如何使用 C++ 11 样式的非默认构造分配器指定初始大小？

Question

In a prior thread about an update to Visual Studio 2015 std::list::sort handling a list with no default allocators, this was one of the examples used to create such a list, based on a Microsoft example for no default allocator.

I'm trying to figure out how to create an instance of a std::list with an initial (non-zero) size, without having to do a resize after creating an empty list.

// this part of the code based on Microsoft example
template <class T>  
struct Mallocator  
{  
    typedef T value_type;  
    Mallocator(T) noexcept {} //default ctor not required by STL  

    // A converting copy constructor:  
    template<class U> Mallocator(const Mallocator<U>&) noexcept {}  
    template<class U> bool operator==(const Mallocator<U>&) const noexcept  
    {  
        return true;  
    }  
    template<class U> bool operator!=(const Mallocator<U>&) const noexcept  
    {  
        return false;  
    }  
    T* allocate(const size_t n) const;  
    void deallocate(T* const p, size_t) const noexcept;  
};  

template <class T>  
T* Mallocator<T>::allocate(const size_t n) const  
{
    if (n == 0)  
    {  
        return nullptr;  
    }  
    if (n > static_cast<size_t>(-1) / sizeof(T))  
    {  
        throw std::bad_array_new_length();  
    }  
    void* const pv = malloc(n * sizeof(T));  
    if (!pv) { throw std::bad_alloc(); }  
    return static_cast<T*>(pv);  
}  

template<class T>  
void Mallocator<T>::deallocate(T * const p, size_t) const noexcept  
{  
    free(p);  
}  

typedef unsigned long long uint64_t;

#define COUNT (4*1024*1024-1)   // number of values to sort

int main(int argc, char**argv)
{
    // this line from a prior answer
    // the (0) is needed to prevent compiler error, but changing the
    // (0) to (COUNT) or other non-zero value has no effect, the size == 0
    std::list <uint64_t, Mallocator<uint64_t>> ll(Mallocator<uint64_t>(0));
    // trying to avoid having to resize the list to get an initial size.
    ll.resize(COUNT, 0);

Answer 1

I tried some more variations on this which triggered Visual Studio to show various combinations of parameters, and variation 12 of 12 showed the parameters in the correct order: (count, value, allocator). Note in the case of VS 2015, there is no option for (count, allocator), the value needs to be included. The value in the last parameter, <uint64_t>(0), doesn't matter, it just needs to be the proper type.

    std::list <uint64_t, Mallocator<uint64_t>> ll(COUNT, 0, Mallocator<uint64_t>(0));