C / C++ / MFC

Re: IDispatch COM Object - returning BSTR incorrectly

3-Jun-09 1:15

I have created a COM object which implements IDispatch so I can call it from scripting languages.

In the constructor, I'm trying to get the path to the App Data folder and store it in a member variable. I know that this is failing and I'm trying (unsuccessfully) to debug.

Until testing is complete, my object has a method which exposes the HRESULT from the last function call to the scripting language as a string.

[id(10), helpstring("Get last function's HRESULT.")] HRESULT GetHRESULT( [out, retval] BSTR * bsHRES);

This function returns the value of another member variable, BSTR m_HR, which I set using m_HR = OLESTR("Some Text") before returning from any member function.

As part of the constructor debugging process, I am trying to set the BSTR m_HR to the path of the App Data folder:

TCHAR * tcPath = new TCHAR;
HRESULT hres = SHGetFolderPath(NULL, CSIDL_APPDATA, NULL, SHGFP_TYPE_CURRENT, tcPath);
	
if ( FAILED(hres) ) {
	m_HR = OLESTR("SHGetFolderPath failed.");
} else {
	_bstr_t bst = _bstr_t(tcPath);
	
	m_HR = bst.copy();
};
delete tcPath;
return;
<p><font size=-2>
//<shlobj.h> is required for SHGetFolderPath.<br>//<comutil.h> and linking with comsupp.lib is required for _bstr_t.</font>

I double checked the SHGetFolderPath bit from a console application and tcPath contains the path desired.

When I use m_HR = OLESTR("Some Text"), calling GetHRESULT returns "Some Text" properly. With this constructor, however, successive object creations (and calls to GetHRESULT) return, alternately, "Files\Microsoft Visual Studio .NET 2003\SDK\v1.1\Lib\" and NULL. (That's not the App Data path.)

I've been banging my head on this for a couple days now - I'd be grateful for any help ya'll can offer.

MZR

P.S.
My apologies for the non-compilable code, but just the complete constructor is 70ish lines, plus the MIDL file, and the header file.... if you think you can help and need to see the complete code to do so, let me know and I'll happily email you the complete source.

CPallini3-Jun-09 1:48

Re: IDispatch COM Object - returning BSTR incorrectly

3-Jun-09 1:48

You say nothing about how bsHRES is set in your method (or am I wrong?).
Smile | :)

If the Lord God Almighty had consulted me before embarking upon the Creation, I would have recommended something simpler.
-- Alfonso the Wise, 13th Century King of Castile.

This is going on my arrogant assumptions. You may have a superb reason why I'm completely wrong.
-- Iain Clarke

[My articles]

Mike the Red3-Jun-09 2:09

Re: IDispatch COM Object - returning BSTR incorrectly

3-Jun-09 2:09

Thanks for taking a look, Pallini.

You're completely right. My apologies - here's the GetHRESULT(...) method definition. (I'm never sure how much code to post, though, in hindsight, this is an important bit.)

HRESULT Man::GetHRESULT(/*out*/BSTR *bsHRES) {
	if ( bsHRES == NULL ) {
		m_HR = OLESTR("ERROR_INVALID_PARAMETER");
		return ERROR_INVALID_PARAMETER;
	};

	*bsHRES = m_HR;
	m_HR = OLESTR("S_OK");
	return S_OK;
};

CPallini3-Jun-09 2:26

Re: IDispatch COM Object - returning BSTR incorrectly

3-Jun-09 2:26

You should use

*bsHRES = SysAllocString( m_HR );

I suppose.
Smile | :)

Mike the Red3-Jun-09 2:39

Re: IDispatch COM Object - returning BSTR incorrectly

3-Jun-09 2:39

Believe it or not, I HAD considered that - I wasn't sure if I needed a call to SysAllocString there or not.. Adding it had no effect, though. Frown | :(

Thanks again for taking a look, though, Pallini. I'll find it eventually... Thumbs Up | :thumbsup:

CPallini3-Jun-09 2:49

Re: IDispatch COM Object - returning BSTR incorrectly

3-Jun-09 2:49

Mike the Red wrote:
Believe it or not, I HAD considered that

I find no diffuculty to believe that. Smile | :)

Mike the Red wrote:
I wasn't sure if I needed a call to SysAllocString there or not..

You should use it.

Mike the Red wrote:
Adding it had no effect, though.

So there is a problem in another piece of your code. Good luck.
Smile | :)

Stuart Dootson3-Jun-09 2:51

Stuart Dootson

3-Jun-09 2:51

Mike the Red wrote:
TCHAR * tcPath = new TCHAR;

You're allocating one (ONE) character to hold the path - that probably won't be enough Smile | :)

Try allocating tcPath like this:

TCHAR * tcPath = new TCHAR[MAX_PATH];

and deallocating it like this:

delete[] tcPath;

or even just declare it on the stack like this:

TCHAR tcPath[MAX_PATH];

and then you don't need to deallocate it....

Mike the Red wrote:
m_HR = OLESTR("SHGetFolderPath failed.");

Yeah, that's bad, m'kay? You should create BSTRs with SysAllocString[^]:

m_HR = ::SysAllocString(OLESTR("SHGetFolderPath failed."));

BSTRs aren't just a null-terminated string of OLECHARs.

Mike the Red wrote:
m_HR = bst.copy();

You could just use m_HR = bst.Detach(); and reduce the number of string copies you do.

Java, Basic, who cares - it's all a bunch of tree-hugging hippy cr*p

Found It ! - Thanks Pallini, Stuart

Mike the Red3-Jun-09 5:09

Re: OK! Look this project

3-Jun-09 5:09

After many, many rebuilds and relocating return; statements, I finally found the problem..

Some bad code... too embarassingly bad to post... was copying bad data to m_HR and returning before execution even reached the SHGetFolderPath bit... Unsure | :~

I thank you both for your help. Thumbs Up | :thumbsup:

MZR

OK! Look this project

agetina3-Jun-09 1:06

agetina

3-Jun-09 1:06

http://www.codeguru.com/dbfiles/get_file/MSlot_src.zip?id=14969&lbl=MSLOT_SRC_ZIP&ds=20080320%20-[^]

It has two cpp files (2 mains)
It functions well, but i am interesed to convert this project in devC++ but i dont know how to do this.

Thank you for spending time for me!

CPallini3-Jun-09 1:41

CFormView with icon style CListCtrl works fine on debug build, but not on release

3-Jun-09 1:41

You're kidding, right? Big Grin | :-D

That is a solution, containing two projects (a client and a server), so two different applications (each application has, of course, its own entry point).
Smile | :)

Switch

navneet19853-Jun-09 0:41

navneet1985

3-Jun-09 0:41

How to read the mac address of machine connected with the switch port?

Re: Switch

«_Superman_»3-Jun-09 0:53

«_Superman_»

3-Jun-09 0:53

Do you want the mac address of a remote machine?

To get the mac address of the local computer you can use GetAdaptersInfo or GetAdaptersAddresses.

«_Superman_»
I love work. It gives me something to do between weekends.

Sternocera2-Jun-09 23:26

Sternocera

2-Jun-09 23:26

Hello,

I'm developing an MFC application - an outlook style splitter window app that displays various CFormViews in its right pane.

Recently, I changed the initial view (The AFX_IDW_PANE_FIRST view) to have an icon style CListCtrl, from a report style CListCtrl. The CListCtrl is populated in OnInitialUpdate. This was not the first view in this app to have an icon CListCtrl, so I imagined it wouldn't present any trouble. It doesn't present any trouble with the debug build. However, on the release build, no icons are initially visible in the CReportCtrl's icon style CListCtrl. I have to press a toolbar button that sends a message to the view, whose handler calls the same reloading utility function called from within OnInitialUpdate to have it populated. Then, it behaves correctly.

Why is my CFormView failing to be populated from within OnInitialUpdate? Control flow does reach OnInitialUpdate/the reloading utility function, so it really ought to work, but it doesn't.

Any help that can be offered is of course greatly appreciated,

Regards,
Sternocera

Re: CFormView with icon style CListCtrl works fine on debug build, but not on release

Sternocera2-Jun-09 23:56

Sternocera

2-Jun-09 23:56

I have come up with what seems like a reasonable enough work around - rather than calling that utility function directly, I PostMessage(ID_RELOAD ) and have it populated that way.

Regards,
Sternocera

My app crash with no apparent reason?

josip cagalj2-Jun-09 22:53

josip cagalj

2-Jun-09 22:53

Hi to all.
When I run my application and start to work with it, after a while it crashes!
Call stack:

00000000()
AfxCallWndProc(CWnd * 0x003af188 {CWnd hWnd=0x00020ae4}, HWND__ * 0x00020ae4, unsigned int 0x00000363, unsigned int 0x00000001, long 0x00000000) line 215 + 26 bytes
CWnd::SendMessageToDescendants(HWND__ * 0x00020ac6, unsigned int 0x00000363, unsigned int 0x00000001, long 0x00000000, int 0x00000001, int 0x00000001) line 2309
CWnd::SendMessageToDescendants(HWND__ * 0x00020ac8, unsigned int 0x00000363, unsigned int 0x00000001, long 0x00000000, int 0x00000001, int 0x00000001) line 2320
CWnd::SendMessageToDescendants(HWND__ * 0x000d09fc, unsigned int 0x00000363, unsigned int 0x00000001, long 0x00000000, int 0x00000001, int 0x00000001) line 2320
CWnd::SendMessageToDescendants(HWND__ * 0x0008099e, unsigned int 0x00000363, unsigned int 0x00000001, long 0x00000000, int 0x00000001, int 0x00000001) line 2320
CWnd::SendMessageToDescendants(unsigned int 0x00000363, unsigned int 0x00000001, long 0x00000000, int 0x00000001, int 0x00000001) line 146 + 32 bytes
CServisiApp::OnIdle(long 0x00000000) line 3694
CWinThread::Run() line 472 + 30 bytes
CWinApp::Run() line 400
AfxWinMain(HINSTANCE__ * 0x00400000, HINSTANCE__ * 0x00000000, char * 0x00151f0b, int 0x00000001) line 49 + 11 bytes
WinMain(HINSTANCE__ * 0x00400000, HINSTANCE__ * 0x00000000, char * 0x00151f0b, int 0x00000001) line 30
WinMainCRTStartup() line 330 + 54 bytes
KERNEL32! 7c817077()

The error I get is: "First-chance exception in MyApp.exe: 0xC0000005: Access Violation."
Any clue?
Win XP, VC 6
Thanks!

_AnsHUMAN_ 3-Jun-09 0:25

_AnsHUMAN_

3-Jun-09 0:25

You should have realized that this is the right time to add some log/traces/Messageboxes at places where you "expect"(blind guess-depends on how much steps in your application have executed already) your application to crash. Also read about the first chance exception handling mechanism here[^] and here[^]

You need to google first, if you have "It's urgent please" mentioned in your question.
Wink | ;-)

_AnShUmAn_

josip cagalj3-Jun-09 0:53

josip cagalj

3-Jun-09 0:53

I'm aware of this.
The thing is there's no pattern when my app will crash, some times on this occasion and on second run on that. No relationship between?! That's what bugging me!

David Crow3-Jun-09 2:54

David Crow

3-Jun-09 2:54

josip cagalj wrote:
The thing is there's no pattern when my app will crash, some times on this occasion and on second run on that. No relationship between?!

But you should still add some gratuitous "logging" code to help narrow it down. Try and remove (unnecessary) parts of your code until the crash subsides.

There is no "silver bullet" for this. Roll up your sleeves and get dirty.

"Old age is like a bank account. You withdraw later in life what you have deposited along the way." - Unknown

"Fireproof doesn't mean the fire will never come. It means when the fire comes that you will be able to withstand it." - Michael Simmons

josip cagalj3-Jun-09 3:10

josip cagalj

3-Jun-09 3:10

Yes so I did.
Found out the thing causing the problem. You see I inherited this app from an colleague from work he had slight different control then my own (it's work internal control we use). When overwritten, all worked OK.
The thing causing the problem is when called OnIdle message notifies some wnd's of an idle time, and some of those aren't wnd at all!

Two main methods?

agetina2-Jun-09 22:37

agetina

2-Jun-09 22:37

I work with DevC++ and i want to make a project with several c++ files.
For example i have two c++ files with two main(). Is it possible? How can i build (run) this? - it takes me an error message.

(
I have seen a project with two main but it is created in visual c++ not in devc++
and he build very well and every .cpp file generate it's .exe file (program for client server)
When i try to create the same project in Dev C++ i can't build!!!
What can i do?
)

Thank you!

Cedric Moonen2-Jun-09 22:43

Cedric Moonen

2-Jun-09 22:43

A executable with two main methods ? It doesn't make a lot of sense to me: when it is executed, which function should be called ? D'Oh! | :doh:

Cédric Moonen
Software developer

Charting control [v2.0]
OpenGL game tutorial in C++

CPallini2-Jun-09 22:47

2-Jun-09 22:47

agetina wrote:
For example i have two c++ files with two main(). Is it possible? How can i build (run) this? - it takes me an error message.

You application must have just one entry point. What is the purpose of two main() functions?
Smile | :)

KarstenK2-Jun-09 22:57

KarstenK

2-Jun-09 22:57

You can only have one main() function.

If you want 2 operation modes, you can control it via a start parameter one the commando line which got operated in your one and only main() function. $Shucks | :-\$

Press F1 for help or google it.
Greetings from Germany