C++ in the kernel?

Eitan Adler lists at eitanadler.com
Fri Jun 29 08:00:26 UTC 2018

This was the contents of a conversation on a different list. Figured
it was more appropriate here:

>> We are experimenting with a C++ library for systems programming and are interested in trying it in the FreeBSD kernel.  Has anyone managed to run C++ code in the kernel before and perhaps have patches to make the kernel headers somewhat less C++-hostile that they’d be willing to share?

>> A friend gave a WIP talk at BSDCan a few years ago doing this very thing.  You can find his work at https://github.com/adamlsd/libcpp.ko

>> I believe few times I've seen this discussion over the years the main concerns raised were uncertainty about handling of exceptions and also lack of the real stable ABI for the C++. Each compiler seems to have its own conventions, which might vary even between compiler revisions. https://youtu.be/JPQWQfDhICA?t=51m55s What might be possible, however, is to have particular C++ "runtime" as a module itself, which is then would be used by the other modules that are compiled with that particular C++ compiler.

>> Most kernels that use C++ require -fno-rtti -fno-exceptions, so don’t rely on a runtime.  The ABI concerns were a problem 20 years ago, but *NIX systems have kept the same C++ ABI since everyone[1] adopted the Itanium ABI.  [1] Well, almost everyone.  AArch32 has a slightly different ABI, but it has also been stable for a similar length of time.

>> Thanks, the include directory of that repo looks to be exactly what I need to get the subset of libc++ that I need working.

Eitan Adler

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