From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: by sourceware.org (Postfix, from userid 48) id 9ACEC386F837; Mon, 15 Jun 2020 12:05:38 +0000 (GMT) DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org 9ACEC386F837 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gcc.gnu.org; s=default; t=1592222738; bh=JaZX7I5jXCIaU9yUiaigHHNwXo9o7EoM67TlYJjE6uM=; h=From:To:Subject:Date:In-Reply-To:References:From; b=E2CZQ90CMY3W0KXS+qDtb9rNVOYtZqIqc8A6cyb8f2V36O61WEc1Yaqu0GOmxu6IW wByaEBlBrtG/8JSQeX5tTLFCMEbB4Gm1MPhXB78EsycZfvZQd5ydD/kjhA1bj+Jrs2 sAVb1FCSqmyN+VS21fGx7Ts+efEzddLjwrkjSqgA= From: "rguenth at gcc dot gnu.org" To: gcc-bugs@gcc.gnu.org Subject: [Bug c++/95677] undefined reference to `(anonymous namespace)::xx' Date: Mon, 15 Jun 2020 12:05:38 +0000 X-Bugzilla-Reason: CC X-Bugzilla-Type: changed X-Bugzilla-Watch-Reason: None X-Bugzilla-Product: gcc X-Bugzilla-Component: c++ X-Bugzilla-Version: 10.1.0 X-Bugzilla-Keywords: lto, wrong-code X-Bugzilla-Severity: normal X-Bugzilla-Who: rguenth at gcc dot gnu.org X-Bugzilla-Status: UNCONFIRMED X-Bugzilla-Resolution: X-Bugzilla-Priority: P3 X-Bugzilla-Assigned-To: unassigned at gcc dot gnu.org X-Bugzilla-Target-Milestone: --- X-Bugzilla-Flags: X-Bugzilla-Changed-Fields: Message-ID: In-Reply-To: References: Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Bugzilla-URL: http://gcc.gnu.org/bugzilla/ Auto-Submitted: auto-generated MIME-Version: 1.0 X-BeenThere: gcc-bugs@gcc.gnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Gcc-bugs mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 15 Jun 2020 12:05:38 -0000 https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D95677 --- Comment #4 from Richard Biener --- (In reply to liusujian from comment #2) > (In reply to Richard Biener from comment #1) > > It's more likely the GENERIC / cgraph output by the C++ frontend is not > > correct > > and works by accident without LTO. Initial symbol table: > >=20 > > Initial Symbol table: > >=20 > > int {anonymous}::xx/3 (int {anonymous}::xx) @0x7f615d2d8180 > > Type: variable > > Visibility: external > > References: > > Referring: _ZN12_GLOBAL__N_13fooEv/0 (write) > > Availability: not-ready > > Varpool flags: > > main/2 (int main()) @0x7f615d421168 > > Type: function definition analyzed > > Visibility: force_output no_reorder public > > Aux: @0x37a5000 > > References: int {anonymous}::xx/1 (write) > > Referring: > > Function flags: body > > Called by: > > Calls: > > int {anonymous}::xx/1 (int {anonymous}::xx) @0x7f615d2d8100 > > Type: variable definition analyzed > > Visibility: force_output no_reorder > > Aux: @0x7f615d421168 > > References: > > Referring: main/2 (write) > > Availability: not-ready > > Varpool flags: initialized > > _ZN12_GLOBAL__N_13fooEv/0 (void {anonymous}::foo()) @0x7f615d421000 > > Type: function definition analyzed > > Visibility: force_output no_reorder > > Aux: @0x7f615d2d8100 > > References: int {anonymous}::xx/3 (write) > > Referring: > > Function flags: body > > Called by: > > Calls: > >=20 > > where you can see there are actually two 'xx' objects and the C++ FE > > takes it up to the linker/assembler to resolve them. But the symtab > > code does not include such "resolving" step. >=20 >=20 > In other words, C++ is currently unable to deal with this scenario ? Or a= ny > other problems cause the error? The C++ frontend creates two distinct objects for 'xx' (thus it does not kn= ow they refer to the same object). Not sure if it is possible to exploit this fact to create a testcase that shows this fact even without LTO. I guess using constexpr and fail to constexpr evaluate a function using constexpr 'xx'? Not sure if there can be a "extern" constexpr though ;) As said the testcase "works" without LTO because both instances mangle to the same symbol name so the assembler/linker figure they _are_ the same object. Just the C++ frontend doesn't know within this TU.=