Re: why it is so.. - C / C++ / MFC Discussion Boards

why it is so..

ramina sen2-Dec-08 4:37

ramina sen

2-Dec-08 4:37

why in mfc programming # prgma once is used??

Re: why it is so..

Code-o-mat2-Dec-08 4:53

Code-o-mat

2-Dec-08 4:53

To avoid multiple inclusion of the same header file. This used to be like this:

#ifndef MY_HEADER_FILE_H__
#define MY_HEADER_FILE_H__

...

#endif

But using pragma once makes it easier.

> The problem with computers is that they do what you tell them to do and not what you want them to do. <

Re: why it is so..

Maximilien2-Dec-08 5:11

Maximilien

2-Dec-08 5:11

Code-o-mat wrote:

But using pragma once makes it easier.

but not portable, it's a Microsoft specific pragma (as far as I know).

Re: why it is so..

Code-o-mat2-Dec-08 5:14

Code-o-mat

2-Dec-08 5:14

As far as i know you are right.

> The problem with computers is that they do what you tell them to do and not what you want them to do. <

Re: why it is so..

Nemanja Trifunovic2-Dec-08 5:20

Nemanja Trifunovic

2-Dec-08 5:20

Recent versions of GNU compiler also support it.

Programming Blog

utf8-cpp

Re: why it is so..

led mike2-Dec-08 6:57

led mike

2-Dec-08 6:57

Maximilien wrote:
it's a Microsoft specific pragma (as far as I know).

My bad, I mistook you for the original poster! I am officially embarrassed Blush | :O

led mike

Re: why it is so..

toxcct2-Dec-08 7:41

toxcct

2-Dec-08 7:41

so are MFC, so it doesn't matter in this case Smile | :)

[VisualCalc][Binary Guide][CommDialogs] | [Forums Guidelines]

Re: why it is so..

Paul Conrad2-Dec-08 5:04

Paul Conrad

2-Dec-08 5:04

Pragma once is used to include the header file only one time when compiling. No sense in having to parse through the same header file multiple times.

"The clue train passed his station without stopping." - John Simmons / outlaw programmer

"Real programmers just throw a bunch of 1s and 0s at the computer to see what sticks" - Pete O'Hanlon

"Not only do you continue to babble nonsense, you can't even correctly remember the nonsense you babbled just minutes ago." - Rob Graham

Re: why it is so..

Code-o-mat2-Dec-08 8:01

Code-o-mat

2-Dec-08 8:01

...not to mention the nice "redeclaration" and "multiple definition" errors you'd get.

> The problem with computers is that they do what you tell them to do and not what you want them to do. <

Re: why it is so..

CPallini2-Dec-08 9:31

CPallini

2-Dec-08 9:31

Code-o-mat wrote:
...not to mention the nice "redeclaration" and "multiple definition" errors you'd get.

or even recursive inclusion Wink | ;)

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]

Re: why it is so..

CPallini2-Dec-08 5:27

CPallini

2-Dec-08 5:27

Bisua wrote:
# prgma once

To irritate the compiler.

#pragma once is not MFC specific and is even documented Roll eyes | :rolleyes:

[^].

Custom ComboBox with “common control version 6”

JacMax2-Dec-08 4:34

JacMax

2-Dec-08 4:34

Hi,

I need a Custom ComboBox with MFC GridCtrl like this from Bahrudin Hrnjica (http://www.codeproject.com/KB/combobox/CustomComboBox.aspx) not with common control version 5 but with version 6.

Compiled with VS 2002 it runs fine, compiled with VS 2008 it doesn’t run.
I found the answer, why it doesn’t run (from dragonhead7):

"I have consulted the developer support engineer of Microsoft, he said the usage of:

VERIFY(::DestroyWindow(m_pcbInfo->hwndList));
if(m_lstPopup->IsKindOf(RUNTIME_CLASS(CPopupMFCGrid)))
VERIFY(static_cast<CPopupMFCGrid>(m_lstPopup)->CreatePopupCtrl(this));

is not supported in common control version 6, although it is supported in common control version 5. He suggested to use the subclass function."

Can anyone tell me the code for common control *version 6*?

Thanks

Crashes in release mode but not in debug

RedSonja2-Dec-08 3:59

RedSonja

2-Dec-08 3:59

My C++ project (embedded real-time stuff) has run nicely for years. Now I split off some of the code to a separate exe. I always test in debug mode, so I didn't worry much about release mode. So when the user starts it in release mode, as soon as the exe is called it comes with "The application has requested runtime to terminate it in an unusual way".

I have seen this before, it was the exe throwing an unhandled exception. But the thing has more exception handlers than code now, and it runs fine in debug. What can be causing this?

I checked the project properties, there is nothing surprising in there. Maybe someone can give me a tip what I should be looking for?

-------------
Bibo ergo sum

Re: Crashes in release mode but not in debug

Alan Balkany2-Dec-08 4:08

Alan Balkany

2-Dec-08 4:08

This is just what you need: http://www.codeproject.com/KB/debug/survivereleasever.aspx[^] (Surviving the Release Version By Joseph M. Newcomer)

Re: Crashes in release mode but not in debug

Hamid_RT2-Dec-08 4:08

Hamid_RT

2-Dec-08 4:08

See Debugging Release Mode Problems[^].

Re: Crashes in release mode but not in debug

bob169722-Dec-08 7:33

bob16972

2-Dec-08 7:33

Make sure to check that any member variable pointers are in the class initialization list and set to NULL. This is usually the number one cause of the behavior you are describing, at least in my shop.

Re: Crashes in release mode but not in debug

RedSonja3-Dec-08 1:24

RedSonja

3-Dec-08 1:24

That was very kind of all of you - I now know that you really can debug in release mode - but the problem was something else entirely.

When I first made my exe it was a dll project, then I decided to make an exe after all, and since I was in a hurry I did this by copying and renaming, then changing the properties to fit.

Anyway, I ended up with both main and InitInstance. Debug runs main, it seems, and release takes InitInstance if it can find one, or maybe main is optimised out. I commented InitInstance out and suddenly all is well.

-------------
Bibo ergo sum

How to access servlet in VC++?

AnithaSubramani2-Dec-08 2:10

AnithaSubramani

2-Dec-08 2:10

Hi All,

I need to access the servlet in VC++ and upload the files to servlet.I dont knoe how to do this?I need some ides for this.

Please help me.....

Thanks & Regards,

Anitha

Re: How to access servlet in VC++?

led mike2-Dec-08 4:15

led mike

2-Dec-08 4:15

AnithaSubramani wrote:
I need some ides for this.

The idea is, you study and learn the technologies that you need to use, then you program your application using the knowledge you gained. Or perhaps you are not a programmer, I just made that assumption because these forums are intended for programmers.

led mike

using select with filehandles (not sockets) under windows

sevenH2-Dec-08 2:02

sevenH

2-Dec-08 2:02

Hi,

I wonder if it´s possible to use the function "select" with serial ports. I think under linux it´s possible but under Windows select returns -1 and WSAGetLastError gives me 10038 (Socket operation on nonsocket. An operation was attempted on something that is not a socket. Either the socket handle parameter did not reference a valid socket, or for select, a member of an fd_set was not valid.)

pseudo code:

HANDLE h = CreateFile( COM1 )
...
FD_SET( (int)h, readfds)

select( 0, readfds, NULL, NULL, timeout )

read the data from serial port

I think the problem is the cast of the HANDLE h to int...

Another possibilty would be the function WaitCommMask but I need a timeout-feature. Has anyone an idea if select can be used with serial ports (under Win)?

Thanks in advance!

Sebastian

Re: using select with filehandles (not sockets) under windows

led mike2-Dec-08 4:30

led mike

2-Dec-08 4:30

Welcome to code project! Beer | [beer]

A little advice for posting here in the forums. It might not be a good idea to ask if something is possible and then follow that up with a system error message that clearly states it is not possible. People here deal with some really dense posters most days and you don't really want to make yourself seem like one of those if you really want some help.

sevenH wrote:
I need a timeout-feature.

Can you be more specific? Timeout for what?

What is your background dealing with asynchronous operations? There are many different solutions to choose from when working in this area, however none of them should be entered into casually. If you lack experience in these areas you need to take some time to study the subject. There is no magic function to use that makes everything work as intended during asynchronous operations.

led mike

Re: using select with filehandles (not sockets) under windows

JudyL_MD2-Dec-08 4:31

JudyL_MD

2-Dec-08 4:31

sevenH wrote:
I need a timeout-feature

Does SetCommTimeouts give you what you need?

Judy

Be wary of strong drink. It can make you shoot at tax collectors - and miss.
Lazarus Long, "Time Enough For Love" by Robert A. Heinlein

something for comipler..

tasumisra2-Dec-08 1:47

tasumisra

2-Dec-08 1:47

Hi All,
i was talking to a guy .. who asked about return 0 or return 1
i told him that it return 0 means code have no run time error and if its return 1 it has some error ...

he asked me from where its coming .. i told its coming from comipler ...

but my answer was not as per his expectation can you please more clerify what should i answer in such cases..

vikas da

Re: something for comipler..

gayatri.neelema2-Dec-08 1:50

gayatri.neelema

2-Dec-08 1:50

I think the return value always comes from your code.
I think the compiler only compiles the code and gives you the .obj file and does not return any value.

Re: something for comipler..

tasumisra2-Dec-08 1:56

tasumisra

2-Dec-08 1:56

lets see a simple code

int main ()
{
  return 0;
}

in above return 0 is defintly user defined .. is there no relation of this return 0 with compiler ...

i am not very sure .. Frown | :(

vikas da

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