[Bug libstdc++/59656] weak_ptr::lock function crashes when compiling with -fno-exceptions flag

[redi at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=59656

--- Comment #5 from Jonathan Wakely <redi at gcc dot gnu.org> ---
Thanks Paul. You mentioned a proposed patch, are you working on that? From a
quick look I didn't see how to fix it without adding a
_Sp_counted_base::_M_add_ref_lock_nothrow() function and adding new
constructors taking an additional std::nothrow_t argument to the whole class
hierarchy. Did you have a simpler fix in mind?