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* [Bug c++/103712] New: variable is not a constant expression because it is used in its own initializer
@ 2021-12-14 16:23 barry.revzin at gmail dot com
2021-12-14 16:25 ` [Bug c++/103712] " pinskia at gcc dot gnu.org
0 siblings, 1 reply; 2+ messages in thread
From: barry.revzin at gmail dot com @ 2021-12-14 16:23 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103712
Bug ID: 103712
Summary: variable is not a constant expression because it is
used in its own initializer
Product: gcc
Version: 12.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: barry.revzin at gmail dot com
Target Milestone: ---
Reduced from StackOverflow (https://stackoverflow.com/q/70342678/2069064):
struct selfref {
selfref* next = nullptr;
};
struct exec {
selfref mem = selfref{};
constexpr exec() {
mem.next = &mem;
}
};
constexpr exec do_thing() {
return exec{};
}
constexpr exec ret = do_thing();
constexpr selfref* ptr = ret.mem.next;
I think this should compile - ret.mem.next points to ret.mem, which is okay
since ret has static storage duration. And then ptr should be pointing to
something that has static storage duration, which is a permitted result.
gcc currently rejects with:
<source>:19:26: error: the value of 'ret' is not usable in a constant
expression
19 | constexpr selfref* ptr = ret.mem.next;
| ^~~
<source>:18:16: note: 'ret' used in its own initializer
18 | constexpr exec ret = do_thing();
| ^~~
This seems vaguely related to CWG 2278, but do_thing() isn't doing copy
elision, so I think this should work.
^ permalink raw reply [flat|nested] 2+ messages in thread
* [Bug c++/103712] variable is not a constant expression because it is used in its own initializer
2021-12-14 16:23 [Bug c++/103712] New: variable is not a constant expression because it is used in its own initializer barry.revzin at gmail dot com
@ 2021-12-14 16:25 ` pinskia at gcc dot gnu.org
0 siblings, 0 replies; 2+ messages in thread
From: pinskia at gcc dot gnu.org @ 2021-12-14 16:25 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103712
Andrew Pinski <pinskia at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|UNCONFIRMED |RESOLVED
Resolution|--- |DUPLICATE
--- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Dup of bug 64989.
*** This bug has been marked as a duplicate of bug 64989 ***
^ permalink raw reply [flat|nested] 2+ messages in thread
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2021-12-14 16:23 [Bug c++/103712] New: variable is not a constant expression because it is used in its own initializer barry.revzin at gmail dot com
2021-12-14 16:25 ` [Bug c++/103712] " pinskia at gcc dot gnu.org
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