Issue with strcpy [modified]

[capricious_001]

Hi guys, I have a function where I am passing a value by reference. Below is the prototype:

bool retrieveLogFileLocation(LPSTR&);

Now within the body of the function definition I have the following function as well.

bool retrieveLogFileLocation(LPSTR& value){
char[255] lszValue;
HKEY hKey;
LONG returnStatus;
DWORD dwType = REG_SZ;
DWORD dwSize =255;
bool success = true;

RegQueryValueEx(hKey, "InstallationPath", NULL, &dwType, (LPBYTE)&lszValue, &dwSize);

strcpy(value, lszValue);

}

The problem I am receiving is that whenever my program runs, it crashes instantly, and I know for sure it is an issue with strcpy(value, lszValue). I have tried in multiple ways through type-casting and such to resolve the issue, but I'm perplexed as to whats causing the problem. Any help would be appreciated :D Robbie -- modified at 4:53 Monday 19th June, 2006 PS: I only included bits and pieces of the function definition simply because the actual function definition is very long. :P

[Laxman Auti]

capricious_001 wrote:

Any help would be appreciated

May be the length of the receiving string variable is short as compared to the data you tring to copy into it. Knock out 't' from can't, You can if you think you can :cool:

[Weiye Chen]

Is there really a need to pass by reference cos i think it can work without it.

[capricious_001]

hmm I didnt initialize the length of the referenced value variable to a certain length. Actually I dont quite understand what you mean lol. Robbie

[_AnsHUMAN_]

It's a problem with RegQueryValue(IMHO). You are not opening the registry before modifying it. Handle to an open key. The key must have been opened with the KEY_QUERY_VALUE access right. This handle is returned by the RegCreateKeyEx or RegOpenKeyEx function, or it can be one of the following predefined keys: HKEY_CLASSES_ROOT HKEY_CURRENT_CONFIG HKEY_CURRENT_USER HKEY_LOCAL_MACHINE HKEY_PERFORMANCE_DATA HKEY_PERFORMANCE_NLSTEXT HKEY_PERFORMANCE_TEXT HKEY_USERS Somethings seem HARD to do, until we know how to do them. ;-) _AnShUmAn_

[capricious_001]

Ya I created a handle to the open key and all of that is fine (closed the handle appropriately etc). Its just with the strcpy that I'm having the problems with. As well, either by passing via reference or returning LPSTR value, I am still receiving the same unhandled exception error. It still crashes when my program is loaded.

[Kevin McFarlane]

An alternative way of doing this is to use a string class, e.g., CString. Here's some old code I dug out - look at the last if block - RegQueryValueEx call...

// Retrieves Operator Console ID from "SOFTWARE\Cegelec AEG\CMS\Operator Console" subkey in registry
// Looks for a value name called, e.g., "ID". May return something like "IB101"

long OcipsAutoInterface::GetConsoleIDEx(LPCTSTR pszValueName, CString& strValueData)
{
HKEY hkOperatorConsole;
long nResult; // return value - ERROR_SUCCESS or some value indicating failure
unsigned long nSize;

// Open subkey to Operator Console

CString strSubKey;
strSubKey.LoadString( IDS\_OP\_CONSOLE\_SUBKEY ); //e.g., "SOFTWARE\\Cegelec AEG\\CMS\\Operator Console "

nResult = ::RegOpenKeyEx( HKEY\_LOCAL\_MACHINE, 
						  LPCTSTR( strSubKey ),
						  0, 
						  KEY\_EXECUTE, // Permission for read access
						  &hkOperatorConsole );

if ( ERROR\_SUCCESS == nResult )
{
	// Search for value name and get size of value data
	nResult = ::RegQueryValueEx( hkOperatorConsole, pszValueName, NULL, NULL, NULL, &nSize );
	
	if ( ERROR\_SUCCESS == nResult )
	{
		// Retrieve value data
		
		// ...first return a writeable buffer for the data
		LPTSTR pszValueData = strValueData.GetBuffer( nSize );

		//...then get the data
		nResult = ::RegQueryValueEx ( hkOperatorConsole, pszValueName, NULL, NULL, LPBYTE( pszValueData ), &nSize );
		strValueData = pszValueData;
	}
}

VERIFY( ERROR\_SUCCESS == ::RegCloseKey( hkOperatorConsole ) );

return nResult;

} // End GetConsoleIDEx()

Kevin

[capricious_001]

There isnt any other way? Because there is a lot of code I have to change if I change the type of that one variable. I'd prefer keeping value as a LPSTR type.

[Weiye Chen]

I just did a test using your code(with some modifications in bold) except without the reference and it works fine.:

void somefunc()
{
   char cBuffer[400];
   retrieveLogFileLocation(cBuffer);
}

bool retrieveLogFileLocation(LPSTR value)
{
    char lszValue[255];
    HKEY hKey = HKEY_LOCAL_MACHINE;
    LONG returnStatus;
    DWORD dwType = REG_SZ;
    DWORD dwSize =255;
    bool success = true;

RegQueryValueEx(hKey, "InstallationPath", NULL, &dwType, (LPBYTE)&lszValue, &dwSize);

strcpy(value, lszValue);

return true;
}

I set hKey just for testing purposes. It could be a problem with your key.

Last modified: Monday, June 19, 2006 4:57:58 AM --

[Kevin McFarlane]

Well, in that case, as Laxman says, you need to carefully check the sizes of your source and destination buffers. For future code though I recommend using string objects (string or CString) instead of C-style strings. You'll have fewer problems of this sort. Kevin

[David Crow]

_AnShUmAn_ wrote:

You are not opening the registry before modifying it.

While it's true that the registry key must be opened prior to use, it's certainly not being modified.

---

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

"Judge not by the eye but by the heart." - Native American Proverb

[David Crow]

capricious_001 wrote:

bool retrieveLogFileLocation(LPSTR& value){

What is the size of the variable that value refers to?

capricious_001 wrote:

char[255] lszValue;

What's this?

capricious_001 wrote:

RegQueryValueEx(hKey, "InstallationPath", NULL, &dwType, (LPBYTE)&lszValue, &dwSize);

What does RegQueryValueEx() return?

capricious_001 wrote:

strcpy(value, lszValue);

Use strncpy() instead.

---

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

"Judge not by the eye but by the heart." - Native American Proverb