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Re: [avr-gcc-list] Structs in program memory.


From: E. Weddington
Subject: Re: [avr-gcc-list] Structs in program memory.
Date: Tue, 27 Apr 2004 12:25:56 -0600

On 27 Apr 2004 at 11:03, Graham Davies wrote:

> 
> New member and first post here.  I hope it's helpful or at least
> interesting.
> 
> ZiLOG's toolset (ZDS II) for the Z8 Encore!, which is also modified Harvard
> architecture, attempts to address the problem under discussion with the 
> storage
> qualifier "rom".  

<zilog toolset discussion>

It's not what the user uses, it's the implementation details that's at issue.

> Anyway, the point is it appears to be possible to put constant data in
> program memory in a modified Harvard machine and make it mostly seamless. 

That part is known.

> I say
> "mostly" because C is rather lenient when it comes to casting pointers and of
> course when you cast a pointer to program memory into a pointer to data memory
> or vice versa it's not going to work.  

That's part of the issue: keeping track of "attributes" of pointers and 
defining error conditions.

> Coming from the Z8 Encore! to the AVR, I was hoping to see something
> better than ZDS II and finding that things are actually in worse shape with 
> GCC
> is a bit of a setback.

You have to remember:  The ZDS II toolset is only for Zilog (I assume from your 
statements). GCC compiles for many, many different processor / operating system 
combinations. GCC was *never* designed, from the beginning, for Harvard 
Architecture. Hence, putting that feature in would take careful consideration 
as many other platforms could be affected.



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