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* [Bug c++/99399] New: why does not a pack expansion that is a using-delcaration which intends to introduce the base classes's constructor accept by GCC
@ 2021-03-05 7:20 xmh970252187 at gmail dot com
2021-03-05 7:22 ` [Bug c++/99399] " xmh970252187 at gmail dot com
` (5 more replies)
0 siblings, 6 replies; 7+ messages in thread
From: xmh970252187 at gmail dot com @ 2021-03-05 7:20 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99399
Bug ID: 99399
Summary: why does not a pack expansion that is a
using-delcaration which intends to introduce the base
classes's constructor accept by GCC
Product: gcc
Version: 10.2.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: xmh970252187 at gmail dot com
Target Milestone: ---
template<typename...T>
struct A:T...{
using T::T...;
};
int main() {
}
This should have to be well-formed code is rejected by GCC while Clang accepts
it.
Here is the result (https://godbolt.org/z/a583Po)
As per [temp.variadic#5.2]
> In a using-declaration; the pattern is a using-declarator.
Which means the pattern is `T::T`.
As per [temp.variadic#7]:
> The pattern of a pack expansion shall name one or more packs that are not expanded by a nested pack expansion; such packs are called unexpanded packs in the pattern. All of the packs expanded by a pack expansion shall have the same number of arguments specified.
There are two unexpanded packs in the pattern and they have the same number of
arguments.
As per [temp.variadic#6] and [temp.variadic#8.1]
> For the purpose of determining whether a pack satisfies a rule regarding entities other than packs, the pack is considered to be the entity that would result from an instantiation of the pattern in which it appears.
> if the pack is a template parameter pack, the element is a template parameter ([temp.param]) of the corresponding kind (type or non-type) designating the ith corresponding type or value template argument;
That means `T` in the pattern would be considered as a type template parameter
designating the corresponding template type argument.
Eventually, as per [class.qual#2.2]
> In a lookup in which function names are not ignored26 and the nested-name-specifier nominates a class C:
>> in a using-declarator of a using-declaration that is a member-declaration, if the name specified after the nested-name-specifier is the same as the identifier or the simple-template-id's template-name in the last component of the nested-name-specifier
Assume the template parameters would be `class T0, class T1,class T2, ...
,class Tn` , the result of instantiating the pattern `T::T` will produce the
list `T0::T0,T1::T1,T2::T2,...Tn::Tn`, which will satisfy the above rule.
Hence, the result of instantiating `T::T` can be considered to nominate the
corresponding constructor of the class named in the nested-name-specifier.
^ permalink raw reply [flat|nested] 7+ messages in thread
* [Bug c++/99399] why does not a pack expansion that is a using-delcaration which intends to introduce the base classes's constructor accept by GCC
2021-03-05 7:20 [Bug c++/99399] New: why does not a pack expansion that is a using-delcaration which intends to introduce the base classes's constructor accept by GCC xmh970252187 at gmail dot com
@ 2021-03-05 7:22 ` xmh970252187 at gmail dot com
2021-08-12 21:52 ` pinskia at gcc dot gnu.org
` (4 subsequent siblings)
5 siblings, 0 replies; 7+ messages in thread
From: xmh970252187 at gmail dot com @ 2021-03-05 7:22 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99399
--- Comment #1 from jim x <xmh970252187 at gmail dot com> ---
All the quotes refer to n4861.
^ permalink raw reply [flat|nested] 7+ messages in thread
* [Bug c++/99399] why does not a pack expansion that is a using-delcaration which intends to introduce the base classes's constructor accept by GCC
2021-03-05 7:20 [Bug c++/99399] New: why does not a pack expansion that is a using-delcaration which intends to introduce the base classes's constructor accept by GCC xmh970252187 at gmail dot com
2021-03-05 7:22 ` [Bug c++/99399] " xmh970252187 at gmail dot com
@ 2021-08-12 21:52 ` pinskia at gcc dot gnu.org
2021-12-08 14:12 ` marxin at gcc dot gnu.org
` (3 subsequent siblings)
5 siblings, 0 replies; 7+ messages in thread
From: pinskia at gcc dot gnu.org @ 2021-08-12 21:52 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99399
--- Comment #2 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Seems fixed in GCC 11+.
^ permalink raw reply [flat|nested] 7+ messages in thread
* [Bug c++/99399] why does not a pack expansion that is a using-delcaration which intends to introduce the base classes's constructor accept by GCC
2021-03-05 7:20 [Bug c++/99399] New: why does not a pack expansion that is a using-delcaration which intends to introduce the base classes's constructor accept by GCC xmh970252187 at gmail dot com
2021-03-05 7:22 ` [Bug c++/99399] " xmh970252187 at gmail dot com
2021-08-12 21:52 ` pinskia at gcc dot gnu.org
@ 2021-12-08 14:12 ` marxin at gcc dot gnu.org
2021-12-08 15:46 ` pinskia at gcc dot gnu.org
` (2 subsequent siblings)
5 siblings, 0 replies; 7+ messages in thread
From: marxin at gcc dot gnu.org @ 2021-12-08 14:12 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99399
Martin Liška <marxin at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Ever confirmed|0 |1
Keywords|needs-bisection |
Status|UNCONFIRMED |NEW
Last reconfirmed| |2021-12-08
Known to work| |12.0
CC| |marxin at gcc dot gnu.org
--- Comment #3 from Martin Liška <marxin at gcc dot gnu.org> ---
Fixed by r11-6942-g9cd7c32549fa3348.
^ permalink raw reply [flat|nested] 7+ messages in thread
* [Bug c++/99399] why does not a pack expansion that is a using-delcaration which intends to introduce the base classes's constructor accept by GCC
2021-03-05 7:20 [Bug c++/99399] New: why does not a pack expansion that is a using-delcaration which intends to introduce the base classes's constructor accept by GCC xmh970252187 at gmail dot com
` (2 preceding siblings ...)
2021-12-08 14:12 ` marxin at gcc dot gnu.org
@ 2021-12-08 15:46 ` pinskia at gcc dot gnu.org
2021-12-08 15:47 ` pinskia at gcc dot gnu.org
2021-12-09 5:52 ` pinskia at gcc dot gnu.org
5 siblings, 0 replies; 7+ messages in thread
From: pinskia at gcc dot gnu.org @ 2021-12-08 15:46 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99399
Andrew Pinski <pinskia at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|NEW |RESOLVED
Resolution|--- |FIXED
--- Comment #4 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
g++.dg/cpp1z/inh-ctor39.C testcase covers this one so closing.
^ permalink raw reply [flat|nested] 7+ messages in thread
* [Bug c++/99399] why does not a pack expansion that is a using-delcaration which intends to introduce the base classes's constructor accept by GCC
2021-03-05 7:20 [Bug c++/99399] New: why does not a pack expansion that is a using-delcaration which intends to introduce the base classes's constructor accept by GCC xmh970252187 at gmail dot com
` (3 preceding siblings ...)
2021-12-08 15:46 ` pinskia at gcc dot gnu.org
@ 2021-12-08 15:47 ` pinskia at gcc dot gnu.org
2021-12-09 5:52 ` pinskia at gcc dot gnu.org
5 siblings, 0 replies; 7+ messages in thread
From: pinskia at gcc dot gnu.org @ 2021-12-08 15:47 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99399
Andrew Pinski <pinskia at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Target Milestone|--- |11.0
^ permalink raw reply [flat|nested] 7+ messages in thread
* [Bug c++/99399] why does not a pack expansion that is a using-delcaration which intends to introduce the base classes's constructor accept by GCC
2021-03-05 7:20 [Bug c++/99399] New: why does not a pack expansion that is a using-delcaration which intends to introduce the base classes's constructor accept by GCC xmh970252187 at gmail dot com
` (4 preceding siblings ...)
2021-12-08 15:47 ` pinskia at gcc dot gnu.org
@ 2021-12-09 5:52 ` pinskia at gcc dot gnu.org
5 siblings, 0 replies; 7+ messages in thread
From: pinskia at gcc dot gnu.org @ 2021-12-09 5:52 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99399
Andrew Pinski <pinskia at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Resolution|FIXED |DUPLICATE
--- Comment #5 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Dup of bug 80417.
*** This bug has been marked as a duplicate of bug 80417 ***
^ permalink raw reply [flat|nested] 7+ messages in thread
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2021-03-05 7:20 [Bug c++/99399] New: why does not a pack expansion that is a using-delcaration which intends to introduce the base classes's constructor accept by GCC xmh970252187 at gmail dot com
2021-03-05 7:22 ` [Bug c++/99399] " xmh970252187 at gmail dot com
2021-08-12 21:52 ` pinskia at gcc dot gnu.org
2021-12-08 14:12 ` marxin at gcc dot gnu.org
2021-12-08 15:46 ` pinskia at gcc dot gnu.org
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