This is the mail archive of the
gdb@sources.redhat.com
mailing list for the GDB project.
Re: dwarf-frame.c question
On Thu, May 29, 2003 at 07:12:53PM -0400, Andrew Cagney wrote:
> Discussed this with AlexO (of gcc). Let us ruin your day.
>
> This problem can occure even without recursion. Consider the C snippet:
>
> foo ()
> {
> if (i)
> abort (with, lots, of parameters)
> do; normal; stuff;
> }
>
> it can be turned into:
>
> branch !i, 1:
> push with
> push lots
> push of
> push parameters
> call abort
> 1:
> do
> normal
> stuff
>
> The return address can end up pointing at the ``do'' / 1: line and
> that's CFI info is definitly not correct for unwinding from abort().
This suggests to me two things:
- that the problem is writing CFI for a trampoline which begins at the
return address. Normally that can't happen except for "magic" like
signals. So there will be an FDE which includes or ends at the return
PC.
- that there should be a DWARF-3 extension to clarify this; is anyone
interested in discussing it with the committee?
> One idea (the origins of which are unknown) is for the compiler to
> generate CFI info containing no addresses and have GDB look for that
> dependant on the PC address being obtained using return or resume
> (sigtramp, sentinel).
>
> However, first, does anyone know if the DWARF 2 spec has something to
> say abou this?
I can't see anything relevant.
--
Daniel Jacobowitz
MontaVista Software Debian GNU/Linux Developer