7f19d64164
git-subtree-dir: third_party/immer git-subtree-split: ad3e3556d38bb75966dd24c61a774970a7c7957e
127 lines
3.2 KiB
C++
127 lines
3.2 KiB
C++
//
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// immer: immutable data structures for C++
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// Copyright (C) 2016, 2017, 2018 Juan Pedro Bolivar Puente
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//
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// This software is distributed under the Boost Software License, Version 1.0.
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// See accompanying file LICENSE or copy at http://boost.org/LICENSE_1_0.txt
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//
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#pragma once
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#include <immer/config.hpp>
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#include <immer/heap/tags.hpp>
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#if IMMER_HAS_LIBGC
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#include <gc/gc.h>
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#else
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#error "Using garbage collection requires libgc"
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#endif
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#include <cstdlib>
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#include <memory>
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namespace immer {
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#ifdef __APPLE__
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#define IMMER_GC_REQUIRE_INIT 1
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#else
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#define IMMER_GC_REQUIRE_INIT 0
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#endif
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#if IMMER_GC_REQUIRE_INIT
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namespace detail {
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template <int Dummy = 0>
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struct gc_initializer
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{
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gc_initializer() { GC_init(); }
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static gc_initializer init;
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};
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template <int D>
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gc_initializer<D> gc_initializer<D>::init{};
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inline void gc_initializer_guard()
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{
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static gc_initializer<> init_ = gc_initializer<>::init;
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(void) init_;
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}
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} // namespace detail
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#define IMMER_GC_INIT_GUARD_ ::immer::detail::gc_initializer_guard()
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#else
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#define IMMER_GC_INIT_GUARD_
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#endif // IMMER_GC_REQUIRE_INIT
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/*!
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* Heap that uses a tracing garbage collector.
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*
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* @rst
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*
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* This heap uses the `Boehm's conservative garbage collector`_ under
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* the hood. This is a tracing garbage collector that automatically
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* reclaims unused memory. Thus, it is not needed to call
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* ``deallocate()`` in order to release memory.
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*
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* .. admonition:: Dependencies
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* :class: tip
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*
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* In order to use this header file, you need to make sure that
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* Boehm's ``libgc`` is your include path and link to its binary
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* library.
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*
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* .. caution:: Memory that is allocated with the standard ``malloc``
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* and ``free`` is not visible to ``libgc`` when it is looking for
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* references. This means that if, let's say, you store a
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* :cpp:class:`immer::vector` using a ``gc_heap`` inside a
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* ``std::vector`` that uses a standard allocator, the memory of
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* the former might be released automatically at unexpected times
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* causing crashes.
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*
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* .. caution:: When using a ``gc_heap`` in combination with immutable
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* containers, the destructors of the contained objects will never
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* be called. It is ok to store containers inside containers as
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* long as all of them use a ``gc_heap`` consistently, but storing
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* other kinds of objects with relevant destructors
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* (e.g. containers with reference counting or other kinds of
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* *resource handles*) might cause memory leaks and other problems.
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*
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* .. _boehm's conservative garbage collector: https://github.com/ivmai/bdwgc
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*
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* @endrst
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*/
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class gc_heap
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{
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public:
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static void* allocate(std::size_t n)
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{
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IMMER_GC_INIT_GUARD_;
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auto p = GC_malloc(n);
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if (IMMER_UNLIKELY(!p))
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throw std::bad_alloc{};
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return p;
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}
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static void* allocate(std::size_t n, norefs_tag)
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{
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IMMER_GC_INIT_GUARD_;
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auto p = GC_malloc_atomic(n);
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if (IMMER_UNLIKELY(!p))
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throw std::bad_alloc{};
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return p;
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}
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static void deallocate(std::size_t, void* data) { GC_free(data); }
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static void deallocate(std::size_t, void* data, norefs_tag)
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{
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GC_free(data);
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}
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};
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} // namespace immer
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