| /* Copyright (C) 2017-2024 Free Software Foundation, Inc. |
| |
| This file is part of GDB. |
| |
| This program is free software; you can redistribute it and/or modify |
| it under the terms of the GNU General Public License as published by |
| the Free Software Foundation; either version 3 of the License, or |
| (at your option) any later version. |
| |
| This program is distributed in the hope that it will be useful, |
| but WITHOUT ANY WARRANTY; without even the implied warranty of |
| MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
| GNU General Public License for more details. |
| |
| You should have received a copy of the GNU General Public License |
| along with this program. If not, see <http://www.gnu.org/licenses/>. */ |
| |
| #ifndef COMMON_DEFAULT_INIT_ALLOC_H |
| #define COMMON_DEFAULT_INIT_ALLOC_H |
| |
| #if __cplusplus >= 202002L |
| #include <memory_resource> |
| #endif |
| |
| namespace gdb { |
| |
| /* An allocator that default constructs using default-initialization |
| rather than value-initialization. The idea is to use this when you |
| don't want to default construct elements of containers of trivial |
| types using zero-initialization. */ |
| |
| /* Mostly as implementation convenience, this is implemented as an |
| adapter that given an allocator A, overrides 'A::construct()'. 'A' |
| defaults to std::allocator<T>. */ |
| |
| template<typename T, |
| typename A |
| #if __cplusplus >= 202002L |
| = std::pmr::polymorphic_allocator<T> |
| #else |
| = std::allocator<T> |
| #endif |
| > |
| class default_init_allocator : public A |
| { |
| public: |
| /* Pull in A's ctors. */ |
| using A::A; |
| |
| /* Override rebind. */ |
| template<typename U> |
| struct rebind |
| { |
| /* A couple helpers just to make it a bit more readable. */ |
| typedef std::allocator_traits<A> traits_; |
| typedef typename traits_::template rebind_alloc<U> alloc_; |
| |
| /* This is what we're after. */ |
| typedef default_init_allocator<U, alloc_> other; |
| }; |
| |
| /* Make the base allocator's construct method(s) visible. */ |
| using A::construct; |
| |
| /* .. and provide an override/overload for the case of default |
| construction (i.e., no arguments). This is where we construct |
| with default-init. */ |
| template <typename U> |
| void construct (U *ptr) |
| noexcept (std::is_nothrow_default_constructible<U>::value) |
| { |
| ::new ((void *) ptr) U; /* default-init */ |
| } |
| }; |
| |
| } /* namespace gdb */ |
| |
| #endif /* COMMON_DEFAULT_INIT_ALLOC_H */ |