**horribly stumped** passing a pointer to C++ from VB - C / C++ / MFC Discussion Boards

Re: shared memory and address?

includeh105-Sep-03 7:21

includeh10

5-Sep-03 7:21

i never use jni before, i only tried pipe but it doesn't work.

could u send real code to my email?

thx

includeh10

Storing a file with an exe

Ricky Koh4-Sep-03 21:07

Ricky Koh

4-Sep-03 21:07

Hi. I have a program that allows a user to select a file and the user presses the Ok button, the program will write out an exe and store or copy the file together with the newly created exe. When the user runs the newly created exe, it will run the file when it presses a button on the exe.

I managed to create the exe already. I now need to solve the storing problem. I tried using the zip and unzip method, but it only unzip it to another folder and not excute it. So how can I go about doing this?

Re: Storing a file with an exe

includeh104-Sep-03 21:10

includeh10

4-Sep-03 21:10

possible u can store it in "resource" part of an exe.
see how to modify resource of an exe in vc help.

includeh10

Re: Storing a file with an exe

Ricky Koh4-Sep-03 21:15

Ricky Koh

4-Sep-03 21:15

I understand what you mean. But my file might keep on changing. So how can I update the resource for the file in the first place?

Re: Storing a file with an exe

Jagadeesh VN5-Sep-03 4:24

Jagadeesh VN

5-Sep-03 4:24

You can use the concept of Self Extractors
See this url :
http://www.codeproject.com/file/self_extractor.asp

"A robust program is resistant to errors -- it either works correctly, or it does not work at all; whereas a fault tolerant program must actually recover from errors."

need some help - todo:

cridaniel4-Sep-03 17:06

cridaniel

4-Sep-03 17:06

I'm writing an SDI application and I cannot get the name of the app that appears in the list box on the system toolbar to change (in winxp when you open the same app many times , he groups all of them on one button with a list box, and the text that is written on it is TODO: <File Description> . I have looked at the document, view, app, and frame titles but none of them change it. The only place that i found this string, was in the resources (versioning), but if i change that, nothing happens .
For projects that are imported from vc6 it writes the name of the app that you gave when you have created the project, but I don't know from where to change it, i did a search and replaced it everywhere where it appears but it doesn't change the text that appears on that button. do you have the same problem, or just i have it ?
If anyone knows how to fix this using VC7 I would greatly appreciate it.

Self extracting files

Dor4-Sep-03 15:51

Dor

4-Sep-03 15:51

Hi,
Im trying to create a self extracting file. I have managed to do it for my home computer by getting the program to open a file pointer to its own exe file, but when i do this on other computers, I get a sharing violation. Is there a way around this?
Cheers

**horribly stumped** passing a pointer to C++ from VB

rajdawg4-Sep-03 15:51

rajdawg

4-Sep-03 15:51

When I pass this pointer from Vb to C++ the value is not recieved. The pAcct variable always has the same value (0x0012fadc). If I change the C++ function so that it merely asks for a long value, or int, or even a BSTR, as an argument, the same thing happens (0x0012fadc). But, if I create the Account object in C++ and pass a pointer OUT to VB, that works fine. Or, if I take the value printed by the message box (0x0014F9F0), and copy that into pAcct after control has entered the GetAccount routine, everything works (the value printed from VB is valid). Its very perplexing.
Thanks for whatever advise you can give!
VB Code

<br />
Private Declare Function GetAccount Lib "C:\...\DataAccess.dll" (ByVal ptr As Long)<br />
<br />
Private Sub Form_Load()<br />
Dim Account As clsAccount<br />
Dim ptr As Long<br />
<br />
Set Account = New clsAccount<br />
ptr = ObjPtr(Account)<br />
MsgBox Hex(ptr), vbInformation <-- Prints the following value - 0x0014F9F0<br />
GetAccount ptr<br />
Label1.Caption = "Account Name = " & CStr(Account.AccountName)<br />
End Sub<br />

C++ Code

<br />
extern "C" void __stdcall GetAccount(_clsAccount* pAcct) <-- recieves the value 0x0012fadc<br />
{<br />
HRESULT hr = CoInitialize(0); //initializes COM library<br />
if (SUCCEEDED(hr))<br />
{<br />
_bstr_t bstr1(_T("TestInfo")); //use constructor to enter string <br />
pAcct->put_AccountName(bstr1); <-- causes access violation error <br />
CoUninitialize(); <br />
}<br />
}<br />

ANY suggestions will be IMMENSELY appreciated!
Thanks

Re: **horribly stumped** passing a pointer to C++ from VB

parths4-Sep-03 17:52

parths

4-Sep-03 17:52

Instead of getting the pointer to you object and then sending the pointer value 'ByVal',
why don't you just send a reference to the object?

rajdawg wrote:
Private Declare Function GetAccount Lib "C:\...\DataAccess.dll" (ByVal ptr As Long)

Private Declare Function GetAccount Lib "C:\...\DataAccess.dll" (ByRef ptr As Long)

rajdawg wrote:
Set Account = New clsAccount
ptr = ObjPtr(Account)
MsgBox Hex(ptr), vbInformation <-- Prints the following value - 0x0014F9F0
GetAccount ptr

Set Account = New clsAccount
GetAccount Account

VB by default uses Byref params

BTW I've never tried passing a class from VB to C. I wasn't sure it was possible. Structs, yes, but classes, with their code sections and all?

"It was when I found out I could make mistakes that I knew I was on to something."
-Ornette Coleman

Re: **horribly stumped** passing a pointer to C++ from VB

rajdawg5-Sep-03 1:20

rajdawg

5-Sep-03 1:20

Thanks for your reply.
I couldn't get that to work either. I received a ByRef Type Mismatch message from VB.
I have also seen an example where the decare statement would look like this...

<br />
Private Declare Function GetAccount Lib "C:\...\DataAccess.dll" (ByVal Account As Any)<br />

and the function call, in VB, would look like:

<br />
GetAccount Account<br />

but that does not work either.
I think you are right. I may need to build a structure that will represent this object in C++, and go that route. I'll keep researching.
Thank you for your response. This is very interesting/frustrating/humbling stuff. Smile | :)

thanks again.
roger

how to get the number of digits

elmahdy4-Sep-03 13:44

elmahdy

4-Sep-03 13:44

how to get the number of digits after the decimal point
ex :
Input : 5.1234
Expected Output : 4
i wrote this code but there are wornings..
what is wrong here ??
double input;
int x=input; // so x=the integeral part of input
int y=input-x; // so y=the fractional part
while(y>0)
{count++;
input*=10;
x=input;
y=input-x;
}
plz help me !!

elmahdy

Re: how to get the number of digits

Dor4-Sep-03 15:47

Dor

4-Sep-03 15:47

you won't get the fractional part in y because it is an int.

Re: how to get the number of digits

Larry J. Siddens5-Sep-03 10:17

Larry J. Siddens

5-Sep-03 10:17

I'm guessing there are a lot of ways to do this. How about this!

double input;
int Num = static_cast< int >( input );
intput -= static_cast< double >( Num );

You should now just have the .XXXX

Char szData[1024];
ssprintf( szData, "%f", &Input );
int iLengt = strlen( szData ) - 2; //For the zero & the '.'

This can give you a start.

Larry J. Siddens
Cornerstone Communications

TAME THE DOCUMENT MONSTER
www.unifier.biz

Environment Vars...

RobJones4-Sep-03 13:41

RobJones

4-Sep-03 13:41

Any one know if it’s possible to change or add to the environment variables of the calling process?

I know it's really easy to change the current processes env vars, and child process env vars...

Thanks,
Rob

Whoever said nothing's impossible never tried slamming a revolving door!

Re: Environment Vars...

Neville Franks5-Sep-03 0:15

Neville Franks

5-Sep-03 0:15

I don't think it is possible. What a you trying to do?

Neville Franks, Author of ED for Windows. Free Trial at www.getsoft.com

Re: Environment Vars...

RobJones5-Sep-03 3:53

RobJones

5-Sep-03 3:53

I am trying to write a console executable that can be used in a batch file to change the environment vars of the batch file depending on user input and or contents of a text file.

Rob

Whoever said nothing's impossible never tried slamming a revolving door!

Error in adding submenu to the File Menu

Binayak4-Sep-03 13:28

Binayak

4-Sep-03 13:28

Hi,

I'm trying to add a submenu into the Main File Menu, and I want to populate the submenu dynamically. But, I'm getting an error on AppendMenu() at runtime.
Here is what I'm doing:

CMenu* menu_bar = AfxGetMainWnd()->GetMenu();
CMenu* file_menu = menu_bar->GetSubMenu(0);

for (int iCount =0; iCount<maximum ;="" icount++)
{
if="" (!uniquehierarchyname[icount].isempty())
{
hierarchysubmenu.appendmenu="" (mf_string,="" id_base_command="" +icount,="" uniquehierarchyname[icount]);
}
}
file_menu-="">AppendMenu (MF_POPUP, (UINT)HierarchySubmenu.m_hMenu, "&Add Hierarchy from Submenu");

Exceptions

Rickard Andersson²⁰4-Sep-03 13:03

Rickard Andersson²⁰

4-Sep-03 13:03

When should I return an error code instead of throwing an exception and vice versa?

Rickard Andersson
Here is my card, contact me later!
UIN: 50302279
Sonork: 37318
Interests: C++, ADO, SQL, Winsock, 0s and 1s

Re: Exceptions

dog_spawn4-Sep-03 13:16

dog_spawn

4-Sep-03 13:16

That is such a massive issue. If you are making a C++ program returning error codes is dumb because you need to return something sensible in proper OO design.

I recommend you buy yourself a C++ book D'Oh! | :doh:

because almost any is bound to have a long description with example code.

I say: never return an error code. With the exception of int main() of course Poke tongue | ;-P

dog_spawn
http://www.hatekill.com[^]

Re: Exceptions

Rickard Andersson²⁰4-Sep-03 22:34

Rickard Andersson²⁰

4-Sep-03 22:34

dog_spawn wrote:
recommend you buy yourself a C++ book

I do have one. But doesn't say when to use exceptions Frown | :(

dog_spawn wrote:
I say: never return an error code. With the exception of int main() of course

Is that real OO? Cool, I'll see what I can do with my class framework I'm current designing.

Rickard Andersson
Here is my card, contact me later!
UIN: 50302279
Sonork: 37318
Interests: C++, ADO, SQL, Winsock, 0s and 1s

Re: Exceptions

Alvaro Mendez4-Sep-03 17:40

Alvaro Mendez

4-Sep-03 17:40

Get into the habit of handling errors via exception handling. Here's more.[^]

Regards,
Alvaro

Hey! It compiles! Ship it.

Re: Exceptions

Rickard Andersson²⁰4-Sep-03 22:41

Rickard Andersson²⁰

4-Sep-03 22:41

Great! Thaks alot for clearing things up!

Rickard Andersson
Here is my card, contact me later!
UIN: 50302279
Sonork: 37318
Interests: C++, ADO, SQL, Winsock, 0s and 1s

Re: Exceptions

jhwurmbach5-Sep-03 1:18

jhwurmbach

5-Sep-03 1:18

Exceptions are for truly exceptional errors. Like the file you are working on has suddely disapeared, or you cant get enough memory etc. That Kind of things that you can never be sure when it happenes.

Return code, to the contrary are the everyday case of an error: All those stuff you know that can happen, but your routine can't cope with on itself, like a file can not be opened, user gave your parser too few arguments, the file format of your data is not as expected etc.
All this are things that happen quite often, and you can think of them easily, but your routine must rely on its caller to solve them (e.g. query the user, something your file-handling routines should do, as they are not part of the GUI).

Who is 'General Failure'? And why is he reading my harddisk?!?

Re: Exceptions

Andrew Walker5-Sep-03 1:32

Andrew Walker

5-Sep-03 1:32

I agree with (almost Wink | ;)

) everything above, but also believe...

That you should only consider throwing exceptions when you fully understand the consequences of doing so, specifically issues to do with the overheads, resource aquistion and stack unwinding. Writing consistantly exception safe c++ code is extremely hard, even for the best programmers.

Herb Sutter and Scott Meyers have some superb articles on Exception safety, I strongly recommend you look at their material.

Error codes are appropriate in situations where performance is absolutely critical or exception safety is not an option. Two examples are some operating systems, old versions of CE AFAIK, and the standard IOStreams library.

The C/C++ Users Journal tend to spend a significant ammount of time covering this type of issue.

If you can keep you head when all about you
Are losing theirs and blaming it on you;
If you can dream - and not make dreams your master;
If you can think - and not make thoughts you aim;
Yours is the Earth and everything that's in it.

Rudyard Kipling

how to schedule a a thread to a specific CPU?

Anonymous4-Sep-03 12:46

Anonymous

4-Sep-03 12:46

In VC++ 6.0, Windows 2000, how to schedule a thread to run on a specific CPU?
Is there any APIs or methods?

Thanks,
Leo

Use Ctrl+Left/Right to switch messages, Ctrl+Up/Down to switch threads, Ctrl+Shift+Left/Right to switch pages.