Is std::list<>::sort stable?

Question

I couldn't find any definitive answer to this question.

I suppose most implementation use merge sort that is stable but, is the stability a requirement or a side effect?

Answer 1

Yes, std::list<>::sort is guaranteed to be stable.

See http://www.sgi.com/tech/stl/List.html

Answer 2

According to "The C++ Programming Language" (Stroustrup p470), yes, stl::list<>::sort is stable.

Answer 3

C++ Standard ISO/IEC 14882:2003 says:

23.2.2.4/31

Notes: Stable: the relative order of the equivalent elements is preserved. If an exception is thrown the order of the elements in the list is indeterminate.