std::uninitialized_default_construct

#include <cstring>
#include <iostream>
#include <memory>
#include <string>
struct S
{
    std::string m{"Default value"};
};
int main()
{
    constexpr int n{3};
    alignas(alignof(S)) unsigned char mem[n * sizeof(S)];
    try
    {
        auto first{reinterpret_cast<S*>(mem)};
        auto last{first + n};
        std::uninitialized_default_construct(first, last);
        for (auto it{first}; it != last; ++ it)
            std::cout << it->m << '\n';
        std::destroy(first, last);
    }
    catch (...)
    {
        std::cout << "Exception!\n";
    }
    // For scalar types, uninitialized_default_construct
    // generally does not zero-fill the given uninitialized memory area.
    int v[]{1, 2, 3, 4};
    const int original[]{1, 2, 3, 4};
    std::uninitialized_default_construct(std::begin(v), std::end(v));
    // Maybe undefined behavior, pending CWG 1997 to be resolved.
    // for (const int i : v)
    //     std::cout << i << ' ';
    // The result is unspecified.
    std::cout <<
        (std::memcmp(v, original, sizeof(v)) == 0 ? "Unmodified\n" : "Modified\n");
}