> Pretty gross, neh?  Well, file vs. func is merely a question of whether we
> stop at main or not, so I added "set backtrace-below-main" in order to let
> the user choose.  Generic vs. not is a question of dummy frames, and the
> generic versions work with non-generic dummy frames, so there's no reason
> for that distinction earlier.  It won't harm those three m68k targets (if
> they still work) to use a more comprehensive frame_chain_valid.  And the
> five more specific ones up above can be retained, since they are only
> _additional_ checks.  I'm not entirely convinced that the Interix one is
> necessary but I left it alone.
> 
> So, after this patch we have FRAME_CHAIN_VALID as a predicated function that
> only five architectures define; everything else just uses the new
> frame_chain_valid () function, which is a more general version of
> generic_func_frame_chain_valid.
> 
> I'm more confident I got the texinfo right this time :)  I tested the patch
> and the new functionality on i386-linux and arm-elf, to make sure I got the
> details of FRAME_CHAIN_VALID_P () right.
> 
> I'll look to commit this in January, if no one has any comments.  Andrew,
> would you rather this went in frame.c?  Since a purpose of that file seems
> to be moving things from blockframe.c to it...

FYI,

Much of this is superseeded by the frame overhaul - in particular the 
introduction of frame_id_unwind().  The new code doesn't even call frame 
chain valid!

Perhaphs wait for the attached [wip] to be committed and then tweak that 
to match your proposed policy (we can then just deprecate 
FRAME_CHAIN_VALID_P :-).  However, making the change in parallel 
wouldn't hurt.

Looking at my WIP, I'll need to tweak the code segment:

+  prev_frame->pc = frame_pc_unwind (next_frame);
+  if (prev_frame->pc == 0)
+    /* The allocated PREV_FRAME will be reclaimed when the frame
+       obstack is next purged.  */
+    return NULL;
+  prev_frame->type = frame_type_from_pc (prev_frame->pc);

so that it checks for where the PC resides and abort accordingly.

The attached is WIP since I still need to see it working once :-)

Andrew