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