Porting Erlang

[Mark Scandariato]

Kent Boortz wrote:
> 
> > Does anyone have any pointers on what it would take to port Erlang
> > to VRTX? (http://www.mentor.com/embedded/vrtxos/index.html)
> >
> > The target system would be an MPC850 running VRTX and it would have
> > only a boot flash - though a ram disk filesystem could be created
> > from the flash image if needed.
> 
> I don't think there is anything written about porting Erlang to a new
> embedded target. There have been prototype ports to some embedded
> operating systems. The only supported embedded port is VxWorks.
> 
> Erlang/OTP is a bit POSIX/Unix oriented but it is possible to port it
> to a non POSIX OS as well, only a bit harder. The Window port shows it
> can be done.
> 
> Some comments:
> 
>   - VRTX seem to have a POSIX library and a complete TCP/IP stack so
>     the libraries needed are probably there. Erlang put some high
>     demands on the socket library so if there are some strange bugs in
>     VRTX TCP/IP stack, especially with non blocking I/O, then you will
>     probably run into it.
> 
>   - All C files, except "beam_emu.c", should compile with any ANSI C
>     compiler. We compile "beam_emu.c" with GCC to use a special GCC
>     feature that makes the decoding of the Erlang virtual instructions
>     twice as fast.  But you should be able to compile without GCC if
>     you define the preprocessor symbol NO_JUMP_TABLE. You define it by
>     running make like
> 
>         % gmake TYPE_FLAGS="-g -O2 -DNO_JUMP_TABLE"
> 
>     Also note that "beam_emu.c" contains a huge switch statement,
>     your C compiler or your machine setup may not be able to handle
>     it. If not, try disabling the optimizations first, "-O1" or
>     even "-O0" but this will of cause reduce the speed even more.
>     I think it is possible to use GCC for compiling to a VRTX target
>     but haven't found any real prof of this.
> 
>   - I assume you have to cross compile. The usual configure script
>     does not handle this. Look at the VxWork specific files and
>     do something similar.
> 
>   - The Erlang distribution, i.e. how Erlang nodes communicate,
>     normally use TCP/IP. But you can write your own driver and enable
>     Erlang nodes to use the native message passing in VRTX. I don't
>     know how much work this is but the process is documented.
> 
> kent

Thanks for the pointers. I'm also evaluating LynxOS (http://www.lynuxworks.com/products/whatislos.html) which appears to be much more POSIX/Unix flavored than VRTX and VxWorks, and fully supports the GNU toolchain.

VRTX & LynxOS have very similar features - the biggest of which are memory protection, deterministic behavior, and interruptable system calls - that VxWorks doesn't.

Mark.