Re: [avr-gcc-list] Array of pointers to functions revisited...

[Ned Konz]

On Sunday 18 July 2004 2:52 pm, Royce & Sharal Pereira wrote:
> Now when I looked at the .lss file it wasn't any fun() :)
>
> The array call_fun had anything but the addresses of fun1, fun2 etc. !!
> In the .lst file I see a   '.word pm(fun1)' instead of a '.word fun1'
> etc.(BTW What's this pm ?)
>
> The second problem is- The line-
>
> fun= pgm_read_word(call_fun[f_cnt]);
>
> does not get the desired address correctly. There is a un-necessary 'ld'
> before 'lpm' which destroys the Z reg, so that the fetched address is
> wrong(I assume you will compile my code & see the result).

Why are you all going through all of the pgm_read_word() stuff? Just good old 
C...

--------
/*
 avr-gcc -O3 -Wall -Wl,-Map,test.map -g -mtiny-stack -mint8 -mmcu=atmega16 -o 
test.elf test.c;
 avr-objdump -h -S  test.elf > test.lst

 R16/17 is call_fun
 R26 is X reg
 R28 is Y reg
 R30 is Z register
*/ 

#include <inttypes.h>
#include <avr/pgmspace.h>

static void fun1(void) { }
static void fun2(void) { }
static void fun3(void) { }

typedef void (PROGMEM * pFun)(void);

static pFun PROGMEM call_fun [3] = { &fun1, &fun2, &fun3 };

int main(void)
{
        uint8_t i;
        for (i = 0; i< 3; i++)
                (call_fun[i])();
        return 0;
}

--------

Which produces (on avr-gcc 3.4.0) the extremely straightforward:

int main(void)
{
  9a:   cf e5           ldi     r28, 0x5F       ; 95
  9c:   d4 e0           ldi     r29, 0x04       ; 4
  9e:   de bf           out     0x3e, r29       ; 62
  a0:   cd bf           out     0x3d, r28       ; 61
  a2:   c2 e0           ldi     r28, 0x02       ; 2
  a4:   04 e5           ldi     r16, 0x54       ; 84
  a6:   10 e0           ldi     r17, 0x00       ; 0
        uint8_t i;
        for (i = 0; i< 3; i++)
                (call_fun[i])();
  a8:   d8 01           movw    r26, r16
  aa:   ed 91           ld      r30, X+
  ac:   fd 91           ld      r31, X+
  ae:   8d 01           movw    r16, r26
  b0:   09 95           icall
  b2:   c1 50           subi    r28, 0x01       ; 1
  b4:   c7 ff           sbrs    r28, 7
  b6:   f8 cf           rjmp    .-16            ; 0xa8
        return 0;
}

-- 
Ned Konz
http://bike-nomad.com