From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: by sourceware.org (Postfix, from userid 48) id 7E3FB3851C23; Thu, 2 Sep 2021 11:07:54 +0000 (GMT) DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org 7E3FB3851C23 From: "johelegp at gmail dot com" To: gcc-bugs@gcc.gnu.org Subject: [Bug c++/102174] New: Unused result of undefined behavior arithmetic is accepted during constant evaluation Date: Thu, 02 Sep 2021 11:07:54 +0000 X-Bugzilla-Reason: CC X-Bugzilla-Type: new X-Bugzilla-Watch-Reason: None X-Bugzilla-Product: gcc X-Bugzilla-Component: c++ X-Bugzilla-Version: 12.0 X-Bugzilla-Keywords: accepts-invalid X-Bugzilla-Severity: normal X-Bugzilla-Who: johelegp at gmail dot com 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 keywords bug_severity priority component assigned_to reporter cc target_milestone 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, 02 Sep 2021 11:07:54 -0000 https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D102174 Bug ID: 102174 Summary: Unused result of undefined behavior arithmetic is accepted during constant evaluation Product: gcc Version: 12.0 Status: UNCONFIRMED Keywords: accepts-invalid Severity: normal Priority: P3 Component: c++ Assignee: unassigned at gcc dot gnu.org Reporter: johelegp at gmail dot com CC: johelegp at gmail dot com Target Milestone: --- See https://godbolt.org/z/d38ozc91x. ```C++ #include constexpr bool f() { 1 / 0; 1.0 / 0; 1 % 0; INT32_MIN / INT32_C(-1); INT32_MIN * INT32_C(-1); INT32_MAX + INT32_C(1); INT16_C(INT32_MAX + INT32_C(1)); return true; } constexpr bool b{f()}; ``` ``` : In function 'constexpr bool f()': :3:5: warning: division by zero [-Wdiv-by-zero] 3 | 1 / 0; | ~~^~~ :3:5: warning: statement has no effect [-Wunused-value] :4:7: warning: division by zero [-Wdiv-by-zero] 4 | 1.0 / 0; | ~~~~^~~ :4:7: warning: statement has no effect [-Wunused-value] :5:5: warning: division by zero [-Wdiv-by-zero] 5 | 1 % 0; | ~~^~~ :5:5: warning: statement has no effect [-Wunused-value] :6:13: warning: integer overflow in expression of type 'int' result= s in '-2147483648' [-Woverflow] 6 | INT32_MIN / INT32_C(-1); | ^ :6:13: warning: statement has no effect [-Wunused-value] :7:13: warning: integer overflow in expression of type 'int' result= s in '-2147483648' [-Woverflow] 7 | INT32_MIN * INT32_C(-1); | ^ :7:13: warning: statement has no effect [-Wunused-value] :8:13: warning: integer overflow in expression of type 'int' result= s in '-2147483648' [-Woverflow] 8 | INT32_MAX + INT32_C(1); | ^ :8:13: warning: statement has no effect [-Wunused-value] In file included from /opt/compiler-explorer/gcc-11.2.0/lib/gcc/x86_64-linux-gnu/11.2.0/include/s= tdint.h:9, from /opt/compiler-explorer/gcc-11.2.0/include/c++/11.2.0/cstdint:41, from :1: :9:21: warning: integer overflow in expression of type 'int' result= s in '-2147483648' [-Woverflow] 9 | INT16_C(INT32_MAX + INT32_C(1)); | ^ :9:21: warning: statement has no effect [-Wunused-value] Compiler returned: 0 ```=