Hi! is_late_template_attribute wants to return false for gnu::unused, gnu::used and maybe_unused attributes, so that -Wunused-local-typedefs sees those attributes applied even to typedefs to dependent types. Before my recent r16-5937 change, for maybe_unused this happened to work through the lookup_attribute_spec returning NULL in that case because there is no gnu::maybe_unused attribute, but when that has been fixed, maybe_unused needs to be listed in the exceptions next to unused and used attributes.
Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk? 2025-12-31 Jakub Jelinek <[email protected]> PR c++/123277 * decl2.cc (is_late_template_attribute): Return false also for [[maybe_unused]] attribute on TYPE_DECLs to dependent types. * g++.dg/warn/Wunused-local-typedefs-5.C: New test. --- gcc/cp/decl2.cc.jj 2025-12-27 11:44:31.534958161 +0100 +++ gcc/cp/decl2.cc 2025-12-31 12:32:56.653139050 +0100 @@ -1480,11 +1480,14 @@ is_late_template_attribute (tree attr, t if (is_attribute_p ("weak", name)) return true; - /* Attributes used and unused are applied directly to typedefs for the - benefit of maybe_warn_unused_local_typedefs. */ + /* Attributes used and unused or std attribute maybe_unused are applied + directly to typedefs for the benefit of + maybe_warn_unused_local_typedefs. */ if (TREE_CODE (decl) == TYPE_DECL && (is_attribute_p ("unused", name) - || is_attribute_p ("used", name))) + || is_attribute_p ("used", name) + || (is_attribute_p ("maybe_unused", name) + && get_attribute_namespace (attr) == NULL_TREE))) return false; /* Attribute tls_model wants to modify the symtab. */ --- gcc/testsuite/g++.dg/warn/Wunused-local-typedefs-5.C.jj 2025-12-31 12:26:55.138450671 +0100 +++ gcc/testsuite/g++.dg/warn/Wunused-local-typedefs-5.C 2025-12-31 12:26:02.483371704 +0100 @@ -0,0 +1,15 @@ +// PR c++/123277 +// { dg-do compile { target c++11 } } +// { dg-options "-Wunused-local-typedefs" } + +template <typename T> +void +foo (T B) +{ + typedef T C [[maybe_unused]]; + typedef T D [[gnu::unused]]; + typedef T E [[gnu::used]]; + typedef T F; + typedef T G; // { dg-warning "typedef 'G' locally defined but not used" } + F f; +} Jakub
