Re: [Caml-list] Ocaml on RaspberryPi bare-metal crashes

[David Scott <scott.dj@gmail.com>]

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Hi,

On Mon, Nov 4, 2013 at 8:38 PM, Goswin von Brederlow <goswin-v-b@web.de>wrote:
...

> 1) doing some kind of output (print_string or Printf.printf) uses
> floating point stuff. I didn't have the FPU enabled yet so that threw
> and undefined exception. Not sure if the float is used somewhere in
> the IO layer or if that triggers something in the GC that uses floats.
> Might not even be IO related at all but caused by allocating a heap
> value. The simple tests that succeeded before all only used stack.
>

FWIW the port of mirage to kFreeBSD (where the ocaml program runs as a
kernel module) hit a similar issue with floats. The workaround was to
replace the floats with a fixed-point implementation:

https://lists.cam.ac.uk/pipermail/cl-mirage/2012-August/msg00012.html

https://lists.cam.ac.uk/pipermail/cl-mirage/2013-September/msg00013.html



> 2) malloc() needs to return 8 byte aligned blocks or storing 64bit
> values fails. Doing output initializes the stdout channel, which calls
> lseek64 and stores the resultint int64_t.
>
>
> So now I have ocaml running barebone on my RaspberryPi in a verry
> minimal way.
>

Nice!


> ToDo:
> - LED module (turn on/off the OK LED)
> - Framebuffer / Graphics modules
> - Timer module
> - implement free()
> - Threads
> - USB module
>   + keyboard
>   + mouse
>   + ethernet
> - tcp/ip stack
>

I'm not sure how difficult USB will be, but once packets start flowing over
the network interface you should be able to use the mirage TCP/IP stack.


> - audio
> - GPIO module
>
> If anyone is interested I can upload what I have so far to github. But
> beware it is verry much a WIP.
>

I'd be interested in checking it out! :-)

Cheers,
Dave

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