How to share data between DLLs - C / C++ / MFC Discussion Boards

Asim N.25-Oct-04 4:15

25-Oct-04 4:15

Three methods for dealing with dangling pointers are tombstones, lock-and-keys and garbage collection. What are the advantages and distadvantages of these ?

Regards,
Asim

Re: dangling pointers ?

David Crow25-Oct-04 4:53

David Crow

25-Oct-04 4:53

Wasn't this covered in class?

"Opinions are neither right nor wrong. I cannot change your opinion of me. I can, however, change what influences your opinion." - David Crow

Re: dangling pointers ?

Antony M Kancidrowski25-Oct-04 6:42

Antony M Kancidrowski

25-Oct-04 6:42

You would have to attend class to know though! Wink | ;)

Ant.

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I'm coloured, yet clear.
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Re: dangling pointers ?

Jim Crafton25-Oct-04 7:18

Jim Crafton

25-Oct-04 7:18

I don't know, but it sounds like an interesting article for you to write and post on CP if you ever find the answer! Smile | :)

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Re: dangling pointers ?

Ravi Bhavnani25-Oct-04 13:37

Ravi Bhavnani

25-Oct-04 13:37

You should really do your own homework, but I'll help you out just this once...

Tombstones
(adv) Not limited by the system's run length encoding limits.
(dis-adv) Can only be used once in an application.

Lock & keys
(adv) Easy to implement.
(dis-adv) Cannot be used in Unicode mode or when an app needs to divide by zero (eg: during complex mathematical computations).

Garbage collection
(adv) Can be used for procedures as well as functions.
(dis-adv) Not supported in languages like Java or C#.

/ravi

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Re: dangling pointers ?

Asim N.25-Oct-04 15:39

Asim N.

25-Oct-04 15:39

OK, you are right.
Thank you very much anyway, Ravi.

Regards,
Asim

Re: dangling pointers ?

One Stone25-Oct-04 22:36

One Stone

25-Oct-04 22:36

Garbage collection
(dis-adv) Not supported in languages like Java or C#.

Are you sure with this? Wink | ;)

How to share data between DLLs

yanping wang25-Oct-04 3:43

yanping wang

25-Oct-04 3:43

I coded like this:

#pragma data_seg("Shared")
HWND g_hWndCaller = NULL;
HHOOK g_hHook = NULL;
#pragma data_seg()

#pragma comment(linker, "/SECTION:Shared, RWS")

but it does not work, why?

Re: How to share data between DLLs

David Crow25-Oct-04 5:00

David Crow

25-Oct-04 5:00

Do MSDN articles Q100634 or Q125677 help?

"Opinions are neither right nor wrong. I cannot change your opinion of me. I can, however, change what influences your opinion." - David Crow

Re: How to share data between DLLs

Blake Miller25-Oct-04 5:11

Blake Miller

25-Oct-04 5:11

Just in case it is sotehing as STUPID as this..

I notice the documentation shows /INCLUDE, but the sample shows this:
#pragma comment(linker, "include:__mySymbol")

So, as a suggestion, why don't you try using all lowercase for the word 'section':

#pragma comment(linker, "/section:Shared, RWS")

Also, you might want to call your section something besides 'Shared' so you don't confuse the compiler or linker over another keyword. Use your company initialz in front of it or something..

#pragma data_seg("YCIShared")
HWND g_hWndCaller = NULL;
HHOOK g_hHook = NULL;
#pragma data_seg()

#pragma comment(linker, "/section:YCIShared, RWS")

Renaming Registry Key

sundu25-Oct-04 3:18

sundu

25-Oct-04 3:18

Hi,

I am working on vc++ project and i have store the details of that application in registry, is it possible to rename a registry key(hive) through coding.

can anyone help me through this.

Thanks and Regards,
R.Sundaram.

R.Sundaram

Re: Renaming Registry Key

David Crow25-Oct-04 4:52

David Crow

25-Oct-04 4:52

There is no single function to do this. One way would be to use RegSaveKey() and RegRestoreKey(), but those only work on Windows NT 3.1 and later. Another way is to use a series of copy and delete calls.

"Opinions are neither right nor wrong. I cannot change your opinion of me. I can, however, change what influences your opinion." - David Crow

Showing a console window launched as hidden with CreateProcess()...

wallacebw25-Oct-04 3:05

wallacebw

25-Oct-04 3:05

All:

I have created a process using CreateProcess() with a NULL executable module and the STARTUPINFO specifies tha the window is to remain hidden (which works). The question is how do I send this 'new' process a message to show the console window which was hidden during startup?

STARTUPINFO Task_SI;
    ZeroMemory(&Task_SI, sizeof(Task_SI));
    Task_SI.wShowWindow=SW_HIDE;
    Task_SI.dwFlags=STARTF_USESHOWWINDOW;
    Task_SI.cb = sizeof(Task_SI);
PROCESS_INFORMATION Task_PI;

    CreateProcess(
        NULL,   // pointer to name of executable module
        CmdStr, // pointer to command line string
        NULL,   // pointer to process security attributes
        NULL,   // pointer to thread security attributes
        0,  // handle inheritance flag
        CREATE_NEW_CONSOLE, // creation flags
        NULL,   // pointer to new environment block
        NULL,   // pointer to current directory name
        &Task_SI,   // pointer to STARTUPINFO
        &Task_PI    // pointer to PROCESS_INFORMATION
    );

After this process is initialized, a loop begins which checks to see if the process has completed and dispatches messages while waiting...

GetExitCodeProcess(Task_PI.hProcess, ExitCode);
while(*ExitCode==STILL_ACTIVE){
    while(PeekMessage(&msg, NULL, 0, 0, PM_REMOVE))
    {
        TranslateMessage(&msg);
        DispatchMessage(&msg);
    }
    Sleep(100);
    GetExitCodeProcess(Task_PI.hProcess, ExitCode);
}

After the process completed the usual cleanup occurs.

CloseHandle(Task_PI.hProcess);
CloseHandle(Task_PI.hThread);

How do I send this process a message to display itself (the console window)?

Thanks In advance,
Wallacebw

Accessing a VB DLL's functions from C++

esordini25-Oct-04 2:48

esordini

25-Oct-04 2:48

Hi all,
I am faced with the following problem. I should call the functions of a DLL (whose source code is not available), which doesn't seem to be implemented using Activex technology, and is downloadable in a package very "Visual Basic-oriented". In fact, the zip file contains only the dll binary and a .bas module, which looks much like the VB version of a C++ header file. Here's an excerpt of the .bas module:

<br />
Attribute VB_Name = "AstronomyFuncs"<br />
<br />
Declare Sub aa_hadec Lib "astro32" (ByVal lat As Double, ByVal Alt As Double, ByVal Az As Double, ByRef ha As Double, ByRef dec As Double)<br />
<br />
Declare Sub cal_mjd Lib "astro32" (ByVal mn As Long, ByVal dy As Double, ByVal yr As Long, ByRef mjd As Double)<br />

Now comes the question: despite there's is no provision for use within a Visual C++ program (no .h, .lib, etc.), anybody know how to overcome this problem, i.e. how to call the methods from C++?

Any help will be highly valued.

Regards,
Emmanuele

Re: Accessing a VB DLL's functions from C++

Cedric Moonen25-Oct-04 2:59

Cedric Moonen

25-Oct-04 2:59

If you know the name of the function, you can dynamically load your dll and then get the adress of the function. Take a look at LoadLibrary and GetProcAddress in the MSDN for more informations

Calling non-activex dlls from Visual C++

esordini25-Oct-04 2:45

esordini

25-Oct-04 2:45

<br />
Attribute VB_Name = "AstronomyFuncs"<br />
<br />
Declare Sub aa_hadec Lib "astro32" (ByVal lat As Double, ByVal Alt As Double, ByVal Az As Double, ByRef ha As Double, ByRef dec As Double)<br />
<br />
Declare Sub cal_mjd Lib "astro32" (ByVal mn As Long, ByVal dy As Double, ByVal yr As Long, ByRef mjd As Double)<br />

Copy tables between 2 SQL Servers

tgprakash25-Oct-04 2:25

tgprakash

25-Oct-04 2:25

Hello All,
I have a requirement wherein have 2 sql server databases(say machine1 & machine2).
I want to run a sql query on machine1 , which would copy 5 tables in a 'XYZ' database on machine2 TO 'XYZ' database on machine1.
Note : I have user/password for both the machines.

I tried this using BCP utility, but problem using BCP is, exceptions cannot be handled And if there is a network failure during the process of data transfer , the process console window window of BCP utility, remains still(stuck) and needs user input to continue.

Please send me a QUERY(I already know about the Export/Import in SQL Server Enterprise Manager, but i need a query to run from vc++) to copy tables between 2 sql servers. that query, i should be able to place between BEGIN & COMMIT Transaction Process.

Waiting for ur reply.

Regards,
Prax.

Re: Copy tables between 2 SQL Servers

David Crow25-Oct-04 4:57

David Crow

25-Oct-04 4:57

It sounds like you want a SELECT INTO query.

"Opinions are neither right nor wrong. I cannot change your opinion of me. I can, however, change what influences your opinion." - David Crow

Re: Copy tables between 2 SQL Servers

tgprakash25-Oct-04 18:32

tgprakash

25-Oct-04 18:32

In my vc++ application i have opened 2 CDatabase objects(dbtraget & dbSource). I want to copy database tables from dbSource to dbTarget , then how do i specify the the particular database in the "SELECT INTO..." query.

And where should i run this query, in
dbSource.ExecuteSQL(".....")
OR dbTraget.ExecuteSQL(".....")

Regards,
Prax Hmmm | :|

Re: Copy tables between 2 SQL Servers

David Crow26-Oct-04 8:08

David Crow

26-Oct-04 8:08

Have you seen here?

"Opinions are neither right nor wrong. I cannot change your opinion of me. I can, however, change what influences your opinion." - David Crow

Fill a tagSAFEARRAY with VARIANTs

anderslundsgard25-Oct-04 2:09

anderslundsgard

25-Oct-04 2:09

Hi!

I’m about to pass a VARIANT to a “COM-function”.
In the API I says I should pass: an Array of VARIANTS.

How do I create the array.

I have looked at the function SafeArrayPutElement(…) and managed to pass an Array of BSTR… but I do need to pass it like an VARIANT Array….?

Tips?

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raw serial IrDA-port

shibby25-Oct-04 1:49

shibby

25-Oct-04 1:49

Hi!

I'm going to code an application which uses the IrDA-devive of my PDA. Until now everything is going ok, but now i stuck at the question how to create specific frequencies and single pulses of a specific length. I've read in the source of win-lirc that pulses can be created by setting SETDTR & SETRTS, but it never worked at my application.

Hope that someone can help me with that

Thx a lot for all replies
shi`BBy

Changing Menu font size

Member 144737325-Oct-04 1:41

Member 1447373

25-Oct-04 1:41

i would like to know how to change the font size using MFC. don't reply that there is an existing article with source code, that one i tried and it has some restrictions as it is not derived from CMenu.

on com in .NET

ppp00125-Oct-04 1:20

ppp001

25-Oct-04 1:20

Hi all,

how can I create a COM in VC++.NET, which project template should I choose ?

Thanks
Patrick

Re: on com in .NET

Kevin McFarlane25-Oct-04 1:32

Kevin McFarlane

25-Oct-04 1:32

There should be a template for MFC app. or ATL app. Choose one of those and you will be presented with further options.

Kevin

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