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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++/97553] [missed optimization] constexprness not noticed when UBsan enabled Date: Fri, 23 Oct 2020 16:34:21 +0000 [thread overview] Message-ID: <bug-97553-4-LGJxExbGux@http.gcc.gnu.org/bugzilla/> (raw) In-Reply-To: <bug-97553-4@http.gcc.gnu.org/bugzilla/> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97553 Jakub Jelinek <jakub at gcc dot gnu.org> changed: What |Removed |Added ---------------------------------------------------------------------------- CC| |jakub at gcc dot gnu.org --- Comment #1 from Jakub Jelinek <jakub at gcc dot gnu.org> --- Whether the function is constexpr or not doesn't really matter when you evaluate it in non-constant expression contexts. In those the ubsan instrumentation is bypassed (the constant expression evaluation does similar checking), but otherwise it is a normal function like any other, which including the instrumentation is inlined etc. And, the runtime sanitization intentionally isn't heavily optimized away, because the intent is to detect when the code is invalid, so it can't e.g. optimize away those checks based on assumption that undefined behavior will not happen. If you want a constant via C++ means, use int foo() { constexpr int x = g().length(); return x; }
next prev parent reply other threads:[~2020-10-23 16:34 UTC|newest] Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top 2020-10-23 16:27 [Bug c++/97553] New: " eyalroz at technion dot ac.il 2020-10-23 16:34 ` jakub at gcc dot gnu.org [this message] 2020-10-26 16:50 ` [Bug c++/97553] " mpolacek at gcc dot gnu.org 2020-10-26 19:40 ` eyalroz at technion dot ac.il 2020-10-26 19:45 ` jakub at gcc dot gnu.org 2020-10-26 20:46 ` eyalroz at technion dot ac.il 2023-02-17 20:21 ` cvs-commit at gcc dot gnu.org 2023-03-02 19:05 ` cvs-commit at gcc dot gnu.org 2023-04-26 13:18 ` ppalka at gcc dot gnu.org
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