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[avr-gcc-list] Initialized data and > 64k program

From: Massimo Medini
Subject: [avr-gcc-list] Initialized data and > 64k program
Date: Fri, 14 Feb 2003 10:43:26 +0100

Hello to everyone.
I don't know if this is pertinent, but I have a curious problem.
Some routines are working fine on an ATMega103, at least until I use less
than 64 kbytes of Flash memory.
They stop to work when I approach the 64 kbytes barrier.
The first try was to use the latest version of avr-gcc, hoping in an already
corrected bug. The latest version had exactly the same result.
So, I didn't switch to the latest version and keep investigating with
version 2.95.2 , which I know better.
After some debug, mainly using an hardware output to track when
the program stops, I found that the problem occurred in a function.
To be concise, consider a code like the following:

unsigned int QQ_SP[MAX_TASK];

.... more data ....

void TaskDoMultiTasking(void)


    int i;

    for( i=0; i<MAX_TASK; i++)


        if( TaskState[i].State==TASK_ACTIVE )



        QQ_ActiveSP=QQ_SP[i];  <-- this will be the problem




it translates in the following assembly portions:

126 .section .data

127 .LC0:

128 0002 0100 .word 1

129 .LC1:

130 0004 0000 .word QQ_SP

131 .section .text


149 00c6 E090 lds r14,.LC1

149 0000

150 00ca F090 lds r15,(.LC1)+1


Following the code in the AVR Studio, the hidden (not explicitily requested) variable .LC1 holds

NULL when the program tries to load the address of the array QQ_SP.

I followed the program also in the startup, and I have that (in the simulation) the address of

.LC1 is filled by zero right when the runtime initializes the data in SRAM. Other data are normally filled

with the correct values. It seems that only the hidden variables like .LC0 are affected.

It could help to know that no one of the arrays use Flash memory past of a few kylobyte.

Only the code is crossing the 64 kbyte boundary.

Thanks to everyone who could help.

Massimo Medini


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