namespace memory_internal {
template <typename T>
struct MakeUniqueResult {
using scalar = std::unique_ptr<T>;
};
template <typename T>
struct MakeUniqueResult<T[]>
{
using array = std::unique_ptr<T[]>;
};
template <typename T, size_t N>
struct MakeUniqueResult<T[N]> {
using invalid = void;
};
} // namespace memory_internal
// overload for non-array types.
template <typename T, typename... Args>
typename memory_internal::MakeUniqueResult<T>::scalar make_unique(
Args&&... args) {
return std::unique_ptr<T>(new T(std::forward<Args>(args)...));
}
// `make_unique` overload for an array T[] of unknown bounds.
// The array allocation needs to use the `new T[size]` form and cannot take
// element constructor arguments. The `std::unique_ptr` will manage destructing
// these array elements.
template <typename T>
typename memory_internal::MakeUniqueResult<T>::array make_unique(size_t n) {
return std::unique_ptr<T>(new typename std::remove_extent<T>::type[n]());
}
// `make_unique` overload for an array T[N] of known bounds.
// This construction will be rejected.
template <typename T, typename... Args>
typename memory_internal::MakeUniqueResult<T>::invalid make_unique(
Args&&... /* args */) = delete;
make_unique实现数组的时候需要知道大小。。
为啥呢??