char array as storage for placement new

Question

Is the following legal C++ with well-defined behaviour?

class my_class { ... };

int main()
{
    char storage[sizeof(my_class)];
    new ((void *)storage) m         


        

Answer 1

It is at least problematic due to alignment.

On most Non-Intel architecture the code will generate a "bus error" due to wrong alignment or be extremely slow because of processor traps needed to fix the unaligned memory access.

On Intel architecture this will normally just be a bit slower than usual. Except if some SSE operations are involved, then it may also crash.