C / C++ / MFC

25-Jan-02 13:59

Hey guys,

I'm going through a debugging phase here, and I'm getting some access violation exceptions in my code. The problem is that these only happen in the release build. In the release build, the timing is a little different, and so with a multithreaded app, different synchronization scenarios show up.

I've used try catch handlers and an error log to trap exactly where the exception is happening. Grrr I just can't figure out how. Perhaps I'm trampling memory somewhere else?

Does anyone have any nifty release build debugging tricks I could try? This is driving me nuts! Cry | :((

Thanks!

swine

Check out Aephid Photokeeper, the powerful digital
photo album solution at www.aephid.com.

Tim Smith25-Jan-02 14:30

Tim Smith

25-Jan-02 14:30

Well, the first trick is to enable debugging information in your release build. This has to be done for both the C compiler settings and the linker. This will at least allow you to see the crash in the debugger or maybe even step through the program.

Tim Smith
Descartes Systems Sciences, Inc.

Swinefeaster25-Jan-02 15:55

25-Jan-02 15:55

That's genius! I didn't think that was possible under release!

Thanks.

swine

Check out Aephid Photokeeper, the powerful digital
photo album solution at www.aephid.com.

Swinefeaster26-Jan-02 11:56

26-Jan-02 11:56

Unfortunately, stepping through the program in release mode is very screwy. I don't even know what to believe anymore. The this pointer keeps changing even where it's not supposed to, and in general the addresses of all the local variables and object data members keep dancing around... Damn! Well, I'll keep trying...

Swine

Check out Aephid Photokeeper, the powerful digital
photo album solution at www.aephid.com.

Michael Dunn25-Jan-02 16:23

Michael Dunn

25-Jan-02 16:23

Make a MAP file (project settings - Link - General - Generate mapfile). That shows the address that each function begins at. When you get a crash, take the address and compare it against the ones in the map file. That should be enough info to tell you which function the crash happened in.

--Mike--
"COM didn't solve the old version of DLL hell - it just provided us with a new and improved version of hell."
-- John Simmons, 1/22/2002
My really out-of-date homepage
Sonork - 100.10414 AcidHelm
Big fan of Alyson Hannigan.

Swinefeaster25-Jan-02 16:31

25-Jan-02 16:31

Thanks! Unfortunately, this hasn't gotten me much father... I've already narrowed down the problem with the try / catch's and so I know where it is happening. Any ideas how to figure out if I'm somehow trampling over memory? Or maybe another thread is trampling over this memory?

Thanks again,

swine

Check out Aephid Photokeeper, the powerful digital
photo album solution at www.aephid.com.

HomeNuke25-Jan-02 19:40

HomeNuke

25-Jan-02 19:40

I had a problem with a multithreaded server I'm writing where I was using WSAEnumProtocols and the return buffer kept overwriting a lot of the other variables I had declared previously. It was changing pointer information to point to invalid areas of memory.

The only way to resolve it was by using GlobalAlloc on the variable, this was because instead of returning a variable with one instance it was returning an array. It took me forever to figure that out because PSDK would describe an array with everything else, besides just saying 'array' Frown | :(

HomeNuke
----
"Nuke'd Your Home, Yet?"
Run your own PostNuke based web server from home
http://www.homenuke.com

Swinefeaster26-Jan-02 12:40

Using CDONTS.NewMail in C++

26-Jan-02 12:40

I sympathize, but unfortunately this doesn't help much Frown | :(

Cheers,

swinefeaster

Check out Aephid Photokeeper, the powerful digital
photo album solution at www.aephid.com.

Version

uo200025-Jan-02 11:27

uo2000

25-Jan-02 11:27

Hi,

I have some problems regarding the version that MSDN gives and what my debug session returns to me!
I have installed WTL and the settings is set for WTL
What else is needed, there are things that just does not work as they should, for instance WM_NOTIFY

What is the correct settings to get WTL working in Visual studio that is?
I debug programs but they do not give me the answer that MSDN documentation says

Kindst regards Ulf

25-Jan-02 10:03

Can you use CDONTS.NewMail in a C++ program? I would certainly think you could, but I can't find any documentation for C++, just VB and ASP, etc. Can anyone point me towards a sample in C++ that instantiates a COM object and calls it? If you haven't already guessed, I'm new to C++.

Re: Using CDONTS.NewMail in C++

Jon Sagara25-Jan-02 10:12

Jon Sagara

25-Jan-02 10:12

You can use this class to send email. It's not CDONTS, but it works. Smile | :)

Jon Sagara

What about ?

Time in milliseconds

25-Jan-02 9:44

I am trying to calculate the elapsed time that occurs while a program in running. I need the time in milliseconds, can anyone help me.

Re: Time in milliseconds

Tim Smith25-Jan-02 9:55

Tim Smith

25-Jan-02 9:55

Depending on how long your program runs, ::GetTickCount () should be good enough.

DWORD dwStart = ::GetTickCount ();
... do work ...
DWORD dwEnd = ::GetTickCount ();
printf ("Elapsed = %d", dwEnd - dwStart);

Now, if you program is only going to be running for a few seconds then GetTickCount might not be good enough. Then you have to use the miltimedia timers.

Tim Smith
Descartes Systems Sciences, Inc.

Re: Time in milliseconds

Xander van Tilburg26-Jan-02 4:48

Xander van Tilburg

26-Jan-02 4:48

Hi,

Take a look at the CHighTime class from the article High resolution date and time class.

Good luck,
Xander

MSXML Help!

25-Jan-02 9:13

I have been trying to get the attributes from some XML all day!! Im slowly going mad! I have an XML file:-

//snip
<date name="12.12.3.98">12.56
//snip

I then have the following code. m_pCurrent is a node. I simply try and extract the attribute called name. Line 2 below works (unless i change the name of retrieval field - so I guess something is working) but when I try to access the value it just crashes with illegal access error... I have tried get_text, get_nodeValue etc etc.

m_pCurrent->get_attributes( &pNodeMap );
pScratchNode = pNodeMap->getNamedItem("name");
pScratchNode->get_text( &str );
AfxMessageBox( CString( str ) );

Thanks in advance
Ben

Re: MSXML Help!

Michael Dunn25-Jan-02 23:03

Michael Dunn

25-Jan-02 23:03

What is "str"?

--Mike--
"COM didn't solve the old version of DLL hell - it just provided us with a new and improved version of hell."
-- John Simmons, 1/22/2002
My really out-of-date homepage
Sonork - 100.10414 AcidHelm
Big fan of Alyson Hannigan.

Re: MSXML Help!

Not Active26-Jan-02 3:33

Not Active

26-Jan-02 3:33

These are COM methods they return HRESULTs not interface pointers.
getNamedItem method takes two parameters.

From MSXML 4.0 documentation

C/C++ Syntax
HRESULT getNamedItem(
    BSTR name,
    IXMLDOMNode **namedItem);

Parameters
   name [in] 
     The name of the attribute.
   namedItem [out, retval]  
     An IXMLDOMNode object for the specified attribute. Returns Null 
     if the attribute node is not in this collection.

displaying hex info graphically

brian scott25-Jan-02 8:14

brian scott

25-Jan-02 8:14

Hi! I am working on an application that requires the display of data graphically - ideally the same as in the AXE hex editor where one colour block represents one byte and a file can be shown as a panel. As a newbie, trying to navigate through the MFC documentation is a nightmare. Anyone able to assist please? If you're anywhere near Ireland, a solution is worth a number of pints of the black stuff!!

Brian Scott

Re: displaying hex info graphically

Ravi Bhavnani25-Jan-02 8:25

Ravi Bhavnani

25-Jan-02 8:25

Brian,

This should fit the bill nicely: http://codeproject.com/tips/frhed.asp.

PS: You can email me the brew. Smile | :)

/ravi

"There is always one more bug..."
ravib@ravib.com
http://www.ravib.com

COM problem urgent HELP needed

Bill Wilson25-Jan-02 7:10

Bill Wilson

25-Jan-02 7:10

I have a COM server (A.exe) it supports two interfaces I1 and I2. I also have two services S1.exe and S2.exe. S1 creates and instance of I1 and S2 creates an instance of I2.

I expected to find only one A.exe running. Instead I find two. This is a problem for two reasons. S2 must release and recreate the interface regularly, causing the initialization of A.exe to happen way too often. The other issue is that I2 and I1 share a global array (protected by a MUTEX). This sharing clearly won't work if there are two separate eA.exes.

Is it possible to do this so only one A.exe is launched? If so, how?

We are supposed to release this today. The cyclic creation and destruction of a second A.exe was just observed for the first time today.

Thanks for the help,
Bill

Ernest Laurentin25-Jan-02 7:18

Ernest Laurentin

25-Jan-02 7:18

Try this, it MAY solve your problem
Add this BEFORE the COM_MAP of your Interface

DECLARE_CLASSFACTORY_SINGLETON(CYourI1InterfaceClass)

- Greatest invention : "The Microchip!"

Bill Wilson25-Jan-02 9:17

Bill Wilson

25-Jan-02 9:17

I tried it, but it didn't help. I think its because there are two apps accessing two different interfaces, rather than two apps accessing the same interface.

Next attempt is to use CoGetClassObject. MSDN says:

"Provides a pointer to an interface on a class object associated with a specified CLSID. CoGetClassObject locates, and if necessary, dynamically loads the executable code required to do this."

Sounds like it won't load the EXE if it's already there. This coincides with VB and GetObject versus CreateObject.

Unfortunately I get an error AND the wrong effect:

hr = CoGetClassObject(ID, CLSCTX_LOCAL_SERVER, NULL,
			IID_IDispatch, (void **)&(m_pBroker));
if(hr = S_OK) 
{
	g_pErrorLog->LogError(4,"Get Class succeeded " + strObjName,_strModule);
} else {

	hr = CoCreateInstance(ID, NULL, CLSCTX_LOCAL_SERVER, 
				IID_IDispatch, (void **)&(m_pBroker));
	g_pErrorLog->LogError(4,"Try to CoCreate",_strModule);
}

When it executes the CoGetClassObject call, I get an ERROR_NO_INTERFACE message 0x80004002. AND a second .EXE is loaded. Cry | :((

Thanks for the help,
Bill

pba_25-Jan-02 9:41

pba_

25-Jan-02 9:41

If you use ATL, Check CComModule::RegisterClassObject call. In your WinMain function , _Module.RegisterClassObject. Check the second parameter - is REGCLS_SINGLEUSE ? If is so , the class factory will be accesible only for one client at a time.