Microsoft_craziness.h (2018)(gist.github.com)

    DWORD required_length;
    auto rc = RegQueryValueExW(key, version, NULL, NULL, NULL, &required_length);
    if (rc != 0)  return NULL;

    DWORD length = required_length + 2;  // The +2 is for the maybe optional zero later on. Probably we are over-allocating.
    wchar_t *value = (wchar_t *)malloc(length);
    if (!value) return NULL;

    rc = RegQueryValueExW(key, version, NULL, NULL, (LPBYTE)value, &length);  // We know that version is zero-terminated...
    if (rc != 0)  return NULL;

    // The documentation says that if the string for some reason was not stored
    // with zero-termination, we need to manually terminate it. Sigh!!

    if (value[length]) {
        value[length+1] = 0;
    }