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* [Bug c++/104512] New: [c++20] consteval constructor does not need to initialize all data members
@ 2022-02-12 9:52 fchelnokov at gmail dot com
2022-02-12 10:02 ` [Bug c++/104512] " pinskia at gcc dot gnu.org
` (3 more replies)
0 siblings, 4 replies; 5+ messages in thread
From: fchelnokov at gmail dot com @ 2022-02-12 9:52 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104512
Bug ID: 104512
Summary: [c++20] consteval constructor does not need to
initialize all data members
Product: gcc
Version: 12.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: fchelnokov at gmail dot com
Target Milestone: ---
In the next program struct B has immediate consteval default constructor, which
does not initialize i field. Then this constructor is used to make a temporary
and its i field remains untouched:
```
struct B {
bool b = true;
int i;
consteval B() {}
};
static_assert( B{}.b );
```
Clang and MSVC are fine with it. But GCC complains:
error: 'B{true}' is not a constant expression
7 | static_assert( B{}.b );
| ^
error: 'B()' is not a constant expression because it refers to an incompletely
initialized variable
Demo: https://gcc.godbolt.org/z/x4n6ezrhT
The requirement that "every non-variant non-static data member must be
initialized" in constexpr/consteval constructor is removed since c++20. Related
discussion: https://stackoverflow.com/a/71085832/7325599
^ permalink raw reply [flat|nested] 5+ messages in thread
* [Bug c++/104512] [c++20] consteval constructor does not need to initialize all data members
2022-02-12 9:52 [Bug c++/104512] New: [c++20] consteval constructor does not need to initialize all data members fchelnokov at gmail dot com
@ 2022-02-12 10:02 ` pinskia at gcc dot gnu.org
2023-01-19 0:33 ` pinskia at gcc dot gnu.org
` (2 subsequent siblings)
3 siblings, 0 replies; 5+ messages in thread
From: pinskia at gcc dot gnu.org @ 2022-02-12 10:02 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104512
--- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
constexpr works but consteval does not.
Also I notice ICC rejects the consteval version but accepts the constexpr one.
^ permalink raw reply [flat|nested] 5+ messages in thread
* [Bug c++/104512] [c++20] consteval constructor does not need to initialize all data members
2022-02-12 9:52 [Bug c++/104512] New: [c++20] consteval constructor does not need to initialize all data members fchelnokov at gmail dot com
2022-02-12 10:02 ` [Bug c++/104512] " pinskia at gcc dot gnu.org
@ 2023-01-19 0:33 ` pinskia at gcc dot gnu.org
2023-01-19 0:34 ` pinskia at gcc dot gnu.org
2023-01-19 1:31 ` pinskia at gcc dot gnu.org
3 siblings, 0 replies; 5+ messages in thread
From: pinskia at gcc dot gnu.org @ 2023-01-19 0:33 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104512
Andrew Pinski <pinskia at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
See Also| |https://github.com/llvm/llv
| |m-project/issues/57627,
| |https://gcc.gnu.org/bugzill
| |a/show_bug.cgi?id=106485
--- Comment #2 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
```
struct B {
bool b = true;
int i;
consteval B() {}
};
static_assert( []() consteval{ return B{}.b; }() );
```
Works for GCC. I think this is a bug in clang ...
static_assert is an immediate function context so B{} needs to be a evaluated
and such.
See https://github.com/llvm/llvm-project/issues/57627 for the clang bug.
See also https://gcc.gnu.org/bugzilla/show_bug.cgi?id=106485#c2 .
^ permalink raw reply [flat|nested] 5+ messages in thread
* [Bug c++/104512] [c++20] consteval constructor does not need to initialize all data members
2022-02-12 9:52 [Bug c++/104512] New: [c++20] consteval constructor does not need to initialize all data members fchelnokov at gmail dot com
2022-02-12 10:02 ` [Bug c++/104512] " pinskia at gcc dot gnu.org
2023-01-19 0:33 ` pinskia at gcc dot gnu.org
@ 2023-01-19 0:34 ` pinskia at gcc dot gnu.org
2023-01-19 1:31 ` pinskia at gcc dot gnu.org
3 siblings, 0 replies; 5+ messages in thread
From: pinskia at gcc dot gnu.org @ 2023-01-19 0:34 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104512
--- Comment #3 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
(In reply to Andrew Pinski from comment #2)
> static_assert is an immediate function context
static_assert is NOT an immediate function context sorry for the typo.
^ permalink raw reply [flat|nested] 5+ messages in thread
* [Bug c++/104512] [c++20] consteval constructor does not need to initialize all data members
2022-02-12 9:52 [Bug c++/104512] New: [c++20] consteval constructor does not need to initialize all data members fchelnokov at gmail dot com
` (2 preceding siblings ...)
2023-01-19 0:34 ` pinskia at gcc dot gnu.org
@ 2023-01-19 1:31 ` pinskia at gcc dot gnu.org
3 siblings, 0 replies; 5+ messages in thread
From: pinskia at gcc dot gnu.org @ 2023-01-19 1:31 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104512
Andrew Pinski <pinskia at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|UNCONFIRMED |RESOLVED
Resolution|--- |INVALID
--- Comment #4 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
(In reply to Andrew Pinski from comment #1)
> constexpr works but consteval does not.
>
> Also I notice ICC rejects the consteval version but accepts the constexpr
> one.
This gives the hint that both MSVC and clang are incorrect really. EDG also
implements correctly static_assert not being an immediate function context.
So closing as invalid.
^ permalink raw reply [flat|nested] 5+ messages in thread
end of thread, other threads:[~2023-01-19 1:31 UTC | newest]
Thread overview: 5+ messages (download: mbox.gz / follow: Atom feed)
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2022-02-12 9:52 [Bug c++/104512] New: [c++20] consteval constructor does not need to initialize all data members fchelnokov at gmail dot com
2022-02-12 10:02 ` [Bug c++/104512] " pinskia at gcc dot gnu.org
2023-01-19 0:33 ` pinskia at gcc dot gnu.org
2023-01-19 0:34 ` pinskia at gcc dot gnu.org
2023-01-19 1:31 ` pinskia at gcc dot gnu.org
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