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# Garbage Collection
---
## Object Definition
```c
typedef struct _kpl_gc {
POOL_HEADER(_kpl_gc);
union {
_Atomic int32_t ref_count;
_Atomic bool mark;
} method;
kpl_any any;
pthread_mutex_t mutex;
} kpl_gc;
static _Atomic size_t marked_threads;
static kpl_gc *old_gc_head, *gc_head, *gc_tail;
```
## Counting
`ref_count` starts at 1
Each assign increments the reference count, each time it goes out of scope the reference count is decreased
When `ref_count` hits 0, data is freed
## Tracing
1. Once triggered add a init task to the async queue
2. This task moves the `gc_head` to the `old_gc_head` and sets the `gc_wait` to off for each thread
3. Each thread will run down its queue queue marking found gc objects
3. Once all have run and `marked_threads == available_threads` add a mark and sweep task to the async queue
4. Async task goes down async queue and does final mark, then a sweep on the `old_gc_head` is done
5. What remains on the `old_gc_head` is added to the gc tail
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