Get value from registry C++ crashes - c++

Question

What's wrong? It crashes when I want to get value of AUVersion. This key exists in registry but I can't get it.
int main(int argc, char *argv[])
{
HKEY key;
if (RegOpenKey(HKEY_LOCAL_MACHINE, TEXT("SOFTWARE\\JavaSoft\\Auto Update\\"), &key) != ERROR_SUCCESS)
{
cout << "Unable to open registry key\n\n";
}
char path[1024];
DWORD value_length = 1024;
//here is the crash
RegQueryValueEx(key, "AUVersion", NULL, (LPDWORD)REG_SZ, (LPBYTE)&path, &value_length);
cout << "the value read from the registry is: " << path << endl;
system("pause");
return 0;
}

Answer 1

That fourth parameter is an LPDWORD -- a pointer to a DWORD. You took a regular integer and cast it to a pointer, which (when dereferenced) will crash.
That parameter receives the type of the registry value. Set it to NULL if you are not interested in knowing the type.

Answer 2

There are two errors with the call to RegQueryValueEx():
the type parameter is written to so must be a valid address, and this is not:
(LPDWORD)REG_SZ
and this is the probable cause of the crash.
&path should be path
Change to:
DWORD type;
RegQueryValueEx(key, "AUVersion", NULL, &type, (LPBYTE) path, &value_length);
You must check the result of RegQueryValueEx() to ensure path has been populated and subsequent code is not processing an unitialized variable:
const DWORD result = RegQueryValueEx(key,
"AUVersion",
NULL,
&type,
(LPBYTE) path,
&value_length);
// Check status of the query and ensure it was a string
// that was read.
if (ERROR_SUCCESS == result && REG_SZ == type)
{
// Success.
}