[OpenIndiana-discuss] Could you update your sysroot, jclulow?

[Joshua M. Clulow]

On Sun, 17 Jan 2021 at 05:24, Peter Tribble <peter.tribble at gmail.com> wrote:
> On Sun, Jan 17, 2021 at 11:15 AM Hung Nguyen Gia via openindiana-discuss <
> openindiana-discuss at openindiana.org> wrote:
> > I wanted to use your sysroot here to build a cross compiler for OI from
> > Linux:
> >
> > https://github.com/illumos/sysroot
> >
> > But it seemed you didn't include the C++ part. I couldn't find them. There
> > is no C++ headers, e.g: cmath, iostream,... nor the C++ standard library
> > itself.
> Those are supplied by the toolchain, in our case usually gcc. And you would
> normally
> need to ensure that the versions in the sysroot are compatible (for
> whatever definition of
> compatible you're interested in) with the toolchain you're using.

Right.  The official illumos sysroot contains, as much as possible,
only things that are delivered directly from illumos-gate.  A small
exception is made for libssp and libgcc_s, after an extensive survey
was undertaken to determine if compatible versions of those libraries
were available in basically all shipping distributions.  As described
in the release notes, the copies of these libraries included within
the archive are stubs: they contain no executable code, and would not
actually _work_ if you attempted to use them on an illumos system.
They're just for cross-compilation.

Unlike libgcc_s and libssp, there aren't sufficiently strong backwards
compatibility guarantees made about any of the C++ runtimes, or
OpenSSL, or many other commonly used components.  On that basis,
they're not good candidates for an illumos sysroot.

You could, on the other hand, select a specific distribution (and
presumably a specific version) to create a different sort of sysroot.
That sysroot archive could then include anything that was guaranteed
to be available within the distribution; a process of selection that
would depend a lot on the policies of that specific distribution and
on your goals.

> > This sysroot is also a bit old, too.
> A sysroot can be used for a variety of uses. This one is targetted at
> building software on
> a current host that will still run correctly on an older system.

More specifically than that, it was built almost exclusively at the
time with Rust in mind.  The Rust project uses this sysroot archive
within a Linux docker container to cross-compile the Rust toolchain
(including Cargo, etc) for illumos.  Selecting the specific version
here was a balance between the widest possible audience (thus, the
oldest contents) and the inclusion of the getrandom(2) public API.
More details on our choice are in the release notes:

    https://github.com/illumos/sysroot/releases/tag/20181213-de6af22ae73b-v1

We will likely at some point select a new version of the gate to
create a new sysroot.  This will probably not happen until we need to
use a new interface of some kind that was added some time after
December 2018.  When we get there, it will likely _still_ seem to be
an old version -- the 20181213 sysroot was, after all, created in
April 2020.

If we were to create a new sysroot in April 2021, it may well be from
gate bits towards the end of 2019 or very early 2020.  Any newer and
it is unlikely to result in binaries that can be used on, as much as
possible, all supported distribution releases.  You can see from the
release schedule at OmniOS that some of their LTS releases are
supported for a long time, and we want the sysroot to produce binaries
that can be used there:

    https://omniosce.org/schedule

The current LTS release is r151030, which was released in May 2019 and
will be supported until May 2022.  That makes it unlikely that the
released sysroot would advance past May 2019 until 2022, unless we
could find a way around the problem.

> Generally I would expect anyone using a sysroot to have a pretty specific
> target in mind.
> It's not that hard to create, either simply copying an existing system that
> has the bits you
> want, or using packaging - pkg has the image-create functionality designed
> for exactly
> this purpose.

Yes, you could definitely use "pkg image-create" to install any set of
OpenIndiana packages into a directory tree.  This is, as it happens,
basically what the Distribution Constructor does today to create the
install media.  The OmniOS folks also use this approach to build cloud
images in their Kayak tools.

You could also use the tools we included in the "illumos/sysroot"
repository, with minor configuration or modification, to make your own
sysroot from any built copy of illumos.


Cheers.

-- 
Joshua M. Clulow
http://blog.sysmgr.org