Date: Tue, 6 Oct 2020 11:23:01 -0600 From: Warner Losh <imp@bsdimp.com> To: kamalp@acm.org Cc: "freebsd-arm@freebsd.org" <freebsd-arm@freebsd.org> Subject: Re: generic q on freebsd Message-ID: <CANCZdfoaZYnsb6str64ezF0O4ORSQG%2BqMh9r0%2B42GqEQjBThOg@mail.gmail.com> In-Reply-To: <CAK=yUGJG=oVfy7XfnMkXB6XRBjbYhaVR8Zdv7R5wGqKjB=425Q@mail.gmail.com> References: <CAK=yUGJG=oVfy7XfnMkXB6XRBjbYhaVR8Zdv7R5wGqKjB=425Q@mail.gmail.com>
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On Tue, Oct 6, 2020, 11:03 AM Kamal R. Prasad <kamalpr@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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