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Re: AW: AW: AW: [avr-gcc-list] Using current avr-gcc for target ATmega25

From: Bernard Fouché
Subject: Re: AW: AW: AW: [avr-gcc-list] Using current avr-gcc for target ATmega2561
Date: Tue, 04 Oct 2005 12:29:39 +0200
User-agent: Mozilla Thunderbird 1.0.2 (Windows/20050317)

Haase Bjoern (PT-BEU/EMT) * wrote:

After reading your message I conclude that you will probably not be having any 
problem unless that you are planing to use pointers to functions in your 
bootloader code. The jump stubs will be used *only* in case that you are using 
a function pointer because this way, we could stick to 2-byte function pointers.
The second restriction for your boot-loader code would probably be that you 
must disable table jump instructions by the appropriate compiler switch because 
these address tables usually do not end up in the bootloader section. This, 
however, probably is a restriction that applies already now.

I think that pointers to functions must not happen often in bootloaders so that would be fine. I did not encounter yet problems with table jumps in bootloaders so I can't say if it is because the compiler never built/used a table jump for switch/case in one of my bootloaders (probably the case) or if table jumps already works (it should since I'm using only atmega128 at the moment).

Now where will it be possible to document these requirements? It could be tricky for someone to discover such problems. What about having some kind of 'application notes' provided with avr-libc documentation?


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