| 1 | /* Copyright (C) 2017-2019 Free Software Foundation, Inc. |
| 2 | |
| 3 | This file is part of GDB. |
| 4 | |
| 5 | This program is free software; you can redistribute it and/or modify |
| 6 | it under the terms of the GNU General Public License as published by |
| 7 | the Free Software Foundation; either version 3 of the License, or |
| 8 | (at your option) any later version. |
| 9 | |
| 10 | This program is distributed in the hope that it will be useful, |
| 11 | but WITHOUT ANY WARRANTY; without even the implied warranty of |
| 12 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
| 13 | GNU General Public License for more details. |
| 14 | |
| 15 | You should have received a copy of the GNU General Public License |
| 16 | along with this program. If not, see <http://www.gnu.org/licenses/>. */ |
| 17 | |
| 18 | #ifndef COMMON_DEFAULT_INIT_ALLOC_H |
| 19 | #define COMMON_DEFAULT_INIT_ALLOC_H |
| 20 | |
| 21 | namespace gdb { |
| 22 | |
| 23 | /* An allocator that default constructs using default-initialization |
| 24 | rather than value-initialization. The idea is to use this when you |
| 25 | don't want to default construct elements of containers of trivial |
| 26 | types using zero-initialization. */ |
| 27 | |
| 28 | /* Mostly as implementation convenience, this is implemented as an |
| 29 | adapter that given an allocator A, overrides 'A::construct()'. 'A' |
| 30 | defaults to std::allocator<T>. */ |
| 31 | |
| 32 | template<typename T, typename A = std::allocator<T>> |
| 33 | class default_init_allocator : public A |
| 34 | { |
| 35 | public: |
| 36 | /* Pull in A's ctors. */ |
| 37 | using A::A; |
| 38 | |
| 39 | /* Override rebind. */ |
| 40 | template<typename U> |
| 41 | struct rebind |
| 42 | { |
| 43 | /* A couple helpers just to make it a bit more readable. */ |
| 44 | typedef std::allocator_traits<A> traits_; |
| 45 | typedef typename traits_::template rebind_alloc<U> alloc_; |
| 46 | |
| 47 | /* This is what we're after. */ |
| 48 | typedef default_init_allocator<U, alloc_> other; |
| 49 | }; |
| 50 | |
| 51 | /* Make the base allocator's construct method(s) visible. */ |
| 52 | using A::construct; |
| 53 | |
| 54 | /* .. and provide an override/overload for the case of default |
| 55 | construction (i.e., no arguments). This is where we construct |
| 56 | with default-init. */ |
| 57 | template <typename U> |
| 58 | void construct (U *ptr) |
| 59 | noexcept (std::is_nothrow_default_constructible<U>::value) |
| 60 | { |
| 61 | ::new ((void *) ptr) U; /* default-init */ |
| 62 | } |
| 63 | }; |
| 64 | |
| 65 | } /* namespace gdb */ |
| 66 | |
| 67 | #endif /* COMMON_DEFAULT_INIT_ALLOC_H */ |