https://gcc.gnu.org/bugzilla/show_bug.cgi?id=117900
Bug ID: 117900
Summary: Spurious call to copy constructor when
list-initializing a const reference
Product: gcc
Version: 15.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: carsonradtke at microsoft dot com
Target Milestone: ---
Consider the following example which is accepted by Clang and MSVC:
```
// https://godbolt.org/z/MT4EdzreK
// -std=c++20
struct S {
S(const S &) = delete;
};
using Sref = const S&;
void foo(S & s)
{
(void)Sref{s};
}
```
GCC rejects this snippet with the following diagnostic:
```
<source>: In function 'void foo(S&)':
<source>:9:16: error: use of deleted function 'S::S(const S&)'
9 | (void)Sref{s};
| ^
<source>:2:5: note: declared here
2 | S(const S &) = delete;
| ^
Compiler returned: 1
```
The call to `Sref{s}` should not invoke the copy constructor because the
reference object should bind directly to the initializer, s (per
https://eel.is/c++draft/dcl.init.ref#5.1).
Some similar issues exist, but I don't think they directly apply here:
- https://gcc.gnu.org/bugzilla/show_bug.cgi?id=90390 - The name, "incorrect
list initialization behavior for references" sounds promising, but the examples
deviate from this snippet.
- https://gcc.gnu.org/bugzilla/show_bug.cgi?id=53931 - Has a similar repro,
but has to do more with casting than with initialization.
