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Re: [avr-libc-dev] Re: Far addresses in flash

From: Björn Haase
Subject: Re: [avr-libc-dev] Re: Far addresses in flash
Date: Thu, 2 Jun 2005 21:31:55 +0200
User-agent: KMail/1.7.1

Am Donnerstag, 2. Juni 2005 14:57 schrieb Per Arnold Blåsmo:
> Although I think it would have been best to have the possibilities to
> support 24bits pointers in avr-gcc.
> Per A.
The root of the problem, IMVHO is that what one is looking for in fact is not 
only 24 bit pointers but various distinct classes of pointers, i.e. support 
for different types of memories: Pointers to Ram (probably 16 bits wide), 
Pointers to Flash (both 16 bits and 24 bits) Pointers to EEPROM (possibly 
also in two flavours with 16 bits and 24 bits , etc.). 

Presently, IIUC, gcc has support only for one single class of pointer: The 
case for conventional C.

IMO, switching PMODE to PSImode (4-Byte integer, only partially used) is not a 
solution since it would change the width of all pointers at the same time. 
E.g. also RAM pointers and EEPROM pointers would happen to be 32 bits wide 
what is certainly not useful.

A real solution of the issue would, IMO, require that someone adds 
functionality for supporting different memory spaces within gcc's C/C++ 
front-end and gcc's mid-end.



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