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* [Bug c++/95269] New: Lambda is allowed to capture any constexpr variable without specifying any captures @ 2020-05-22 8:30 dragondreamer at live dot com 2021-08-28 22:34 ` [Bug c++/95269] " pinskia at gcc dot gnu.org ` (2 more replies) 0 siblings, 3 replies; 4+ messages in thread From: dragondreamer at live dot com @ 2020-05-22 8:30 UTC (permalink / raw) To: gcc-bugs https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95269 Bug ID: 95269 Summary: Lambda is allowed to capture any constexpr variable without specifying any captures Product: gcc Version: 10.1.0 Status: UNCONFIRMED Severity: normal Priority: P3 Component: c++ Assignee: unassigned at gcc dot gnu.org Reporter: dragondreamer at live dot com Target Milestone: --- G++ (at least these versions: 8.2.1, 9.2.1, 10.1.0, trunk) successfully compiles the following code: // =================================== template<typename Lambda> constexpr void test(Lambda lambda) { constexpr auto result = lambda(); static_assert(result.value == 1); } struct teststruct { int value = 0; }; constexpr auto get_value() { teststruct result{}; result.value = 1; return result; } int main() { constexpr auto value = get_value(); //Here's a lambda without any captures auto options_lambda = []() { return value; }; test(options_lambda); } // =================================== This code instead should produce an error when trying to create a lambda which uses "value" without capturing it. This is the exact behavior of Clang and MSVC, which both produce an error message. As far as I understand, the following rule must be applied here: "If a lambda expression (or an instantiation of a generic lambda's function call operator) ODR-uses this or any variable with automatic storage duration, it must be captured by the lambda expression." ^ permalink raw reply [flat|nested] 4+ messages in thread
* [Bug c++/95269] Lambda is allowed to capture any constexpr variable without specifying any captures 2020-05-22 8:30 [Bug c++/95269] New: Lambda is allowed to capture any constexpr variable without specifying any captures dragondreamer at live dot com @ 2021-08-28 22:34 ` pinskia at gcc dot gnu.org 2021-08-28 22:42 ` pinskia at gcc dot gnu.org 2022-02-03 5:00 ` pinskia at gcc dot gnu.org 2 siblings, 0 replies; 4+ messages in thread From: pinskia at gcc dot gnu.org @ 2021-08-28 22:34 UTC (permalink / raw) To: gcc-bugs https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95269 --- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> --- GCC and ICC accept this while clang and MSVC reject this. Without constexpr for value, GCC and ICC do reject this. ^ permalink raw reply [flat|nested] 4+ messages in thread
* [Bug c++/95269] Lambda is allowed to capture any constexpr variable without specifying any captures 2020-05-22 8:30 [Bug c++/95269] New: Lambda is allowed to capture any constexpr variable without specifying any captures dragondreamer at live dot com 2021-08-28 22:34 ` [Bug c++/95269] " pinskia at gcc dot gnu.org @ 2021-08-28 22:42 ` pinskia at gcc dot gnu.org 2022-02-03 5:00 ` pinskia at gcc dot gnu.org 2 siblings, 0 replies; 4+ messages in thread From: pinskia at gcc dot gnu.org @ 2021-08-28 22:42 UTC (permalink / raw) To: gcc-bugs https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95269 Andrew Pinski <pinskia at gcc dot gnu.org> changed: What |Removed |Added ---------------------------------------------------------------------------- See Also| |https://gcc.gnu.org/bugzill | |a/show_bug.cgi?id=93842 --- Comment #2 from Andrew Pinski <pinskia at gcc dot gnu.org> --- So I don't think this is an ODR use of the constexpr. If I change the lambda be this, GCC rejects it correctly. auto options_lambda = []() ->auto& { return value; }; So it all depends on what the return type of the original lambda should be really. ^ permalink raw reply [flat|nested] 4+ messages in thread
* [Bug c++/95269] Lambda is allowed to capture any constexpr variable without specifying any captures 2020-05-22 8:30 [Bug c++/95269] New: Lambda is allowed to capture any constexpr variable without specifying any captures dragondreamer at live dot com 2021-08-28 22:34 ` [Bug c++/95269] " pinskia at gcc dot gnu.org 2021-08-28 22:42 ` pinskia at gcc dot gnu.org @ 2022-02-03 5:00 ` pinskia at gcc dot gnu.org 2 siblings, 0 replies; 4+ messages in thread From: pinskia at gcc dot gnu.org @ 2022-02-03 5:00 UTC (permalink / raw) To: gcc-bugs https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95269 Andrew Pinski <pinskia at gcc dot gnu.org> changed: What |Removed |Added ---------------------------------------------------------------------------- Resolution|--- |DUPLICATE Status|UNCONFIRMED |RESOLVED --- Comment #3 from Andrew Pinski <pinskia at gcc dot gnu.org> --- Dup of bug 88164. *** This bug has been marked as a duplicate of bug 88164 *** ^ permalink raw reply [flat|nested] 4+ messages in thread
end of thread, other threads:[~2022-02-03 5:00 UTC | newest] Thread overview: 4+ messages (download: mbox.gz / follow: Atom feed) -- links below jump to the message on this page -- 2020-05-22 8:30 [Bug c++/95269] New: Lambda is allowed to capture any constexpr variable without specifying any captures dragondreamer at live dot com 2021-08-28 22:34 ` [Bug c++/95269] " pinskia at gcc dot gnu.org 2021-08-28 22:42 ` pinskia at gcc dot gnu.org 2022-02-03 5:00 ` pinskia at gcc dot gnu.org
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