The C++ GC is not for V8 code, it's for the users of the V8 API eg. Chrome (Blink). It's not being used for big internal systems like the compilers or GC.
V8 has its first module in Rust and I'm sure more are coming, but it's not necessarily an easy integration.
JS is a GCed language. Are there good examples of Rust interacting well with a GCed language runtime where it is able to free unreachable cross domain pointer cycles? Like a JS object that has a reference to a Rust object, which itself has a reference to a JS object. Add more steps and hopefully you can see that collecting such cycles is a hard problem. This is the problem the C++ GC solves.
By the way you can't always break cycles with weak pointers. The browser standards have semantics you have to adhere to.
V8 has its first module in Rust and I'm sure more are coming, but it's not necessarily an easy integration.
JS is a GCed language. Are there good examples of Rust interacting well with a GCed language runtime where it is able to free unreachable cross domain pointer cycles? Like a JS object that has a reference to a Rust object, which itself has a reference to a JS object. Add more steps and hopefully you can see that collecting such cycles is a hard problem. This is the problem the C++ GC solves.
By the way you can't always break cycles with weak pointers. The browser standards have semantics you have to adhere to.