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Re: [avr-gcc-list] forcing address

From: Marlin Unruh
Subject: Re: [avr-gcc-list] forcing address
Date: Tue, 20 Aug 2002 07:55:21 -0600

Hi J"org,

Ten years ago I wrote some assembly language for the Motorola
MC68HC11 and we are still selling that product. But anyway, it must
have been an absolute assembler.  The code was passed thru a
linker. Using the org "origin" directive the code was placed where
you wanted it. I thought maybe the compiler had way to pass info to
the linker, and the linker would pack the code and place it at a given
location. But, I understand what you are saying.  It is as it is.

Where could I get a list of the directives for the GCC assembler?

Thank you for you reply.

At 02:08 PM 8/19/2002 +0200, you wrote:
Marlin Unruh <address@hidden> wrote:

> I am writing an assembly file to include some time, and sequence
> sensitive code. I have a lookup table that I defined in the .s
> file. I cannot get the compiler to place the lookup table at a given
> location.

Sure.  This is a linker issue, and usually, in an environment that
uses compilation that results in relocatable object files, you cannot
arbitrarily place your code at predetermined locations.  This is only
possible when using absolute assembly.  (Even in the old days of the
Z80, it was common to use relocatable assembly, and have the linker
put all the pieces into place.)

Using linker directives, you can tell the linker at which address to
place the beginning of your program.

How else would you expect the whole thing to work?  Say, you want some
particular piece of code at address 0x100, but the startup code starts
at 0x0.  How should the compiler be told that there are some XXX bytes
free between the startup code and your code at 0x100 (that could be
filled by the compiler)?

J"org Wunsch                                           Unix support engineer
address@hidden        http://www.interface-systems.de/~j/
avr-gcc-list at http://avr1.org

avr-gcc-list at http://avr1.org

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