Re: [avr-gcc-list] Calling function with hard coded address

[Claude Sylvain]

>
> I am trying to call functions with hard coded address as follow.
>
> typedef void (*func_type)( void );
>
> ((func_type) 0x1D400)();
>
> The problem is that the generated code is slightly different...
> (shown below)
>
> ff 95 00 ea     call    0x7fd400
>
> Compare to standard function call (shown below)
>
> 0e 94 00 ea   call   0x1d400
>
> What happened was that the upper 8 bits (bit16 to bit23 of address
> bits) are set to 1's instead of 0's.
>
> My questions are following.
>
> 1. Is this a bug?
>
> 2. is there a way to get around this?
>
> I am using avr-gcc 3.4.3 and binutil 2.15.


Hello,

I think you are right,  this is a compiler bug.

To get partially rid of that, you can do the following...


typedef void (*func_type)(void);

        ...

        func_type       pfunc   = (func_type) 0xD400;

        ...

        pfunc();

- GCC-AVR do not seem to support EICALL, so address space for
  function pointers are limited to the first 64K.
  Also EICALL does not exist on some ATMega (the ATMega128 is one
  of them).


Claude