Some opinions by Linus Torvalds regarding C++ ( ;) ):
An interviws 1998:
Many people ask why the kernel is written in C instead of C++. What is your
point against using C++ in the kernel? What is the language you like best,
excluding C?
Linus: C++ would have allowed us to use certain compiler features that I
would have liked, and it was in fact used for a very short timeperiod just
before releasing Linux-1.0. It turned out to not be very useful, and I don't
think we'll ever end up trying that again, for a few reasons.
One reason is that C++ simply is a lot more complicated, and the compiler
often does things behind the back of the programmer that aren't at all obvious
when looking at the code locally. Yes, you can avoid features like virtual
classes and avoid these things, but the point is that C++ simply allows a lot
that C doesn't allow, and that can make finding the problems later harder.
Another reason was related to the above, namely compiler speed and
stability. Because C++ is a more complex language, it also has a propensity for
a lot more compiler bugs and compiles are usually slower. This can be
considered a compiler implementation issue, but the basic complexity of C++
certainly is something that can be objectively considered to be harmful for
kernel development.
An email reply 2007:
>
> When I first looked at Git source code two things struck me as odd:
> 1. Pure C as opposed to C++. No idea why. Please don't talk about portability,
> it's BS.
*YOU* are full of bullshit.
C++ is a horrible language. It's made more horrible by the fact that a lot
of substandard programmers use it, to the point where it's much much
easier to generate total and utter crap with it. Quite frankly, even if
the choice of C were to do *nothing* but keep the C++ programmers out,
that in itself would be a huge reason to use C.
In other words: the choice of C is the only sane choice. I know Miles
Bader jokingly said "to piss you off", but it's actually true. I've come
to the conclusion that any programmer that would prefer the project to be
in C++ over C is likely a programmer that I really *would* prefer to piss
off, so that he doesn't come and screw up any project I'm involved with.
C++ leads to really really bad design choices. You invariably start using
the "nice" library features of the language like STL and Boost and other
total and utter crap, that may "help" you program, but causes:
- infinite amounts of pain when they don't work (and anybody who tells me
that STL and especially Boost are stable and portable is just so full
of BS that it's not even funny)
- inefficient abstracted programming models where two years down the road
you notice that some abstraction wasn't very efficient, but now all
your code depends on all the nice object models around it, and you
cannot fix it without rewriting your app.
In other words, the only way to do good, efficient, and system-level and
portable C++ ends up to limit yourself to all the things that are
basically available in C. And limiting your project to C means that people
don't screw that up, and also means that you get a lot of programmers that
do actually understand low-level issues and don't screw things up with any
idiotic "object model" crap.
So I'm sorry, but for something like git, where efficiency was a primary
objective, the "advantages" of C++ is just a huge mistake. The fact that
we also piss off people who cannot see that is just a big additional
advantage.
If you want a VCS that is written in C++, go play with Monotone. Really.
They use a "real database". They use "nice object-oriented libraries".
They use "nice C++ abstractions". And quite frankly, as a result of all
these design decisions that sound so appealing to some CS people, the end
result is a horrible and unmaintainable mess.
But I'm sure you'd like it more than git.
Linus
> -----Ursprungligt meddelande-----
> Från: IBM Mainframe Discussion List
> [mailto:[EMAIL PROTECTED] För Mark S. Waterbury
> Skickat: den 18 februari 2008 21:03
> Till: [email protected]
> Ämne: Re: Linux zSeries questions
>
> C++ is a low-level language comparable to C, being only slightly
> higher-level than assembler or machine language. So, there is no
> technical reason why parts of an OS kernel (even the z/OS
> nucleus) could
> not be written in C++.
>
> It is well-documented that when IBM transitioned the AS/400 from CISC
> (IMPI) to RISC (PowerPC) hardware, they re-wrote the IMPI
> HLIC and VLIC
> (Horizontal and Vertical Licensed Internal Code) in C++ for
> the PowerPC
> RISC, to create what is now called "SLIC" (System :Licensed Internal
> Code). See:
>
> http://www.research.ibm.com/journal/sj/372/schmidt.html
>
> It is possible that some parts of z/OS might now be written
> in C++, but
> I expect that the nucleus is fairly stable and so probably remains in
> PL/X or BAL.
>
> > Ted MacNEIL wrote:
> >> Now, does anybody know if C or C++ is used in the "kernal" of z/OS?
> >>
> >
> > When I first took a C++ course, I was told that it should
> not be used to write operating systems (too slow).
> > But, I would like to know if C is used in the 'kernal'.
> >
>
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