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* [Bug c++/95849] New: Universal forwarding constructor inheritance resolution issue
@ 2020-06-23 21:13 njormrod at fb dot com
2021-08-28 23:03 ` [Bug c++/95849] " herring at lanl dot gov
2021-09-01 18:37 ` [Bug c++/95849] [DR2356] " mpolacek at gcc dot gnu.org
0 siblings, 2 replies; 3+ messages in thread
From: njormrod at fb dot com @ 2020-06-23 21:13 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95849
Bug ID: 95849
Summary: Universal forwarding constructor inheritance
resolution issue
Product: gcc
Version: 10.1.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: njormrod at fb dot com
Target Milestone: ---
Universal forwarding constructors have a known oddity: they are a better match
than the copy constructor for non-const objects.
If a derived class inherits its parent's constructors, where the parent has a
universal forwarding constructor, then the derived class's default copy
constructor (having signature `const Derived&`) should likewise be usurped by
the non-const universal-forwarding constructor.
This is not the case in gcc.
Code demonstrating the bug: foo() and bar() should both return 8, but bar()
actually returns 7.
```
struct A {
A(const A&) : x(7) {}
template <typename U>
A(U&&) : x(8) {}
int x;
};
int foo() {
A o1(true);
A o2(o1);
return o2.x;
}
struct B : A {
using A::A;
};
int bar() {
B o1(true);
B o2(o1);
return o2.x;
}
```
Godbolt link for gcc: https://gcc.godbolt.org/z/Y_sXD6. Bug is present.
Godbolt link for clang: https://gcc.godbolt.org/z/BFjYph. Bug is present.
Godbolt link for msvc: https://gcc.godbolt.org/z/GQ2z3x. msvc has the correct
behavior.
^ permalink raw reply [flat|nested] 3+ messages in thread
* [Bug c++/95849] Universal forwarding constructor inheritance resolution issue
2020-06-23 21:13 [Bug c++/95849] New: Universal forwarding constructor inheritance resolution issue njormrod at fb dot com
@ 2021-08-28 23:03 ` herring at lanl dot gov
2021-09-01 18:37 ` [Bug c++/95849] [DR2356] " mpolacek at gcc dot gnu.org
1 sibling, 0 replies; 3+ messages in thread
From: herring at lanl dot gov @ 2021-08-28 23:03 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95849
S. Davis Herring <herring at lanl dot gov> changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |herring at lanl dot gov
--- Comment #1 from S. Davis Herring <herring at lanl dot gov> ---
This is CWG2356
<http://www.open-std.org/jtc1/sc22/wg21/docs/cwg_defects.html#2356>; GCC (along
with Clang) is correct.
^ permalink raw reply [flat|nested] 3+ messages in thread
* [Bug c++/95849] [DR2356] Universal forwarding constructor inheritance resolution issue
2020-06-23 21:13 [Bug c++/95849] New: Universal forwarding constructor inheritance resolution issue njormrod at fb dot com
2021-08-28 23:03 ` [Bug c++/95849] " herring at lanl dot gov
@ 2021-09-01 18:37 ` mpolacek at gcc dot gnu.org
1 sibling, 0 replies; 3+ messages in thread
From: mpolacek at gcc dot gnu.org @ 2021-09-01 18:37 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95849
Marek Polacek <mpolacek at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|UNCONFIRMED |RESOLVED
Resolution|--- |WORKSFORME
CC| |mpolacek at gcc dot gnu.org
--- Comment #2 from Marek Polacek <mpolacek at gcc dot gnu.org> ---
Thanks Davis. Closing.
^ permalink raw reply [flat|nested] 3+ messages in thread
end of thread, other threads:[~2021-09-01 18:37 UTC | newest]
Thread overview: 3+ messages (download: mbox.gz / follow: Atom feed)
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2020-06-23 21:13 [Bug c++/95849] New: Universal forwarding constructor inheritance resolution issue njormrod at fb dot com
2021-08-28 23:03 ` [Bug c++/95849] " herring at lanl dot gov
2021-09-01 18:37 ` [Bug c++/95849] [DR2356] " mpolacek at gcc dot gnu.org
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