RegOpenKeyEx return ERROR_SUCCESS but it shouldn't (windows 7)

I've got a problem about RegOpenKeyEx, the code:

#include <tchar.h>
#include <stdio.h>
#include <windows.h>

#pragma comment (lib, "Advapi32.lib")


int main () {
    TCHAR *keyName = _T("SOFTWARE\\foobar2000\\capabilities");
    HKEY key = NULL;
    if (RegOpenKeyEx(HKEY_LOCAL_MACHINE, keyName, 0, KEY_ALL_ACCESS, &key) != ERROR_SUCCESS) {
        printf("open key failed!\n");
        return -1;
    } else {
            printf("open key success!\n");
    }

    TCHAR *value = _T("123");
    if (RegSetValueEx(key, _T("xxx"), 0, REG_SZ,
     开发者_开发知识库       (const BYTE *)value, sizeof(TCHAR) * (_tcslen(value) + 1)) != ERROR_SUCCESS) {
        printf("set value failed!\n");
    }
    RegCloseKey(key);
    return 0;
}

Save the code in such as reg.cpp, and in command mode:

cl reg.cpp

and I got reg.exe, run it:

D:\tmp>reg.exe

open key success!

But the value hasn't been written in the registry.

Another strange thing is that if I use the visual studio to create a CLI project, and paste the code into main(), the RegOpenKeyEx() will return false.

The platform is windows 7, and UAC is enabled.

Sounds like you're running into virtualization. IF the app has no manifest, when you try to write to HKLM\Software it actually writes to HKEY_USERS\<User SID>_Classes\VirtualStore\Machine\Software. To prevent this, you can run the app elevated. You might want to add a manifest forcing it to run elevated every time. Alternatively, stop writing to HKLM and use HKCU instead.

As for the C++/CLI part, my guess would be you are given an asInvoker manifest for that one, which suppresses virtualization and results in the attempt to get to HKLM failing.