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Ownership Types, Views and Type Erasure · 3:24
shared_ptr and the Control Block
A std::shared_ptr is two pointers: one to the object and one to a control block that counts owners. We watch the count rise and fall to zero, read the assembly clang generates for a copy (one atomic add) versus a move (none), break it with two control blocks from one raw pointer, and fix member functions with enable_shared_from_this.
You will learn
- Describe shared_ptr's layout: object pointer plus control block
- Predict use_count through copies, moves and resets
- Explain why copies cost an atomic increment and moves are free
- Avoid two control blocks and use enable_shared_from_this