Re: Does push_back() do a copy?

=?ISO-8859-1?Q?Erik_Wikstr=F6m?= <>
Thu, 28 Jun 2007 17:52:24 GMT
On 2007-06-28 18:20, Angus wrote:

On 28 Jun, 16:11, Erik Wikstr?m <> wrote:

On 2007-06-28 14:59, Angus wrote:

On 28 Jun, 12:45, Stefan Naewe <> wrote:

On 6/28/2007 1:30 PM, Bobbin wrote:

Yes, push_back, in your case, pushes a copy of the *pointer*. And then
you destroy the object it points to.

As Sumit Rajan said, you just make a copy of the pointer, when you
push_back(*pTemp), it will works the way you expect.


The OP had this:


You can't put CTestClientSocket _object_ into that!.

Stefan Naewe stefan dot naewe at atlas-elektronik dot com
Don't top-post
Plain text mails only, please

This is someone elses code. I have just noticed this:

// operator= NOT IMPLEMENTED
const CTestClientSocket & operator=(
                       const CTestClientSocket & krobToAssign)

As there is no copy implemented then when I push_back() then the
object is not properly copied? Is this my problem? I implement the
copy consstructor and then I can uncomment the delete pTemp?

Probably not, there's a good reason why a socket should not be copyable
(meaning that it should have no copy-constructor or assignment
operator). The reason is that a socket is considered a resource, and
there can only be one instance of each socket (where socket ==
connection). I'm just guessing, but I think the socket class looks
something like this:

class Socket {
// stuff to keep track of a conenction
   Socket(string host, int port) {
     // Connect to host
   void send();
   void receive();
   ~Socket() {
     // Disconnect


So if you add an assignment operator and do something like

for (int i = 0; i < 5; i++)
   Socket s(host, ip);


What will happen? First you create a socket, then you add a copy of the
socket to the collection. Then the socket you created goes out of scop,
which means that the destructor is called, which in turn means that the
connection is broken. So the socket you then have in the collection
would no longer have a working connection.

The correct solution is to do like you did, use new to create the
sockets, add the pointers to the collection, and *don't* call delete.
Then, later when you are done with the sockets you go through the
collection and calls delete on each element in it.

Erik Wikstr?m- Hide quoted text -

- Show quoted text -

Thank you.

So to delete I do this:

for (std::vector<CTestClientSocket*>::iterator it =
it != m_collClients.end(); it++)
      delete *it;
m_collClients.erase(m_collClients.begin(), m_collClients.end());

Does that look right to you?


Erik Wikstr?m

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