Tamas Rudnai escreveu:
> On Tue, Oct 6, 2009 at 3:24 PM, Isaac Marino Bavaresco <
> isaacbavaresco@yahoo.com.br> wrote:
>
>   =

>> Indeed, your heap must be declared as a normal variable (big array of
>> char) so the compiler and linker locate it properly. If you just use an
>> address range you *think* is not in use then next time you link it, it
>> may be on top of some other variable.
>>
>>     =

>
> I think it is more common to declare a chunk of memory in linker script so
> that area will not be used by the linker therefore free to use. With a
> variable it could happen that the compiler thinks that it was not used and
> then the optimization chops it off...
>
>   =


Yes, you will need to change the linker-script to define an area big
enough for your heap, but you must declare also a variable so you can
take its address, initialize it, etc.
There are other approaches, usually needing knowledge of the compiler=B4s
internals (automatically defined symbols, etc). When the compiler
manufacturers provide heap management they make the compiler help/know
about it. Without this "privileged" knowledge the simplest way is to
declare it as a a big array, and it is more portable too.

> BTW: I think what Olin is trying to express is that a dynamic memory
> allocator needs an overhead plus some trouble with the memory fragmentati=
on
> so overall it is not the best choice for a small device.
>
> Tamas

I use FreeRTOS with PIC18 and dsPICs and it doesn't work without dynamic
allocation.


Best regards,

Isaac

__________________________________________________
Fa=E7a liga=E7=F5es para outros computadores com o novo Yahoo! Messenger =

http://br.beta.messenger.yahoo.com/ =

-- =

http://www.piclist.com PIC/SX FAQ & list archive
View/change your membership options at
http://mailman.mit.edu/mailman/listinfo/piclist