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       1             : //
       2             : // immer: immutable data structures for C++
       3             : // Copyright (C) 2016, 2017, 2018 Juan Pedro Bolivar Puente
       4             : //
       5             : // This software is distributed under the Boost Software License, Version 1.0.
       6             : // See accompanying file LICENSE or copy at http://boost.org/LICENSE_1_0.txt
       7             : //
       8             : 
       9             : #pragma once
      10             : 
      11             : #include <immer/config.hpp>
      12             : #include <immer/heap/identity_heap.hpp>
      13             : 
      14             : #include <cassert>
      15             : #include <cstddef>
      16             : #include <type_traits>
      17             : #include <memory>
      18             : 
      19             : namespace immer {
      20             : 
      21             : #if IMMER_ENABLE_DEBUG_SIZE_HEAP
      22             : 
      23             : /*!
      24             :  * A heap that in debug mode ensures that the sizes for allocation and
      25             :  * deallocation do match.
      26             :  */
      27             : template <typename Base>
      28             : struct debug_size_heap
      29             : {
      30             : #if defined(__MINGW32__) && !defined(__MINGW64__)
      31             :     // There is a bug in MinGW 32bit:
      32             :     // https://sourceforge.net/p/mingw-w64/bugs/778/ It causes different
      33             :     // versions of std::max_align_t to be defined, depending on inclusion order
      34             :     // of stddef.h and stdint.h. As we have no control over the inclusion order
      35             :     // here (as it might be set in stone by the outside world), we can't easily
      36             :     // pin it to one of both versions of std::max_align_t. This means, we have
      37             :     // to hardcode extra_size for MinGW 32bit builds until the mentioned bug is
      38             :     // fixed.
      39             :     constexpr static auto extra_size = 8;
      40             : #else
      41             :     constexpr static auto extra_size = sizeof(
      42             :         std::aligned_storage_t<sizeof(std::size_t), alignof(std::max_align_t)>);
      43             : #endif
      44             : 
      45             :     template <typename... Tags>
      46       66954 :     static void* allocate(std::size_t size, Tags... tags)
      47             :     {
      48       66954 :         auto p = (std::size_t*) Base::allocate(size + extra_size, tags...);
      49       30239 :         new (p) std::size_t{size};
      50       30239 :         return ((char*) p) + extra_size;
      51             :     }
      52             : 
      53             :     template <typename... Tags>
      54       65790 :     static void deallocate(std::size_t size, void* data, Tags... tags)
      55             :     {
      56       65790 :         auto p = (std::size_t*) (((char*) data) - extra_size);
      57       65790 :         assert(*p == size);
      58       65790 :         Base::deallocate(size + extra_size, p, tags...);
      59       65790 :     }
      60             : };
      61             : 
      62             : #else // IMMER_ENABLE_DEBUG_SIZE_HEAP
      63             : 
      64             : template <typename Base>
      65             : using debug_size_heap = identity_heap<Base>;
      66             : 
      67             : #endif // !IMMER_ENABLE_DEBUG_SIZE_HEAP
      68             : 
      69             : } // namespace immer