Circular references and garbage collection

[Aaron Jacobs]

Hi golang-nuts,

Does the Go garbage collector have any trouble with circular references? For
example, if a struct has a function field containing a closure that refers back
to that struct, will the struct be garbage collected if it's not otherwise
referenced?

I imagine the answer is "duh, of course it will be collected", but I want to
check to be sure. Both for the current version of Go and any planned future GC
work.

Thank you,
Aaron

[David Symonds]

Go's GC is a mark-and-sweep collector. It works fine with cycles.

[Aaron Jacobs]

On Tue, Mar 31, 2015 at 1:24 PM, David Symonds <dsym...@golang.org> wrote:
> Go's GC is a mark-and-sweep collector. It works fine with cycles.

Great, and I'll take that to include the upcoming new collector, too.
Thanks for confirming.

[djhe...@gmail.com]

Well the following circular ref doesn't get collected: https://play.golang.org/p/zGjhGrvnPJ

If you break the circle it does: https://play.golang.org/p/9z77l64Ii3

That would lead me to believe that it has a hard time collecting circular refs, can someone comment otherwise?

[Ian Lance Taylor]

On Mon, Mar 30, 2015 at 7:40 PM, <djhe...@gmail.com> wrote:
>
> Well the following circular ref doesn't get collected:
> https://play.golang.org/p/zGjhGrvnPJ
> If you break the circle it does: https://play.golang.org/p/9z77l64Ii3
>
> That would lead me to believe that it has a hard time collecting circular
> refs, can someone comment otherwise?

The GC does fine at collecting circular references.

Finalizers don't work with circular references. This is documented in
the description of runtime.SetFinalizer.

Ian

[djhe...@gmail.com]

Ah, thanks I missed that.