* [Bug c++/107958] Ambiguity with uniform initialization in overloaded operator and explicit constructor
2022-12-03 16:48 [Bug c++/107958] New: Ambiguity with uniform initialization in overloaded operator and explicit constructor nruslan_devel at yahoo dot com
@ 2022-12-03 17:01 ` pinskia at gcc dot gnu.org
2022-12-03 17:05 ` pinskia at gcc dot gnu.org
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From: pinskia at gcc dot gnu.org @ 2022-12-03 17:01 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107958
--- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Note MSVC (with /std:c++latest) also rejects the source that is in comment #0
for the same reason as GCC:
<source>(39): error C2593: 'operator =' is ambiguous
<source>(25): note: could be 'PairPtr &PairPtr::operator =(const std::pair<int
*,int *> &)'
<source>(19): note: or 'PairPtr &PairPtr::operator =(const PairPtr &)'
<source>(39): note: while trying to match the argument list '(PairPtr,
initializer list)'
^ permalink raw reply [flat|nested] 11+ messages in thread
* [Bug c++/107958] Ambiguity with uniform initialization in overloaded operator and explicit constructor
2022-12-03 16:48 [Bug c++/107958] New: Ambiguity with uniform initialization in overloaded operator and explicit constructor nruslan_devel at yahoo dot com
2022-12-03 17:01 ` [Bug c++/107958] " pinskia at gcc dot gnu.org
@ 2022-12-03 17:05 ` pinskia at gcc dot gnu.org
2022-12-03 17:11 ` pinskia at gcc dot gnu.org
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From: pinskia at gcc dot gnu.org @ 2022-12-03 17:05 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107958
Andrew Pinski <pinskia at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
See Also| |https://gcc.gnu.org/bugzill
| |a/show_bug.cgi?id=85577
--- Comment #2 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Maybe related to C++ defect report 2137 (see PR 85577 for other details on
that) which GCC is known to implement but clang does not:
https://cplusplus.github.io/CWG/issues/2137.html
^ permalink raw reply [flat|nested] 11+ messages in thread
* [Bug c++/107958] Ambiguity with uniform initialization in overloaded operator and explicit constructor
2022-12-03 16:48 [Bug c++/107958] New: Ambiguity with uniform initialization in overloaded operator and explicit constructor nruslan_devel at yahoo dot com
2022-12-03 17:01 ` [Bug c++/107958] " pinskia at gcc dot gnu.org
2022-12-03 17:05 ` pinskia at gcc dot gnu.org
@ 2022-12-03 17:11 ` pinskia at gcc dot gnu.org
2022-12-03 18:12 ` pinskia at gcc dot gnu.org
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From: pinskia at gcc dot gnu.org @ 2022-12-03 17:11 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107958
--- Comment #3 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Obvious workaround is to do:
p = PairPtr{ a, b };
^ permalink raw reply [flat|nested] 11+ messages in thread
* [Bug c++/107958] Ambiguity with uniform initialization in overloaded operator and explicit constructor
2022-12-03 16:48 [Bug c++/107958] New: Ambiguity with uniform initialization in overloaded operator and explicit constructor nruslan_devel at yahoo dot com
` (2 preceding siblings ...)
2022-12-03 17:11 ` pinskia at gcc dot gnu.org
@ 2022-12-03 18:12 ` pinskia at gcc dot gnu.org
2022-12-03 18:22 ` pinskia at gcc dot gnu.org
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From: pinskia at gcc dot gnu.org @ 2022-12-03 18:12 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107958
--- Comment #4 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
I think GCC and MSVC are correct here:
[over.match.list]/16.3.1.7
. In copy-listinitialization, if an explicit constructor is chosen, the
initialization is ill-formed. [ Note: This differs from
other situations (16.3.1.3, 16.3.1.4), where only converting constructors are
considered for copy-initialization.
This restriction only applies if this initialization is part of the final
result of overload resolution. — end note ]
Even though the note is techincally not part of the standard, it describes why
clang is wrong here. That is the explicit constructors are used too to figure
out the overload and only if there was no ambiguous, it would be considered as
ill-formed.
^ permalink raw reply [flat|nested] 11+ messages in thread
* [Bug c++/107958] Ambiguity with uniform initialization in overloaded operator and explicit constructor
2022-12-03 16:48 [Bug c++/107958] New: Ambiguity with uniform initialization in overloaded operator and explicit constructor nruslan_devel at yahoo dot com
` (3 preceding siblings ...)
2022-12-03 18:12 ` pinskia at gcc dot gnu.org
@ 2022-12-03 18:22 ` pinskia at gcc dot gnu.org
2022-12-03 18:46 ` pinskia at gcc dot gnu.org
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From: pinskia at gcc dot gnu.org @ 2022-12-03 18:22 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107958
--- Comment #5 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Actually I think there is some disagreement if dcl.init.list/3.4 (that is
aggregate initialization) applies ...
Because if I make the two fields private, then gcc (and MSVC) accepts it ...
^ permalink raw reply [flat|nested] 11+ messages in thread
* [Bug c++/107958] Ambiguity with uniform initialization in overloaded operator and explicit constructor
2022-12-03 16:48 [Bug c++/107958] New: Ambiguity with uniform initialization in overloaded operator and explicit constructor nruslan_devel at yahoo dot com
` (4 preceding siblings ...)
2022-12-03 18:22 ` pinskia at gcc dot gnu.org
@ 2022-12-03 18:46 ` pinskia at gcc dot gnu.org
2022-12-03 18:49 ` pinskia at gcc dot gnu.org
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From: pinskia at gcc dot gnu.org @ 2022-12-03 18:46 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107958
--- Comment #6 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
(In reply to Andrew Pinski from comment #4)
> I think GCC and MSVC are correct here:
> [over.match.list]/16.3.1.7
> . In copy-listinitialization, if an explicit constructor is chosen, the
> initialization is ill-formed. [ Note: This differs from
> other situations (16.3.1.3, 16.3.1.4), where only converting constructors
> are considered for copy-initialization.
> This restriction only applies if this initialization is part of the final
> result of overload resolution. — end note ]
>
>
> Even though the note is techincally not part of the standard, it describes
> why clang is wrong here. That is the explicit constructors are used too to
> figure out the overload and only if there was no ambiguous, it would be
> considered as ill-formed.
Also see clang bug https://github.com/llvm/llvm-project/issues/28016
^ permalink raw reply [flat|nested] 11+ messages in thread
* [Bug c++/107958] Ambiguity with uniform initialization in overloaded operator and explicit constructor
2022-12-03 16:48 [Bug c++/107958] New: Ambiguity with uniform initialization in overloaded operator and explicit constructor nruslan_devel at yahoo dot com
` (5 preceding siblings ...)
2022-12-03 18:46 ` pinskia at gcc dot gnu.org
@ 2022-12-03 18:49 ` pinskia at gcc dot gnu.org
2022-12-03 18:50 ` pinskia at gcc dot gnu.org
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From: pinskia at gcc dot gnu.org @ 2022-12-03 18:49 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107958
Andrew Pinski <pinskia at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Resolution|--- |INVALID
Status|UNCONFIRMED |RESOLVED
See Also| |https://github.com/llvm/llv
| |m-project/issues/28016
--- Comment #7 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Yes https://github.com/llvm/llvm-project/issues/28016 is the clang bug which
shows GCC is correct. This is also
https://www.open-std.org/JTC1/SC22/WG21/docs/cwg_closed.html#1228 .
So clang is wrong in accepting the code as not ambiguous .
^ permalink raw reply [flat|nested] 11+ messages in thread
* [Bug c++/107958] Ambiguity with uniform initialization in overloaded operator and explicit constructor
2022-12-03 16:48 [Bug c++/107958] New: Ambiguity with uniform initialization in overloaded operator and explicit constructor nruslan_devel at yahoo dot com
` (6 preceding siblings ...)
2022-12-03 18:49 ` pinskia at gcc dot gnu.org
@ 2022-12-03 18:50 ` pinskia at gcc dot gnu.org
2022-12-04 4:19 ` nruslan_devel at yahoo dot com
2022-12-04 4:39 ` nruslan_devel at yahoo dot com
9 siblings, 0 replies; 11+ messages in thread
From: pinskia at gcc dot gnu.org @ 2022-12-03 18:50 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107958
Andrew Pinski <pinskia at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Resolution|INVALID |DUPLICATE
--- Comment #8 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Dup of bug 60027.
*** This bug has been marked as a duplicate of bug 60027 ***
^ permalink raw reply [flat|nested] 11+ messages in thread
* [Bug c++/107958] Ambiguity with uniform initialization in overloaded operator and explicit constructor
2022-12-03 16:48 [Bug c++/107958] New: Ambiguity with uniform initialization in overloaded operator and explicit constructor nruslan_devel at yahoo dot com
` (7 preceding siblings ...)
2022-12-03 18:50 ` pinskia at gcc dot gnu.org
@ 2022-12-04 4:19 ` nruslan_devel at yahoo dot com
2022-12-04 4:39 ` nruslan_devel at yahoo dot com
9 siblings, 0 replies; 11+ messages in thread
From: nruslan_devel at yahoo dot com @ 2022-12-04 4:19 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107958
--- Comment #9 from Ruslan Nikolaev <nruslan_devel at yahoo dot com> ---
Interestingly, if I change the code a little bit and have a pair in the
constructor rather than two arguments, gcc seems to compile the code:
#include <iostream>
#include <utility>
struct PairPtr {
PairPtr() {}
PairPtr(const PairPtr &s) {
a = s.a;
b = s.b;
}
explicit PairPtr(const std::pair<int *, int *>& pair) {
a = pair.first;
b = pair.second;
}
PairPtr& operator=(const PairPtr &s) {
a = s.a;
b = s.b;
return *this;
}
PairPtr& operator=(const std::pair<int *, int *>& pair) {
a = pair.first;
b = pair.second;
return *this;
}
private:
int *a;
int *b;
};
void func(int *a, int *b)
{
PairPtr p({a,b}); // works
p = { a, b }; // also works
}
^ permalink raw reply [flat|nested] 11+ messages in thread
* [Bug c++/107958] Ambiguity with uniform initialization in overloaded operator and explicit constructor
2022-12-03 16:48 [Bug c++/107958] New: Ambiguity with uniform initialization in overloaded operator and explicit constructor nruslan_devel at yahoo dot com
` (8 preceding siblings ...)
2022-12-04 4:19 ` nruslan_devel at yahoo dot com
@ 2022-12-04 4:39 ` nruslan_devel at yahoo dot com
9 siblings, 0 replies; 11+ messages in thread
From: nruslan_devel at yahoo dot com @ 2022-12-04 4:39 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107958
--- Comment #10 from Ruslan Nikolaev <nruslan_devel at yahoo dot com> ---
The latter example seems to work well for both gcc and clang. The behavior is
also consistent for both explicit and implicit constructors.
Thank you for clarifying that it was not a bug!
^ permalink raw reply [flat|nested] 11+ messages in thread