer_);
  for (int i = 0; i < stack_size; i++)
    EXPECT_EQ(i, other[i]);
}

TEST(StackContainer, VectorDoubleDelete) {
  // Regression testing for double-delete.
  typedef StackVector<scoped_refptr<Dummy>, 2> Vector;
  typedef Vector::ContainerType Container;
  Vector vect;

  int alive = 0;
  scoped_refptr<Dummy> dummy(new Dummy(&alive));
  EXPECT_EQ(alive, 1);

  vect->push_back(dummy);
  EXPECT_EQ(alive, 1);

  Dummy* dummy_unref = dummy.get();
  dummy = nullptr;
  EXPECT_EQ(alive, 1);

  Container::iterator itr = std::find(vect->begin(), vect->end(), dummy_unref);
  EXPECT_EQ(itr->get(), dummy_unref);
  vect->erase(itr);
  EXPECT_EQ(alive, 0);

  // Shouldn't crash at exit.
}

namespace {

template <size_t alignment>
class AlignedData {
 public:
  AlignedData() { memset(data_, 0, alignment); }
  ~AlignedData() = default;
  alignas(alignment) char data_[alignment];
};

}  // anonymous namespace

#define EXPECT_ALIGNED(ptr, align) \
    EXPECT_EQ(0u, reinterpret_cast<uintptr_t>(ptr) & (align - 1))

TEST(StackContainer, BufferAlignment) {
  StackVector<wchar_t, 16> text;
  text->push_back(L'A');
  EXPECT_ALIGNED(&text[0], alignof(wchar_t));

  StackVector<double, 1> doubles;
  doubles->push_back(0.0);
  EXPECT_ALIGNED(&doubles[0], alignof(double));

  StackVector<AlignedData<16>, 1> aligned16;
  aligned16->push_back(AlignedData<16>());
  EXPECT_ALIGNED(&aligned16[0], 16);

#if !defined(__GNUC__) || defined(ARCH_CPU_X86_FAMILY)
  // It seems that non-X86 gcc doesn't respect greater than 16 byte alignment.
  // See http://gcc.gnu.org/bugzilla/show_bug.cgi?id=33721 for details.
  // TODO(sbc):re-enable this if GCC starts respecting higher alignments.
  StackVector<AlignedData<256>, 1> aligned256;
  aligned256->push_back(AlignedData<256>());
  EXPECT_ALIGNED(&aligned256[0], 256);
#endif
}

template class StackVector<int, 2>;
template class StackVector<scoped_refptr<Dummy>, 2>;

}  // namespace base