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* [Bug libstdc++/114354] New: std::shared_ptr constructor constraints are checked too late @ 2024-03-15 15:36 redi at gcc dot gnu.org 2024-03-15 15:37 ` [Bug libstdc++/114354] " redi at gcc dot gnu.org ` (2 more replies) 0 siblings, 3 replies; 4+ messages in thread From: redi at gcc dot gnu.org @ 2024-03-15 15:36 UTC (permalink / raw) To: gcc-bugs https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114354 Bug ID: 114354 Summary: std::shared_ptr constructor constraints are checked too late Product: gcc Version: 14.0 Status: UNCONFIRMED Severity: normal Priority: P3 Component: libstdc++ Assignee: unassigned at gcc dot gnu.org Reporter: redi at gcc dot gnu.org Blocks: 88322 Target Milestone: --- The standard says: template<class Y> explicit shared_ptr(Y* p); Constraints: When T is an array type, the expression delete[] p is well-formed and either T is U[N] and Y(*)[N] is convertible to T*, or T is U[] and Y(*)[] is convertible to T*. When T is not an array type, the expression delete p is well-formed and Y* is convertible to T*. We do not constrain that constructor with checks for the delete expressions being well-formed, so this gives the wrong answer: #include <memory> struct A { private: ~A(); }; static_assert( ! std::is_constructible_v<std::shared_ptr<A>, A*> ); Similarly for the constructors taking a deleter: template<class Y, class D> shared_ptr(Y* p, D d); template<class Y, class D, class A> shared_ptr(Y* p, D d, A a); template<class D> shared_ptr(nullptr_t p, D d); template<class D, class A> shared_ptr(nullptr_t p, D d, A a); Constraints: is_move_constructible_v<D> is true, and d(p) is a well-formed expression. [...] We check that with a static assert in the constructor body, which is too late, so this fails: struct D { }; static_assert( ! std::is_constructible_v<std::shared_ptr<A>, A*, D> ); Prior to C++20 the requirements were just preconditions, so not required to be SFINAE-able. So we must fix this for C++20, and could do so for C++11 as QoI. Referenced Bugs: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=88322 [Bug 88322] Implement C++20 library features. ^ permalink raw reply [flat|nested] 4+ messages in thread
* [Bug libstdc++/114354] std::shared_ptr constructor constraints are checked too late 2024-03-15 15:36 [Bug libstdc++/114354] New: std::shared_ptr constructor constraints are checked too late redi at gcc dot gnu.org @ 2024-03-15 15:37 ` redi at gcc dot gnu.org 2024-03-16 7:33 ` de34 at live dot cn 2024-03-16 10:07 ` redi at gcc dot gnu.org 2 siblings, 0 replies; 4+ messages in thread From: redi at gcc dot gnu.org @ 2024-03-15 15:37 UTC (permalink / raw) To: gcc-bugs https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114354 Jonathan Wakely <redi at gcc dot gnu.org> changed: What |Removed |Added ---------------------------------------------------------------------------- Status|UNCONFIRMED |ASSIGNED Ever confirmed|0 |1 Assignee|unassigned at gcc dot gnu.org |redi at gcc dot gnu.org Last reconfirmed| |2024-03-15 ^ permalink raw reply [flat|nested] 4+ messages in thread
* [Bug libstdc++/114354] std::shared_ptr constructor constraints are checked too late 2024-03-15 15:36 [Bug libstdc++/114354] New: std::shared_ptr constructor constraints are checked too late redi at gcc dot gnu.org 2024-03-15 15:37 ` [Bug libstdc++/114354] " redi at gcc dot gnu.org @ 2024-03-16 7:33 ` de34 at live dot cn 2024-03-16 10:07 ` redi at gcc dot gnu.org 2 siblings, 0 replies; 4+ messages in thread From: de34 at live dot cn @ 2024-03-16 7:33 UTC (permalink / raw) To: gcc-bugs https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114354 Jiang An <de34 at live dot cn> changed: What |Removed |Added ---------------------------------------------------------------------------- CC| |de34 at live dot cn --- Comment #1 from Jiang An <de34 at live dot cn> --- The constraints were transformed from preconditions by LWG2874 (https://cplusplus.github.io/LWG/issue2874). So perhaps the actually issue is not having implemented LWG2874, and I think the constraints need to be implemented for C++17. The wording change in LWG2874 seems to be on the top of P0414R2 + P0497R0. I'm not sure what the "backported form of LWG2874" exactly is. Perhaps it's simply "This constructor shall not participate in overload resolution unless the expression delete p is well-formed and Y* is convertible to T*." (not considering whether T or Y is an array type)? ^ permalink raw reply [flat|nested] 4+ messages in thread
* [Bug libstdc++/114354] std::shared_ptr constructor constraints are checked too late 2024-03-15 15:36 [Bug libstdc++/114354] New: std::shared_ptr constructor constraints are checked too late redi at gcc dot gnu.org 2024-03-15 15:37 ` [Bug libstdc++/114354] " redi at gcc dot gnu.org 2024-03-16 7:33 ` de34 at live dot cn @ 2024-03-16 10:07 ` redi at gcc dot gnu.org 2 siblings, 0 replies; 4+ messages in thread From: redi at gcc dot gnu.org @ 2024-03-16 10:07 UTC (permalink / raw) To: gcc-bugs https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114354 --- Comment #2 from Jonathan Wakely <redi at gcc dot gnu.org> --- Ah yes, thanks. It looks like I converted them to constraints for array support with g:a2e0054e1d169984ec64d64145b71a88a9628537 but only for the pointer conversions, I missed the delete expression. ^ permalink raw reply [flat|nested] 4+ messages in thread
end of thread, other threads:[~2024-03-16 10:07 UTC | newest] Thread overview: 4+ messages (download: mbox.gz / follow: Atom feed) -- links below jump to the message on this page -- 2024-03-15 15:36 [Bug libstdc++/114354] New: std::shared_ptr constructor constraints are checked too late redi at gcc dot gnu.org 2024-03-15 15:37 ` [Bug libstdc++/114354] " redi at gcc dot gnu.org 2024-03-16 7:33 ` de34 at live dot cn 2024-03-16 10:07 ` redi at gcc dot gnu.org
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