Re: [patch] Fix a glitch in debugging 32-bit process with 64-bit GDB.

[Daniel Jacobowitz <drow@false.org>]

On Mon, Dec 08, 2008 at 05:32:52PM -0800, Paul Pluzhnikov wrote:
> The problem is that in findvar.c:
> 
>     case LOC_ARG:
>       if (frame == NULL)
> 	return 0;
>       addr = get_frame_args_address (frame);
>       if (!addr)
> 	return 0;
>       addr += SYMBOL_VALUE (var);
>       break;
> 
> What happens if sizeof(addr) == 8 (64-bit gdb), len == 4 (32-bit target),
> get_frame_args_address() returns 0xffffbf98 (typical stack address)
> and SYMBOL_VALUE() returns -16? 
> 
> We end up with an impossible target address of 0x1ffffbf88.

Conclusion doesn't follow from example, but I think I'm just
confused...  Do you mean that SYMBOL_VALUE is -16U or -16UL, and
that's where the wrapping comes from?  But SYMBOL_VALUE is a long,
signed.  Is SYMBOL_VALUE (long) 0xfffffff0?  If that's the case then
the debug reader might be to blame.

-- 
Daniel Jacobowitz
CodeSourcery