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From: "jakub at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org> To: gcc-bugs@gcc.gnu.org Subject: [Bug c++/54046] [4.6/4.7/4.8 Regression] wrong control reaches end of non-void function for switch case with throw and default Date: Fri, 20 Jul 2012 12:58:00 -0000 [thread overview] Message-ID: <bug-54046-4-RJ2ADDFWum@http.gcc.gnu.org/bugzilla/> (raw) In-Reply-To: <bug-54046-4@http.gcc.gnu.org/bugzilla/> http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54046 Jakub Jelinek <jakub at gcc dot gnu.org> changed: What |Removed |Added ---------------------------------------------------------------------------- CC| |jakub at gcc dot gnu.org --- Comment #3 from Jakub Jelinek <jakub at gcc dot gnu.org> 2012-07-20 12:57:42 UTC --- Or: void foo (void) __attribute__((noreturn)); void bar (void); struct A { ~A () {} }; bool check (int x) { A z; switch (x) { case 0: return false; default: foo (); bar (); } } The problem is related to pass ordering. EH lowering is done before CFG cleanups, so if there is code after a noreturn spot (whether throw or noreturn function, endless loop etc. doesn't matter), when trying to lower try .. finally EH will see gimple_seq_may_fallthru to be true because of the extra code after it hiding that it in fact can't fall thru. We end up then with: switch (x) <default: <D.2213>, case 0: <D.2212>> <D.2212>: D.2216 = 0; finally_tmp.0 = 0; goto <D.2220>; <D.2213>: foo (); bar (); finally_tmp.0 = 1; <D.2220>: A::~A (&z); switch (finally_tmp.0) <default: <D.2223>, default: <D.2223>, case 1: <D.2221>> where D.2221 falls thru to exit without returning a value, while D.2223 doesn't. Then cfg cleanup during cfg pass cleans that up to: finally_tmp.0 = 0; A::~A (&z); switch (finally_tmp.0) <default: <L12>, case 1: <L11>> after finding out that foo is noreturn and can't fallthru. But there is no constant propagation and switch optimization pass that would simplify switch (0) <default: something; case 1: somethingelse> into goto something; scheduled before the pass_warn_function_return is scheduled. As we aren't in SSA form at that point, doing it wouldn't be very easy.
next prev parent reply other threads:[~2012-07-20 12:58 UTC|newest] Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top 2012-07-20 11:49 [Bug c++/54046] New: " plasmahh at gmx dot net 2012-07-20 12:10 ` [Bug c++/54046] " redi at gcc dot gnu.org 2012-07-20 12:15 ` [Bug c++/54046] [4.6/4.7/4.8 Regression] " redi at gcc dot gnu.org 2012-07-20 12:40 ` jakub at gcc dot gnu.org 2012-07-20 12:58 ` jakub at gcc dot gnu.org [this message] 2012-07-20 15:15 ` ebotcazou at gcc dot gnu.org 2012-09-07 10:03 ` rguenth at gcc dot gnu.org 2012-11-20 16:03 ` jakub at gcc dot gnu.org 2012-11-20 17:27 ` jakub at gcc dot gnu.org 2012-11-23 16:04 ` jakub at gcc dot gnu.org 2013-02-01 14:03 ` [Bug c++/54046] [4.6/4.7 " jakub at gcc dot gnu.org 2013-02-01 14:26 ` jakub at gcc dot gnu.org
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