https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102000
Hubert Tong <hstong at ca dot ibm.com> changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |hstong at ca dot ibm.com
--- Comment #4 from Hubert Tong <hstong at ca dot ibm.com> ---
(In reply to Johel Ernesto Guerrero Peña from comment #3)
> https://bugs.llvm.org/show_bug.cgi?id=51560#c1 points out
> > I'm not sure what you think the problem is here. The constructor isn't
> > getting called; see http://eel.is/c++draft/dcl.init.general#8 .
> It seems to me that they are right and the example above is well-formed.
That depends on what "the semantic constraints for default-initialization are
checked" means.
(In reply to Johel Ernesto Guerrero Peña from comment #0)
> ```
> An immediate invocation shall be a constant expression. --
> https://eel.is/c++draft/expr.const#13.sentence-3
>
> Lots of wording in between...
>
> 2 A variable or temporary object o is constant-initialized if
> (2.1) either it has an initializer or its default-initialization results
> in some initialization being performed, and
> -- https://eel.is/c++draft/expr.const#2
> 7 To default-initialize an object of type T means:
> (7.3) Otherwise, no initialization is performed.
> -- https://eel.is/c++draft/dcl.init.general#7
> ```
That wording would be relevant for a similar case involving `constinit`. Here,
the relevant wording is in 7.7 [expr.const] paragraph 12 (and the uninitialized
`int` is fine with the current wording). The example needs to be changed to use
pointers:
```
struct A {
consteval A() = default;
private:
int *m;
};
struct B {
consteval B() = default;
private:
int *m, *n = 0;
};
void f() {
A a; // GCC accepts this despite pointer with indeterminate value
B b; // GCC rejects this
}
```
So it seems GCC just doesn't do certain checking when the constructor is
trivial.
