ATL / WTL / STL

#include <iostream>
#include <list>

using namespace std;

class test
{
   public:
   int m_i;

   test(int i = 0)
   {
   m_i = i;
   cout << "test object with m_i=" << m_i << " being constructed" << endl;
   };

   test(test const& t) : m_i(t.m_i)
   {
   cout << "test object with m_i=" << m_i << " being copy constructed" << endl;
   };

   test& operator=(test const& t)
   {
      m_i = t.m_i;return *this;
   cout << "test object with m_i=" << m_i << " being copy constructed" << endl;
   };

   ~test()
   {
   cout << "test object with m_i=" << m_i << " being deleted" << endl;
   };
};

typedef list<test> TESTLIST;

int main(int argc, char* argv[])
{
   TESTLIST myTestList;
   myTestList.push_front(1);
   myTestList.push_front(2);

   return 0;
}

test object with m_i=1 being constructed
test object with m_i=1 being copy constructed
test object with m_i=1 being deleted
test object with m_i=2 being constructed
test object with m_i=2 being copy constructed
test object with m_i=2 being deleted
test object with m_i=2 being deleted
test object with m_i=1 being deleted

Zac Howland wrote:

basically does a memcpy

The implicitly defined copy constructor for class X performs a memberwise copy of its subobjects. The
order of copying is the same as the order of initialization of bases and members in a userdefined
constructor (see 12.6.2). Each subobject is copied in the manner appropriate to its type:

• if the subobject is of class type, the copy constructor for the class is used;
• if the subobject is an array, each element is copied, in the manner appropriate to the element type;
• if the subobject is of scalar type, the builtin assignment operator is used.

Virtual base class subobjects shall be copied only once by the implicitlydefined
copy constructor (see
12.6.2).

Stuart Dootson wrote:

Personally, I only define copy constructor/assignment operator when I've got a member that's not RAII compliant...and then I think 'Why doesn't that sub-object manage itself' and change it so I can use the implicit copy-constructor and assignment operator!

Stuart Dootson wrote:

Sorry - what I should have said was that I didn't like the comparison of the copy constructor to memcpy - it copies each member individually, it doesn't just copy the raw bytes of the object. Which is why I'm quite happy to rely on implicit copy constructors - because 99% of the time, they're implementing what I'd be implementing anyway.

Stuart Dootson wrote:

I take your point about having copy constructors to step through @ debug time - it's just not something I find myself doing.

rana74 wrote:

Is there any special setting to be done for reease build?