C / C++ / MFC

2-Mar-02 23:10

Guys

As a few of you might be aware of, I am trying ATL out.
Say I have a function like this :-

STDMETHODIMP CIniEdit::TestMethod(BSTR *pbstr)
{
	OLECHAR tmpString[512];
	wcscpy(tmpString,L"Nish is learning ATL");
	*pbstr=SysAllocString(tmpString);
	return S_OK;
}

and from ASP or VB say, I do this :-

Dim x
Set x = CreateObject("SIMPLE.SimpleStuff")
MsgBox x.TestMethod()
Set x = Nothing

You'd think, all was fine. But to my utmost horror I suddenly realized that I had happily allocated a string using SysAllocString, but I am not calling SysFreeString.

Horror of horrors!!!!

What is the work-around to this, dear friends?

Am I doomed to be stuck among the ultimate dangers of memory leaks?

Writing another function just to free the string seems pathetic. And I am sure that from ASP/VB this function might be called several times, thus resulting in a memory leak, each single time Frown | :-(

Nish

It's seven o'clock
On the dot
I'm in my drop top
Cruisin' the streets - Oh yeah
I got a real pretty, pretty little thing that's waiting for me

Christian Graus2-Mar-02 23:31

Christian Graus

2-Mar-02 23:31

An out parameter should not be assumed to contain anything valid and should be initialised before use ( for exmaple, set pointers to NULL). Responsiblity for freeing the memory belongs to the calling function. All of this is laid out in COM, and I believe there are special functions for allocating the memory and freeing it as well, but I forget them ( I'm a beginner at this, too ).

Christian

The tragedy of cyberspace - that so much can travel so far, and yet mean so little.

Mazdak2-Mar-02 23:35

2-Mar-02 23:35

Nish [BusterBoy] wrote:
Am I doomed to be stuck among the ultimate dangers of memory leaks?

No,It's ok Nish.
In COM, it is the client's responsibility to free resources allocated by a server at a client's request.

Mazy

"So,so you think you can tell,
Heaven from Hell,
Blue skies from pain,...
How I wish,how I wish you were here."
Wish You Were Here-Pink Floyd-1975

Nish Nishant2-Mar-02 23:54

2-Mar-02 23:54

Mazdak wrote:
In COM, it is the client's responsibility to free resources allocated by a server at a client's request.

oh?
But how can I free resources using VB or ASP???
They dont have a delete operator/function Frown | :-(

Nish

It's seven o'clock
On the dot
I'm in my drop top
Cruisin' the streets - Oh yeah
I got a real pretty, pretty little thing that's waiting for me

Mazdak3-Mar-02 0:24

3-Mar-02 0:24

Nish [BusterBoy] wrote:
how can I free resources using VB or ASP???

I don't know about VB or ASP,but when I use C++ or MFC as clients I use SysFreeStrnig() for those BSTR.

And After all I use Release() for my component before CoUninitialize() so if those things exist in VB or ASP,I think the operation of FREEDOM Laugh | :laugh:

happend in Release().

Mazy

"So,so you think you can tell,
Heaven from Hell,
Blue skies from pain,...
How I wish,how I wish you were here."
Wish You Were Here-Pink Floyd-1975

Mazdak3-Mar-02 0:26

3-Mar-02 0:26

Just another hint Nish:
If you use _bstr_t you'll get rid of those allocated and deallocated hell,but you don't have BSTR* .It isn't provided in _bstr_t.

Mazy

"So,so you think you can tell,
Heaven from Hell,
Blue skies from pain,...
How I wish,how I wish you were here."
Wish You Were Here-Pink Floyd-1975

3-Mar-02 1:52

You don't need to free it, the scripting engine automatically frees it for you by calling SysFreeString (actually it calls VariantFree. That's why you use SysAllocString and not the operator new in C++.

Here is what happens from scripting engine point of view

1. Gets IDispatch interface to your object

2. Calls GetIDsOfNames to get ID of "TestMethod"

3. Calls Invoke method with that ID

4. The return value comes in pvarResult

5. Calls VariantFree to pvarResult after MsgBox function is called

6. VariantFree checks for the type of the Variant and sess that it is a BSTR and calls SysFreeString

That's the reason why you use BSTR because you have standard functions for allocating and deallocating which are known by both you and the consumer (script engine).

Nish Nishant3-Mar-02 14:16

3-Mar-02 14:16

Thanks

Nish

It's seven o'clock
On the dot
I'm in my drop top
Cruisin' the streets - Oh yeah
I got a real pretty, pretty little thing that's waiting for me

pba_3-Mar-02 2:45

pba_

3-Mar-02 2:45

OLE automation uses only VARIANT data types. So any parameters, which are passed between your server and VB, ASP, scripting engines, or any client, which use ole automation should be VARIANT compatible. The VB runtime will simply free the resources by calling VariantClear or some similar mechanism when the resource will go out of scope.

Nish Nishant3-Mar-02 14:18

3-Mar-02 14:18

solon wrote:
The VB runtime will simply free the resources by calling VariantClear or some similar mechanism when the resource will go out of scope.

Cool Smile | :)

And thanks too

Nish

It's seven o'clock
On the dot
I'm in my drop top
Cruisin' the streets - Oh yeah
I got a real pretty, pretty little thing that's waiting for me

Mazdak3-Mar-02 4:02

3-Mar-02 4:02

I asked an expert and this is what he said:

In VB and ASP you do not need to call SysFreeString() because VB makes that call for you.

Mazy

"So,so you think you can tell,
Heaven from Hell,
Blue skies from pain,...
How I wish,how I wish you were here."
Wish You Were Here-Pink Floyd-1975

Nish Nishant3-Mar-02 14:17

ADSI: Problem with Binding

3-Mar-02 14:17

Thanks a lot Mazy Rose | [Rose]

You are a big help Smile | :)

Nish

It's seven o'clock
On the dot
I'm in my drop top
Cruisin' the streets - Oh yeah
I got a real pretty, pretty little thing that's waiting for me

Re: Hmmmmm

Tim Smith3-Mar-02 5:12

Tim Smith

3-Mar-02 5:12

VARIANT v;

V_VT (&v) = VT_ENIGMA;
V_ENIGMA (&v) = ::CoCreateEnigma ();

Tim Smith

I know what you're thinking punk, you're thinking did he spell check this document? Well, to tell you the truth I kinda forgot myself in all this excitement. But being this here's CodeProject, the most powerful forums in the world and would blow your head clean off, you've got to ask yourself one question, Do I feel lucky? Well do ya punk?

hph2-Mar-02 22:59

hph

2-Mar-02 22:59

First of all, my equipment:

I use the Win2kServer OS with the following settings:
Name:iras
Workgroup: HTBL
Domain for Windows: htlpinkafeld.at
Domain for Netware: HTBl\
TestUser: testuser@htlpinkafeld.at (HTBL\testuser)
The TestUser is placed in hltpinkafeld.at\edvoschueler and uses no password

My goal is to get access to this testuser with Visual C++ 6.0 from a remote workstation (in the same network). The OS of the workstation is Win2kProf.
The MSDN which i use is the April 2001 version.

At first i tried to get the function
HRESULT ADsOpenObject(
LPWSTR lpszPathName,
LPWSTR lpszUserName,
LPWSTR lpszPassword,
DWORD dwReserved,
REFIID riid,
VOID FAR * FAR *ppObject
);

work!

And according to this the problems began!

1. I don't know how the first three parameters should look like!
2. The 5th parameter needs the library ADSIID.lib. The function needs also the library ActiveDS.lib to work right. But within these two libs declarations are redefined which means i can't execute the program! I found out that this sometimes happens, and that i should add the prefix "/force:multiple" to the menu Project\Settings...\Link\"Project Options". It works but i don't know if this is allowed!

Please help me!

DLL

Peter Liddle2-Mar-02 22:58

Peter Liddle

2-Mar-02 22:58

Hey Guys

Below is the funvtion i am exporting from my DLL.
bool DLLVerifySignature(BYTE *pFileNameAndPath)

This is called when a file is double clicked by rundll32 and i have put %1 at the end to pass the filepath as well. How do i pick this filename up in my dll so i can use it.

Peter

Re: DLL

Michael Dunn3-Mar-02 7:33

Michael Dunn

3-Mar-02 7:33

Calling that with Rundll32 will not work. The function needs this prototype:

void CALLBACK FuncName ( HWND hwndParent, HINSTANCE hinstDLL, LPTSTR szCmdLine, int nCmdShow );

The szCmdLine param contains everything on the rundll32 command line after the function name.

--Mike--
Best score on the mini-putt game: 27
My really out-of-date homepage
Sonork - 100.10414 AcidHelm
Big fan of Alyson Hannigan and Jamie Salé.

how do i use DeleteObject()...

John Cruz2-Mar-02 21:44

John Cruz

2-Mar-02 21:44

do i use delete object like this to prevent resource leaks???

// Destructor
CBoard::~CBoard()
{
// Delete the object to prevent resource leaks
mpPen->DeleteObject();
mpFont->DeleteObject();

// Destroys all the pointers to all objects
delete mpPen;
delete mpFont;

for (int r = 0; r < MAXROW; r++)
for (int c= 0; c < MAXCOL; c++)
delete mpGrid[r][c];
}

or i can just destroy it by deleting it or do i have to release it before i delete it when i called it like this:

// Change the Font Height and Width to the values entered
void CBoard::SetFontSize(CDC* pDC, int Height, int Width)
{
mpFont = new CFont;
VERIFY(mpFont->CreateFont(Height,Width,0,0,0,0,0,0,0,0,0,0,
DEFAULT_PITCH|FF_DONTCARE,"Tictactoe"));

VERIFY(mpDefaultFont = pDC->SelectObject(mpFont));
}

anyways, can anyone tell me if i am doing it right or what i am doing can cause memory or resource leaks... well, thank you in advance for your help Smile | :)

John

Re: how do i use DeleteObject()...

Christian Graus2-Mar-02 21:44

Christian Graus

2-Mar-02 21:44

The most important step is selecting the original pen/brush/font into the DC before destroying it. OTherwise you will leak GDI resources and your program will eventually kill the graphics subsystem on any non-NT based OS.

You don't need to call DeleteObject before calling delete. Delete allows you to delete the handle being encapsulated without destroying the class object.

Christian

The tragedy of cyberspace - that so much can travel so far, and yet mean so little.

Re: how do i use DeleteObject()...

John Cruz2-Mar-02 21:57

John Cruz

2-Mar-02 21:57

Thanks for the help Christian. ill remember that Smile | :)

Texture filter in OpenGL

Mazdak2-Mar-02 19:30

Re: Texture filter in OpenGL

2-Mar-02 19:30

I have very basic question.I read some tutorials but didn't get one thing,I want to know what is "texture filters".I don't know what is it and what's they are good for?
Can anybody tell me about it in simple words?

thanks

Mazy

"So,so you think you can tell,
Heaven from Hell,
Blue skies from pain,...
How I wish,how I wish you were here."
Wish You Were Here-Pink Floyd-1975

alex.barylski2-Mar-02 22:55

alex.barylski

2-Mar-02 22:55

I'm surprised Christian hasn't answered you...? Christian where are you...?

Textures are the images you map to polygons, this I assume you know...filters are usually...ummm just that...filter certain content...

Graphics filters...in psp7 seem to allow you to apply special effects...IE 4.0+ supports a feature called Filters and Transitions which again apply certain effects to elements.

So it's my best reasoning that texture filters are probably filters you apply to images(textures) for a certian effect...like changing the alpha-factor (which I think is what gives textures semi-transluecency)

Yup...these are my guesses from my work with graphics...

Cheers!

"An expert is someone who has made all the mistakes in his or her field" - Niels Bohr

Re: Texture filter in OpenGL

Mazdak2-Mar-02 23:23

Using Delimiter EOF :: C++

2-Mar-02 23:23

hmmm,thanks HockeyDude.

HockeyDude wrote:
I'm surprised Christian hasn't answered you...? Christian where are you...?

I was waiting for his answer too Wink | ;)

Mazy

"So,so you think you can tell,
Heaven from Hell,
Blue skies from pain,...
How I wish,how I wish you were here."
Wish You Were Here-Pink Floyd-1975

valikac2-Mar-02 19:26

valikac

2-Mar-02 19:26

Hi.

I am working on a small practice program for a C++ class. I need to implement a way to delimite using EOF. The user can break out of a while, for example, with ctrl-d (dos) or ctrl-z (unix).

What is the best way to implement something like that?

I have tried this:

while((num = cin.get()) != EOF) // from Deitel
{}

The above does not work.

Thanks,
Kuphryn

Re: Using Delimiter EOF :: C++

Mazdak2-Mar-02 19:29