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The unique_ptr_slab variation of the std::unique_ptr<T> addresses the issue of new/delete mismatches in code that allocates a _memory slab_ with the global _operator_ new but de-allocates an _object_ with a delete _expression_. The use case that manifests the mismatch is as follows: Allocate a slab of memory that has a C struct at the head of the slab, with a "my_type mt[0];" as the head's last member. The slab is cast to the type of the C struct, but sized to contain N my_type items. The object based de-allocation is the behavior of the std::default_delete<T> template; it is used by the std::unique_ptr<T> if the user does not specify an alternative deleter. The unique_ptr_slab resolves the mismatch with an alternative deleter that de-allocates the _memory slab_ with the global _operator_ delete. Signed-off-by: Mark Deric <jmark@openvpn.net>
65 lines
2.4 KiB
C++
65 lines
2.4 KiB
C++
// OpenVPN -- An application to securely tunnel IP networks
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// over a single port, with support for SSL/TLS-based
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// session authentication and key exchange,
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// packet encryption, packet authentication, and
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// packet compression.
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//
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// Copyright (C) 2012-2020 OpenVPN Inc.
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//
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// This program is free software: you can redistribute it and/or modify
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// it under the terms of the GNU Affero General Public License Version 3
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// as published by the Free Software Foundation.
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//
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// This program is distributed in the hope that it will be useful,
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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// GNU Affero General Public License for more details.
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//
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// You should have received a copy of the GNU Affero General Public License
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// along with this program in the COPYING file.
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// If not, see <http://www.gnu.org/licenses/>.
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#ifndef OPENVPN_COMMON_UNIQUEPTR_H
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#define OPENVPN_COMMON_UNIQUEPTR_H
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#include <memory>
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#include <functional>
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#include <type_traits>
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namespace openvpn {
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template<typename T>
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using unique_ptr_del = std::unique_ptr<T, std::function<void(T*)>>;
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// The unique_ptr_slab variation of the std::unique_ptr<T> addresses the issue of
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// new/delete mismatches in code that allocates a _memory slab_ with the global
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// _operator_ new but de-allocates an _object_ with a delete _expression_. The use
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// case that manifests the mismatch is as follows: Allocate a slab of memory that has
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// a C struct at the head of the slab, with a "my_type mt[0];" as the head's last
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// member. The slab is cast to the type of the C struct, but sized to contain N
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// my_type items.
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//
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// The object based de-allocation is the behavior of the std::default_delete<T>
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// template; it is used by the std::unique_ptr<T> if the user does not specify an
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// alternative deleter. The unique_ptr_slab resolves the mismatch with an alternative
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// deleter that de-allocates the _memory slab_ with the global _operator_ delete.
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template<typename T>
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void delete_slab(T* ptr) {
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::operator delete(const_cast<typename std::remove_cv<T>::type*>(ptr));
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}
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template<typename T>
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class slab_deleter
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{
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public:
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slab_deleter() {}
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void operator()(T* ptr){
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delete_slab(ptr);
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}
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};
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template<typename T>
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using unique_ptr_slab = std::unique_ptr<T, slab_deleter<T>>;
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}
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#endif
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