ref: 7927dfd2e32ac3e977937389663f5ce02ad6e313
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