If you write programs with a gc there is always a level which you can't get your hands on to change. If you want to create a piece of a puzzle that is tiny, does one thing, and does it right, like a shared library, a command, a linkable object, or any tiny standalone binary, the gc is always a thorn.

Anything where memory or interactivity needs to be tightly controlled is problematic with a gc. Not only that, but a gc doesn't scale as well with lots of threads. Ultimately you need thread local allocation since you will eventually be bottlenecked by the fact that typical allocation (with malloc, VirtualAlloc, mmap, etc) is protected by a mutex, and deallocation suffers the same fate.