PR libstdc++/56383 * testsuite/20_util/enable_shared_from_this/56383.cc: New. * include/bits/shared_ptr_base.h (__enable_shared_from_this): Make friend declaration match previous declaration of __enable_shared_from_this_helper. * include/bits/shared_ptr.h (enable_shared_from_this): Likewise. From-SVN: r231181