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Re: Add frame_is_callee_p(), use in dwarf2-frame.c?
- From: Daniel Jacobowitz <drow at mvista dot com>
- To: gdb-patches at sources dot redhat dot com
- Date: Wed, 2 Jul 2003 15:12:49 -0400
- Subject: Re: Add frame_is_callee_p(), use in dwarf2-frame.c?
- References: <3F0328AF.9080706@redhat.com>
On Wed, Jul 02, 2003 at 02:47:11PM -0400, Andrew Cagney wrote:
> Hello,
>
> Following up the comment:
>
> > /* Unwind the PC.
> >
> > Note that if NEXT_FRAME is never supposed to return (i.e. a call
> > to abort), the compiler might optimize away the instruction at
> > NEXT_FRAME's return address. As a result the return address will
> > point at some random instruction, and the CFI for that
> > instruction is probably wortless to us. GCC's unwinder solves
> > this problem by substracting 1 from the return address to get an
> > address in the middle of a presumed call instruction (or the
> > instruction in the associated delay slot). This should only be
> > done for "normal" frames and not for resume-type frames (signal
> > handlers, sentinel frames, dummy frames).
> >
> > We don't do what GCC's does here (yet). It's not clear how
> > reliable the method is. There's also a problem with finding the
> > right FDE; see the comment in dwarf_frame_p. If dwarf_frame_p
> > selected this frame unwinder because it found the FDE for the
> > next function, using the adjusted return address might not yield
> > a FDE at all. The problem isn't specific to DWARF CFI; other
> > unwinders loose in similar ways. Therefore it's probably
> > acceptable to leave things slightly broken for now. */
> > fs->pc = frame_pc_unwind (next_frame);
>
>
> Given MichaelC's flurry of bugs on this, should the fix be added to 6?
>
> As for the dwarf2_frame_p test, outch! Any ideas? Change the parameter
> to ``address_in_block'', instead of a PC?
That sounds reasonable...
> Regardless, for a ``normal frame'' test, I'd like to suggest
> ``frame_is_callee_p()'' as something suitable descriptive. Thoughts?
You've leapt ahead of me again. What would frame_is_callee_p mean?
--
Daniel Jacobowitz
MontaVista Software Debian GNU/Linux Developer