C / C++ / MFC

12-Mar-08 5:27

I would like to know the behavior of strlen() when an uninitilized char array is passed as a parameter

char my_str[6];
int len = strlen(my_str);
HKEY hKey;
RegOpenKey(HKEY_LOCAL_MACHINE,"HKEY_LOCAL_MACHINE\\SOFTWARE\\Analog Devices\\SMWDMIF\\Settings",&hKey);
RegQueryValueEx(hKey, "Mode", 0, NULL, (LPBYTE)my_str, &len);

what value would len have when the above code gets executed? Will it cause any compiler/runtime errors?

modified on Wednesday, March 12, 2008 11:33 AM

Rajkumar R12-Mar-08 5:33

Rajkumar R

12-Mar-08 5:33

still, it searches for the '\0' character.

koumodaki wrote:
what value would len have when the above code gets executed?

len = number of character preceeding a '\0' character.

koumodaki wrote:
RegQueryValueEx(hKey, "Mode", 0, NULL, (LPBYTE)my_str, &len);

here it expects the buffer size not the string len.

Re: behavior of strlen()

koumodaki12-Mar-08 5:36

12-Mar-08 5:36

but '\0' is not present. So how does it know the end of the char array? what value gets stored in len?

Re: behavior of strlen()

Rajkumar R12-Mar-08 5:37

Rajkumar R

12-Mar-08 5:37

i modified my reply please look at it.

Re: behavior of strlen()

David Crow12-Mar-08 5:43

David Crow

12-Mar-08 5:43

koumodaki wrote:
but '\0' is not present.

It is, just not at the location you desire. For example, if my_str resides at memory address 0x1234, then strlen() will start counting from that locaton until it finds a '\0' character. Use your debugger to see this in action.

"Normal is getting dressed in clothes that you buy for work and driving through traffic in a car that you are still paying for, in order to get to the job you need to pay for the clothes and the car and the house you leave vacant all day so you can afford to live in it." - Ellen Goodman

"To have a respect for ourselves guides our morals; to have deference for others governs our manners." - Laurence Sterne

koumodaki12-Mar-08 5:44

12-Mar-08 5:44

my_str is actualy buffer to store the registry key data. Since I am using strlen() to ge the buffer size, I wanted to know the side-effects of using the function this way.
Also I have not initilized my_str to any value. As far as I know only memory is alocatd by the compiler when I define the array. So can I safetly assume that the variable len = 6, the size of decalred array?

David Crow12-Mar-08 5:47

David Crow

12-Mar-08 5:47

koumodaki wrote:
Since I am using strlen() to ge the buffer size...

strlen() dos not get the size of anything. Use sizeof instead.

koumodaki wrote:
...I wanted to know the side-effects of using the function this way.

At a minimum, the program won't work.

koumodaki wrote:
Also I have not initilized my_str to any value.

But it does get initialized, whether you did it or not.

koumodaki wrote:
So can I safetly assume that the variable len = 6, the size of decalred array?

You can, but you'd be wrong.

koumodaki12-Mar-08 5:54

12-Mar-08 5:54

Thanks for explaining

Rajkumar R12-Mar-08 5:47

Rajkumar R

12-Mar-08 5:47

koumodaki wrote:
Since I am using strlen() to ge the buffer size

buffer size and string len cannot interpretted same.

koumodaki wrote:
As far as I know only memory is alocatd by the compiler when I define the array

size of array is the buffer size here.

koumodaki wrote:
So can I safetly assume that the variable len = 6, the size of decalred array?

yes, but if your regvalue string length is greater than 5 you won't get the complete string.

koumodaki12-Mar-08 5:54

12-Mar-08 5:54

Thanks

image processing toolkits | batch image processing

C^hris L^osinger12-Mar-08 8:16

C^hris L^osinger

12-Mar-08 8:16

koumodaki wrote:
I wanted to know the side-effects of using the function this way.

high probability of an Access Violation error, followed by a nasty dialog box and the termination of your application.

Query about Tray Icon

ramana.g12-Mar-08 5:16

ramana.g

12-Mar-08 5:16

Hi all,
I have developed a dialog based application. In CMyDialog::OnInitDialog() i wrote code to add TrayIcon.

HICON hIcon = NULL;
m_NotifyIconData.cbSize = sizeof(NOTIFYICONDATA);
m_NotifyIconData.hWnd = m_hWnd;
m_NotifyIconData.uID = IDR_MAINFRAME;
m_NotifyIconData.uFlags = NIF_ICON | NIF_MESSAGE | NIF_TIP;
m_NotifyIconData.uCallbackMessage = ID_TRAY_MESSAGE; //WM_USER + 1
hIcon = (HICON) LoadIcon(AfxGetInstanceHandl(),MAKEINTRESOURCE (IDR_MAINFRAME));
m_NotifyIconData.hIcon = hIcon;
strcpy(m_NotifyIconData.szTip, "My Tray Icon");
Shell_NotifyIcon(NIM_ADD, &m_NotifyIconData);
if (hIcon)
DestroyIcon(hIcon);

It successfully added Tray Icon to the Notification area.

My sample application is running well. But, when i kill windows "explorer.exe" process from task manager and start "explorer" again, TrayIcon is missing in Notification area. I want Tray icon to be added again in this scenario. How to do this?

Thank you...

Re: Query about Tray Icon

David Crow12-Mar-08 5:44

David Crow

12-Mar-08 5:44

ramana.g wrote:
How to do this?

By reading this article.

Re: Query about Tray Icon

ramana.g12-Mar-08 6:00

ramana.g

12-Mar-08 6:00

thank you David Smile | :)

How to count no. of folders in a directory?

vandana712-Mar-08 5:15

vandana7

12-Mar-08 5:15

Hello
Can i get help to count no. of folders in a directory.

Justin Perez12-Mar-08 5:17

Justin Perez

12-Mar-08 5:17

Yes, you may. I have 10 fingers and 10 toes. What are you working with?

I'm going to become rich when I create a device that allows me to punch people in the face over the internet.

"If an Indian asked a programming question in the forest, would it still be urgent?" - John Simmons / outlaw programmer

Mark Salsbery12-Mar-08 5:22

Mark Salsbery

12-Mar-08 5:22

You could use FindFirstFile()/FindNextFile() and count only files with the FILE_ATTRIBUTE_DIRECTORY
attribute.

The code could be similar to this[^]

Mark

Mark Salsbery
Microsoft MVP - Visual C++
Java | [Coffee]

ptr_Electron12-Mar-08 5:59

ptr_Electron

12-Mar-08 5:59

int iCountDir=0;
BOOL bWorkingff = Finderff.FindFile("*.*");
bWorkingff = Finderff.FindNextFile();

while(bWorkingff)
{
if (Finderff.IsDirectory()==TRUE)
iCountDir++;

bWorkingff = Finderff.FindNextFile();
}

Finderff.Close()

// iCountDir --Use it now

Hamid_RT12-Mar-08 7:46

Hamid_RT

12-Mar-08 7:46

See DlgDirList.