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From: "redi at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org> To: gcc-bugs@gcc.gnu.org Subject: [Bug libstdc++/105844] [10/11/12/13 Regression] std::lcm(50000, 49999) is UB but accepted in a constexpr due to cast to unsigned Date: Mon, 06 Jun 2022 15:19:45 +0000 [thread overview] Message-ID: <bug-105844-4-5OHapVPxry@http.gcc.gnu.org/bugzilla/> (raw) In-Reply-To: <bug-105844-4@http.gcc.gnu.org/bugzilla/> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105844 --- Comment #5 from Jonathan Wakely <redi at gcc dot gnu.org> --- I think the fix we want is simply: --- a/libstdc++-v3/include/std/numeric +++ b/libstdc++-v3/include/std/numeric @@ -68,6 +68,7 @@ #if __cplusplus >= 201402L # include <type_traits> # include <bit> +# include <ext/numeric_traits.h> #endif #if __cplusplus >= 201703L @@ -102,7 +103,15 @@ namespace __detail static_assert(is_unsigned<_Up>::value, "result type must be unsigned"); static_assert(sizeof(_Up) >= sizeof(_Tp), "result type must be at least as wide as the input type"); - return __val < 0 ? -(_Up)__val : (_Up)__val; + + if (__val >= 0) + return static_cast<_Up>(__val); + + if _GLIBCXX17_CONSTEXPR (sizeof(_Up) == sizeof(_Tp)) + { + __glibcxx_assert(__val != __gnu_cxx::__int_traits<_Tp>::__min); + } + return -static_cast<_Up>(__val); } template<typename _Up> void __absu(bool) = delete;
next prev parent reply other threads:[~2022-06-06 15:19 UTC|newest] Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top 2022-06-04 1:08 [Bug libstdc++/105844] New: " goswin-v-b at web dot de 2022-06-04 1:11 ` [Bug libstdc++/105844] " goswin-v-b at web dot de 2022-06-04 1:32 ` goswin-v-b at web dot de 2022-06-04 8:24 ` goswin-v-b at web dot de 2022-06-06 14:22 ` [Bug libstdc++/105844] [10/11/12/13 Regression] " redi at gcc dot gnu.org 2022-06-06 15:19 ` redi at gcc dot gnu.org [this message] 2022-06-07 10:07 ` redi at gcc dot gnu.org 2022-06-10 14:24 ` cvs-commit at gcc dot gnu.org 2022-06-28 10:49 ` jakub at gcc dot gnu.org 2022-08-03 13:46 ` [Bug libstdc++/105844] [10/11/12 " cvs-commit at gcc dot gnu.org 2022-08-03 13:49 ` [Bug libstdc++/105844] [10/11 " redi at gcc dot gnu.org 2023-05-03 15:02 ` cvs-commit at gcc dot gnu.org 2023-05-03 15:16 ` cvs-commit at gcc dot gnu.org 2023-05-03 16:34 ` cvs-commit at gcc dot gnu.org 2023-05-03 16:35 ` redi at gcc dot gnu.org 2023-05-03 20:59 ` cvs-commit at gcc dot gnu.org
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