C / C++ / MFC

Re: Heap Corruption issue

21-Jun-16 10:47

Isn't the WM_CLOSE message being sent whether you terminate the app via Task Manager or by using Alt+F4?

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Ben Aldhouse21-Jun-16 12:45

Ben Aldhouse

21-Jun-16 12:45

Thanks for your reply!

I don't know, to be honest. The problem was occurring when I AltF4ed or clicked on Close Window but not when I clicked on my 'Exit' button. However, it looks like it was a corrupt memory problem I had with a member variable I'd assigned to the heap and was using to pass data between threads.

I've changed the communication to the following:

In the sending thread:

ControlDlg * pParent = (ControlDlg *) this->GetParent();
ColourAlphaEnvelope * s = new ColourAlphaEnvelope;
*s = m_ColourEnvelope;
pParent->PostMessage(CM_COLOURBOUNDS, reinterpret_cast<WPARAM>(s));

and in the recieving dialog I used

afx_msg LRESULT CRectArtDlg::OnCmColourbounds(WPARAM wParam, LPARAM lParam)
{
	std::auto_ptr<ColourAlphaEnvelope> s(reinterpret_cast<ColourAlphaEnvelope*>(wParam));
	m_colourEnvelope = *s;
	return 0;
}

I bet there are dozens of better ways of doing this (not least since a quick Google reveals that auto_ptr is depracated) but I haven't had a crash and the compiler isn't telling me there is a memory leak.

Winsock - FD_WRITE

Vijjuuu.21-Jun-16 4:54

Vijjuuu.

21-Jun-16 4:54

Hi all,

i am developing client program using WSAAsyncselect() in Winsock2.
i have few queries regarding FD_WRITE.
i understood that when client is connected to server. There will be FD_WRITE event posted stating that we can send the data to server. However, i want to send data to server based on some other events that the application is interested in. i am not quite sure how the FD_WRITE event will be fired when i want send data to server.

here is the pseudo.

C++

LRESULT CALLBACK WndProc(HWND hWnd, UINT message, WPARAM wParam, LPARAM lParam)
{
	switch (message)
	{
	case WM_SOMEOTHEREVENT:
		// collect the data. we need to send collected data to sever (right now data is stored in a list).  
		break;
	case WM_SOCKET:
		switch (WSAGETSELECTEVENT(lParam))
		{
             // how to fire this event when application wants to send data ?
		     case FD_WRITE:

		     break;
		}
		break;
	}
	return 0;
}

Thanks in advance.

David Crow21-Jun-16 7:19

21-Jun-16 7:19

Your application will receive an FD_WRITE event shortly after a connection is made. If your "write" operation receives a WSAEWOULDBLOCK result, your application will find out that sends are again possible when an FD_WRITE network event is recorded and the associated event object is set.

Vijjuuu.21-Jun-16 8:04

Vijjuuu.

21-Jun-16 8:04

Hi David,

Thanks for your reply.

i am sorry, i couldn't get what you mean.

i understand that application will receive an FD_WRITE event shortly after a connection is made but there is no data to send at that time.

here is scenario i am trying for

1) connect to server
2) Connection established - FD_WRITE event is receive.
3) there is no data to send to server
4) some other event fired (not related to socket) -- data arrived, so store the data.
5) now data is available to send to server

in the above steps 4 and 5 will happen one after the another. how can i raise FD_Write event after the data is available (means step 4) ?

David Crow21-Jun-16 8:12

21-Jun-16 8:12

Vijjuuu. wrote:
how can i raise FD_Write event after the data is available (means step 4) ?

Why would you need to raise the FD_WRITE event? It is sent to your application to let it know that it can now send data to the socket.

Vijjuuu.21-Jun-16 8:21

Vijjuuu.

21-Jun-16 8:21

Thanks again David,

i understood that its lets application know that it can send data to the socket, but when there is no data to send ?
and does it mean after initial FD_Write (the time after connection established) , FD_WRITE will be polled to application to let know that it can send data ?

i really appreciate your patience. Thanks.

David Crow21-Jun-16 9:19

21-Jun-16 9:19

Vijjuuu. wrote:
...but when there is no data to send ?

Then don't send any.

Vijjuuu. wrote:

and does it mean after initial FD_Write (the time after connection established) , FD_WRITE will be polled to application to let know that it can send data ?

Did you read the documentation that goes with that event? Your application gets the initial FD_WRITE event which means it can start sending data to the socket. In the event that whatever "send" function you are using returns WSAEWOULDBLOCK, you would then have to wait for the next FD_WRITE event to resume sending data to the socket.

Member 1260667928-Jun-16 20:47

Member 12606679

28-Jun-16 20:47

As I understand it, the FD_WRITE message means you have a
connection and room in the output buffer to accept data.

After you get FD_WRITE, use send() to send data
when you have it.

modified 29-Jun-16 2:58am.

DLL files from wmi

Member 1253112919-Jun-16 22:10

Member 12531129

19-Jun-16 22:10

when i am using wmi functions "SELECT * FROM Win32_Processor", can i somehow get dll files from which is that information loaded?

Re: DLL files from wmi

Jochen Arndt19-Jun-16 22:30

Jochen Arndt

19-Jun-16 22:30

The information is not stored in a DLL. It is stored in a database file (the WMI Repository) in the directory %windir%System32\Wbem\Repository\.

See also WMI Overview[^] and Windows Management Instrumentation - Wikipedia, the free encyclopedia[^].

Print class Members?

bosfan16-Jun-16 5:29

bosfan

16-Jun-16 5:29

Hi,
is it possible to print class members, like in Visual Studio in the "Immediate Window", when i write a class name there is an output with all members/variables in the window?

Is there an API for this?

Thanks for help
bosfan

Maximilien16-Jun-16 5:41

Maximilien

16-Jun-16 5:41

In the debugger or as a simple output (printf/cout) ?

I'd rather be phishing!

David Crow16-Jun-16 6:12

16-Jun-16 6:12

Are you wanting reflection, like Java has?

bosfan5-Aug-16 4:24

bosfan

5-Aug-16 4:24

Hello,
sorry to all because its late answer, yes reflections should be the solution.

Thanks

David Crow5-Aug-16 4:27

5-Aug-16 4:27

Such a thing does not exist, at least not directly, in C++.

CPallini17-Jun-16 0:22

CPallini

17-Jun-16 0:22

Nope, you have to develop it yourself.

bosfan5-Aug-16 4:25

bosfan

5-Aug-16 4:25

Hi,
sorry ,i'm little late, thanks for answer.

regards

Can define a function with same name and signature?

CPallini7-Aug-16 20:42

CPallini

7-Aug-16 20:42

You are welcome.

sandeep manzhi16-Jun-16 4:22

sandeep manzhi

16-Jun-16 4:22

In C++ this concept are overloading and overriding
Can i use this concept in C?

modified 16-Jun-16 10:40am.

Re: define a function

David Crow16-Jun-16 4:26