C++ uninitialized local variable

Question

I have a function:

VOID GetOSVersion(PDWORD major, PDWORD minor, PDWORD build)
{
    OSVERSIONINFO osver;
    ZeroMemory(&osver, sizeof(OSVERSIONINFO));
         


        

Answer 1

You probably meant to have your variable declarations and to call your function like this

DWORD major;
DWORD minor;
DWORD build;
GetOSVersion(&major, &minor, &build);

You use pointers to reference the output parameters, thus these need to point them to valid memory addresses. You can refer to those variables to get a valid pointer using the 'address-of' (&) operator as shown above.

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With c++ you can use by reference parameters, which will make things a bit clearer

VOID GetOSVersion(DWORD& major, DWORD& minor, DWORD& build) {
    OSVERSIONINFO osver;
    ZeroMemory(&osver, sizeof(OSVERSIONINFO));
    osver.dwOSVersionInfoSize = sizeof(OSVERSIONINFO);
    GetVersionEx(&osver);
    // Note there's no check needed if the pointers are valid!
    major = osver.dwMajorVersion;
    minor = osver.dwMinorVersion;
    build = osver.dwBuildNumber;
}

DWORD major;
DWORD minor;
DWORD build;
GetOSVersion(major, minor, build);

No need to call the new() allocator (and bother with correct dynamic memory allocation management) with any of the above samples in 1st place.