I have updated GCC, but g++ still seems to be using the stl files from the old GCC

Question

I run ubuntu 12.04. Recently, I have followed this post and updated GCC to 4.8.1. Now, when I compile with g++, I get compiler output like these:

/usr/include/c++/4.6/bits/stl_algobase.h:743: note:   Profitability threshold = 6
/usr/include/c++/4.6/bits/stl_algobase.h:743: note: Profitability threshold is 6 loop iterations.
/usr/include/c++/4.6/bits/stl_algobase.h:743: note: LOOP VECTORIZED.

My question is why is g++ using the STLs from GCC 4.6? Is this normal or does this show that I didn't updated GCC thoroughly? If the latter, how can I direct g++ to the new STLs?

Edit0: i installed package g++-4.8 (just now, thanks steeldriver) but still get the same messages~

Edit1: I followed kenn's suggestion and just ran sudo ldconfig...but I still get those messages

Thanks in advance,

Answer 1

OK, I've answered my question by combining these two answers to related quetions. answer 1: update g++ to g++4.8

answer 2: create new Symlinking