Release or Snapshot for Mission-Critical System

[Ralf Corsepius]

On Tue, 2003-01-21 at 07:34, Jason Hinze wrote:
> Hello,
> 
> I'm new to RTEMS and I'm trying to get a feel for the community's
> consensus on which version of RTEMS to use for mission-critical
> development.  I've poked around the ftp site, and perused the
> 'RTEMS Users' and 'RTEMS Snapshots' mailing lists, and I can't
> get a good idea of what the accepted best practice is.
> 
> As far as I can tell, 4.5.0 is the latest full release; but it seems to
> be 2 - 2.5 years old. 

Yep, it old and should have been replaced for long ;)

>  I see quite a bit of discussion that seems to
> indicate that people are happily using snapshots, but it also seems
> that they do encounter a fair number of early-adopter issues.
Exactly. 

Basically, the snapshots are supposed to be stable, however also serve
the purpose of sorting out issues by "mass trials".
Anyway, at present time we are slowly approaching a new release, so,
though there might be (there definitely are ;) ) a nit here and there,
the status of snapshots can be considered to be very close to the "next
release" (call it "beta-stable", if you like to).

And yes, IMO, most of the issues reported by users are "early-adopter
issues" of people not being familiar with the gnu-tools. 
As working with RTEMS often seems to be their first contact with
Unix-ish systems and cross-building, I am inclined to think most of
these problems to stem from general unfamiliarity with such systems and
the general complexity of cross-building.

> For the system we will be developing, stability is paramount.
> I'll gladly give up on features, tidiness, and such, for a proven-
> stable foundation. 
It depends on how you define "stability" and is almost impossible to
answer: 

1 Building stability.
4.5.0 is known to suffer from problems wrt. this topic. snapshots/4.6.0
should be _much_ better.

2 integration/extension (source-tree layout)-stability 
Much has changed since 4.5.0 here. If you want to "lean to community
support for assistance/bugfixes/upgrades", use 4.6.0/snapshots.

3 code-structure/API stability
Many things have changed since 4.5.0, however, essentially the APIs
should be backward compatible to 4.5.0.

4 run-time-stability
As far as RTEMS code is concerned: Many bugs have been fixed, developers
believe to have improved the code, but ... ;)

This also is highly target and tool-chain dependent - Here, only
personal experience with your own hardware will be able to tell you.

>  Once our system has been deployed, it
> will be somewhere between extremely difficult and completely
> impossible to fix any software issues.

> So, what do y'all think?  Do we use 4.5.0, the latest snapshot,
> or some known-by-many-to-be-good snapshot?
Well, at present time, I would recommend you to try the latest
snapshots. They are scheduled to converge to rtems-4.6.0 in near future.
 
Also remember, RTEMS is an OpenSource community project, so whenever you
think to have encountered a problem, you have the opportunity to share
the "mutual benefits" of "OpenSource" :-), i.e. report bugs/receive bug
reports from others, contribute bugs fixes etc.

> Also, if we use 4.5.0 or a non-current snapshot, do we want
> to use the versions of the GNU tools that were originally
> associated with that release / snapshot of RTEMS,
Yes.

>  or the latest versions of the GNU tools?
Generally no, but ...YMMV.

Basically, each new version of the gnu-tools fixes known issues with the
toolchain, but also can trigger new issues with RTEMS or suffer from
incompatibilities. (The most significant incompatibilities are
introduced from RTEMS interaction with newlib - Since 4.5.0 many files
have moved between newlib and RTEMS, so you can't expect a toolchain
which worked with older RTEMS to work with newer RTEMS versions).

Ralf