class CS
{   public:
    char *data;
    CS()
    {

    };
};

int main(int argc, char *argv[])
{
    void *z;
    CS *x=new(z)  CS();
    return 0;
}

А>    void *z;
А>    CS *x=new(z)  CS();
А>

char here[sizeof(CS)]; // лучше взять boost::aligned_storage<sizeof(CS)>
void* there = malloc(sizeof(CS)); // или MS-specific - aligned_malloc(sizeof(CS),__alignof(CS))

CS* x = new(here) CS();
CS* y = new(there) CS();

x->~CS();
y->~CS();

free(there);

//#include <memory>
class CS
{   public:
    char *data;
    /*
    CS()
    {

    };
    */
};

int main0000(int argc, char *argv[])
{
   // void *z;
    int z[16];
    CS *x=new(z)  CS();   // ТОЛЬКО ЗДЕСЬ ОШИБКА
    return 0;
}


#include <iostream>
using namespace std;

class MyClass {

   public:

    // Placement new operator
    /*
    void* operator new (size_t sz, void* v) {
        cout << "Placement new invoked" << endl;
        return v;
    }
     */
    ~MyClass() {
        // Cleanup
    }
};

int main()
{
    // Create a buffer to store the object
    int buffer[16];
    cout << "Starting address of my buffer = " << &buffer << endl;

    // Create the object. Use placement new
    MyClass* obj = new (buffer) MyClass();
    cout << "Location of my object = " << obj << endl;

    // Don't delete object created with placement delete
    // Call the destructor explicitly
    obj->~MyClass();
}