| Issue |
175483
|
| Summary |
potentially incorrect `error: invalid application of 'sizeof' to an incomplete type` with `-std=c++23`
|
| Labels |
clang:diagnostics,
c++23,
diverges-from:gcc,
diverges-from:msvc
|
| Assignees |
|
| Reporter |
firewave
|
```cpp
#include <memory>
class C
{
public:
C();
~C();
private:
struct Impl;
std::unique_ptr<Impl> mImpl;
};
C::C() = default;
C::~C() = default;
struct C::Impl {};
```
This fails with `-std=c++23`:
```
In file included from <source>:1:
In file included from /opt/compiler-explorer/gcc-snapshot/lib/gcc/x86_64-linux-gnu/16.0.0/../../../../include/c++/16.0.0/memory:80:
/opt/compiler-explorer/gcc-snapshot/lib/gcc/x86_64-linux-gnu/16.0.0/../../../../include/c++/16.0.0/bits/unique_ptr.h:90:16: error: invalid application of 'sizeof' to an incomplete type 'C::Impl'
90 | static_assert(sizeof(_Tp)>0,
| ^~~~~~~~~~~
/opt/compiler-explorer/gcc-snapshot/lib/gcc/x86_64-linux-gnu/16.0.0/../../../../include/c++/16.0.0/bits/unique_ptr.h:398:4: note: in instantiation of member function 'std::default_delete<C::Impl>::operator()' requested here
398 | get_deleter()(std::move(__ptr));
| ^
<source>:14:4: note: in instantiation of member function 'std::unique_ptr<C::Impl>::~unique_ptr' requested here
14 | C::C() = default;
| ^
<source>:14:10: note: in defaulted default constructor for 'C' first required here
14 | C::C() = default;
| ^
<source>:10:12: note: forward declaration of 'C::Impl'
10 | struct Impl;
| ^
```
It builds fine with all previous standards as well as GCC and MSVC using C++23.
https://godbolt.org/z/9rx9j3KhP
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