C++ new operator thread safety in linux and gcc 4

You will have to look very hard to find a platform that supports threads but doesn't have a thread safe new. In fact, the thread safety of new (and malloc) is one of the reasons it's so slow.

If you want a thread safe STL on the other hand, you may consider Intel TBB which has thread aware containers (although not all operations on them are thread safe).

Generally the new operator is thread safe - however thread safety guarantees for calls into the STL and the standard library are governed by the standard - this doesn't mean that they are thread unaware - they tend to have very well defined guarantees of thread safety for certain operations. For example iterating through a list in a read-only fashion is thread safe for multiple readers, while iterating through a list and making updates is not. You have to read the documentation and see what the various guarantees are, although they aren't that onerous and they tend to make sense.