Re: this->EndDialog hangs with thread

From:

David Wilkinson <no-reply@effisols.com>

Newsgroups:

microsoft.public.vc.mfc

Date:

Thu, 30 Aug 2007 04:52:30 -0400

Message-ID:

<OmgpVMu6HHA.1204@TK2MSFTNGP03.phx.gbl>

Scott Kraemer wrote:

Joeseph,

Great essays. I have to admit I had to read them, re-read them in order
for it to sync in just a little!
I found that if I close my socket, it will end the tread and exit
gracefully (i hope for everyone now)
but now I get massive memory leaks calling the PostMessage functions.
I found in your essay I should get hWnd prior to starting my thread and
pass it in the paramaters to the thread. I did it a little differently
because I need my thread to have more information. I used a structure
such as this:

typedef struct IRCTHREAD
{
SOCKET clisock;
CString username;
HWND hWnd;
} IRCTHREAD;

I start my thread this way:
void CTest1Dlg::startIRC() {
......some code....
...
IRCTHREAD*_param = new IRCTHREAD;
_param->clisock = clisock;
_param->username=m_username;
_param->hWnd=AfxGetApp()->m_pMainWnd->m_hWnd;
ircThread = AfxBeginThread(thread, _param);
ircThreadID = ircThread->m_nThreadID;

Everything appears to be working good at this point. IRC works, dialog
controls are updated....except visual studio shows massive
memory leaks detected with the new code as shown below commented..

I modified mine to pass in hWnd from the thread:

void AddChatText(HWND hWnd,CString & name)
   {
    CString * s = new CString(name); //this is where the memory leak is
detected.
   // HWND hWnd=AfxGetApp()->m_pMainWnd->m_hWnd; // This is the old
way I did it, could get NULL as you stated in essay
::PostMessage(hWnd,UWM_ADDSTRING, 0, (LPARAM)s);
   }

Scott:

Obviously you are new-ing the CString without deleting it, so you will
get memory leaks. With this PostMessage() pattern the handler in the
main thread should delete the string. If you use SendMessage() then you
can pass a stack object (but many will warn you against this).

Also how do you free the memory for your IRCTHREAD object? I would make
a IRCTHREAD member variable in my CtestDlg class and use that. Most uses
of "new" in C++ (outside of library code) are a mistake.

BTW, you do not need the typedef pattern for structs in C++. Just do

struct IRCTHREAD
{
   SOCKET clisock;
   CString username;
   HWND hWnd;
};

It's the same as a class, but with public access by default.

--
David Wilkinson
Visual C++ MVP