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

[Jesper Hansen]

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[];


/Jesper


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 :-/
>
> $make
> 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
> here
> 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...
>
>
> Regards,
>
>
> --
> Vince
>
>
>
> The complete test program is as follows, can't make it simpler :
>
>
> main.c
> ------
>
> #include "ui.h"
>
> void main (void){
>
> }
>
> ui.c
> ----
> #include "ui.h"
>
>
> 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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