> I have created a registry entry and want to read it through C program.
But the RegQueryValueEx() function is failing and I am not seeing any
error.
I directly get the command prompt.
Here is the code snippet:
#define REG_KEY TEXT(“Software\MyCompany\XYZ”) // XYZ is
also a key and
has a
default
value
REG_SZ in
it
HKEY hKey;
LONG lResult;
DWORD BufferSize = MAX_PATH;
DWORD dwValue, dwSize = sizeof(dwValue);
******
I consider it to be exceptionally bad style to use a comma in a
declaration, and it is very evil to mix initialized and uninitialized
declarations like this. I find this code nearly unreadablee
*****
_tprintf( _T(“\nInside delOEMInf.”) );
if((RegOpenKeyEx(HKEY_LOCAL_MACHINE,
REG_KEY,
0,
KEY_ALL_ACCESS,
&hKey)) == ERROR_SUCCESS)
{
_tprintf( _T(“\ RegOpenKeyEx OPENED”));
lResult = RegQueryValueEx(hKey, “”, NULL, NULL, (LPBYTE)&dwValue,
BufferSize);
*****
I’m surprised this even compiles! From the documentation
LONG WINAPI RegQueryValueEx(
__in HKEY hKey,
__in_opt LPCTSTR lpValueName,
__reserved lpReserved,
__ out_opt LPDWORD lpType,
__out_opt LPBYTE lpData,
__in_out_opt LPDWORD lpCbData)
There are several things wrong with your call. From a rbustness
perspective, you CANNOT set lpType to NULL, because this naively expects
that the type will be REG_DWORD. This is an unwarranted assumption, and
your world will disintegrate quickly if a fumble-fingered user with
regedit has made it something else. This actually happened to me sometime
in the late 1990s, and I NEVER assume the value type. If it is not
REG_DWORD, feel free to complain in some fashion, but do NOT assume that
it is!
Now look at the last parameter. It is SUPPOSED to be a pointer to a DWORD
that contains the maximum buffer size, and on completion, this variable
will reflect the ACTUAL buffer size used. You do not pass in an LPDWORD;
you pass in a DWORD. The compiler should complain. But let’s guess that
you had actually written &Buffersize. Then it is still wrong, because
lpData is the address of a DWORD and is certainly NOT going to be able to
accomodate MAX_PATH bytes. In fact you have just created a potential
security hole, since you ignore the type and give an absurd size; knowing
this, I could create a REG_BINARY value that could get me control in your
program. This Is Not A Pretty Sight.
In addition, I always check the size used after the call. You should set
it to sizeof(dwValue) before the call, and make sure that upon completion
it is ==sizeof(dwValue). I learned that Registry types and lengths are
never to be trusted.
And I have no idea why you used an 8-bit string literal for the name. Use
TEXT(“”) or _T(“”) or, since you want the unnamed default value, just
NULL.
As for debugging it, the very first thing you try is single-step
execution. Debug print statements are sometimes very convenient, but
there’s no substitute for seeing what’s really happening!
*****
_tprintf( _T(“\nRegQueryValueEx %d”), lResult);
RegCloseKey( hKey);
}
I get only the first printf “RegOpenKeyEx OPENED”.
The second printf does not gets printed and I see directly the command
prompt.
I am not abel to get the return value of regqueryvalueex().
What might be the issue and how to debug and resolve it?
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