[ 2014-02-08: Daniel comments ]

All functions that return a path value such as canonical, current_path, read_symlink, system_complete, temp_directory_path, unique_path, or any member function returning a path value or basic_string value might legally throw an exception, if the allocator of the underlying string complains about insufficient memory. This is an anti-pattern for noexcept, because the exception-specification includes the return statement of a function and given the fact that the language currently does declare RVO as an optional action, we cannot rely on it.

The Standard is currently very careful not to specify functions as noexcept, if this case can happen, see e.g. std::locale::name(). To the contrary, enforcing them to be noexcept, would cause a similar problem as the unconditional noexcept specifier of the value-returning kill_dependency as denoted by LWG 2236.

Basically this requirement conflicts with the section "Adopted Guidelines", second bullet of N3279.