I can't use RegOpenKeyEx - c++

Question

I am having problems with reading the registry.
This function finds the number of entries in a registry path. It works perfectly, I have tested it:
void findNumberEntries(registryTest &INSTALLKEY) {
char buffer[50];
char size = sizeof(buffer);
int index = 0;
if(RegOpenKeyEx(INSTALLKEY.hKey,(LPTSTR)(INSTALLKEY.regpath.c_str()),0,KEY_ALL_ACCESS,&INSTALLKEY.hKey) == ERROR_SUCCESS) {
DWORD readEntry;
do {
readEntry = RegEnumValue(INSTALLKEY.hKey,index,(LPTSTR)buffer,(LPDWORD)&size,NULL,NULL,NULL,NULL);
index++;
}
while(readEntry != ERROR_NO_MORE_ITEMS);
}
INSTALLKEY.number = index;
RegCloseKey(INSTALLKEY.hKey);
}
now, the main function:
std::string regpath32 = "SOFTWARE\\Microsoft\\Windows\\CurrentVersion\\Run\\";
struct registryTest {
HKEY hKey;
std::string regpath;
int number;
};
registryTest INSTALLKEY = {HKEY_LOCAL_MACHINE, regpath32};
findNumberEntries(INSTALLKEY);
printf("%d\n",INSTALLKEY.number);
system("PAUSE");
//until here everything works as it should
HKEY hKey = INSTALLKEY.hKey;
std::string regpath = INSTALLKEY.regpath;
char buffer[50];
char size = sizeof(buffer);
std::string bufferString;
DWORD regOpen = RegOpenKeyEx(INSTALLKEY.hKey,(LPTSTR)INSTALLKEY.regpath.c_str(),0,KEY_READ,&INSTALLKEY.hKey);
if(regOpen == ERROR_SUCCESS) //this is the part that fails.
{
printf("Registry Key was successfully opened\n");
}
else
{
printf("Unable to open registry key\n");
LPVOID message;
FormatMessage(FORMAT_MESSAGE_ALLOCATE_BUFFER | FORMAT_MESSAGE_FROM_SYSTEM | FORMAT_MESSAGE_IGNORE_INSERTS,
NULL, GetLastError(), NULL,(LPTSTR) &message, 0, NULL );
MessageBox(NULL,(LPCTSTR)message,"ERROR",MB_OK|MB_ICONINFORMATION);
}
...rest of the code
I always get "Unable to open registry" and the error message I get is "There are no more files". What is the problem??

Answer 1

your problem is that when you first open the registry key ,you assign it to hkey-member of your struct. So the second time this hkey doesn't contain the original basekey anymore.
change :
DWORD regOpen =
RegOpenKeyEx(INSTALLKEY.hKey,(LPTSTR)INSTALLKEY.regpath.c_str(),0,KEY_READ,&INSTALLKEY.hKey);
into
DWORD regOpen = RegOpenKeyEx(
HKEY_LOCAL_MACHINE
,(LPTSTR)INSTALLKEY.regpath.c_str(),0,KEY_READ,&INSTALLKEY.hKey);
or change this:
void findNumberEntries( registryTest &INSTALLKEY)
{
char buffer[50];
char size = sizeof(buffer);
int index = 0;
HKEY hkOpen = 0; // can't use INVALID_HANDLE_VALUE for HKEY's;
if (RegOpenKeyEx( INSTALLKEY.hKey ,(LPTSTR)(INSTALLKEY.regpath.c_str())
,0,&hkOpen ) == ERROR_SUCCESS)
{
// You should use RegQueryInfoKey for below code !
DWORD readEntry;
do {
readEntry = RegEnumValue( hkOpen ,index,(LPTSTR)buffer
,(LPDWORD size,NULL,NULL,NULL,NULL);
index++;
}
while(readEntry != ERROR_NO_MORE_ITEMS); }
INSTALLKEY.number = index;
RegCloseKey( hkOpen );
}

Answer 2

You may need to specify KEY_ALL_ACCESS in the second call as well, rather than just in the first. And on Win7 64-bit you may be running into the registry redirect craziness (http://msdn.microsoft.com/en-us/library/aa384232%28VS.85%29.aspx).
EDIT: ah, you might just be getting an ERROR_CANTWRITE back (error code number 5). You might be able to ignore that and see if it still works.

Answer 3

It's very likely that on Windows 7 64-bit that you are being redirected via Registry Virtualization. You can determine what keys are being redirected by calling RegQueryReflectionKey.
If you modify your code to output the actual integer value that is returned rather than a generic "Unable to open key", then it would be helpful. For example,
long n = RegOpenKeyEx(HKEY_LOCAL_MACHINE,TEXT("\\SOFTWARE"),
0,KEY_QUERY_VALUE, &hk );
if ( n == ERROR_SUCCESS ) {
cout << "OK" << endl;
}
else {
cout << "Failed with value " << n << endl;
}