https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63811
--- Comment #2 from Francois-Xavier Coudert <fxcoudert at gcc dot gnu.org> --- The libstdc++'s own manual says that __unused is a bad identifier, because it's reserved by BSD: https://gcc.gnu.org/onlinedocs/libstdc++/manual/source_code_style.html#coding_style.bad_identifiers So renaming it to anything else makes bootstrap work again: Index: include/bits/stl_deque.h =================================================================== --- include/bits/stl_deque.h (revision 217342) +++ include/bits/stl_deque.h (working copy) @@ -642,7 +642,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER // Create a copy of the current allocator. _Tp_alloc_type __alloc{_M_get_Tp_allocator()}; // Put that copy in a moved-from state. - _Tp_alloc_type __unused __attribute((__unused__)) {std::move(__alloc)}; + _Tp_alloc_type __unused1 __attribute((__unused__)) {std::move(__alloc)}; // Create an empty map that allocates using the moved-from allocator. _Deque_base __empty{__alloc}; // Now safe to modify current allocator and perform non-throwing swaps.
