2006/7/11, [EMAIL PROTECTED] <[EMAIL PROTECTED]>:
Why do you all consider importing C++ code to FreeBSD kernel to be so
complicated at the beginning?
Matthias Andree wrote:
> (please don't Cc me on list replies; chopping down the Cc list)
>
> On Tue, 11 Jul 2006, [EMAIL PROTECTED] wrote:
>
>> Just as you said, C++ is more complicated than C. However, without
>> C++ exception and other advanced features, it hasn't brought much
>> complexity to C++ runtime library. Early C++ compiler even translates
>> C++ code into C code before real compilation.
>
> But what's the point of C++ if it is mutilated below minimum standard
> compliance levels so that you can no longer call it C++?
>
> This discussion has been through for other systems such as Linux long
> ago, and it wasn't lack of manpower, but lack of technical feasibility,
> or in other words, what was still useful for a kernel wasn't that much
> different from C any more. C99 already adressed several concerns of C89,
> and ISTR that FreeBSD kernels are C99 code these days.
>
>> We can judge whether a C++ feature can or cannot be imported into FreeBSD
>> kernel by assemble code generated by GNU CC.
>
> Great, make the whole kernel depend on compiler internals.
> Can you imagine a single vendor who'd have interest in hauling so many
> dependencies into their software and handle all the support? I can't.
Please complain about the portability of runtime library after reading
codes in /usr/src/contrib/libstdc++/libsupc++/.
Are they really so difficult to port?
>
> Write a C stub and put the rest into userspace where C++ works.
>
>> For example, I think C++ exception handling is really poorly suited for
>> low-level code.
>
> Which chops off one of C++'s legs to stand on.
Aside from the complexity of implementing C++ exception, in kernel, every
exception must be carefully processed. A simple exception throw may lay
memory leak and unfreed resource allocation. And outer exception catch
is difficult to help inner exception.
Even if I have no proof-of-concepts (so maybe somebody can show that
this is not fair), if we have setjmp/longjmp in the kernel we can have
a correct exception handling mechanism without not great problems.
Attilio
--
Peace can only be achieved by understanding - A. Einstein
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