Re: [6.2] PROBLEMS file

H. J. Lu
2004-07-22T21:33:31Z

On Thu, Jul 22, 2004 at 10:51:48PM +0200, Mark Kettenis wrote:
> Date: Wed, 21 Jul 2004 14:16:32 -0700
> From: "H. J. Lu" <hjl@lucon.org>
>
> FYI, the i386 psABI, which is also used by the x86-64 psABI, says:
>
> %ebp The content of this register is unspecified at process
> initialization time, but the user code should mark the
> deepest stack frame by setting the frame pointer to zero.
> No other frame's %ebp should have a zero value.
>
> Which contradicts the optional nature of %ebp as a frame pointer. So
> the standard contradicts itself. Anyway, in practice the %ebp == 0
> condition is useless.

Not at all. Standard is quite clear to me. According to i386 psABI,
%ebp has to be preserved for the caller. If the first instruction of a
function in an ABI compliant application is to clear %ebp, it must be
marking the deepest stack frame.

But I can be convinced if you can show me an example otherwise.

H.J.