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The STL from the Inside · 3:28
Coroutines
A coroutine is a function that can hand back a value, pause, and pick up later with its locals intact. We see why an ordinary stack frame can't do that, build a Fibonacci generator with co_yield and a hand-written promise_type (std::generator is C++23 and missing on the Mac), measure its 56-byte frame (which clang removes entirely at -O2), interleave two coroutines on one thread, and compare that frame with a thread's 512 KB stack.
You will learn
- Explain why a coroutine's frame must outlive a single call
- Describe what co_yield, promise_type, initial_suspend and coroutine_handle::resume do
- Trace a generator producing values one resume at a time
- Compare the cost of a coroutine frame with a thread's stack