[Bug c++/114395] [c++20+] std::is_constructible_v result of const reference incorrect
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114395 Marek Polacek changed: What|Removed |Added Ever confirmed|0 |1 Assignee|unassigned at gcc dot gnu.org |mpolacek at gcc dot gnu.org Status|UNCONFIRMED |ASSIGNED Last reconfirmed||2024-03-20
[Bug c++/114395] [c++20+] std::is_constructible_v result of const reference incorrect
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114395 Jiang An changed: What|Removed |Added CC||de34 at live dot cn --- Comment #10 from Jiang An --- I think this is basically CWG2709 (https://cplusplus.github.io/CWG/issues/2709.html). Given CWG2709 is closed as NAD, we should reject such initializations.
[Bug c++/114395] [c++20+] std::is_constructible_v result of const reference incorrect
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114395 --- Comment #9 from Andrew Pinski --- https://eel.is/c++draft/dcl.init.general#16.2 applies here I think. Which comes before the `Parenthesized aggregates initialization` clause. But I could be wrong. https://github.com/cplusplus/papers/issues/1494 is kinda of related.
[Bug c++/114395] [c++20+] std::is_constructible_v result of const reference incorrect
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114395 --- Comment #8 from Andrew Pinski --- (In reply to Jonathan Wakely from comment #7) > All of Clang, MSVC and EDG disagree with GCC though, so maybe there's a DR > that we're missing. Maybe https://cplusplus.github.io/CWG/issues/1467.html (again). See clang bug https://github.com/llvm/llvm-project/pull/77768 .
[Bug c++/114395] [c++20+] std::is_constructible_v result of const reference incorrect
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114395 --- Comment #7 from Jonathan Wakely --- All of Clang, MSVC and EDG disagree with GCC though, so maybe there's a DR that we're missing.
[Bug c++/114395] [c++20+] std::is_constructible_v result of const reference incorrect
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114395
--- Comment #6 from Marek Polacek ---
Right, another design principle is that () should work where {} works, and
const B {a}; works. A(b) previously didn't work so it's not really changing
meaning. So not a bug IMHO.
[Bug c++/114395] [c++20+] std::is_constructible_v result of const reference incorrect
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114395 --- Comment #5 from Jonathan Wakely --- I disagree, A(b) definitely changed meaning. It now initializes A by copying the base part of b This is a combination of aggregates being allowed to have base classes and paren-init doing aggregate-init.
[Bug c++/114395] [c++20+] std::is_constructible_v result of const reference incorrect
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114395 --- Comment #4 from Andrew Pinski --- (In reply to Marek Polacek from comment #3) > Changed with r10-5137-g43aae289866f5e: > > commit 43aae289866f5ea55d187444520412554aa2e171 > Author: Marek Polacek > Date: Tue Dec 3 15:59:40 2019 + > > PR c++/91363 - P0960R3: Parenthesized initialization of aggregates. Hmm, reading the paper, I am not 100% sure if GCC implemented this correctly due to the wording of the design principles: ``` Any existing meaning of A(b) should not change. ```
[Bug c++/114395] [c++20+] std::is_constructible_v result of const reference incorrect
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114395 Marek Polacek changed: What|Removed |Added CC||mpolacek at gcc dot gnu.org --- Comment #3 from Marek Polacek --- Changed with r10-5137-g43aae289866f5e: commit 43aae289866f5ea55d187444520412554aa2e171 Author: Marek Polacek Date: Tue Dec 3 15:59:40 2019 + PR c++/91363 - P0960R3: Parenthesized initialization of aggregates.
[Bug c++/114395] [c++20+] std::is_constructible_v result of const reference incorrect
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114395
--- Comment #2 from Andrew Pinski ---
Except this works with C++20+ for GCC:
```
struct A {
int a;
};
struct B : public A {};
void f(const A )
{
typedef const B & Btype;
Btype b(a);
}
```
[Bug c++/114395] [c++20+] std::is_constructible_v result of const reference incorrect
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114395 Andrew Pinski changed: What|Removed |Added Summary|std::is_constructible_v |[c++20+] |result of const reference |std::is_constructible_v |incorrect |result of const reference ||incorrect --- Comment #1 from Andrew Pinski --- Hmm, this fails only for C++20+.
