On Sun, 15 Sept 2024 at 16:24, Jonathan Wakely wrote:
>
> Tested x86_64-linux.
>
> -- >8 --
>
> PR 116529 shows that std::unique_ptr<X&, D> is currently unusable
> because the constructor taking std::auto_ptr (which is a non-standard
> extension since C++17) tries to form the invalid type X&* during
> overload resolution. We can use the `pointer` type in the constructor
> constraints, instead of trying to form an invalid type. The
> std::auto_ptr constructor can never actually match for the case where
> element_type is a reference, so we just need it to produce a
> substitution failure instead of being ill-formed.
>
> LWG 4144 might make std::unique_ptr<X&, D> ill-formed, which would
> invalidate this new test. We would have to remove this test in that
> case. Using `pointer` in the constructor from std::auto_ptr would not be
> needed to support the std::unique_ptr<X&, D> case, but would not cause
> any harm either.
Pushed to trunk now.
>
> libstdc++-v3/ChangeLog:
>
> PR libstdc++/116529
> * include/bits/unique_ptr.h (unique_ptr(auto_ptr<U>&&)):
> Use pointer instead of T*.
> * testsuite/20_util/unique_ptr/creation/116529.cc: New test.
> ---
> libstdc++-v3/include/bits/unique_ptr.h | 5 +--
> .../20_util/unique_ptr/creation/116529.cc | 35 +++++++++++++++++++
> 2 files changed, 38 insertions(+), 2 deletions(-)
> create mode 100644
> libstdc++-v3/testsuite/20_util/unique_ptr/creation/116529.cc
>
> diff --git a/libstdc++-v3/include/bits/unique_ptr.h
> b/libstdc++-v3/include/bits/unique_ptr.h
> index 0f600db32f9..edcff78bff9 100644
> --- a/libstdc++-v3/include/bits/unique_ptr.h
> +++ b/libstdc++-v3/include/bits/unique_ptr.h
> @@ -379,8 +379,9 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
> #pragma GCC diagnostic push
> #pragma GCC diagnostic ignored "-Wdeprecated-declarations"
> /// Converting constructor from @c auto_ptr
> - template<typename _Up, typename = _Require<
> - is_convertible<_Up*, _Tp*>, is_same<_Dp, default_delete<_Tp>>>>
> + template<typename _Up,
> + typename = _Require<is_convertible<_Up*, pointer>,
> + is_same<_Dp, default_delete<_Tp>>>>
> unique_ptr(auto_ptr<_Up>&& __u) noexcept;
> #pragma GCC diagnostic pop
> #endif
> diff --git a/libstdc++-v3/testsuite/20_util/unique_ptr/creation/116529.cc
> b/libstdc++-v3/testsuite/20_util/unique_ptr/creation/116529.cc
> new file mode 100644
> index 00000000000..323fc7cb27c
> --- /dev/null
> +++ b/libstdc++-v3/testsuite/20_util/unique_ptr/creation/116529.cc
> @@ -0,0 +1,35 @@
> +// { dg-do run { target c++11 } }
> +
> +// Bug libstdc++/116529 - Construction of unique_ptr with reference type
> +// is rejected because of auto_ptr constructor
> +
> +#include <memory>
> +#include <testsuite_hooks.h>
> +
> +int count = 0;
> +
> +struct X
> +{
> + ~X() { ++count; }
> +};
> +
> +struct deleter : std::default_delete<X>
> +{
> + using pointer = X*;
> +};
> +
> +void
> +test01()
> +{
> + {
> + std::unique_ptr<X&, deleter> up(new X);
> + // { dg-bogus "forming pointer to reference" "" { target *-*-* } 0 }
> + VERIFY( count == 0 );
> + }
> + VERIFY( count == 1 );
> +}
> +
> +int main()
> +{
> + test01();
> +}
> --
> 2.46.0
>
