When I switched from C to Java, I experienced a considerable bump in development speed. Just the collections framework was a godsend, not to mention things like GC etc.
Quite literally I would write things in days instead of weeks. Same thing goes for Java -> Clojure. And just to be clear, it is not my favorite language.
My point is - are you sure you just aren't better programmer overall and attributing that (somewhat underservedly because GC and a huge choice of collections) to Java/Clojure/<insert language>?
C++ has stl with many of the same collections, and if you want to use auto_ptr, you don't even need to remember to call delete.
I am not saying there are not productivity gains to be had from using java, but as in this case, it typically comes from not having the relevant experience elsewhere.
From a quick glance at the docs glib looks good but it is still too low-level for normal app development (for example, the size of a hashing table created by hcreate() is fixed; so you have to create & copy & destroy a hash table if you want to add more elements than it can hold at a time) and it should be, that's the whole point.
C++ is a whole other story, sure.