[riot-devel] 6LowPAN on STM32F3

Somaraju Abhinav abhinav.somaraju at tridonic.com
Sat Sep 20 01:38:02 CEST 2014


Hi Hauke,
hope you had a nice holiday and thank you for the input. I have removed oneway_malloc.c from my build paths and the malloc and free are now working fine for me. It is a bit strange but I am not able to tell for sure how this is working. It seems that there is a some standard implementation of these calls that the gnu-arm compiler knows where to find. So right now my program is working okay. I will let you know how things are going if I find out more.
Regards,
Abhinav


-----Original Message-----
From: devel on behalf of Hauke Petersen
Sent: Sat 9/20/2014 12:29 AM
To: RIOT OS kernel developers
Subject: Re: [riot-devel] 6LowPAN on STM32F3
 
Hi Abhinav,

sorry for the late reply, just came back from holidays...

You have to be careful about using dynamic memory allocation on the Arm 
Cortex-M platforms (especially the ones I ported, which include the 
discovery boards). As malloc is implemented, free does nothing. So 
switching from oneway_malloc.c to libc calls won't really bring any 
benefits at the moment. The only viable workaround is to use static 
memory and manage it yourself (-> which is what Martine is preparing as 
we speak...).

Cheers,
Hauke

On 17.09.2014 08:52, Somaraju Abhinav wrote:
>
> Thanks Martine,
>
> I have been using the oneway_malloc.c implementation and not libc! I 
> will change that now. I definitely like the idea of a static 
> implementation much better.
>
> Regards,
>
> Abhinav
>
> *From:*devel [mailto:devel-bounces at riot-os.org] *On Behalf Of *Martine 
> Lenders
> *Sent:* Mittwoch, 17. September 2014 08:50
> *To:* RIOT OS kernel developers
> *Subject:* Re: [riot-devel] 6LowPAN on STM32F3
>
> Hi,
>
> currently the reassembly buffer is implemented with libc's malloc/free 
> but my new implementation will utilize a static approach via my own 
> packet buffer implementation [1]. For your purposes I think it is ok 
> for now to use malloc/free as a workaround, but keep in mind that for 
> some boards where the libc is not offering this, there is currently 
> not even a free implementation [2].
>
> Regards,
>
> Martine
>
> [1] https://github.com/RIOT-OS/RIOT/pull/1638
>
> [2] 
> https://github.com/RIOT-OS/RIOT/blob/master/sys/oneway-malloc/include/malloc.h#L60
>
> 2014-09-17 8:43 GMT+02:00 Somaraju Abhinav 
> <abhinav.somaraju at tridonic.com <mailto:abhinav.somaraju at tridonic.com>>:
>
> Hello Martine,
>
> Thank you for the quick reply. I am trying to figure out work around 
> this problem. Do you think it makes sense for me to use the libc 
> malloc and free functions? I am a bit hesitant to include the library 
> because it might be too big and/or interfere with how the RIOT core is 
> using the syscalls.
>
> Thanks,
>
> Abhinav
>
> *From:*devel [mailto:devel-bounces at riot-os.org 
> <mailto:devel-bounces at riot-os.org>] *On Behalf Of *Martine Lenders
> *Sent:* Dienstag, 16. September 2014 17:18
> *To:* RIOT OS kernel developers
> *Subject:* Re: [riot-devel] 6LowPAN on STM32F3
>
> Hello Abhinav,
>
> I'm currently refactoring this part, so thanks for pointing that out. 
> I will look out for this.
>
> Regards,
>
> Martine
>
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