TestNotNull.cpp

/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim: set ts=8 sts=2 et sw=2 tw=80: */
/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this file,
 * You can obtain one at http://mozilla.org/MPL/2.0/. */

#include <type_traits>

#include "mozilla/NotNull.h"
#include "mozilla/RefPtr.h"
#include "mozilla/UniquePtr.h"
#include "mozilla/Unused.h"

using mozilla::MakeNotNull;
using mozilla::NotNull;
using mozilla::UniquePtr;
using mozilla::WrapNotNull;

#define CHECK MOZ_RELEASE_ASSERT

class Blah {
 public:
  Blah() : mX(0) {}
  void blah(){};
  int mX;
};

// A simple smart pointer that implicity converts to and from T*.
template <typename T>
class MyPtr {
  T* mRawPtr;

 public:
  MyPtr() : mRawPtr(nullptr) {}
  MOZ_IMPLICIT MyPtr(T* aRawPtr) : mRawPtr(aRawPtr) {}

  T* get() const { return mRawPtr; }
  operator T*() const { return get(); }

  T* operator->() const { return get(); }
};

// A simple class that works with RefPtr. It keeps track of the maximum
// refcount value for testing purposes.
class MyRefType {
  int mExpectedMaxRefCnt;
  int mMaxRefCnt;
  int mRefCnt;

 public:
  explicit MyRefType(int aExpectedMaxRefCnt)
      : mExpectedMaxRefCnt(aExpectedMaxRefCnt), mMaxRefCnt(0), mRefCnt(0) {}

  ~MyRefType() { CHECK(mMaxRefCnt == mExpectedMaxRefCnt); }

  uint32_t AddRef() {
    mRefCnt++;
    if (mRefCnt > mMaxRefCnt) {
      mMaxRefCnt = mRefCnt;
    }
    return mRefCnt;
  }

  uint32_t Release() {
    CHECK(mRefCnt > 0);
    mRefCnt--;
    if (mRefCnt == 0) {
      delete this;
      return 0;
    }
    return mRefCnt;
  }
};

void f_i(int* aPtr) {}
void f_my(MyPtr<int> aPtr) {}

void f_nni(NotNull<int*> aPtr) {}
void f_nnmy(NotNull<MyPtr<int>> aPtr) {}

void TestNotNullWithMyPtr() {
  int i4 = 4;
  int i5 = 5;

  MyPtr<int> my4 = &i4;
  MyPtr<int> my5 = &i5;

  NotNull<int*> nni4 = WrapNotNull(&i4);
  NotNull<int*> nni5 = WrapNotNull(&i5);
  NotNull<MyPtr<int>> nnmy4 = WrapNotNull(my4);

  // WrapNotNull(nullptr);                       // no wrapping from nullptr
  // WrapNotNull(0);                             // no wrapping from zero

  // NotNull<int*> construction combinations
  // NotNull<int*> nni4a;                        // no default
  // NotNull<int*> nni4a(nullptr);               // no nullptr
  // NotNull<int*> nni4a(0);                     // no zero
  // NotNull<int*> nni4a(&i4);                   // no int*
  // NotNull<int*> nni4a(my4);                   // no MyPtr<int>
  NotNull<int*> nni4b(WrapNotNull(&i4));  // WrapNotNull(int*)
  NotNull<int*> nni4c(WrapNotNull(my4));  // WrapNotNull(MyPtr<int>)
  NotNull<int*> nni4d(nni4);              // NotNull<int*>
  NotNull<int*> nni4e(nnmy4);             // NotNull<MyPtr<int>>
  CHECK(*nni4b == 4);
  CHECK(*nni4c == 4);
  CHECK(*nni4d == 4);
  CHECK(*nni4e == 4);

  // NotNull<MyPtr<int>> construction combinations
  // NotNull<MyPtr<int>> nnmy4a;                 // no default
  // NotNull<MyPtr<int>> nnmy4a(nullptr);        // no nullptr
  // NotNull<MyPtr<int>> nnmy4a(0);              // no zero
  // NotNull<MyPtr<int>> nnmy4a(&i4);            // no int*
  // NotNull<MyPtr<int>> nnmy4a(my4);            // no MyPtr<int>
  NotNull<MyPtr<int>> nnmy4b(WrapNotNull(&i4));  // WrapNotNull(int*)
  NotNull<MyPtr<int>> nnmy4c(WrapNotNull(my4));  // WrapNotNull(MyPtr<int>)
  NotNull<MyPtr<int>> nnmy4d(nni4);              // NotNull<int*>
  NotNull<MyPtr<int>> nnmy4e(nnmy4);             // NotNull<MyPtr<int>>
  CHECK(*nnmy4b == 4);
  CHECK(*nnmy4c == 4);
  CHECK(*nnmy4d == 4);
  CHECK(*nnmy4e == 4);

  // NotNull<int*> assignment combinations
  // nni4b = nullptr;                            // no nullptr
  // nni4b = 0;                                  // no zero
  // nni4a = &i4;                                // no int*
  // nni4a = my4;                                // no MyPtr<int>
  nni4b = WrapNotNull(&i4);  // WrapNotNull(int*)
  nni4c = WrapNotNull(my4);  // WrapNotNull(MyPtr<int>)
  nni4d = nni4;              // NotNull<int*>
  nni4e = nnmy4;             // NotNull<MyPtr<int>>
  CHECK(*nni4b == 4);
  CHECK(*nni4c == 4);
  CHECK(*nni4d == 4);
  CHECK(*nni4e == 4);

  // NotNull<MyPtr<int>> assignment combinations
  // nnmy4a = nullptr;                           // no nullptr
  // nnmy4a = 0;                                 // no zero
  // nnmy4a = &i4;                               // no int*
  // nnmy4a = my4;                               // no MyPtr<int>
  nnmy4b = WrapNotNull(&i4);  // WrapNotNull(int*)
  nnmy4c = WrapNotNull(my4);  // WrapNotNull(MyPtr<int>)
  nnmy4d = nni4;              // NotNull<int*>
  nnmy4e = nnmy4;             // NotNull<MyPtr<int>>
  CHECK(*nnmy4b == 4);
  CHECK(*nnmy4c == 4);
  CHECK(*nnmy4d == 4);
  CHECK(*nnmy4e == 4);

  NotNull<MyPtr<int>> nnmy5 = WrapNotNull(&i5);
  CHECK(*nnmy5 == 5);
  CHECK(nnmy5 == &i5);    // NotNull<MyPtr<int>> == int*
  CHECK(nnmy5 == my5);    // NotNull<MyPtr<int>> == MyPtr<int>
  CHECK(nnmy5 == nni5);   // NotNull<MyPtr<int>> == NotNull<int*>
  CHECK(nnmy5 == nnmy5);  // NotNull<MyPtr<int>> == NotNull<MyPtr<int>>
  CHECK(&i5 == nnmy5);    // int*                == NotNull<MyPtr<int>>
  CHECK(my5 == nnmy5);    // MyPtr<int>          == NotNull<MyPtr<int>>
  CHECK(nni5 == nnmy5);   // NotNull<int*>       == NotNull<MyPtr<int>>
  CHECK(nnmy5 == nnmy5);  // NotNull<MyPtr<int>> == NotNull<MyPtr<int>>
  // CHECK(nni5 == nullptr);  // no comparisons with nullptr
  // CHECK(nullptr == nni5);  // no comparisons with nullptr
  // CHECK(nni5 == 0);        // no comparisons with zero
  // CHECK(0 == nni5);        // no comparisons with zero

  CHECK(*nnmy5 == 5);
  CHECK(nnmy5 != &i4);    // NotNull<MyPtr<int>> != int*
  CHECK(nnmy5 != my4);    // NotNull<MyPtr<int>> != MyPtr<int>
  CHECK(nnmy5 != nni4);   // NotNull<MyPtr<int>> != NotNull<int*>
  CHECK(nnmy5 != nnmy4);  // NotNull<MyPtr<int>> != NotNull<MyPtr<int>>
  CHECK(&i4 != nnmy5);    // int*                != NotNull<MyPtr<int>>
  CHECK(my4 != nnmy5);    // MyPtr<int>          != NotNull<MyPtr<int>>
  CHECK(nni4 != nnmy5);   // NotNull<int*>       != NotNull<MyPtr<int>>
  CHECK(nnmy4 != nnmy5);  // NotNull<MyPtr<int>> != NotNull<MyPtr<int>>
  // CHECK(nni4 != nullptr);  // no comparisons with nullptr
  // CHECK(nullptr != nni4);  // no comparisons with nullptr
  // CHECK(nni4 != 0);        // no comparisons with zero
  // CHECK(0 != nni4);        // no comparisons with zero

  // int* parameter
  f_i(&i4);         // identity int*                        --> int*
  f_i(my4);         // implicit MyPtr<int>                  --> int*
  f_i(my4.get());   // explicit MyPtr<int>                  --> int*
  f_i(nni4);        // implicit NotNull<int*>               --> int*
  f_i(nni4.get());  // explicit NotNull<int*>               --> int*
  // f_i(nnmy4);         // no implicit NotNull<MyPtr<int>>      --> int*
  f_i(nnmy4.get());        // explicit NotNull<MyPtr<int>>         --> int*
  f_i(nnmy4.get().get());  // doubly-explicit NotNull<MyPtr<int>> --> int*

  // MyPtr<int> parameter
  f_my(&i4);        // implicit int*                         --> MyPtr<int>
  f_my(my4);        // identity MyPtr<int>                   --> MyPtr<int>
  f_my(my4.get());  // explicit MyPtr<int>                   --> MyPtr<int>
  // f_my(nni4);         // no implicit NotNull<int*>             --> MyPtr<int>
  f_my(nni4.get());   // explicit NotNull<int*>                --> MyPtr<int>
  f_my(nnmy4);        // implicit NotNull<MyPtr<int>>          --> MyPtr<int>
  f_my(nnmy4.get());  // explicit NotNull<MyPtr<int>>          --> MyPtr<int>
  f_my(
      nnmy4.get().get());  // doubly-explicit NotNull<MyPtr<int>> --> MyPtr<int>

  // NotNull<int*> parameter
  f_nni(nni4);   // identity NotNull<int*>       --> NotNull<int*>
  f_nni(nnmy4);  // implicit NotNull<MyPtr<int>> --> NotNull<int*>

  // NotNull<MyPtr<int>> parameter
  f_nnmy(nni4);   // implicit NotNull<int*>       --> NotNull<MyPtr<int>>
  f_nnmy(nnmy4);  // identity NotNull<MyPtr<int>> --> NotNull<MyPtr<int>>

  // CHECK(nni4);        // disallow boolean conversion / unary expression usage
  // CHECK(nnmy4);       // ditto

  // '->' dereferencing.
  Blah blah;
  MyPtr<Blah> myblah = &blah;
  NotNull<Blah*> nnblah = WrapNotNull(&blah);
  NotNull<MyPtr<Blah>> nnmyblah = WrapNotNull(myblah);
  (&blah)->blah();   // int*
  myblah->blah();    // MyPtr<int>
  nnblah->blah();    // NotNull<int*>
  nnmyblah->blah();  // NotNull<MyPtr<int>>

  (&blah)->mX = 1;
  CHECK((&blah)->mX == 1);
  myblah->mX = 2;
  CHECK(myblah->mX == 2);
  nnblah->mX = 3;
  CHECK(nnblah->mX == 3);
  nnmyblah->mX = 4;
  CHECK(nnmyblah->mX == 4);

  // '*' dereferencing (lvalues and rvalues)
  *(&i4) = 7;  // int*
  CHECK(*(&i4) == 7);
  *my4 = 6;  // MyPtr<int>
  CHECK(*my4 == 6);
  *nni4 = 5;  // NotNull<int*>
  CHECK(*nni4 == 5);
  *nnmy4 = 4;  // NotNull<MyPtr<int>>
  CHECK(*nnmy4 == 4);

  // Non-null arrays.
  static const int N = 20;
  int a[N];
  NotNull<int*> nna = WrapNotNull(a);
  for (int i = 0; i < N; i++) {
    nna[i] = i;
  }
  for (int i = 0; i < N; i++) {
    nna[i] *= 2;
  }
  for (int i = 0; i < N; i++) {
    CHECK(nna[i] == i * 2);
  }
}

void f_ref(NotNull<MyRefType*> aR) { NotNull<RefPtr<MyRefType>> r = aR; }

void TestNotNullWithRefPtr() {
  // This MyRefType object will have a maximum refcount of 5.
  NotNull<RefPtr<MyRefType>> r1 = WrapNotNull(new MyRefType(5));

  // At this point the refcount is 1.

  NotNull<RefPtr<MyRefType>> r2 = r1;

  // At this point the refcount is 2.

  NotNull<MyRefType*> r3 = r2;
  (void)r3;

  // At this point the refcount is still 2.

  RefPtr<MyRefType> r4 = r2;
  mozilla::Unused << r4;

  // At this point the refcount is 3.

  RefPtr<MyRefType> r5 = r3.get();
  mozilla::Unused << r5;

  // At this point the refcount is 4.

  // No change to the refcount occurs because of the argument passing. Within
  // f_ref() the refcount temporarily hits 5, due to the local RefPtr.
  f_ref(r2);

  // At this point the refcount is 4.

  NotNull<RefPtr<MyRefType>> r6 = std::move(r2);
  mozilla::Unused << r6;

  CHECK(r2.get());
  CHECK(r6.get());

  // At this point the refcount is 5 again, since NotNull is not movable.

  // At function's end all RefPtrs are destroyed and the refcount drops to 0
  // and the MyRefType is destroyed.
}

// Create a derived object and store its base pointer.
struct Base {
  virtual ~Base() = default;
  virtual bool IsDerived() const { return false; }
};
struct Derived : Base {
  bool IsDerived() const override { return true; }
};

void TestMakeNotNull() {
  // Raw pointer.
  auto nni = MakeNotNull<int*>(11);
  static_assert(std::is_same_v<NotNull<int*>, decltype(nni)>,
                "MakeNotNull<int*> should return NotNull<int*>");
  CHECK(*nni == 11);
  delete nni;

  // Raw pointer to const.
  auto nnci = MakeNotNull<const int*>(12);
  static_assert(std::is_same_v<NotNull<const int*>, decltype(nnci)>,
                "MakeNotNull<const int*> should return NotNull<const int*>");
  CHECK(*nnci == 12);
  delete nnci;

  auto nnd = MakeNotNull<Derived*>();
  static_assert(std::is_same_v<NotNull<Derived*>, decltype(nnd)>,
                "MakeNotNull<Derived*> should return NotNull<Derived*>");
  CHECK(nnd->IsDerived());
  delete nnd;
  NotNull<Base*> nnb = MakeNotNull<Derived*>();
  static_assert(std::is_same_v<NotNull<Base*>, decltype(nnb)>,
                "MakeNotNull<Derived*> should be assignable to NotNull<Base*>");
  // Check that we have really built a Derived object.
  CHECK(nnb->IsDerived());
  delete nnb;

  // Allow smart pointers.
  auto nnmi = MakeNotNull<MyPtr<int>>(23);
  static_assert(std::is_same_v<NotNull<MyPtr<int>>, decltype(nnmi)>,
                "MakeNotNull<MyPtr<int>> should return NotNull<MyPtr<int>>");
  CHECK(*nnmi == 23);
  delete nnmi.get().get();

  auto nnui = MakeNotNull<UniquePtr<int>>(24);
  static_assert(
      std::is_same_v<NotNull<UniquePtr<int>>, decltype(nnui)>,
      "MakeNotNull<UniquePtr<int>> should return NotNull<UniquePtr<int>>");
  CHECK(*nnui == 24);

  // Expect only 1 RefCnt (from construction).
  auto nnr = MakeNotNull<RefPtr<MyRefType>>(1);
  static_assert(std::is_same_v<NotNull<RefPtr<MyRefType>>, decltype(nnr)>,
                "MakeNotNull<RefPtr<MyRefType>> should return "
                "NotNull<RefPtr<MyRefType>>");
  mozilla::Unused << nnr;
}

mozilla::MovingNotNull<UniquePtr<int>> CreateNotNullUniquePtr() {
  return mozilla::WrapMovingNotNull(mozilla::MakeUnique<int>(42));
}

void TestMovingNotNull() {
  UniquePtr<int> x1 = CreateNotNullUniquePtr();
  CHECK(x1);
  CHECK(42 == *x1);

  NotNull<UniquePtr<int>> x2 = CreateNotNullUniquePtr();
  CHECK(42 == *x2);

  NotNull<UniquePtr<Base>> x3 =
      mozilla::WrapMovingNotNull(mozilla::MakeUnique<Derived>());

  // Must not compile:
  // auto y = CreateNotNullUniquePtr();
}

int main() {
  TestNotNullWithMyPtr();
  TestNotNullWithRefPtr();
  TestMakeNotNull();
  TestMovingNotNull();

  return 0;
}