Re: Help: address vs pointer

[Tristan Gingold <gingold@adacore.com>]

On Nov 2, 2009, at 4:48 PM, Joel Brobecker wrote:

>> So what should be the type of the pc register ?  If it is a pointer  
>> to
>> instructions, 'print $pc' would be wrong as it  would be multiplied  
>> by
>> 4 (once by read_pc and once during evaluation).
>
> My not-so-educated feeling on this issue is that PC should be a  
> pointer
> to instruction.  What seems strange is that the PC value gets doubled
> twice.  I understand why during the read, but not why during the eval.
> Perhaps there is something we can do there?

I was able to work-around this issue by creating a pseudo-register  
named 'pc'.  This pseudo register
is a pointer to instruction whose value is really the program counter  
(not multiplied by 2).

Using this pseudo-register, everything work well.  So I think this is  
the simplest solution!

However it is still difficult to set a breakpoint to a 'random' address:
break *0x1234 doesn't work because 0x1234 is interpreted as an integer  
which is converted to a pointer
in the data space.
Unfortunately, break *(void (*)())0x1234 works only when addresses are  
in the lower 64KW instruction
address space (because a pointer is 16 bits).  But some AVR have 128KW/ 
256KB of instructions...
But we can still use 'break *(&func + 0x1234)' !

Tristan.