ref: 9646f15b59b88e7edfc0a339e08a1a102b130696
dir: /include/defaultinitalloc.hpp/
/** * Allocator adaptor that interposes construct() calls to convert value-initialization * (which is what you get with e.g. `vector::resize`) into default-initialization (which does not * zero out non-class types). * From * https://stackoverflow.com/questions/21028299/is-this-behavior-of-vectorresizesize-type-n-under-c11-and-boost-container/21028912#21028912 */ #ifndef DEFAULT_INIT_ALLOC_H #define DEFAULT_INIT_ALLOC_H #include <memory> #include <vector> template<typename T, typename A = std::allocator<T>> class default_init_allocator : public A { using a_t = std::allocator_traits<A>; public: template<typename U> struct rebind { using other = default_init_allocator<U, typename a_t::template rebind_alloc<U>>; }; using A::A; // Inherit the allocator's constructors template<typename U> void construct(U *ptr) noexcept(std::is_nothrow_default_constructible_v<U>) { ::new (static_cast<void *>(ptr)) U; } template<typename U, typename... Args> void construct(U *ptr, Args &&...args) { a_t::construct(static_cast<A &>(*this), ptr, std::forward<Args>(args)...); } }; template<typename T> using DefaultInitVec = std::vector<T, default_init_allocator<T>>; #endif