On Fri, Feb 06, 2026 at 03:30:27AM -0500, Nathan Myers wrote:
> Fixed in 786e316de5c25a3fddeaa2003f6efb64fb5ab4a9 2026-02-06 03:25:21
>
> libstdc++: fix C++17 regression in concept __heterogeneous_key
>
> The commit 3f7905550483408a2c4c5096a1adc8d7e863eb12 defined a
> concept using a name not defined in C++17. This is fixed by
> using an older name.
>
> https://gcc.gnu.org/pipermail/gcc-patches/2026-February/707814.html
>
> libstdc++-v3/ChangeLog
> * include/bits/stl_function.h (__heterogeneous_key): Use
> C++17-defined remove_cvref<>::type instead.
Does that really work?
remove_cvref is also C++20 like remove_cvref_t, only __remove_cvref_t
is C++11 and later.
#ifdef __cpp_lib_remove_cvref // C++ >= 20
# if _GLIBCXX_USE_BUILTIN_TRAIT(__remove_cvref)
template<typename _Tp>
struct remove_cvref
{ using type = __remove_cvref(_Tp); };
# else
template<typename _Tp>
struct remove_cvref
{ using type = typename remove_cv<_Tp>::type; };
template<typename _Tp>
struct remove_cvref<_Tp&>
{ using type = typename remove_cv<_Tp>::type; };
template<typename _Tp>
struct remove_cvref<_Tp&&>
{ using type = typename remove_cv<_Tp>::type; };
# endif
template<typename _Tp>
using remove_cvref_t = typename remove_cvref<_Tp>::type;
/// @}
#endif // __cpp_lib_remove_cvref
Jakub
