Hi! The following marks these two templates with [[_Clang::no_specializations]] because the P3019R14 paper which introduced them already added the restrictions that they shouldn't be specialized by users.
Tested on x86_64-linux, ok for trunk? I think I'll defer the rest to others (i.e. P2652R2 - std::allocator_traits, P0912R5 - std::coroutine_handle and LWG4535 - <simd>). 2026-07-16 Jakub Jelinek <[email protected]> PR c++/120635 * include/bits/indirect.h (std::indirect, std::polymorphic): Add _GLIBCXX_NO_SPECIALIZATIONS. * testsuite/std/memory/indirect/specialization.cc: New test. * testsuite/std/memory/polymorphic/specialization.cc: New test. --- libstdc++-v3/include/bits/indirect.h.jj 2026-04-24 14:30:10.752144148 +0200 +++ libstdc++-v3/include/bits/indirect.h 2026-07-16 11:24:31.563762066 +0200 @@ -68,7 +68,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION // [indirect], class template indirect template<typename _Tp, typename _Alloc> - class indirect + class _GLIBCXX_NO_SPECIALIZATIONS indirect { static_assert(is_object_v<_Tp>); static_assert(!is_array_v<_Tp>); @@ -467,7 +467,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION // [polymorphic], class template polymorphic template<typename _Tp, typename _Alloc> - class polymorphic + class _GLIBCXX_NO_SPECIALIZATIONS polymorphic { static_assert(is_object_v<_Tp>); static_assert(!is_array_v<_Tp>); --- libstdc++-v3/testsuite/std/memory/indirect/specialization.cc.jj 2026-07-16 11:57:09.678788363 +0200 +++ libstdc++-v3/testsuite/std/memory/indirect/specialization.cc 2026-07-16 12:41:25.312399734 +0200 @@ -0,0 +1,13 @@ +// { dg-do compile { target c++26 } } + +#include <memory> + +struct A {}; +template<typename T> +struct B {}; + +template<> +class std::indirect<A, std::pmr::polymorphic_allocator <A>> {}; // { dg-error "cannot be specialized" } + +template<typename T> +class std::indirect<B<T>, std::pmr::polymorphic_allocator <B<T>>> {}; // { dg-error "cannot be specialized" } --- libstdc++-v3/testsuite/std/memory/polymorphic/specialization.cc.jj 2026-07-16 11:57:09.679876265 +0200 +++ libstdc++-v3/testsuite/std/memory/polymorphic/specialization.cc 2026-07-16 12:41:35.006279624 +0200 @@ -0,0 +1,13 @@ +// { dg-do compile { target c++26 } } + +#include <memory> + +struct A {}; +template<typename T> +struct B {}; + +template<> +class std::polymorphic<A, std::pmr::polymorphic_allocator <A>> {}; // { dg-error "cannot be specialized" } + +template<typename T> +class std::polymorphic<B<T>, std::pmr::polymorphic_allocator <B<T>>> {}; // { dg-error "cannot be specialized" } Jakub
