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1 // Copyright (c) 2012 The Chromium Authors. All rights reserved. | 1 // Copyright (c) 2012 The Chromium Authors. All rights reserved. |
2 // Use of this source code is governed by a BSD-style license that can be | 2 // Use of this source code is governed by a BSD-style license that can be |
3 // found in the LICENSE file. | 3 // found in the LICENSE file. |
4 | 4 |
5 // Scopers help you manage ownership of a pointer, helping you easily manage a | 5 // Scopers help you manage ownership of a pointer, helping you easily manage a |
6 // pointer within a scope, and automatically destroying the pointer at the end | 6 // pointer within a scope, and automatically destroying the pointer at the end |
7 // of a scope. There are two main classes you will use, which correspond to the | 7 // of a scope. There are two main classes you will use, which correspond to the |
8 // operators new/delete and new[]/delete[]. | 8 // operators new/delete and new[]/delete[]. |
9 // | 9 // |
10 // Example usage (scoped_ptr<T>): | 10 // Example usage (scoped_ptr<T>): |
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209 | 209 |
210 template <typename U, typename V> | 210 template <typename U, typename V> |
211 void TakeState(scoped_ptr_impl<U, V>* other) { | 211 void TakeState(scoped_ptr_impl<U, V>* other) { |
212 // See comment in templated constructor above regarding lack of support | 212 // See comment in templated constructor above regarding lack of support |
213 // for move-only deleters. | 213 // for move-only deleters. |
214 reset(other->release()); | 214 reset(other->release()); |
215 get_deleter() = other->get_deleter(); | 215 get_deleter() = other->get_deleter(); |
216 } | 216 } |
217 | 217 |
218 ~scoped_ptr_impl() { | 218 ~scoped_ptr_impl() { |
219 if (data_.ptr != nullptr) { | 219 // Match libc++, which calls reset() in its destructor. |
220 // Not using get_deleter() saves one function call in non-optimized | 220 // Use nullptr as the new value for three reasons: |
221 // builds. | 221 // 1. libc++ does it. |
222 static_cast<D&>(data_)(data_.ptr); | 222 // 2. Avoids infinitely recursing into destructors if two classes are owned |
223 } | 223 // in a reference cycle (see ScopedPtrTest.ReferenceCycle). |
| 224 // 3. If |this| is accessed in the future, in a use-after-free bug, attempts |
| 225 // to dereference |this|'s pointer should cause either a failure or a |
| 226 // segfault closer to the problem. If |this| wasn't reset to nullptr, |
| 227 // the access would cause the deleted memory to be read or written |
| 228 // leading to other more subtle issues. |
| 229 reset(nullptr); |
224 } | 230 } |
225 | 231 |
226 void reset(T* p) { | 232 void reset(T* p) { |
227 // This is a self-reset, which is no longer allowed for default deleters: | 233 // This is a self-reset, which is no longer allowed for default deleters: |
228 // https://crbug.com/162971 | 234 // https://crbug.com/162971 |
229 assert(!ShouldAbortOnSelfReset<D>::value || p == nullptr || p != data_.ptr); | 235 assert(!ShouldAbortOnSelfReset<D>::value || p == nullptr || p != data_.ptr); |
230 | 236 |
231 // Match C++11's definition of unique_ptr::reset(), which requires changing | 237 // Match C++11's definition of unique_ptr::reset(), which requires changing |
232 // the pointer before invoking the deleter on the old pointer. This prevents | 238 // the pointer before invoking the deleter on the old pointer. This prevents |
233 // |this| from being accessed after the deleter is run, which may destroy | 239 // |this| from being accessed after the deleter is run, which may destroy |
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572 scoped_ptr<T> make_scoped_ptr(T* ptr) { | 578 scoped_ptr<T> make_scoped_ptr(T* ptr) { |
573 return scoped_ptr<T>(ptr); | 579 return scoped_ptr<T>(ptr); |
574 } | 580 } |
575 | 581 |
576 template <typename T> | 582 template <typename T> |
577 std::ostream& operator<<(std::ostream& out, const scoped_ptr<T>& p) { | 583 std::ostream& operator<<(std::ostream& out, const scoped_ptr<T>& p) { |
578 return out << p.get(); | 584 return out << p.get(); |
579 } | 585 } |
580 | 586 |
581 #endif // BASE_MEMORY_SCOPED_PTR_H_ | 587 #endif // BASE_MEMORY_SCOPED_PTR_H_ |
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