Первый второму?
#include <iostream>
#include <cstddef>
#include <new>
int main()
{
alignas(float) std::byte stor[3*sizeof(float)];
for (int i = 0; i < 3; ++i)
new (stor + i*sizeof(float)) float(i);
for (int i = 0; i < 3; ++i)
std::cout << *std::launder( reinterpret_cast<float*>(stor + i*sizeof(float)) ) << std::endl;
}
#include <iostream>
#include <cstddef>
int main()
{
alignas(float) std::byte stor[3*sizeof(float)];
for (int i = 0; i < 3; ++i)
new (stor + i*sizeof(float)) float(i);
for (int i = 0; i < 3; ++i)
std::cout << ((float*)stor)[i] << std::endl;
}