Re: Certified C compilers for safety-critical embedded systems

[iddw@hotmail.com (Dave Hansen)]

On Wed, 24 Dec 2003 20:41:41 +0000, Chris Hills <chris@phaedsys.org>
wrote:

>In article <3fe9f0d7.104475725@News.CIS.DFN.DE>, Dave Hansen
><iddw@hotmail.com> writes
[...]
>>The AVR is supported by GCC,
>GCC is not usually suitable for 8 and 16 bit embedded systems. IT is a
>generic compiler system that is not usually a patch onthe commercial
>ones.. 

Avr-gcc actually generates _very_ nice code for the AVR, better than
one commercial compiler I use, and comparable with another.  Of
course, unlike the 8051, the AVR was developed with HLL (esp. C) in
mind.  For example, it has 32 general-purpose registers.

[...re: 8051...]
>>though there is a Modula-2
>>compiler.
>
>But is it any good? 

You'd have to ask Mr. Granville.  Though I think I know what he'd say.
;-)

But as a datapoint, it was able to come within one instruction of my
handwritten assembly on a pathological checksum routine I posted back
in January of 1999 (seven instructions vs. six).  The Keil C compiler
I was usingat the time (v5.5 IIRC) was unable to do better than 13,
even when using the intrinsics for byte rotation and testing the carry
bit.

So from what little I've seen, I'd say it looks quite good.

>
>I once had to work on an embedded system using Mod2 a none of the
>compilers supported the basic language in the same way.  Let alone
>extensions.  It turned out that the most stable compiler was the least
>standard :-( 
>
>A theoretically good language is no use at all if the compiler
>implementations are no good. 

Fewer implementations implies fewer good implementations, true.  At
least the odds are reduced.  Fewer targetted platforms means your code
is less portable as well.

>
>At least with C there will usually be several commercial compilers and a
>multitude of testing and checking tools.  

I think I said it earlier in this thread: The only processors I'm
aware of that don't have a C or NQC (Not Quite C) compiler are
four-bitters.  It's ubiquitous.

But C can be, umm, subtle, and static checking tools (particularly
Lint) are IMHO _required_.  Sadly, they're not often used.

>
>It's one thing having a compiler but what about the rest. How many ICE
>support ADA? 

Nit: ICE is hardware.  And the various debuggers I've seen shipped
with most ICE systems don't support C particularly well either.

And I haven't used an ICE in years.  

Regards,

                               -=Dave
-- 
Change is inevitable, progress is not.