What do you know about the garbage collector in Dart?

Dart uses a single-threaded garbage collector based on generational garbage collection.

Key features:

• Generational Collection: Objects are divided into two generations:
  • Young generation: New, short-lived objects. Collected frequently.
  • Old generation: Long-lived objects that have survived several collections in the young generation. Collected less frequently.
• Stop-the-World: Garbage collection requires pausing the program execution (Dart Isolates). However, thanks to single-threading and optimizations, delays are minimized.
• Mark-and-Sweep: The old generation uses the Mark-and-Sweep algorithm. Reachable objects are marked first, then unreachable ones are removed. The young generation uses a Copying Collector algorithm, which quickly moves live objects to another memory space.
• No cyclic garbage collection: Developers do not need to manually manage memory or invoke GC. The system handles it automatically.
• Optimizations: Include function inlining, type specialization, and object allocation on the stack, reducing the load on the garbage collector.

For example, when creating a new object:

// Creating a new object in the "young" generation of memory
var myObject = MyClass();

If myObject remains accessible for a long time, it will eventually be moved to the "old" generation. If it becomes unreachable, the garbage collector will free it sooner or later.

// myObject is now unreachable and may be collected by the garbage collector
myObject = null;

It is important to understand that Dart's garbage collector is efficient but not a panacea for memory leaks, which can occur due to keeping strong references to objects that are no longer needed (e.g., subscriptions that were not canceled).