This is an unofficial snapshot of the ISO/IEC JTC1 SC22 WG21 Core Issues List revision 112e. See http://www.open-std.org/jtc1/sc22/wg21/ for the official list.
According to 4.1 [intro.compliance] paragraph 7,
A freestanding implementation is one in which execution may take place without the benefit of an operating system, and has an implementation-defined set of libraries that includes certain language-support libraries (184.108.40.206 [compliance]).
This definition links two relatively separate topics: the lack of an operating system and the minimal set of libraries. Furthermore, 220.127.116.11 [basic.start.main] paragraph 1 says:
[Note: in a freestanding environment, start-up and termination is implementation-defined; start-up contains the execution of constructors for objects of namespace scope with static storage duration; termination contains the execution of destructors for objects with static storage duration. —end note]
It would be helpful if the two characteristics (lack of an operating system and restricted set of libraries) were named separately and if these statements were clarified to identify exactly what is implementation-defined.
Notes from the October, 2009 meeting:
The CWG felt that it needed a specific proposal in a paper before attempting to resolve this issue.