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      1 /*
      2  * Copyright (C) 2014 The Android Open Source Project
      3  *
      4  * Licensed under the Apache License, Version 2.0 (the "License");
      5  * you may not use this file except in compliance with the License.
      6  * You may obtain a copy of the License at
      7  *
      8  *      http://www.apache.org/licenses/LICENSE-2.0
      9  *
     10  * Unless required by applicable law or agreed to in writing, software
     11  * distributed under the License is distributed on an "AS IS" BASIS,
     12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
     13  * See the License for the specific language governing permissions and
     14  * limitations under the License.
     15  */
     16 
     17 #ifndef ART_LIBARTBASE_BASE_DEBUG_STACK_H_
     18 #define ART_LIBARTBASE_BASE_DEBUG_STACK_H_
     19 
     20 #include <android-base/logging.h>
     21 #include <android-base/macros.h>
     22 
     23 #include "globals.h"
     24 
     25 namespace art {
     26 
     27 // Helper classes for reference counting to enforce construction/destruction order and
     28 // usage of the top element of a stack in debug mode with no overhead in release mode.
     29 
     30 // Reference counter. No references allowed in destructor or in explicitly called CheckNoRefs().
     31 template <bool kIsDebug>
     32 class DebugStackRefCounterImpl;
     33 // Reference. Allows an explicit check that it's the top reference.
     34 template <bool kIsDebug>
     35 class DebugStackReferenceImpl;
     36 // Indirect top reference. Checks that the reference is the top reference when used.
     37 template <bool kIsDebug>
     38 class DebugStackIndirectTopRefImpl;
     39 
     40 typedef DebugStackRefCounterImpl<kIsDebugBuild> DebugStackRefCounter;
     41 typedef DebugStackReferenceImpl<kIsDebugBuild> DebugStackReference;
     42 typedef DebugStackIndirectTopRefImpl<kIsDebugBuild> DebugStackIndirectTopRef;
     43 
     44 // Non-debug mode specializations. This should be optimized away.
     45 
     46 template <>
     47 class DebugStackRefCounterImpl<false> {
     48  public:
     49   size_t IncrementRefCount() { return 0u; }
     50   void DecrementRefCount() { }
     51   size_t GetRefCount() const { return 0u; }
     52   void CheckNoRefs() const { }
     53 };
     54 
     55 template <>
     56 class DebugStackReferenceImpl<false> {
     57  public:
     58   explicit DebugStackReferenceImpl(DebugStackRefCounterImpl<false>* counter ATTRIBUTE_UNUSED) {}
     59   DebugStackReferenceImpl(const DebugStackReferenceImpl& other) = default;
     60   DebugStackReferenceImpl& operator=(const DebugStackReferenceImpl& other) = default;
     61   void CheckTop() { }
     62 };
     63 
     64 template <>
     65 class DebugStackIndirectTopRefImpl<false> {
     66  public:
     67   explicit DebugStackIndirectTopRefImpl(DebugStackReferenceImpl<false>* ref ATTRIBUTE_UNUSED) {}
     68   DebugStackIndirectTopRefImpl(const DebugStackIndirectTopRefImpl& other) = default;
     69   DebugStackIndirectTopRefImpl& operator=(const DebugStackIndirectTopRefImpl& other) = default;
     70   void CheckTop() { }
     71 };
     72 
     73 // Debug mode versions.
     74 
     75 template <bool kIsDebug>
     76 class DebugStackRefCounterImpl {
     77  public:
     78   DebugStackRefCounterImpl() : ref_count_(0u) { }
     79   ~DebugStackRefCounterImpl() { CheckNoRefs(); }
     80   size_t IncrementRefCount() { return ++ref_count_; }
     81   void DecrementRefCount() { --ref_count_; }
     82   size_t GetRefCount() const { return ref_count_; }
     83   void CheckNoRefs() const { CHECK_EQ(ref_count_, 0u); }
     84 
     85  private:
     86   size_t ref_count_;
     87 };
     88 
     89 template <bool kIsDebug>
     90 class DebugStackReferenceImpl {
     91  public:
     92   explicit DebugStackReferenceImpl(DebugStackRefCounterImpl<kIsDebug>* counter)
     93     : counter_(counter), ref_count_(counter->IncrementRefCount()) {
     94   }
     95   DebugStackReferenceImpl(const DebugStackReferenceImpl& other)
     96     : counter_(other.counter_), ref_count_(counter_->IncrementRefCount()) {
     97   }
     98   DebugStackReferenceImpl(DebugStackReferenceImpl&& other)
     99     : counter_(other.counter_), ref_count_(other.ref_count_) {
    100     other.counter_ = nullptr;
    101   }
    102   DebugStackReferenceImpl& operator=(const DebugStackReferenceImpl& other) {
    103     CHECK(counter_ == other.counter_);
    104     return *this;
    105   }
    106   ~DebugStackReferenceImpl() {
    107     if (counter_ != nullptr) {
    108       counter_->DecrementRefCount();
    109     }
    110   }
    111   void CheckTop() { CHECK_EQ(counter_->GetRefCount(), ref_count_); }
    112 
    113  private:
    114   DebugStackRefCounterImpl<true>* counter_;
    115   size_t ref_count_;
    116 };
    117 
    118 template <bool kIsDebug>
    119 class DebugStackIndirectTopRefImpl {
    120  public:
    121   explicit DebugStackIndirectTopRefImpl(DebugStackReferenceImpl<kIsDebug>* ref)
    122       : ref_(ref) {
    123     CheckTop();
    124   }
    125   DebugStackIndirectTopRefImpl(const DebugStackIndirectTopRefImpl& other)
    126       : ref_(other.ref_) {
    127     CheckTop();
    128   }
    129   DebugStackIndirectTopRefImpl& operator=(const DebugStackIndirectTopRefImpl& other) {
    130     CHECK(ref_ == other.ref_);
    131     CheckTop();
    132     return *this;
    133   }
    134   ~DebugStackIndirectTopRefImpl() {
    135     CheckTop();
    136   }
    137   void CheckTop() {
    138     ref_->CheckTop();
    139   }
    140 
    141  private:
    142   DebugStackReferenceImpl<kIsDebug>* ref_;
    143 };
    144 
    145 }  // namespace art
    146 
    147 #endif  // ART_LIBARTBASE_BASE_DEBUG_STACK_H_
    148