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

Daniel Jacobowitz
2003-07-02T21:39:06Z

On Wed, Jul 02, 2003 at 02:33:11PM -0700, Richard Henderson wrote:
> On Wed, Jul 02, 2003 at 03:19:07PM -0400, Daniel Jacobowitz wrote:
> > So if the initial row assumes all registers are valid, we'd print out a
> > value in the caller's $eax incorrectly.
>
> Ok, so? Except you forget that variables that are live across
> that call are either (1) in call saved registers or (2) on the
> stack. So I don't see that the problem will actually affect
> folk debugging real programs.
>
> The only time you get a false positive is when the variable is
> dead at the call site. And the results you get there will be
> no different than when the variable is dead and the register
> gets re-used /in the same function/ without location expressions
> to note the exact time of death.

We'll have that information someday... but I see your point.

> The best argument, IMO, is that if you switch the default from
> undefined to samevalue, then you'll get useful information some
> of the time as opposed to none of the time.

That's good enough for me.