From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: by sourceware.org (Postfix, from userid 48) id 2E2623857346; Thu, 28 Apr 2022 13:29:44 +0000 (GMT) DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org 2E2623857346 From: "byteslice at airmail dot cc" To: gcc-bugs@gcc.gnu.org Subject: [Bug tree-optimization/105423] New: Bogus -Werror=maybe-uninitialized with definitely initialized variable Date: Thu, 28 Apr 2022 13:29:43 +0000 X-Bugzilla-Reason: CC X-Bugzilla-Type: new X-Bugzilla-Watch-Reason: None X-Bugzilla-Product: gcc X-Bugzilla-Component: tree-optimization X-Bugzilla-Version: 12.0 X-Bugzilla-Keywords: X-Bugzilla-Severity: normal X-Bugzilla-Who: byteslice at airmail dot cc 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: bug_id short_desc product version bug_status bug_severity priority component assigned_to reporter target_milestone attachments.created Message-ID: 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: Thu, 28 Apr 2022 13:29:44 -0000 https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D105423 Bug ID: 105423 Summary: Bogus -Werror=3Dmaybe-uninitialized with definitely initialized variable Product: gcc Version: 12.0 Status: UNCONFIRMED Severity: normal Priority: P3 Component: tree-optimization Assignee: unassigned at gcc dot gnu.org Reporter: byteslice at airmail dot cc Target Milestone: --- Created attachment 52896 --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=3D52896&action=3Dedit Cvised example On gcc 12.0.1 20220413 (Fedora 36 Beta), with c++ -O1 -Werror=3Dmaybe-uninitialized, the attachment fails to compile, with the following message: In member function 'void std::Trans_NS___cxx11_basic_string<_CharT, , >::_S_copy(_CharT*) [with _CharT =3D char; _Traits =3D std::char_traits; =3D= char]', inlined from 'constexpr std::Trans_NS___cxx11_basic_string<_CharT, _Tra= its, _Alloc>& std::Trans_NS___cxx11_basic_string<_CharT, , >::_M_replace(const _CharT*, long int) [with _Char= T =3D char; _Traits =3D std::char_traits; =3D char]' at :49:12, inlined from 'void std::Trans_NS___cxx11_basic_string<_CharT, , >::operator=3D(const _Ch= arT*) [with _CharT =3D char; _Traits =3D std::char_traits; =3D char]' at :40:15, inlined from 'void Shuffle()' at :55:8: :36:46: error: '((char*)((char*)&mask + offsetof(std::Trans_NS___cxx11_basic_string,std::Trans_NS___cxx11_basic_string::)))[2]' may be used uninitialized [-Werror=3Dmaybe-uninitia= lized] 36 | void _S_copy(_CharT *__s) { _Traits::assign(_S_copy___d, *__s); } | ~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~ : In function 'void Shuffle()': :54:44: note: 'mask' declared here 54 | std::Trans_NS___cxx11_basic_string mask{}; | ^~~~ In member function 'void std::Trans_NS___cxx11_basic_string<_CharT, , >::_S_copy(_CharT*) [with _CharT =3D char; _Traits =3D std::char_traits; =3D= char]', inlined from 'constexpr std::Trans_NS___cxx11_basic_string<_CharT, _Tra= its, _Alloc>& std::Trans_NS___cxx11_basic_string<_CharT, , >::_M_replace(const _CharT*, long int) [with _Char= T =3D char; _Traits =3D std::char_traits; =3D char]' at :49:12, inlined from 'void std::Trans_NS___cxx11_basic_string<_CharT, , >::operator=3D(const _Ch= arT*) [with _CharT =3D char; _Traits =3D std::char_traits; =3D char]' at :40:15, inlined from 'void Shuffle()' at :55:8: :36:47: error: 'mask.std::Trans_NS___cxx11_basic_string::_S_copy___d' may be used uninitialized [-Werror=3Dmaybe-uninitialized] 36 | void _S_copy(_CharT *__s) { _Traits::assign(_S_copy___d, *__s); } | ^~~~~~~~~~~ : In function 'void Shuffle()': :54:44: note: 'mask' declared here 54 | std::Trans_NS___cxx11_basic_string mask{}; | ^~~~ cc1plus: some warnings being treated as errors Compiler returned: 1 This warning is bogus because the variable mask is default brace-initialized and thus its member _S_copy___d is also initialized. The bogus warning does= not appear in older versions of GCC. Adding -fno-inline to options allows compilation to succeed.=