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:
IncrementRefCount()48   size_t IncrementRefCount() { return 0u; }
DecrementRefCount()49   void DecrementRefCount() { }
GetRefCount()50   size_t GetRefCount() const { return 0u; }
CheckNoRefs()51   void CheckNoRefs() const { }
52 };
53 
54 template <>
55 class DebugStackReferenceImpl<false> {
56  public:
DebugStackReferenceImpl(DebugStackRefCounterImpl<false> * counter)57   explicit DebugStackReferenceImpl(DebugStackRefCounterImpl<false>* counter) { UNUSED(counter); }
58   DebugStackReferenceImpl(const DebugStackReferenceImpl& other) = default;
59   DebugStackReferenceImpl& operator=(const DebugStackReferenceImpl& other) = default;
CheckTop()60   void CheckTop() { }
61 };
62 
63 template <>
64 class DebugStackIndirectTopRefImpl<false> {
65  public:
DebugStackIndirectTopRefImpl(DebugStackReferenceImpl<false> * ref)66   explicit DebugStackIndirectTopRefImpl(DebugStackReferenceImpl<false>* ref) { UNUSED(ref); }
67   DebugStackIndirectTopRefImpl(const DebugStackIndirectTopRefImpl& other) = default;
68   DebugStackIndirectTopRefImpl& operator=(const DebugStackIndirectTopRefImpl& other) = default;
CheckTop()69   void CheckTop() { }
70 };
71 
72 // Debug mode versions.
73 
74 template <bool kIsDebug>
75 class DebugStackRefCounterImpl {
76  public:
DebugStackRefCounterImpl()77   DebugStackRefCounterImpl() : ref_count_(0u) { }
~DebugStackRefCounterImpl()78   ~DebugStackRefCounterImpl() { CheckNoRefs(); }
IncrementRefCount()79   size_t IncrementRefCount() { return ++ref_count_; }
DecrementRefCount()80   void DecrementRefCount() { --ref_count_; }
GetRefCount()81   size_t GetRefCount() const { return ref_count_; }
CheckNoRefs()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:
DebugStackReferenceImpl(DebugStackRefCounterImpl<kIsDebug> * counter)91   explicit DebugStackReferenceImpl(DebugStackRefCounterImpl<kIsDebug>* counter)
92     : counter_(counter), ref_count_(counter->IncrementRefCount()) {
93   }
DebugStackReferenceImpl(const DebugStackReferenceImpl & other)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   }
~DebugStackReferenceImpl()101   ~DebugStackReferenceImpl() { counter_->DecrementRefCount(); }
CheckTop()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:
DebugStackIndirectTopRefImpl(DebugStackReferenceImpl<kIsDebug> * ref)112   explicit DebugStackIndirectTopRefImpl(DebugStackReferenceImpl<kIsDebug>* ref)
113       : ref_(ref) {
114     CheckTop();
115   }
DebugStackIndirectTopRefImpl(const DebugStackIndirectTopRefImpl & other)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   }
~DebugStackIndirectTopRefImpl()125   ~DebugStackIndirectTopRefImpl() {
126     CheckTop();
127   }
CheckTop()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