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Re: [avr-gcc-list] Initilizing complex const arrays : syntax ?

From: Jesper Hansen
Subject: Re: [avr-gcc-list] Initilizing complex const arrays : syntax ?
Date: Sun, 18 Sep 2005 20:11:37 +0200
User-agent: Mozilla Thunderbird 1.0.6 (Windows/20050716)

Your problem is probably that you _define_ the array in ui.h. You'll then get memory reserved for it twice, and the linker will throw up.
You really shouldn't do that. You can _declare_ it in the .h file,
like :

//data type for one engine parameter
struct param {
                char    desc[12];
                char    unit[4];
                char    format[6];

But the _definition_ needs to be in a C file, in your case ui.c

struct param __ATTR_PROGMEM__ param_list[] = {
        { "Engine Spd", "RPM", "%4d" },
        { "Coolant Tmp", " °C", "%3.1f" },
        { "Turbo Pres.", "Bar", "%2.1" },
        { "", "", "" },

In ui.h you can have an extern declaration to let main.c know about the array, like :

extern struct param __ATTR_PROGMEM__ param_list[];


Vincent Trouilliez wrote:
Thanks guys for the help,

I appear to have one last little problem about this :

if I do as David did, that is declare my array in main.c, then it works
fine. If I declare the array in ui.h ("ui" stands for User Interface in
my case), and include ui.h in main.c, then it's good too. However if I
do as intended, that is, create an ui.c file which will contain
functions that make use of the array defined in ui.h, well.....in this
case main.c and ui.c compile fine, but the linker will fail sadly :-/

avr-gcc -O -g -Wall -ffreestanding -mmcu=atmega32 -c main.c
avr-gcc -O -g -Wall -ffreestanding -mmcu=atmega32 -c ui.c
avr-gcc -o object.elf -O -g -Wall -ffreestanding -mmcu=atmega32
-Wl,-Map,object.elf.map -Wl,--section-start=.eeprom=00810001 main.o ui.o
ui.o(.progmem.data+0x0): multiple definition of `param_list'
main.o(.progmem.data+0x0): ~/avr/Projects/test2/main.c:3: first defined
make: *** [object.elf] Error 1

I can't make sense of the error messages.
I did notice that it does link fine, if I comment out the "include
ui.h" in ui.c, but you just all taught me the other day to always
include foo.h at the top of foo.c, when writing a module, which makes
sense since modules are compiled independently so need their .h file to
be complete. So I am lost again...



The complete test program is as follows, can't make it simpler :


#include "ui.h"

void main (void){


#include "ui.h"


#include <avr/pgmspace.h>

//data type for one engine parameter
struct param {
        char    desc[11];                       
        char    unit[4];
        char    format[6];

extern const struct param __ATTR_PROGMEM__ param_list[] = {
        { "Throttle", "  %", "%2d" },
        { "Eng. Speed", "RPM", "%4d" },
        { "M. A. T.", " °C", "%2d" },
        { "M. A. P.", "Bar", "3.2f"}

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