// placenew.cpp -- new, placement new, no delete
#include <iostream>
#include <string>
#include <new>using namespace std;
const int BUF = 512;class JustTesting
{
private:string words;int number;
public:JustTesting(const string &s = "Just Testing", int n = 0){words = s; number = n; cout << words << " constructed\n";}~JustTesting() { cout << words << " destroyed\n"; }void Show() const { cout << words << ", " << number << endl; }
};int main(void)
{char *buffer = new char [BUF];    // get a block of memoryJustTesting *pc1, *pc2;pc1 = new (buffer)JustTesting;    // place object in bufferpc2 = new JustTesting("heap1", 20);    // place object on heap
cout << "Memory block address:\n" << "buffer: "<< (void *)buffer << "    heap: " << pc2 << endl;cout << "Memory contents: \n";cout << pc1 << ": ";pc1->Show();cout << pc2 << ": ";pc2->Show();JustTesting *pc3, *pc4;pc3 = new (buffer) JustTesting("bad Idea", 6);pc4 = new JustTesting("Heap2", 10);cout << "Memory contents: \n";cout << pc3 << ": ";pc3->Show();cout << pc4 << ": ";pc4->Show();delete pc2;    // free heap1delete pc4;    // free heap2delete [] buffer;    // free buffercout << "Done\n";return 0;
}

[root@localhost 桌面]# ./new
Just Testing constructed
heap1 constructed
Memory block address:
buffer: 0x936a008    heap: 0x936a248
Memory contents:
0x936a008: Just Testing, 0
0x936a248: heap1, 20
bad Idea constructed
Heap2 constructed
Memory contents:
0x936a008: bad Idea, 6
0x936a290: Heap2, 10
heap1 destroyed
Heap2 destroyed
Done

pc1 = new (buffer) JustTesting;
pc3 = new (buffer + sizeof(JustTesting)) JustTesting("Better Idea", 6);

int main(void)
{char *buffer = new char[BUF];    // get a block of memoryJustTesting *pc1, *pc2;pc1 = new (buffer) JustTesting;    // place object in bufferpc2 = new JustTesting("Heap1", 20);    // place object on heap
cout << "Memory block addresses: /n" << "buffer: "<< (void *)buffer << "    heap: " << pc2 << endl;cout << "Memory contents: ";cout << pc1 << ": ";pc1->Show();cout << pc2 << ": ";pc2->Show();JustTesting *pc3, *pc4;// fix placement new location pc3 = new (buffer + sizeof(JustTesting)) JustTesting("better Idea", 6);pc4 = new JustTesting("Heap2", 10);cout << "Memory contents: ";cout << pc3 << ": ";pc3->Show();cout << pc4 << ": ";pc4->Show();delete pc2;        // free heap1delete pc4;        // free heap2// explicitly destroy placement new object
    pc3->~JustTesting();    // destroy object pointed to by pc3pc1->~JustTesting();    // destroy object pointed to by pc1delete []buffer;    // free buffercout << "Done/n";return 0;
}