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Ownership Types, Views and Type Erasure · 3:45
weak_ptr
A std::weak_ptr watches an object without owning it, using the control block's weak count. We use lock() to get a real owner or null, see that the control block outlives the object, build a cache and an observer list that never keep anything alive by themselves, watch two objects that own each other leak, and fix the cycle with a weak back edge.
You will learn
- Explain what a weak_ptr is and what it counts
- Explain why the control block outlives the object until the weak count reaches zero
- Use lock() instead of expired()-then-use
- Recognise a shared_ptr cycle and break it with weak_ptr
- Choose unique_ptr down and raw pointers up for trees