Using C++ in an NDIS driver

Are NDIS drivers allowed to use C++?

The first question is easy: can NDIS drivers be written in C++?  The answer: yes.  In this case, NDIS doesn’t have any official stance on C++, so we just fall back on the WDK’s general rules.  As of Windows Driver Kit 8, Microsoft officially supports using a subset of the C++ language in drivers.  (“Subset?  What subset?”  There’s more precise information here.)

The inevitable follow-up question is more nuanced: should NDIS drivers be written in C++?  The answer is: it depends.  Here are some facts that will help you derive a more specific answer:

• The NDIS API is a C API.  There is no NDIS API that magically gets better or worse when you’re coming from C++ versus C.
• The NDIS team has no future plans to make a feature that requires C++.  We are well-aware that many of our developers are dedicated fans of C, and have strong opinions on C++.  Don't worry — C isn’t going anywhere.
• The NDIS team may, in the future, add minor conveniences that only light up in C++.  For example, the WDK macro ARRAYSIZE is defined differently for a C++ driver, which gives it better abilities to detect misuse with pointers.  NDIS.H may start adding macros that offer minor improvements for C++ code, just like WDM.H already has today.
• Several major IHVs build their production NDIS miniport drivers using C++.
• Several major IHVs build their production NDIS miniport drivers using C.
• Microsoft builds some drivers in C and some drivers in C++.
• Our NDIS sample drivers are all in C.  (This is largely for historical reasons, as these drivers were created before C++ was officially supported.  If we were creating a new sample today, we’d consider writing it in C++.)

In summary, then, either language works fine, and it all comes down to a matter of your preference.