https://gcc.gnu.org/g:ae04c1afd1526a6d468777809c50a9d02816ded9
commit r16-7359-gae04c1afd1526a6d468777809c50a9d02816ded9 Author: Nathan Myers <[email protected]> Date: Fri Feb 6 03:56:42 2026 -0500 libstdc++: fix C++17 regression in concept __heterogeneous_key (2nd) The commit 3f7905550483408a2c4c5096a1adc8d7e863eb12 defined a concept __heterogeneous_key using a name not defined in C++17. This is fixed by guarding the definition behind a name defined in C++23 the earliest Standard that uses the definition. https://gcc.gnu.org/pipermail/gcc-patches/2026-February/707814.html libstdc++-v3/ChangeLog * include/bits/stl_function.h (concept __heterogeneous_key): Guard with __glibcxx_associative_heterogeneous_erasure Diff: --- libstdc++-v3/include/bits/stl_function.h | 5 ++--- 1 file changed, 2 insertions(+), 3 deletions(-) diff --git a/libstdc++-v3/include/bits/stl_function.h b/libstdc++-v3/include/bits/stl_function.h index 657f40bca2ee..1312564216bd 100644 --- a/libstdc++-v3/include/bits/stl_function.h +++ b/libstdc++-v3/include/bits/stl_function.h @@ -1525,7 +1525,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION #endif #endif -#ifdef __cpp_concepts +#ifdef __glibcxx_associative_heterogeneous_erasure template <typename _Kt, typename _Container> concept __not_container_iterator = (!is_convertible_v<_Kt&&, typename _Container::iterator> && @@ -1533,8 +1533,7 @@ template <typename _Kt, typename _Container> template <typename _Kt, typename _Container> concept __heterogeneous_key = - (!is_same_v<typename _Container::key_type, - typename remove_cvref<_Kt>::type>) && + (!is_same_v<typename _Container::key_type, remove_cvref_t<_Kt>>) && __not_container_iterator<_Kt, _Container>; #endif
