is list::size() unequivocally o(n)?

recently, i beheld mentioning std::list::size() linear complexity.

according , fact doing contingent customary doesn't contend complexity be.

the critique says:

actually, depends stl you
using. microsoft visible studio v6
implements size() {return (_size);
} since gcc (at slightest versions
3.3.2 4.1.0) { relapse std::distance(begin(), end()); } the
initial consistent speed, second
o(n) speed

1. so speculation vc++ throng size() consistent complexity dinkumware
   probably won't have altered fact given vc6. am i right there?
   


2. what does feeling now gcc? unequivocally o(n), since the
   developers select so?