Linux C/C++ IDE

Good evening,

been using Geany under Ubuntu since I started studying Business Informatics. Now being in the second semester our classes changed from C to C++ and I found that Geany isn't so good for C++ because it lacks a decent auto-completion (e.g. member functions of STL are not shown).
Does anyone know a light IDE with decent auto completion?

I use vim (minimally configured), my terminal emulator, coreutils, and a tiling WM to do everything. No graphical file manager, no IDE autocomplete, etc.

Is it the most efficient way to work? No.
Do I find myself wishing I had a decent C/Lua autocompleter for Vim? Yes, and I'm sure there already are a few.
Could I eliminate most of my switches from Vim to terminal emulators if I studied Vim commands just a little bit more? Probably.

What I do get with this setup is an incredibly simple working environment that never gets in my way, even if it often refuses to lend a helping hand.