Messages in this thread | | | Date | Tue, 09 Apr 2002 10:00:25 -0400 | From | Chris Friesen <> | Subject | Re: C++ and the kernel |
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"Richard B. Johnson" wrote: > > On Tue, 9 Apr 2002, Dr. David Alan Gilbert wrote: > > There are many places in the kernel that are actually very OO - look at > > filesystems for example. The super_operations sturcture is in effect a > > virtual function table. > > The file operations structure(s) are structures. They are not object- > oriented in any way, and they are certainly not virtual. The code that > manipulates them is quite physical and procedural, well defined, and > visible to the rest of the kernel.
I disagree. A filesystem has a certain set of semantics. There are numerous types of filesystems, each of which implements that set of semantics (and possibly additional ones as well) in a different way. This is a classic example of a situation where oo style programming can be useful. There are many cases where C code is in essence implementing virtual functions using function pointers. C++ allows the compiler to do the hard work of keeping track of the virtual functions.
> It is quite unlikely that a C++ compiler will make more efficient > code than a C compiler. In fact, the code generator will likely > be the same. The C++ compiler will end up generating some preamble > code as part of the function-calling mechanism, that is not necessary > in C. This means that it will generate a bit more code.
C++ has tigher constraints on code than C. This can allow a compiler to generate better code because it has more knowledge about what is going on.
> Making code "cleaner" is a matter of perspective. > > class A { > public: void func(char *st) { cout << st << endl; } > }; > using A::func; > A a; > a.func("Hello World!"); > > Is not all that clean. In fact, I'm not sure I have it right. It's > easier and clearer to write puts("Hello World!");
Your example is needlessly complex, and I'm sure you know this. A more realistic comparison would be:
cout << "Hello World!\n";
Now I don't for a moment think that we should go and convert everything to C++. But I do think that certain features of the language can be useful, and that there are cases when OO style programming makes the code easier to read and understand.
-- Chris Friesen | MailStop: 043/33/F10 Nortel Networks | work: (613) 765-0557 3500 Carling Avenue | fax: (613) 765-2986 Nepean, ON K2H 8E9 Canada | email: cfriesen@nortelnetworks.com - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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