[PATCH] libstdc++: Fix attribute order on __normal_iterator friends [PR120949]

[Tomasz Kaminski]

On Sat, Jul 5, 2025 at 1:27 AM Jonathan Wakely <jwakely@redhat.com> wrote:

> In r16-1911-g6596f5ab746533 I claimed to have reordered some attributes
> for compatibility with Clang, but it looks like I got the Clang
> restriction backwards and put them all in the wrong order.
>
> libstdc++-v3/ChangeLog:
>
>         PR libstdc++/120949
>         * include/bits/stl_iterator.h (__normal_iterator): Fix order of
>         always_inline and nodiscard attributes for Clang compatibility.
> ---
>
> Tested x86_64-linux, and tested lightly with Clang.
>
LGTM.
I have also checked that this is indeed an order that is accepted by clang.
The fact that this restriction is only put on hidden friends is strange.

>
>  libstdc++-v3/include/bits/stl_iterator.h | 30 +++++++++++++-----------
>  1 file changed, 16 insertions(+), 14 deletions(-)
>
> diff --git a/libstdc++-v3/include/bits/stl_iterator.h
> b/libstdc++-v3/include/bits/stl_iterator.h
> index a7188f46f6db..75e794f6c020 100644
> --- a/libstdc++-v3/include/bits/stl_iterator.h
> +++ b/libstdc++-v3/include/bits/stl_iterator.h
> @@ -1211,7 +1211,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
>  #else
>         // Forward iterator requirements
>        template<typename _Iter>
> -       __attribute__((__always_inline__)) _GLIBCXX_NODISCARD
> +       _GLIBCXX_NODISCARD __attribute__((__always_inline__))
>         friend
>         _GLIBCXX_CONSTEXPR
>         bool
> @@ -1220,7 +1220,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
>         _GLIBCXX_NOEXCEPT
>         { return __lhs.base() == __rhs.base(); }
>
> -      __attribute__((__always_inline__)) _GLIBCXX_NODISCARD
> +      _GLIBCXX_NODISCARD __attribute__((__always_inline__))
>        friend
>        _GLIBCXX_CONSTEXPR
>        bool
> @@ -1229,7 +1229,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
>        { return __lhs.base() == __rhs.base(); }
>
>        template<typename _Iter>
> -       __attribute__((__always_inline__)) _GLIBCXX_NODISCARD
> +       _GLIBCXX_NODISCARD __attribute__((__always_inline__))
>         friend
>         _GLIBCXX_CONSTEXPR
>         bool
> @@ -1238,7 +1238,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
>         _GLIBCXX_NOEXCEPT
>         { return __lhs.base() != __rhs.base(); }
>
> -      __attribute__((__always_inline__)) _GLIBCXX_NODISCARD
> +      _GLIBCXX_NODISCARD __attribute__((__always_inline__))
>        friend
>        _GLIBCXX_CONSTEXPR
>        bool
> @@ -1248,15 +1248,16 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
>
>        // Random access iterator requirements
>        template<typename _Iter>
> +       _GLIBCXX_NODISCARD __attribute__((__always_inline__))
>         friend
> -       __attribute__((__always_inline__)) _GLIBCXX_NODISCARD
> _GLIBCXX_CONSTEXPR
> +       _GLIBCXX_CONSTEXPR
>         inline bool
>         operator<(const __normal_iterator& __lhs,
>                   const __normal_iterator<_Iter, _Container>& __rhs)
>         _GLIBCXX_NOEXCEPT
>         { return __lhs.base() < __rhs.base(); }
>
> -      __attribute__((__always_inline__)) _GLIBCXX_NODISCARD
> +      _GLIBCXX_NODISCARD __attribute__((__always_inline__))
>        friend
>        _GLIBCXX20_CONSTEXPR
>        bool
> @@ -1265,15 +1266,16 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
>        { return __lhs.base() < __rhs.base(); }
>
>        template<typename _Iter>
> +       _GLIBCXX_NODISCARD __attribute__((__always_inline__))
>         friend
> -       __attribute__((__always_inline__)) _GLIBCXX_NODISCARD
> _GLIBCXX_CONSTEXPR
> +       _GLIBCXX_CONSTEXPR
>         bool
>         operator>(const __normal_iterator& __lhs,
>                   const __normal_iterator<_Iter, _Container>& __rhs)
>         _GLIBCXX_NOEXCEPT
>         { return __lhs.base() > __rhs.base(); }
>
> -      __attribute__((__always_inline__)) _GLIBCXX_NODISCARD
> +      _GLIBCXX_NODISCARD __attribute__((__always_inline__))
>        friend
>        _GLIBCXX_CONSTEXPR
>        bool
> @@ -1282,7 +1284,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
>        { return __lhs.base() > __rhs.base(); }
>
>        template<typename _Iter>
> -       __attribute__((__always_inline__)) _GLIBCXX_NODISCARD
> +       _GLIBCXX_NODISCARD __attribute__((__always_inline__))
>         friend
>         _GLIBCXX_CONSTEXPR
>         bool
> @@ -1291,7 +1293,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
>         _GLIBCXX_NOEXCEPT
>         { return __lhs.base() <= __rhs.base(); }
>
> -      __attribute__((__always_inline__)) _GLIBCXX_NODISCARD
> +      _GLIBCXX_NODISCARD __attribute__((__always_inline__))
>        friend
>        _GLIBCXX_CONSTEXPR
>        bool
> @@ -1300,7 +1302,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
>        { return __lhs.base() <= __rhs.base(); }
>
>        template<typename _Iter>
> -       __attribute__((__always_inline__)) _GLIBCXX_NODISCARD
> +       _GLIBCXX_NODISCARD __attribute__((__always_inline__))
>         friend
>         _GLIBCXX_CONSTEXPR
>         bool
> @@ -1309,7 +1311,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
>         _GLIBCXX_NOEXCEPT
>         { return __lhs.base() >= __rhs.base(); }
>
> -      __attribute__((__always_inline__)) _GLIBCXX_NODISCARD
> +      _GLIBCXX_NODISCARD __attribute__((__always_inline__))
>        friend
>        _GLIBCXX_CONSTEXPR
>        bool
> @@ -1341,7 +1343,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
>  #endif
>         { return __lhs.base() - __rhs.base(); }
>
> -      __attribute__((__always_inline__)) _GLIBCXX_NODISCARD
> +      _GLIBCXX_NODISCARD __attribute__((__always_inline__))
>        friend
>        _GLIBCXX_CONSTEXPR
>        difference_type
> @@ -1349,7 +1351,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
>         _GLIBCXX_NOEXCEPT
>        { return __lhs.base() - __rhs.base(); }
>
> -      __attribute__((__always_inline__)) _GLIBCXX_NODISCARD
> +      _GLIBCXX_NODISCARD __attribute__((__always_inline__))
>        friend
>        _GLIBCXX_CONSTEXPR
>        __normal_iterator
> --
> 2.50.0
>
>
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