00001 // Copyright 2018 The Abseil Authors. 00002 // 00003 // Licensed under the Apache License, Version 2.0 (the "License"); 00004 // you may not use this file except in compliance with the License. 00005 // You may obtain a copy of the License at 00006 // 00007 // https://www.apache.org/licenses/LICENSE-2.0 00008 // 00009 // Unless required by applicable law or agreed to in writing, software 00010 // distributed under the License is distributed on an "AS IS" BASIS, 00011 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 00012 // See the License for the specific language governing permissions and 00013 // limitations under the License. 00014 00015 #ifndef ABSL_BASE_INTERNAL_HIDE_PTR_H_ 00016 #define ABSL_BASE_INTERNAL_HIDE_PTR_H_ 00017 00018 #include <cstdint> 00019 00020 namespace absl { 00021 namespace base_internal { 00022 00023 // Arbitrary value with high bits set. Xor'ing with it is unlikely 00024 // to map one valid pointer to another valid pointer. 00025 constexpr uintptr_t HideMask() { 00026 return (uintptr_t{0xF03A5F7BU} << (sizeof(uintptr_t) - 4) * 8) | 0xF03A5F7BU; 00027 } 00028 00029 // Hide a pointer from the leak checker. For internal use only. 00030 // Differs from absl::IgnoreLeak(ptr) in that absl::IgnoreLeak(ptr) causes ptr 00031 // and all objects reachable from ptr to be ignored by the leak checker. 00032 template <class T> 00033 inline uintptr_t HidePtr(T* ptr) { 00034 return reinterpret_cast<uintptr_t>(ptr) ^ HideMask(); 00035 } 00036 00037 // Return a pointer that has been hidden from the leak checker. 00038 // For internal use only. 00039 template <class T> 00040 inline T* UnhidePtr(uintptr_t hidden) { 00041 return reinterpret_cast<T*>(hidden ^ HideMask()); 00042 } 00043 00044 } // namespace base_internal 00045 } // namespace absl 00046 00047 #endif // ABSL_BASE_INTERNAL_HIDE_PTR_H_