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From: "pinskia at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org> To: gcc-bugs@gcc.gnu.org Subject: [Bug c++/110401] [10/11/12/13/14 Regression] Unhelpful "goto is not a constant expression" in ill-formed pre c++20 constexpr function template Date: Sun, 25 Jun 2023 13:15:07 +0000 [thread overview] Message-ID: <bug-110401-4-rt1iKUw491@http.gcc.gnu.org/bugzilla/> (raw) In-Reply-To: <bug-110401-4@http.gcc.gnu.org/bugzilla/> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110401 Andrew Pinski <pinskia at gcc dot gnu.org> changed: What |Removed |Added ---------------------------------------------------------------------------- Summary|Unhelpful "goto is not a |[10/11/12/13/14 Regression] |constant expression" in |Unhelpful "goto is not a |ill-formed pre c++20 |constant expression" in |constexpr function template |ill-formed pre c++20 | |constexpr function template Last reconfirmed| |2023-06-25 Target Milestone|--- |10.5 Status|UNCONFIRMED |NEW Known to fail| |7.3.0 Known to work| |7.1.0, 7.2.0 Ever confirmed|0 |1 --- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> --- Compiling it with -std=c++11 is even worse as it does not show the reason: ``` <source>:12:36: error: 'constexpr std::array<int, N> get_sqr() [with int N = 10000]' called in a constant expression 12 | constexpr auto sqr = get_sqr<10000>(); | ~~~~~~~~~~~~~~^~ <source>:4:30: note: 'constexpr std::array<int, N> get_sqr() [with int N = 10000]' is not usable as a 'constexpr' function because: 4 | constexpr std::array<int, N> get_sqr() | ^~~~~~~ ``` GCC 7.1 and 7.2 used to have the correct explanation for C++11+: ``` <source>: In instantiation of 'constexpr std::array<int, N> get_sqr() [with int N = 10000]': <source>:12:37: required from here <source>:6:24: error: uninitialized variable 'ret' in 'constexpr' function std::array<int, N> ret; ^~~ In file included from <source>:1:0: /opt/compiler-explorer/gcc-7.2.0/include/c++/7.2.0/array:94:12: note: 'struct std::array<int, 10000>' has no user-provided default constructor struct array ^~~~~ /opt/compiler-explorer/gcc-7.2.0/include/c++/7.2.0/array:110:56: note: and the implicitly-defined constructor does not initialize 'int std::array<int, 10000>::_M_elems [10000]' typename _AT_Type::_Type _M_elems; ^~~~~~~~ <source>:12:37: error: 'constexpr std::array<int, N> get_sqr() [with int N = 10000]' called in a constant expression constexpr auto sqr = get_sqr<10000>(); ^ <source>:4:30: note: 'constexpr std::array<int, N> get_sqr() [with int N = 10000]' is not usable as a constexpr function because: constexpr std::array<int, N> get_sqr() ^~~~~~~ ``` GCC 7.3+ removed the "uninitialized variable 'ret' in 'constexpr' function". GCC 10+ then removed the 2 notes at the beginning. Note this is actually valid C++20 so maybe the change in GCC 10 is related to that ...
next prev parent reply other threads:[~2023-06-25 13:15 UTC|newest] Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top 2023-06-25 8:56 [Bug c++/110401] New: Unhelpful "goto is not a constant expression" in ill-formed " xry111 at gcc dot gnu.org 2023-06-25 13:15 ` pinskia at gcc dot gnu.org [this message] 2023-07-07 10:45 ` [Bug c++/110401] [11/12/13/14 Regression] Unhelpful "goto is not a constant expression" in ill-formed pre c++20 " rguenth at gcc dot gnu.org 2024-03-22 13:43 ` law at gcc dot gnu.org
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