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From: Florian Weimer <fweimer@redhat.com>
To: Andreas Krebbel via Gcc <gcc@gcc.gnu.org>
Subject: Re: CFI for saved argument registers
References: <7d266787-9a64-07e6-bf7b-1bd01119517c@linux.ibm.com>
Date: Mon, 16 May 2022 15:25:52 +0200
In-Reply-To: <7d266787-9a64-07e6-bf7b-1bd01119517c@linux.ibm.com> (Andreas
 Krebbel via Gcc's message of "Mon, 16 May 2022 08:29:32 +0200")
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* Andreas Krebbel via Gcc:

> For that purpose I save the argument registers to the stack as we
> would do for a variable argument lists. But this time I also provide
> the CFI to allow the unwinder to locate the save slots.  Since I never
> actually intend to restore the content there is no matching
> cfi_restore for the cfi_offset and dwarf2cfi complains about the
> traces being inconsistent because of that. I couldn't find a way to
> prevent this.
>
> The only way I see right now is adding a new reg note to invalidate
> the save information in the reg_save array in dwarf2cfi.
>
> Would this be acceptable? Is there perhaps an easier way to achieve that?

This is very interesting.  I think we should do this in glibc for abort
and __assert_fail for as many registers as possible, hopefully
preserving more information for debuggers.

Thanks,
Florian