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Re: ppc_linux_init_extra_frame_info
- From: Kevin Buettner <kevinb at redhat dot com>
- To: Andreas Schwab <schwab at suse dot de>, gdb-patches at sources dot redhat dot com
- Date: Thu, 20 Feb 2003 21:53:36 -0700
- Subject: Re: ppc_linux_init_extra_frame_info
- References: <m3ptpm1odr.fsf@whitebox.local>
On Feb 21, 1:14am, Andreas Schwab wrote:
> ppc_linux_init_extra_frame_info is clobbering the frame type which
> causes dummy_frame_pop to bail out. The frame type is now set before
> INIT_FRAME_INFO is called.
Not always, it would appear. In create_new_frame(), the type is
set before INIT_EXTRA_FRAME_INFO() is called. However, in
legacy_get_prev_frame(), the setting of the type occurs both
before and possibly after the call to INIT_EXTRA_FRAME_INFO().
In fact, the "after" part has me concerned. I suspect that it could
cause a signal handler's frame to be marked as a sigtramp frame.
Andrew even comments on this:
/* FIXME: cagney/2002-11-10: This should be moved to before the
INIT code above so that the INIT code knows what the frame's
type is (in fact, for a [generic] dummy-frame, the type can
be set and then the entire initialization can be skipped.
Unforunatly, its the INIT code that sets the PC (Hmm, catch
22). */
[...]
> - behavior is ever fixed.)
> -
> - PC_IN_SIGTRAMP is called from blockframe.c as well in order to set
> - the frame's type (if a SIGTRAMP_FRAME). Because of our strange
> - definition of in_sigtramp below, we can't rely on the frame's type
> - getting set correctly from within blockframe.c. This is why we
> - take pains to set it in init_extra_frame_info().
> -
> - NOTE: cagney/2002-11-10: I suspect the real problem here is that
> - the get_prev_frame() only initializes the frame's type after the
> - call to INIT_FRAME_INFO. get_prev_frame() should be fixed, this
> - code shouldn't be working its way around a bug :-(. */
> + behavior is ever fixed.) */
I'd prefer to have these comments left in place.
I don't agree with Andrew's comment BTW. My memory on this is rather
hazy, but I think that the problem is that we really want different
functions for PC_IN_SIGTRAMP as called from infrun.c vs frame.c.
If we could have the frame.c PC_IN_SIGRAMP calls call
ppc_linux_at_sigtramp_return_path() and the infrun.c calls call
ppc_linux_in_sigtramp(), things would work right. This suggests
that we really need two different methods.
(Take my current remarks with a grain of salt. It's been a while
since I've worked on this code...)
If you'd like to add you own notes to this comment block (or anywhere
else), I have no problem with that.
> int
> ppc_linux_in_sigtramp (CORE_ADDR pc, char *func_name)
> @@ -374,10 +363,6 @@ ppc_linux_init_extra_frame_info (int fro
> at trampoline code */
> if (ppc_linux_at_sigtramp_return_path (fi->pc))
> deprecated_set_frame_type (fi, SIGTRAMP_FRAME);
> - else
> - /* FIXME: cagney/2002-11-10: Is this double bogus? What
> - happens if the frame has previously been marked as a dummy? */
> - deprecated_set_frame_type (fi, NORMAL_FRAME);
> }
> }
This part is fine. (I.e, I think this part should be committed.)
Thanks,
Kevin