I've never seen a GCd heap where you can explicitly free things outside of the Boehm conservative GC. I haven't seen any reference to Go supporting such a thing either.

I think all that happens when a string goes out of scope is that the byte array becomes eligible for GC.

That sounds trivial to fix... go cheats on all sorts of things with the built-in types (maps/slices/strings) that you can't do as a user of the language, seems they could easily implement something that explicitly frees the heap space when the string pops off... the free call could be inlined right into the compiled code by the compiler.

Go has a mark-and-sweep gc so in principle they can support explicit deallocation.

> This kind of thing happens in Ruby a lot; the VM will allocate stuff through malloc that never actually hits the GC; see Aaron Patterson's work.

IIUC there's a really huge difference here. Go can quickly allocate the byte array into the GC managed heap. MRI Ruby has to make a slow call to malloc(). Worse still, when collecting we can't just mark that memory available again. Ruby has to detect the type of each object and call free() accordingly.