>>If efficiency is not a prime concern, using C++ is hardly justified.
Well, yes and no. Yes, I agree with you as C++ gives you more control than most other high level languages out there, e.g. more control over how you manage your memory. I can hardly imagine someone writing kernel in managed languages, like, Java.
No, I don't agree with you because sometimes, when very low-level aspects of machine also become prime efficiency concern, using C++ is hardly justified. See my point about C++ not forcing any abstractions on you, given at the end.
It reminds me what someone once half-jokingly said about C and assembly: "C gives you all the power of assembly language with the same ease of use".
In the kernel world, it becomes a joke, as the level of abstraction provided by C is very high as compared to the one provided by assembly language (e.g. mainly due to struct, union and cleaner subroutine syntax) and the cost of this abstraction is extremely low.
The benefits of using C are tremendous: e.g. code portability and readability.
>>Nor does C++.
Yes, but when you don't use any non-c abstraction provided by C then it reduces, almost entirely, to C (barring templates).
Templates are extremely good mechanism to provide abstraction (especially as compared to inheritance) but their cost (e.g. cost in terms of code bloat and in terms of the cognitive load if one actually wants to dig deeper and see/tweak the generated code to investigate/address some performance issues) seems prohibitive at least in the performance sensitive kernel programming.
The kernel hackers have found a neat-but-not-so-neat way around it: by using C macros. Macros are in fact C's templates. I am not saying macros lead to cleaner code and so on but when you compare them to C++ templates, their cost-benefit equation in the kernel programming world seems justifiable.
>>and that's perfectly fine, if one feels more productive in a certain language, more power to him, but please let's not spread FUD.
I agree with you whole heartedly about one's choice of language. I personally would have chosen C++ and even Python over C to implement an application like git or its parts.
Not to play advocate for Linus here (he doesn't need a half-witted advocate like me), but he seemed to be spreading FUD about C++ because, supposing C++ were allowed, he seems to feel that many people will start using its abstractions without being aware of their costs. It's very easy to get tempted to use available abstractions and if the abstractions start leaking (as he pointed out) then fixing the code that relied on those abstractions becomes a difficult issue.