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* [Bug c++/98752] New: wrong "error: ‘this’ is not a constant expression" with consteval constructor
@ 2021-01-19 19:59 sbergman at redhat dot com
2021-01-19 20:20 ` [Bug c++/98752] " mpolacek at gcc dot gnu.org
` (6 more replies)
0 siblings, 7 replies; 8+ messages in thread
From: sbergman at redhat dot com @ 2021-01-19 19:59 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98752
Bug ID: 98752
Summary: wrong "error: ‘this’ is not a constant expression"
with consteval constructor
Product: gcc
Version: unknown
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: sbergman at redhat dot com
Target Milestone: ---
At least with gcc-c++-10.2.1-9.fc33.x86_64 and with a local GCC 11 trunk build:
> $ cat test.cc
> struct S1 { consteval S1(int) {} };
> struct S2 {
> S1 x;
> S2(): x(0) {}
> };
> $ g++ -std=c++20 -fsyntax-only test.cc
> test.cc: In constructor ‘S2::S2()’:
> test.cc:4:12: error: ‘this’ is not a constant expression
> 4 | S2(): x(0) {}
> | ^
^ permalink raw reply [flat|nested] 8+ messages in thread
* [Bug c++/98752] wrong "error: ‘this’ is not a constant expression" with consteval constructor
2021-01-19 19:59 [Bug c++/98752] New: wrong "error: ‘this’ is not a constant expression" with consteval constructor sbergman at redhat dot com
@ 2021-01-19 20:20 ` mpolacek at gcc dot gnu.org
2021-01-19 20:31 ` jakub at gcc dot gnu.org
` (5 subsequent siblings)
6 siblings, 0 replies; 8+ messages in thread
From: mpolacek at gcc dot gnu.org @ 2021-01-19 20:20 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98752
Marek Polacek <mpolacek at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |mpolacek at gcc dot gnu.org
Status|UNCONFIRMED |NEW
Last reconfirmed| |2021-01-19
Ever confirmed|0 |1
--- Comment #1 from Marek Polacek <mpolacek at gcc dot gnu.org> ---
Confirmed. Not a regression.
^ permalink raw reply [flat|nested] 8+ messages in thread
* [Bug c++/98752] wrong "error: ‘this’ is not a constant expression" with consteval constructor
2021-01-19 19:59 [Bug c++/98752] New: wrong "error: ‘this’ is not a constant expression" with consteval constructor sbergman at redhat dot com
2021-01-19 20:20 ` [Bug c++/98752] " mpolacek at gcc dot gnu.org
@ 2021-01-19 20:31 ` jakub at gcc dot gnu.org
2021-01-19 20:37 ` mpolacek at gcc dot gnu.org
` (4 subsequent siblings)
6 siblings, 0 replies; 8+ messages in thread
From: jakub at gcc dot gnu.org @ 2021-01-19 20:31 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98752
Jakub Jelinek <jakub at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |jakub at gcc dot gnu.org
--- Comment #2 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
But if we can fix it, I'd think it would be worth an exception.
^ permalink raw reply [flat|nested] 8+ messages in thread
* [Bug c++/98752] wrong "error: ‘this’ is not a constant expression" with consteval constructor
2021-01-19 19:59 [Bug c++/98752] New: wrong "error: ‘this’ is not a constant expression" with consteval constructor sbergman at redhat dot com
2021-01-19 20:20 ` [Bug c++/98752] " mpolacek at gcc dot gnu.org
2021-01-19 20:31 ` jakub at gcc dot gnu.org
@ 2021-01-19 20:37 ` mpolacek at gcc dot gnu.org
2021-01-20 9:25 ` jakub at gcc dot gnu.org
` (3 subsequent siblings)
6 siblings, 0 replies; 8+ messages in thread
From: mpolacek at gcc dot gnu.org @ 2021-01-19 20:37 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98752
--- Comment #3 from Marek Polacek <mpolacek at gcc dot gnu.org> ---
(In reply to Jakub Jelinek from comment #2)
> But if we can fix it, I'd think it would be worth an exception.
Given the fix would likely only affect C++20 code, I think that would be
reasonable.
^ permalink raw reply [flat|nested] 8+ messages in thread
* [Bug c++/98752] wrong "error: ‘this’ is not a constant expression" with consteval constructor
2021-01-19 19:59 [Bug c++/98752] New: wrong "error: ‘this’ is not a constant expression" with consteval constructor sbergman at redhat dot com
` (2 preceding siblings ...)
2021-01-19 20:37 ` mpolacek at gcc dot gnu.org
@ 2021-01-20 9:25 ` jakub at gcc dot gnu.org
2021-12-09 7:47 ` pinskia at gcc dot gnu.org
` (2 subsequent siblings)
6 siblings, 0 replies; 8+ messages in thread
From: jakub at gcc dot gnu.org @ 2021-01-20 9:25 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98752
Jakub Jelinek <jakub at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |jason at gcc dot gnu.org
--- Comment #4 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
Due to the consteval we call cxx_constant_value with
S1::S1 (&((struct S2 *) this)->x, NON_LVALUE_EXPR <0>)
and
((struct S2 *) this)->x
arguments. Shall we turn it into construction on a dummy object instead
somewhere, or shall cxx_eval_* for arguments equal to ctx->object be more
permissive in certain cases?
^ permalink raw reply [flat|nested] 8+ messages in thread
* [Bug c++/98752] wrong "error: ‘this’ is not a constant expression" with consteval constructor
2021-01-19 19:59 [Bug c++/98752] New: wrong "error: ‘this’ is not a constant expression" with consteval constructor sbergman at redhat dot com
` (3 preceding siblings ...)
2021-01-20 9:25 ` jakub at gcc dot gnu.org
@ 2021-12-09 7:47 ` pinskia at gcc dot gnu.org
2023-12-06 19:46 ` sberg.fun at gmail dot com
2024-02-16 16:39 ` mpolacek at gcc dot gnu.org
6 siblings, 0 replies; 8+ messages in thread
From: pinskia at gcc dot gnu.org @ 2021-12-09 7:47 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98752
Andrew Pinski <pinskia at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Last reconfirmed|2021-01-19 00:00:00 |2021-12-8
--- Comment #5 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
struct S1 { consteval S1(int) {} };
struct S2 {
S1 x;
S2(): x(0) {}
};
^ permalink raw reply [flat|nested] 8+ messages in thread
* [Bug c++/98752] wrong "error: ‘this’ is not a constant expression" with consteval constructor
2021-01-19 19:59 [Bug c++/98752] New: wrong "error: ‘this’ is not a constant expression" with consteval constructor sbergman at redhat dot com
` (4 preceding siblings ...)
2021-12-09 7:47 ` pinskia at gcc dot gnu.org
@ 2023-12-06 19:46 ` sberg.fun at gmail dot com
2024-02-16 16:39 ` mpolacek at gcc dot gnu.org
6 siblings, 0 replies; 8+ messages in thread
From: sberg.fun at gmail dot com @ 2023-12-06 19:46 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98752
--- Comment #6 from Stephan Bergmann <sberg.fun at gmail dot com> ---
While the original reproducer from comment 0 appears to be fixed in recent GCC
14 trunk, a slight modification still fails at least with recent GCC 14 trunk:
> $ cat test.cc
> struct S1 {
> int a;
> consteval S1(int n): a(n) {}
> };
> struct S2 {
> S1 x;
> S2(): x(0) {}
> };
> $ g++ -fsyntax-only -std=c++20 test.cc
> test.cc: In constructor ‘S2::S2()’:
> test.cc:7:11: error: call to consteval function ‘((S2*)this)->S2::x.S1::S1(0)’ is not a constant expression
> 7 | S2(): x(0) {}
> | ^~~~
> test.cc:7:11: in ‘constexpr’ expansion of ‘((S2*)this)->S2::x.S1::S1(0)’
> test.cc:3:26: error: modification of ‘*(S2*)this’ is not a constant expression
> 3 | consteval S1(int n): a(n) {}
> | ^~~~
^ permalink raw reply [flat|nested] 8+ messages in thread
* [Bug c++/98752] wrong "error: ‘this’ is not a constant expression" with consteval constructor
2021-01-19 19:59 [Bug c++/98752] New: wrong "error: ‘this’ is not a constant expression" with consteval constructor sbergman at redhat dot com
` (5 preceding siblings ...)
2023-12-06 19:46 ` sberg.fun at gmail dot com
@ 2024-02-16 16:39 ` mpolacek at gcc dot gnu.org
6 siblings, 0 replies; 8+ messages in thread
From: mpolacek at gcc dot gnu.org @ 2024-02-16 16:39 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98752
--- Comment #7 from Marek Polacek <mpolacek at gcc dot gnu.org> ---
Comment 5 test was fixed by r14-5979-g99d114c15523e0
commit 99d114c15523e0bfe7a89ef1947f82eb5ff0260b
Author: Marek Polacek <polacek@redhat.com>
Date: Fri Nov 17 14:48:44 2023 -0500
c++: P2280R4, Using unknown refs in constant expr [PR106650]
the comment 6 one still doesn't work.
^ permalink raw reply [flat|nested] 8+ messages in thread
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2021-01-19 19:59 [Bug c++/98752] New: wrong "error: ‘this’ is not a constant expression" with consteval constructor sbergman at redhat dot com
2021-01-19 20:20 ` [Bug c++/98752] " mpolacek at gcc dot gnu.org
2021-01-19 20:31 ` jakub at gcc dot gnu.org
2021-01-19 20:37 ` mpolacek at gcc dot gnu.org
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