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,
$ 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.
