From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <sourceware-bugzilla@sourceware.org>
Received: by sourceware.org (Postfix, from userid 48)
	id 347C63858002; Thu, 29 Feb 2024 19:39:32 +0000 (GMT)
DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org 347C63858002
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=sourceware.org;
	s=default; t=1709235572;
	bh=lAxpsaLDMmips2bTNRpWILl0/LpMHSgcVB6cvePxrR8=;
	h=From:To:Subject:Date:In-Reply-To:References:From;
	b=Mm6qtIrFaoDDdnmdA1sMWCxzfa9lbB5UfYfOrI2KSp8ohnIVZb0OWb8f/5AmNO1DU
	 mDiDkFG/j3ffOqrrQe2oQbSPYMKWavRz9wGjnxC1RFMirNEmtKlD19F7gGuh04JV5f
	 HVKNT8Gfv4GUsBxXEhYiZoBuEWlqIfco7vTZiAjQ=
From: "lukas.graetz@tu-darmstadt.de" <sourceware-bugzilla@sourceware.org>
To: gdb-prs@sourceware.org
Subject: [Bug gdb/31436] <error reading variable: value has been optimized
 out> with .cfi_undefined
Date: Thu, 29 Feb 2024 19:39:31 +0000
X-Bugzilla-Reason: CC
X-Bugzilla-Type: changed
X-Bugzilla-Watch-Reason: None
X-Bugzilla-Product: gdb
X-Bugzilla-Component: gdb
X-Bugzilla-Version: 15.1
X-Bugzilla-Keywords: 
X-Bugzilla-Severity: normal
X-Bugzilla-Who: lukas.graetz@tu-darmstadt.de
X-Bugzilla-Status: UNCONFIRMED
X-Bugzilla-Resolution: 
X-Bugzilla-Priority: P2
X-Bugzilla-Assigned-To: unassigned at sourceware dot org
X-Bugzilla-Target-Milestone: ---
X-Bugzilla-Flags: 
X-Bugzilla-Changed-Fields: 
Message-ID: <bug-31436-4717-5QZZoOU29l@http.sourceware.org/bugzilla/>
In-Reply-To: <bug-31436-4717@http.sourceware.org/bugzilla/>
References: <bug-31436-4717@http.sourceware.org/bugzilla/>
Content-Type: text/plain; charset="UTF-8"
Content-Transfer-Encoding: quoted-printable
X-Bugzilla-URL: http://sourceware.org/bugzilla/
Auto-Submitted: auto-generated
MIME-Version: 1.0
List-Id: <gdb-prs.sourceware.org>

https://sourceware.org/bugzilla/show_bug.cgi?id=3D31436

--- Comment #1 from Lukas Gr=C3=A4tz <lukas.graetz@tu-darmstadt.de> ---
(In reply to Lukas Gr=C3=A4tz from comment #0)=20
> The backtrace is still incorrect (also observed in [2]):
>=20
> $ gdb bar-artificial-fix-undefined
> GNU gdb (GDB) 15.0.50.20240229-git
>=20
> (gdb) run
> Starting program: bar-artificial-fix-undefined
>=20
> Program received signal SIGABRT, Aborted.
> 0x00007ffff7dee00b in raise () from /lib/x86_64-linux-gnu/libc.so.6
> (gdb) bt
> #0  0x00007ffff7dee00b in raise () from /lib/x86_64-linux-gnu/libc.so.6
> #1  0x00007ffff7dcd859 in abort () from /lib/x86_64-linux-gnu/libc.so.6
> #2  0x00000000004011b0 in bar () at bar-artificial.c:30
> #3  0x00000000004011d1 in baz (
>     a=3D<error reading variable: value has been optimised out>,=20
>     b=3D<optimised out>, c=3D<optimised out>, d=3D<optimised out>,=20
>     e=3D<optimised out>, f=3D<optimised out>, g=3D48, h=3D49) at bar-arti=
ficial.c:38
>=20
>=20
> Here, the backtrace did not reach the functions qux() and main(). In this
> case, the stack base pointer rbp was clobbered and marked with
> .cfi_undefined. But it still should be possible without rbp to reconstruct
> the backtrace.


Edit: The last sentence was partly incorrect, I re-checked the assembler co=
de.
In qux(), there is a:

        movq    %rsp, %rbp
        .cfi_def_cfa_register 6

And then rsp is clobbered in qux(). And rbp is clobbert in bar(). So the re=
turn
address from qux() is lost and main() cannot be reached by the backtrace. B=
ut
the backtrace should still have reached qux(). And the parameters a,b,c of
baz() are also reconstructable.

--=20
You are receiving this mail because:
You are on the CC list for the bug.=