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Re: Help: address vs pointer
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.