C / C++ / MFC

managed String in Visual C++ / call a function like void f(int& x, String* s)

2-Jun-06 9:43

Good luck on your exam Roll eyes | :rolleyes:

"The largest fire starts but with the smallest spark." - David Crow

karlheinzsteinhart2-Jun-06 6:05

karlheinzsteinhart

2-Jun-06 6:05

Hi,
I have some problems with managed Strings as function parameter.

See:

void f(int& x, String* s)
{
x=10;
s="hello"
return;
}

.....
String *s ="start";
int x= 0;
f(x,s);
....

Problem:
s doesn't get the new vale "hello"
is it possible to use a managed String in a function by reference ??
Thx

Re: managed String in Visual C++ / call a function like void f(int& x, String* s)

C^hris L^osinger2-Jun-06 7:05

C^hris L^osinger

2-Jun-06 7:05

try the Managed C++ forum : http://www.codeproject.com/script/comments/forums.asp?forumid=3785[^]

Cleek | Image Toolkits | Thumbnail maker

wcscpy_s issues [modified]

big_denny_2002-Jun-06 5:13

2-Jun-06 5:13

Hi all

Please help, I have next code :

I am building in Unicode

TCHAR array[100];

CString strText = _T("Cool");

_tcscpy_s(array,//Location of destination string buffer
          sizeof(array),// Size of the destination string buffer.
          strText//Null-terminated source string buffer.
         )

But the program halts and hangs, when performs _tcscpy_s method.

thank you

-- modified at 11:16 Friday 2nd June, 2006

Nish Nishant2-Jun-06 5:22

Nish Nishant

2-Jun-06 5:22

There's no problem in the snippet of code you have shown. The error, presumably, lies elsewhere.

Regards,
Nish

Nish’s thoughts on MFC, C++/CLI and .NET (my blog)
Currently working on C++/CLI in Action for Manning Publications.
Also visit the Ultimate Toolbox blog (New)

David Crow2-Jun-06 5:33

2-Jun-06 5:33

big_denny_200 wrote:
But the program halts and hangs, when performs _tcscpy_s method.

How are you verifying this?

"The largest fire starts but with the smallest spark." - David Crow

Viorel.2-Jun-06 5:33

Viorel.

2-Jun-06 5:33

Since _tcscpy_s is expanded to wcscpy_s call in Unicode version, you must specify the size of destination buffer in 2-byte unicode characters, not in bytes. Universal solution can look like this:

_tcscpy_s(array,
          sizeof(array) / sizeof(TCHAR),
          strText);

You got halts even if the source string was short enought, because -- in Debug version -- this function fills the buffer with 0xFD value.

-- modified at 11:33 Friday 2nd June, 2006

Zac Howland2-Jun-06 5:36

Zac Howland

2-Jun-06 5:36

Try explicitly casting the CString object:

<br />
TCHAR array[100];<br />
<br />
CString strText = _T("Cool");<br />
<br />
_tcscpy_s(array,//Location of destination string buffer<br />
          sizeof(array),// Size of the destination string buffer.<br />
          (LPCTSTR)strText//Null-terminated source string buffer.<br />
         );<br />

If you decide to become a software engineer, you are signing up to have a 1/2" piece of silicon tell you exactly how stupid you really are for 8 hours a day, 5 days a week

Zac

Viorel.2-Jun-06 5:42

Viorel.

2-Jun-06 5:42

(Actually, explicit casting from CString to LPCTSTR is not required even in printf-like calls -- at least in VS 6.0).

big_denny_2002-Jun-06 6:03

2-Jun-06 6:03

Could you be more explicit ?

MSDN says, that second parameter of wcscpy_s must specify size of destination buffer in bytes, therefore in Unicode build destination size will be 100 * sizeof(TCHAR) (which is equal to sizeof(array)), but in you case it will be 100(which is not the size of destination buffer)

I am little confused.

thanks

-- modified at 12:02 Friday 2nd June, 2006

Zac Howland2-Jun-06 6:02

Zac Howland

2-Jun-06 6:02

It shouldn't be, but I've run into problems with it converting (implicitly) to char* instead of wchar_t* when I didn't explicitly cast it.

Looking back at the code again, I think he will run into another problem though. In non-UNICODE builds, he shouldn't notice anything, but in UNICODE builds, the sizeof(array) will actually return twice the size of the actual buffer. I believe the wstcpy_s function requires array size in elements, not bytes (I'll have to double-check that though). If I'm correct, he would just need to change that line from sizeof(array) to sizeof(array) / sizeof(TCHAR).

If you decide to become a software engineer, you are signing up to have a 1/2" piece of silicon tell you exactly how stupid you really are for 8 hours a day, 5 days a week

Zac

big_denny_2002-Jun-06 6:07

2-Jun-06 6:07

What is happening ? I am replying to Viorel Bejan and this post gooes in reply to Zac Howland's post Confused | :confused:

Viorel Bejan wrote:
Since _tcscpy_s is expanded to wcscpy_s call in Unicode version, you must specify the size of destination buffer in 2-byte unicode characters, not in bytes. Universal solution can look like this:

_tcscpy_s(array,
sizeof(array) / sizeof(TCHAR),
strText);

You got halts even if the source string was short enought, because -- in Debug version -- this function fills the buffer with 0xFD value.

George L. Jackson2-Jun-06 8:17

George L. Jackson

2-Jun-06 8:17

Actually, it says the second parameter of wcscpy_s must specify size of destination buffer in words (in bytes for non-Unicode). Thus, it is the size in characters and not size in bytes! If you are using a statically-allocated array as a destination, you can use the _countof macro instead of sizeof. However, sizeof(array) / sizeof(TCHAR) also returns the correct size.

big_denny_2002-Jun-06 8:25

2-Jun-06 8:25

thanks, I did not pay attention to the WORD

George L. Jackson2-Jun-06 11:14

George L. Jackson

2-Jun-06 11:14

Word, man! Smile | :)

Nish Nishant2-Jun-06 6:11

Nish Nishant

2-Jun-06 6:11

Viorel Bejan wrote:
You got halts even if the source string was short enought, because -- in Debug version -- this function fills the buffer with 0xFD value.

But in this specific case, it's not bad enough to cause a halt - since he has a 100 byte buffer and a 5 character string.

Regards,
Nish

Nish’s thoughts on MFC, C++/CLI and .NET (my blog)
Currently working on C++/CLI in Action for Manning Publications.
Also visit the Ultimate Toolbox blog (New)

Nemanja Trifunovic2-Jun-06 5:41

Nemanja Trifunovic

2-Jun-06 5:41

big_denny_200 wrote:
But the program halts and hangs, when performs _tcscpy_s method.

(Offtopic sarcasm)

Glad to see these "safe" functions in action.

My programming blahblahblah blog. If you ever find anything useful here, please let me know to remove it.

Nish Nishant2-Jun-06 6:10

Nish Nishant

2-Jun-06 6:10

Nemanja Trifunovic wrote:
(Offtopic sarcasm)

Glad to see these "safe" functions in action.

Regards,
Nish

Nish’s thoughts on MFC, C++/CLI and .NET (my blog)
Currently working on C++/CLI in Action for Manning Publications.
Also visit the Ultimate Toolbox blog (New)

Wndows application with buttons and controls

georgeraafat2-Jun-06 15:06

georgeraafat

2-Jun-06 15:06

According to:
http://msdn2.microsoft.com/en-us/library/td1esda9.aspx[^]

the sizeof(array) should correspond to the number of 'characters' - not 'bytes'.
So - in case of ANSI, it's bytes. In case of unicode, it's words (2-bytes).

When the code you listed compiles for unicode, sizeof(array) is 200 - which is double the actual number of characters.

Note that _tcscpy_s() zeros out the buffer after copying... and that's when you get the buffer overrun. You can find that out by stepping into _tcscppy().

You can use (sizeof(array)/sizeof(array[0])) or the _countof() macro.

gmileka

LCI2-Jun-06 4:47

LCI

2-Jun-06 4:47

I am using Visual Studio C++.NET
I am familiar with creating dialog applications. But i want to include menus
However, i would like to create a windows application with menu options, file etc.. and at the same time, include controls like buttons drop down boxes, picture control area. Can anyone direct me to a good tutorial or if you can explain some basic steps i'd be grateful... I know that it should be easy, i just don't know where to start...

Thanks,

Re: Wndows application with buttons and controls

David Crow2-Jun-06 5:12

Re: Wndows application with buttons and controls

2-Jun-06 5:12

LCI wrote:
...at the same time, include controls like buttons drop down boxes, picture control area.

In the menu, or the client area?

"The largest fire starts but with the smallest spark." - David Crow

LCI2-Jun-06 5:25

LCI

2-Jun-06 5:25

Well, in the client area. I suspect that if i create an MFC Single or multiple document application, i will get the menu. But if i do that. Now i have a menu, but i want to be able to add controls and buttons in the client area just like i would in a dialog based application.

Do you recommend me generating the project as a win32 project?

I am currently creating projects of different types just to see if i can get a feel for doing the above but cannot seem to figure it out.

Re: Wndows application with buttons and controls

David Crow2-Jun-06 5:31