https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102399
Bug ID: 102399 Summary: Cannot mix GCC and C++11 / C23 attribute syntax Product: gcc Version: 12.0 Status: UNCONFIRMED Severity: normal Priority: P3 Component: c++ Assignee: unassigned at gcc dot gnu.org Reporter: dangelog at gmail dot com Target Milestone: --- Hello, If one tries to mix GCC's attribute syntax (__attribute__) and with C++11 / C23 ([[attribute]]), GCC rejects the code (no matter what the order of the attributes is): #define EXPORT __attribute__((visibility("default"))) struct [[nodiscard]] EXPORT Foo { Foo(); }; https://gcc.godbolt.org/z/W868xjeMq While a workaround exists (by sticking to the same "kind" of attribute syntax), it's not always possible or easy to achieve in big codebases, where for compatibility/legacy reasons the attributes are expanded via macros and can expand to a random combination of GCC or C++ attributes. For comparison, Clang and MSVC allow mixed syntaxes.