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From: "rguenth at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org> To: gcc-bugs@gcc.gnu.org Subject: [Bug tree-optimization/57199] [4.8/4.9 Regression] Bogus warning: iteration NNNN invokes undefined behavior -Waggressive-loop-optimizations Date: Wed, 08 May 2013 08:58:00 -0000 [thread overview] Message-ID: <bug-57199-4-tN1bNav5DQ@http.gcc.gnu.org/bugzilla/> (raw) In-Reply-To: <bug-57199-4@http.gcc.gnu.org/bugzilla/> http://gcc.gnu.org/bugzilla/show_bug.cgi?id=57199 Richard Biener <rguenth at gcc dot gnu.org> changed: What |Removed |Added ---------------------------------------------------------------------------- Status|NEW |RESOLVED Resolution| |INVALID --- Comment #1 from Richard Biener <rguenth at gcc dot gnu.org> 2013-05-08 08:57:45 UTC --- Note that there seems to be an error in the source: void resize(size_t n) { size_t s = size(); DestroyElements(mutable_array() + n, s - n); for the call with n == size () + 1 the function calls DestroyElements with -1U elements which we figure out and optimize the caller to <bb 3>: _13 = i_12 * 80; _14 = _11 + _13; Foo::~Foo (_14); i_15 = i_12 + 1; <bb 4>: # i_12 = PHI <0(2), i_15(3)> if (i_12 != 18446744073709551615) goto <bb 3>; else goto <bb 5>; which then causes the addition to overflow and invoke undefined behavior and we warn. Thus, the warning, while not 100% helpful, points at a real problem.
next prev parent reply other threads:[~2013-05-08 8:58 UTC|newest] Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top 2013-05-07 22:09 [Bug c++/57199] New: [4.8, 4.9] " ppluzhnikov at google dot com 2013-05-07 23:01 ` [Bug c++/57199] [4.8/4.9 Regression] " paolo.carlini at oracle dot com 2013-05-08 8:58 ` rguenth at gcc dot gnu.org [this message] 2013-05-08 12:55 ` [Bug tree-optimization/57199] " ppluzhnikov at google dot com 2013-05-15 13:29 ` rguenth at gcc dot gnu.org 2013-05-20 8:12 ` jakub at gcc dot gnu.org 2013-05-20 14:10 ` ppluzhnikov at google dot com 2013-05-20 14:26 ` jakub at gcc dot gnu.org 2013-05-20 15:19 ` ppluzhnikov at google dot com 2014-03-26 20:39 ` dichlofos-mv at yandex dot ru 2014-03-26 20:56 ` ppluzhnikov at google dot com
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