C ++分配对象的存储,而不初始化它? [英] C++ Allocate Storage for Object without Initializing it?
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问题描述
是否有一个接受的习语为现场分配对象的后备存储,但不初始化它?这是我天真的解决方案:
Is there an accepted idiom for allocating the backing store for an object in-place but not initializing it? Here's my naive solution:
#include <utility>
template<typename T>
union Slot {
T inst;
Slot() {}
~Slot() {}
template<typename... Args>
T* init(Args&&... args) { return new(&inst) T(std::forward<Args>(args) ...); }
void release() { inst.~T(); }
};
我的直接用例是一个对象池,但也更有用。 p>
My immediate use case is for an object pool, but it would also be more generally useful.
推荐答案
在C ++ 11中, a href =http://en.cppreference.com/w/cpp/types/aligned_storage =nofollow> see also ):
In C++11 you can use std::aligned_storage
(see also ):
template<typename T>
struct Slot {
typename std::aligned_storage<sizeof(T)>::type _storage;
Slot() {}
~Slot() {
// check if destroyed!
...
}
template<typename... Args>
T* init(Args&&... args) {
return new(address()) T(std::forward<Args>(args) ...);
}
void release() { (*address()).~T(); }
T* address() {
return static_cast<T*>(static_cast<void*>(&_storage));
}
};
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