Re: Dwarf unwinder problems with store.exp and preserved regs

Richard Henderson
2003-07-02T19:11:00Z

On Tue, Jul 01, 2003 at 05:44:30PM -0400, Daniel Jacobowitz wrote:
> However, GCC only emits information about the CFA, not about the default
> saved-ness of registers. So we get:
>
> 168 /* Initialize newly allocated registers. */
> 169 memset (rs->reg + rs->num_regs, 0, (num_regs - rs->num_regs) * size);
>
> And 0 is UNDEFINED. So $ebx - a call-saved register on i386 - shows up as
> undefined.

I think this is your bug.

> - Fix GCC. I -believe-, from reading the spec, that GCC is to blame for
> not emiting this information.

No, what GCC doesn't provide is clobber information. It *does*
provide save information. GDB should be assuming the register
is valid in the previous frame unless it sees DW_CFA_undefined.

Leastwise, that's certainly what gcc's frame unwinder assumes,
and I don't see anything that contradicts this in the standard.

r~