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Re: [avr-gcc-list] Pointer to a function in a structure in flash?

From: Theodore A. Roth
Subject: Re: [avr-gcc-list] Pointer to a function in a structure in flash?
Date: Tue, 28 Oct 2003 08:50:28 -0800 (PST)

On Tue, 28 Oct 2003, Bob Paddock wrote:

> On Mon, 27 Oct 2003 22:20:30 GMT, E.Weddington <address@hidden> wrote:
> >>  #if defined( __GCC_VERSION__ )
> >>     retval =
> >>     (*((functype_t)(pgm_read_word(&cmd_func_table[i].function))))(
> >>         (char const *)token,
> >>         (char const *)tokptr);
> >>  #endif


> I tried that and the system goes off to never-never-land, what I have
> above works, below does not (I did change [0] to [i] as required).
> > #if defined( __GCC_VERSION__ )
> > retval = cmd_func_table[0].function((CONST char *) token,
> > (CONST char *) tokptr);
> > #endif

I don't think this second version is ever reading the function pointer
from program space which is why is goes to never-never-land.  It
should probably look something like this:

#if defined( __GCC_VERSION__ )
  functype_t func = (functype_t)pgm_read_word(&cmd_func_table[i].function);
  retval = func ((CONST char *) token, (CONST char *) tokptr);

The code that Eric posted yesterday had the same problem. If you look
at the assembly listing, there was no LPM insn to pull the function
from program space.

Ted Roth

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