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Re: AW: AW: [avr-gcc-list] Compiler error

From: Julius Luukko
Subject: Re: AW: AW: [avr-gcc-list] Compiler error
Date: Wed, 1 Jun 2005 09:01:24 +0300
User-agent: KMail/1.6.2

On Tuesday 31 May 2005 18:34, Jeff Barlow wrote:
> "Haase Bjoern (PT-BEU/EMT) *" <address@hidden>  wrote:
> >IIUC, Marek is trying hard to keep working with 2-Byte pointers by
> > introducing jump stubs in the lower 64k memory for functions residing in
> > > 128k memory. So there will most probably never be need for 3-Byte
> > pointers.
> Keep in mind that it is common for RTOS task schedulers to save
> pointers to arbitrary locations in the code. Jump stubs will
> never work for that.

But at least with uC/OS-II (with avr-gcc port) the program counter is not 
directly manipulated. The processor stacks the PC before the actual context 
switch, and ret or reti instruction pops it. uC/OS-II only needs to know the 
starting address of tasks for initializing task stacks, for which 2-byte 
pointers and jump stubs should work. I assume that other schedulers work 
simularly, not directly manipulating PC.


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