generic q on freebsd

[Kamal Prasad]

Thanks. Why is it difficult to port the C++ runtime to the kernel? I mean what is the technological hurdle?

thanks
-kamal






On Oct 6, 2020, at 10:53 PM, Warner Losh <imp at bsdimp.com> wrote:
> 
> On Tue, Oct 6, 2020, 11:03 AM Kamal R. Prasad <kamalpr at gmail.com> wrote:
> 
>> hello,
>> 
>> i am curious if it is possible to compile c++ code inside the freebsd
>> kernel.
>> 
> 
> 
> Possible? Yes, with restrictions. Easy? No.
> 
> There are a number of restrictions on doing this. There is no C++ runtime
> support provided in stock FreeBSD. You have to write your own, or find
> someone else that has published theirs. And the code is likely to be
> compiler dependent. People have done it and talked or blogged about it.
> 
> Generally, if you don't use exceptions, templates, RTTI, expressions that
> result in the automatic allocation of objects, have large objects (> 1k) on
> the stack, etc, it may be possible. I tried it in the 90s and had to write
> just a few routines to make simple classes work, but there's a lot of
> dragons here and very little C++ code is written these days w/o reference
> to the standard libraries, which aren't present in the kernel.
> 
> Some googling turns up:
> https://github.com/adamlsd/libcpp.ko from 6 years ago
> https://lists.freebsd.org/pipermail/freebsd-arch/2018-June/019069.html has
> some details from 2 years ago about command line args you might need.
> 
> Many have tried. Few have succeeded. Those that have write all their code
> to conform to a subset of the language. Few have had success moving C++
> code for other purposes into the kernel, though if it was written using the
> proposed (but never ratified) eC++ (embedded subset), then chances are
> greater.
> 
> Good luck
> 
> Warner
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