Hi! The C and C++ FEs when parsing attributes already canonicalize them (i.e. if they start with __ and end with __ substrings, we remove those). lookup_attribute already verifies in gcc_assert that the first character of name is not an underscore, and even lookup_scoped_attribute_spec doesn't attempt to canonicalize the namespace it is passed. But for some historic reason it was canonicalizing the name argument, which misbehaves when an attribute starts with ____ and ends with ____. I believe it is just wrong to try to canonicalize lookup_scope_attribute_spec name attribute, it should have been canonicalized already, in other spots where it is called it is already canonicalized before.
Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk? 2024-02-12 Jakub Jelinek <ja...@redhat.com> PR c++/113674 * attribs.cc (extract_attribute_substring): Remove. (lookup_scoped_attribute_spec): Don't call it. * c-c++-common/Wattributes-3.c: New test. --- gcc/attribs.cc.jj 2024-01-03 11:51:39.392622088 +0100 +++ gcc/attribs.cc 2024-02-12 12:50:00.660458907 +0100 @@ -116,15 +116,6 @@ get_gnu_namespace () return gnu_namespace_cache; } -/* Return base name of the attribute. Ie '__attr__' is turned into 'attr'. - To avoid need for copying, we simply return length of the string. */ - -static void -extract_attribute_substring (struct substring *str) -{ - canonicalize_attr_name (str->str, str->length); -} - /* Insert SPECS into its namespace. IGNORED_P is true iff all unknown attributes in this namespace should be ignored for the purposes of -Wattributes. The function returns the namespace into which the @@ -398,7 +389,6 @@ lookup_scoped_attribute_spec (const_tree attr.str = IDENTIFIER_POINTER (name); attr.length = IDENTIFIER_LENGTH (name); - extract_attribute_substring (&attr); return attrs->attribute_hash->find_with_hash (&attr, substring_hash (attr.str, attr.length)); --- gcc/testsuite/c-c++-common/Wattributes-3.c.jj 2024-02-12 13:04:21.964502985 +0100 +++ gcc/testsuite/c-c++-common/Wattributes-3.c 2024-02-12 13:06:32.659688900 +0100 @@ -0,0 +1,13 @@ +/* PR c++/113674 */ +/* { dg-do compile { target { c || c++11 } } } */ +/* { dg-options "" } */ + +[[____noreturn____]] int foo (int i) /* { dg-warning "'__noreturn__' attribute (directive )?ignored" } */ +{ + return i; +} + +[[____maybe_unused____]] int bar (int i) /* { dg-warning "'__maybe_unused__' attribute (directive )?ignored" } */ +{ + return i; +} Jakub