C / C++ / MFC

11-Nov-07 23:45

Hi!

I have an app that uses Crystal Reports for reports. Some functions cannot be easily realised in crystal, so I thought about calling my main app for that work.

Now, I can add custom fn's to Crystal, by writing a U25 DLL. The idea I tested was to have a function in this DLL that gets called from my main app and there deposits, in shared storage, the addresses I need to call to get my data. When the DLL gets loaded from Crystal, then it calls my app through those pointers.

I have tested it and it works, but I have been told in is a bad idea.

Suggestions?

Matthew Faithfull12-Nov-07 0:28

12-Nov-07 0:28

As a general rule this sort of thing is considered unsafe and using Sockets or COM IPC from your Dll would be preferred as more robust and flexible than rolling your own solution in shared memory. I have used COM Connection Points in the past to communicate between a Dll loaded into the Microsoft Management Console and an external process. Not easy but it worked and was pleasingly fast.

Nothing is exactly what it seems but everything with seems can be unpicked.

Anders Gustafsson12-Nov-07 0:40

12-Nov-07 0:40

OK. Not sure what to do at this point. Implementing COM for this seems an awful lot of work for such a simple task. Any good pointers where to get started?

Matthew Faithfull12-Nov-07 1:13

12-Nov-07 1:13

That's going to depend a lot on what you know and what your requirements are.
On one hand if it works leave it be. On the other it does sound like a temporary solution so perhaps try some separate experiments with COM, ATL makes this easy, to see if you can find a replacement architecture that you're happy with.
If you want to avoid COM give Socket comms a try, there's loads of examples available. This has the added advantage that you can transparently run your application on the same or a separate machine. Either way CP is probably going to be the best place to find examples. If you've managed to write your own shared memory exchange system that works you'll have nothing to fear from either of these approaches and probably don't need advice from me. Smile | :)

Nothing is exactly what it seems but everything with seems can be unpicked.

Anders Gustafsson12-Nov-07 6:45

12-Nov-07 6:45

Well, it is a commercial app, so I'd rather not do anything dangerous Wink | ;)

I have been banging my head against the limitations of Crystal Reports for the last 10 years Wink | ;)

And we do some pretty cool stuff, manipulating the innards of the reports ar runtime, using the CR apis. The New CR apis are all COM anyway so I had to learn those.

I found a good, two-part article on COM here and I am currently reading it. It might be that implementing a small COM server in my app might be worth the peace of mind here.

App and report will always be on the same machine so.. Also, COM feels quite logical as it is just a (synchronous) function call.

KarstenK12-Nov-07 0:56

KarstenK

12-Nov-07 0:56

It is better that the dll has its own data, and the dll makes it own copies of the data. Preprocess the data in the App and THAN call the dll to finish the job.

Try to develop a data model which is clearly structered!! A clear structure helps you to develop good code and debug it easy.

Ask a friend/colegue for a half hour to discuss it. This is really worth it. Cool | :cool:

Greetings from Germany

Anders Gustafsson12-Nov-07 1:06

Running multiple Instances of an application

12-Nov-07 1:06

I am discussing it, here Wink | ;)

Problem is that there are aspects of the data model that I cannot control since I do not have access to the Crystal Reports sources. The crystal reports viewer is for all intents and purposes a black box. Only way to extend it is to create a custom DLL that gets registered with Crystal and called at runtime.

So, preprocessing in the app is really what I do, let me elaborate. The functions I need are along the lines of "workdays", input in the report is two dates. The result is not just a range, but it must take into account the employee-specific calendar.

Alternatively could I duplicate this logic in the DLL, but then again would I have to have a separate Db connection (with a separate login) for the report.

So when I call "Arbetsdagar(date,date) from within my crystal report definition, crystal calls the DLL and it is just a wrapper that calls the real function in the app.

Chirag_kalra11-Nov-07 23:23

Chirag_kalra

11-Nov-07 23:23

Hi
I'm facing some problem in standard MFC application. In my application, I'm able to run only 3 instances of my application simultaneously.That is, I'm able to open only three login screens at the same time, but I dont want this limitaton. I'm currently working in Windows XP. However, when I ran my application in Windows NT, only 4 instances can ber run at a time. When I tried to open it fourth time in Windows XP, it gets crashed at the following line of code.

//winfrm.cpp

BOOL CFrameWnd::Create(LPCTSTR lpszClassName,
LPCTSTR lpszWindowName,
DWORD dwStyle,
const RECT& rect,
CWnd* pParentWnd,
LPCTSTR lpszMenuName,
DWORD dwExStyle,
CCreateContext* pContext)
{
HMENU hMenu = NULL;
if (lpszMenuName != NULL)
{
// load in a menu that will get destroyed when window gets destroyed
HINSTANCE hInst = AfxFindResourceHandle(lpszMenuName, RT_MENU);
if ((hMenu = ::LoadMenu(hInst, lpszMenuName)) == NULL)
{
TRACE(traceAppMsg, 0, "Warning: failed to load menu for CFrameWnd.\n");
PostNcDestroy(); // perhaps delete the C++ object
return FALSE;
}}

m_strTitle = lpszWindowName; // save title for later

if (!CreateEx(dwExStyle, lpszClassName, lpszWindowName, dwStyle,
rect.left, rect.top, rect.right - rect.left, rect.bottom - rect.top,
pParentWnd->GetSafeHwnd(), hMenu, (LPVOID)pContext))
{
TRACE(traceAppMsg, 0, "Warning: failed to create CFrameWnd.\n");
if (hMenu != NULL)
DestroyMenu(hMenu);
return FALSE;
}

return TRUE;
}

Hi,

Can you please suggest me how to ensure if this much objects are successfully created?

I have the following thing in my code:

//Inside ::InitInstance

if (pDocTemplate = new CMultiDocTemplate(IDR_mdiflsTYPE,

RUNTIME_CLASS(CmdiflsDoc),

RUNTIME_CLASS(CChildFrame), // custom MDI child frame

RUNTIME_CLASS(CmdiflsView) ) != NULL)

cout<<"Successful"

else

cout<<"Failure"

I have such 140 CMULTIDOCTEMPLATE (using new) objects and I got 140 message: "Successful".
Comments from another person:-
If you call the constructor so many times, without freeing, then you probably reach a maximum space of Windows handles, if the constructor loads menu and other resources. That’s why next resource-allocation functions fails. Can you confirm that you really create and keep so many objects?

Is there any better way to ensure if it is a resource allocation/ storage limitation problem? If yes. how can I overcome this?

Thanks in advance!

Chirag Kalra

Naveen11-Nov-07 23:51

Naveen

11-Nov-07 23:51

Chirag_kalra wrote:
if ((hMenu = ::LoadMenu(hInst, lpszMenuName)) == NULL)

can you tell me the error code generated at this time( put @err,hr in watch window of the msdev to get the error string)

Also after the 4th instance is crached, are you able to start other window based applications?

nave

[OpenedFileFinder]

Chirag_kalra11-Nov-07 23:59

Chirag_kalra

11-Nov-07 23:59

Thanks for u r response
How to put the error code...Can u explain me in detail.

and Yes I am able to start any other application except mine..

Chirag Kalra

Naveen12-Nov-07 0:08

Naveen

12-Nov-07 0:08

Chirag_kalra wrote:
How to put the error code...Can u explain me in detail.

Actually when the fourth instance is started, your application is crashing or LoadMenu just return the failure?

If it is failing, put a breakpoint in the "TRACE(traceAppMsg, 0, "Warning: failed to load menu for CFrameWnd.\n");" statement and when breakpoint hits, take the watch window in the msdev and put "@err,hr" in it. This will display any error strings if any. And let me know the result.

nave

[OpenedFileFinder]

Chirag_kalra12-Nov-07 0:23

Chirag_kalra

12-Nov-07 0:23

Mine application is not crashing.When I run the 4th instance, It is not able to show login screen while the other 3 login screens are visible.
When I debugged then I found the above mentioned line of code due to which it is failing.
I put @err,hr in my watch and found S_OK when I run 4th instance.

Chirag Kalra

Naveen12-Nov-07 0:52

Naveen

12-Nov-07 0:52

Chirag_kalra wrote:
@err,hr in my watch and found S_OK

nave

[OpenedFileFinder]

\\systemname\\C$

p_11-Nov-07 23:22

11-Nov-07 23:22

Hello all masters
I use \\systemname\\C$ to access other systems C: drive
Then I will ask for username and password I enter right username and password
But it will popup the same username and password window
But should I do please suggest me
Thanks all superiors
Rose | [Rose]

Matthew Faithfull11-Nov-07 23:31

11-Nov-07 23:31

Using the defualt share represented by C$ is not recommended. It also does not work on a lot of pre WinXP systems. If you want to access this C drive as a share I recommend sharing it explicitly by creating a new share. You can then set the permissions exactly as they should be and you will get access.

Nothing is exactly what it seems but everything with seems can be unpicked.

p_12-Nov-07 0:12

12-Nov-07 0:12

thanks sir
please suggest me other way to do this if anyother
actually this is project work and i have tried a lot
but not succedded please tell me
thanks

p_12-Nov-07 0:18

12-Nov-07 0:18

and one more thing sir
i dont use other system and both systems has windows XP

Matthew Faithfull12-Nov-07 0:32

12-Nov-07 0:32

If you are using the correct user name and password but don't have access to change the configuration of the other system then you are probably out of luck, it is misconfigured or is set up to block you out. The solution is administrative rather than programming. You will need access to or reconfiguration of the other system. Good luck.

Nothing is exactly what it seems but everything with seems can be unpicked.