RE: [avr-gcc-list] calling function pointers via pointers ?

[Dave Hansen]

From: Vincent Trouilliez <address@hidden>
[...]
> Problem: my function pointers are in an array, within a structure, which
> itself is accessed via pointers... oh dear.
[...]
> //data type for a menu
> struct menu {
>         .....;
>         .....;
>         int (*fp)()[];  //table to store all the pointers

Err...  Read it from the inside-out: fp is a pointer to a function that 
returns an array of pointers to int.  I don't think that works, let alone is 
what you want.  And you need to specify the size, and it's a good idea to 
specify the formal parameters needed by the function.  I think you mean 
something like

  int (*fp[3])(void);

fp is an array of 3 pointers to function taking void and returning int.

> };
>
>
> //definition for a menu
> const struct menu __ATTR_PROGMEM__ menu_foo = {
>         .....,
>         .....,
>         {fn1, fn2, ... }
> };

Note: menu_foo is PROGMEM.

> //run the specified menu using the structure passed as argument
> void menu_run(const struct menu * p)

Do you have to make p point to PROGMEM?  I'm not sure, but I do know that...
> {
>         int r;
>         .....
>         r = (p->fp[0])();    //call the first function

...this won't work if you call menu_run with &menu_foo as the parameter.  
You need to read the pointer out of PROGMEM first, then call using that:

     int (*fp)(void);
     fp = pgm_read_word(&p->fp[0]);
     fp();

Warning: untested code.  You might need a cast in there.

HTH,
  -=Dave