Has anyone tried to port Mono to RTEMS

[Russell Haley]

On Tue, Jul 11, 2017 at 9:31 PM, xuelin.tian at qkmtech.com
<xuelin.tian at qkmtech.com> wrote:
> Dear Joel,
> Recently, I continue to port Mono to RTEMS.
> Porting consists of two parts, according to the Mono documents online, JIT
> engine and OS support.
> JIT part is already done, since I use ARM platform.
> And I am confuesd about OS part and how to build Mono on RTEMS.
> Could you recall any details about how to build Mono on RTEMS? Thank you.

I'm not sure that's quite right. There are really 3 parts: The
application framework, the 'JIT' (Mono Runtime, or Common Language
Runtime in Microsoft .Net) and the OS specific layer. The application
framework and the JIT are common to all platforms. The OS specific
parts are in the Mono Runtime where it translates the Interediate
Language (IL) to machine specific code at ... er ... runtime. The Mono
Runtime is being slowly replaced by the Roslyn compiler, which is open
source from Microsoft (very very cool stuff).

Building Mono requires a number of parts, including boot strapping the
build and downloading binaries from nuget (last time I did it,
anyway). I've never attempted to cross compile Mono. I would assume
you would change the make file to point to a cross compiler such as
arm-unknown-gcc (not sure about the RTEMS specifics).

In my opinion the best bet is to pull the mono repository from GitHub
and build it for your host platform first. Then you could look at
modifying it to build on arm.

That said, Mono is a dead/dying platform. Microsoft has bought
Xamarian (Mono sponsor company). Now the Mono Dev Team is slowly
porting everything over to the Microsoft .Net Core code. Once the
majority of libraries are converted, they can then write Mono specific
modules for legacy applications and then shuffle everyone over to
DotNet Core. It might be wise to look at using the DotNet Core instead
of Mono. There are a number of reasons to prefer the DotNet Core:

- Designed to be small and use a package manager to import required
external libraries. This was done with embedded systems in mind.
- Better interpreter: the new interpreters (Rosylin and the other that
I don't remember the name of) are very efficient compared to the Mono
mc.
- More efficient runtime. The Mono Runtime is known to be slow.

 Here would be a good place to start with the DotNet Core as they have
nightly arm builds.

https://stevedesmond.ca/blog/net-core-on-arm


HTH,

Russ

> ________________________________
> Best wishes,
> xuelin.tian at qkmtech.com
>
>
> From: Joel Sherrill
> Date: 2017-05-24 20:19
> To: xuelin.tian
> CC: rtems-users at rtems.org
> Subject: Re: Has anyone tried to port Mono to RTEMS
>
>
> On May 23, 2017 8:58 PM, "xuelin.tian at qkmtech.com" <xuelin.tian at qkmtech.com>
> wrote:
>
> Dear all,
> Is that possible to port Mono to RTEMS? Has anyone tried this before?
> As I notice that there is an open project in RTEMS projects.
>
>
> Sometime ago, I was asked to provide an estimate for this. It had to be
> between five and ten years ago because we were at the old office but after
> we had done a few years of GSoC. I did enough work preparing the estimate
> where I had the code building without too much effort. I saw the challenge
> as getting the test suite running since you would have to create a test
> harness and build/assembly helper that packaged the interpreted code with
> the interpreter in order to run it. At that time, I envisioned having to
> create a base image and a filesystem image per test.
>
> Our POSIX was good enough then to avoid much trouble. It should only be
> easier now since the POSIX support has improved.
>
> There were a lot of Mono tests and I expected most to pass quickly. But
> there was no way to know how many issues would be encountered and how many
> root causes there would be. I expected to fix one or two things and then run
> all the tests. That was where I expected time to be consumed.
>
> FWIW I recall the GSoC date part because they thought we could magically get
> students to do testing for free on a schedule. :)
>
> I hope that helps. It is feasible but the key is testing.
>
> --joel
>
>
> ________________________________
> Best wishes,
> xuelin.tian at qkmtech.com
>
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