复制构造函数问题

#include <iostream>#include <list>using namespace std;int gid = 0;class ctest{public: ctest() {  m_v = gid++;  cout << m_v << "\tconstructor" << endl; }  ctest(const ctest &v) {  m_v = gid++;  cout << m_v << "\tcopy constructor" << endl; } ~ctest() {  cout << m_v << "\tdestructor" << endl; }public: int m_v;};ctest test(ctest &v){ return v;}int main(){ list<ctest> lst; ctest v; lst.push_back(test(v));  return 0;}