On Sun, 6 Jul 2025 at 19:53, Stephan Bergmann <sberg....@gmail.com> wrote: > > On 6/12/25 10:46, Jonathan Wakely wrote: > > It now says: > > > > I also had to reorder the __attribute__((always_inline)) and > > [[nodiscard]] attributes on the pre-c++20 operators, because Clang won't > > allow [[foo]] after __attribute__((bar)) on a friend function: > > > > <source>:4:36: error: an attribute list cannot appear here > > 4 | __attribute__((always_inline)) [[nodiscard]] friend bool > > | ^~~~~~~~~~~~~ > > Just noting that at least with recent Clang 21 trunk,
Yes, this is https://gcc.gnu.org/bugzilla/show_bug.cgi?id=120949 > > > $ cat test.cc > > #include <iterator> > > > $ clang++ -std=c++17 -fsyntax-only test.cc > > In file included from test.cc:1: > > In file included from > > ~/gcc/inst/lib/gcc/x86_64-pc-linux-gnu/16.0.0/../../../../include/c++/16.0.0/iterator:65: > > ~/gcc/inst/lib/gcc/x86_64-pc-linux-gnu/16.0.0/../../../../include/c++/16.0.0/bits/stl_iterator.h:1252:37: > > error: > > an attribute list cannot appear here > > 1252 | __attribute__((__always_inline__)) _GLIBCXX_NODISCARD > > _GLIBCXX_CONSTEXPR > > | ^~~~~~~~~~~~~~~~~~ > > ~/gcc/inst/lib/gcc/x86_64-pc-linux-gnu/16.0.0/../../../../include/c++/16.0.0/x86_64-pc-linux-gnu/bits/c++config.h:173:29: > > note: > > expanded from macro '_GLIBCXX_NODISCARD' > > 173 | # define _GLIBCXX_NODISCARD [[__nodiscard__]] > > | ^~~~~~~~~~~~~~~~~ > > In file included from test.cc:1: > > In file included from > > ~/gcc/inst/lib/gcc/x86_64-pc-linux-gnu/16.0.0/../../../../include/c++/16.0.0/iterator:65: > > ~/gcc/inst/lib/gcc/x86_64-pc-linux-gnu/16.0.0/../../../../include/c++/16.0.0/bits/stl_iterator.h:1269:37: > > error: > > an attribute list cannot appear here > > 1269 | __attribute__((__always_inline__)) _GLIBCXX_NODISCARD > > _GLIBCXX_CONSTEXPR > > | ^~~~~~~~~~~~~~~~~~ > > ~/gcc/inst/lib/gcc/x86_64-pc-linux-gnu/16.0.0/../../../../include/c++/16.0.0/x86_64-pc-linux-gnu/bits/c++config.h:173:29: > > note: > > expanded from macro '_GLIBCXX_NODISCARD' > > 173 | # define _GLIBCXX_NODISCARD [[__nodiscard__]] > > | ^~~~~~~~~~~~~~~~~ > > 2 errors generated. > > now fails (while with --std=c++20) it works, where something like > > > diff --git a/libstdc++-v3/include/bits/stl_iterator.h > > b/libstdc++-v3/include/bits/stl_iterator.h > > index a7188f46f6d..26bb0206375 100644 > > --- a/libstdc++-v3/include/bits/stl_iterator.h > > +++ b/libstdc++-v3/include/bits/stl_iterator.h > > @@ -1248,8 +1248,9 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION > > > > // Random access iterator requirements > > template<typename _Iter> > > + __attribute__((__always_inline__)) _GLIBCXX_NODISCARD > > friend > > - __attribute__((__always_inline__)) _GLIBCXX_NODISCARD > > _GLIBCXX_CONSTEXPR > > + _GLIBCXX_CONSTEXPR > > inline bool > > operator<(const __normal_iterator& __lhs, > > const __normal_iterator<_Iter, _Container>& __rhs) > > @@ -1265,8 +1266,9 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION > > { return __lhs.base() < __rhs.base(); } > > > > template<typename _Iter> > > + __attribute__((__always_inline__)) _GLIBCXX_NODISCARD > > friend > > - __attribute__((__always_inline__)) _GLIBCXX_NODISCARD > > _GLIBCXX_CONSTEXPR > > + _GLIBCXX_CONSTEXPR > > bool > > operator>(const __normal_iterator& __lhs, > > const __normal_iterator<_Iter, _Container>& __rhs) > > would fix that. >
