There are plenty of examples of well-used operating systems (or parts of them) implemented in C++ - IOKit - the device driver subsystem of MacOSX and IOS is implemented in EC++. Then there's the eCOS RTOS - where the kernel is implemented in C++, even making use of templates.
Operating systems are traditionally awash with examples of OO concepts implemented the hard way in C. In the linux device model kobject is effectively the base-class for driver and device objects, complete with DIY v-tables and some funky arrangements implemented in macros for up and down-casting.
The Windows NT kernel has an even more deeply rooted inheritance hierarchy of kernel objects. And for all of the neigh-sayers complaining about the suitability of exception handling in kernel code, exactly such a mechanism is provided.
Traditionally, the arguments against using C++ in kernel code have been:
- Portability: availability of C++ compilers for all intended target platforms. This is not really an issue any more
- Cost of C++ language mechanisms such as RTTI and exceptions. Clearly if they were to be used, the standard implementation isn't suitable and a kernel-specific variant needs using. This is generally the driver behind the use of EC++
- Robustness of C++ APIs, and particularly the Fragile base-class problem
Undoubtedly, the use of exceptions and RAII paradigm would vastly improve kernel code quality - you only have to look at source code for BSD or linux to see the alternative - enormous amounts of error handling code implemented with gotos.
