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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_RUNTIME_BASE_DEBUG_STACK_H_
     18 #define ART_RUNTIME_BASE_DEBUG_STACK_H_
     19 
     20 #include "base/logging.h"
     21 #include "base/macros.h"
     22 #include "globals.h"
     23 
     24 namespace art {
     25 
     26 // Helper classes for reference counting to enforce construction/destruction order and
     27 // usage of the top element of a stack in debug mode with no overhead in release mode.
     28 
     29 // Reference counter. No references allowed in destructor or in explicitly called CheckNoRefs().
     30 template <bool kIsDebug>
     31 class DebugStackRefCounterImpl;
     32 // Reference. Allows an explicit check that it's the top reference.
     33 template <bool kIsDebug>
     34 class DebugStackReferenceImpl;
     35 // Indirect top reference. Checks that the reference is the top reference when used.
     36 template <bool kIsDebug>
     37 class DebugStackIndirectTopRefImpl;
     38 
     39 typedef DebugStackRefCounterImpl<kIsDebugBuild> DebugStackRefCounter;
     40 typedef DebugStackReferenceImpl<kIsDebugBuild> DebugStackReference;
     41 typedef DebugStackIndirectTopRefImpl<kIsDebugBuild> DebugStackIndirectTopRef;
     42 
     43 // Non-debug mode specializations. This should be optimized away.
     44 
     45 template <>
     46 class DebugStackRefCounterImpl<false> {
     47  public:
     48   size_t IncrementRefCount() { return 0u; }
     49   void DecrementRefCount() { }
     50   size_t GetRefCount() const { return 0u; }
     51   void CheckNoRefs() const { }
     52 };
     53 
     54 template <>
     55 class DebugStackReferenceImpl<false> {
     56  public:
     57   explicit DebugStackReferenceImpl(DebugStackRefCounterImpl<false>* counter ATTRIBUTE_UNUSED) {}
     58   DebugStackReferenceImpl(const DebugStackReferenceImpl& other) = default;
     59   DebugStackReferenceImpl& operator=(const DebugStackReferenceImpl& other) = default;
     60   void CheckTop() { }
     61 };
     62 
     63 template <>
     64 class DebugStackIndirectTopRefImpl<false> {
     65  public:
     66   explicit DebugStackIndirectTopRefImpl(DebugStackReferenceImpl<false>* ref ATTRIBUTE_UNUSED) {}
     67   DebugStackIndirectTopRefImpl(const DebugStackIndirectTopRefImpl& other) = default;
     68   DebugStackIndirectTopRefImpl& operator=(const DebugStackIndirectTopRefImpl& other) = default;
     69   void CheckTop() { }
     70 };
     71 
     72 // Debug mode versions.
     73 
     74 template <bool kIsDebug>
     75 class DebugStackRefCounterImpl {
     76  public:
     77   DebugStackRefCounterImpl() : ref_count_(0u) { }
     78   ~DebugStackRefCounterImpl() { CheckNoRefs(); }
     79   size_t IncrementRefCount() { return ++ref_count_; }
     80   void DecrementRefCount() { --ref_count_; }
     81   size_t GetRefCount() const { return ref_count_; }
     82   void CheckNoRefs() const { CHECK_EQ(ref_count_, 0u); }
     83 
     84  private:
     85   size_t ref_count_;
     86 };
     87 
     88 template <bool kIsDebug>
     89 class DebugStackReferenceImpl {
     90  public:
     91   explicit DebugStackReferenceImpl(DebugStackRefCounterImpl<kIsDebug>* counter)
     92     : counter_(counter), ref_count_(counter->IncrementRefCount()) {
     93   }
     94   DebugStackReferenceImpl(const DebugStackReferenceImpl& other)
     95     : counter_(other.counter_), ref_count_(counter_->IncrementRefCount()) {
     96   }
     97   DebugStackReferenceImpl& operator=(const DebugStackReferenceImpl& other) {
     98     CHECK(counter_ == other.counter_);
     99     return *this;
    100   }
    101   ~DebugStackReferenceImpl() { counter_->DecrementRefCount(); }
    102   void CheckTop() { CHECK_EQ(counter_->GetRefCount(), ref_count_); }
    103 
    104  private:
    105   DebugStackRefCounterImpl<true>* counter_;
    106   size_t ref_count_;
    107 };
    108 
    109 template <bool kIsDebug>
    110 class DebugStackIndirectTopRefImpl {
    111  public:
    112   explicit DebugStackIndirectTopRefImpl(DebugStackReferenceImpl<kIsDebug>* ref)
    113       : ref_(ref) {
    114     CheckTop();
    115   }
    116   DebugStackIndirectTopRefImpl(const DebugStackIndirectTopRefImpl& other)
    117       : ref_(other.ref_) {
    118     CheckTop();
    119   }
    120   DebugStackIndirectTopRefImpl& operator=(const DebugStackIndirectTopRefImpl& other) {
    121     CHECK(ref_ == other.ref_);
    122     CheckTop();
    123     return *this;
    124   }
    125   ~DebugStackIndirectTopRefImpl() {
    126     CheckTop();
    127   }
    128   void CheckTop() {
    129     ref_->CheckTop();
    130   }
    131 
    132  private:
    133   DebugStackReferenceImpl<kIsDebug>* ref_;
    134 };
    135 
    136 }  // namespace art
    137 
    138 #endif  // ART_RUNTIME_BASE_DEBUG_STACK_H_
    139