C++ coroutines lab presentations. WORK IN PROGRESS

Presentations

• Problem domain
• Mechanics
• std::generator
• Scoped coroutines
  • TODO discuss issue with reference parameters, lambda captures, pointers, string_views
    • the generator problems with scope
  • TODO the (invalid) std::move trick to call once
  • TODO the co_await by value trick
    • TODO still (potential) scope issue
  • TODO why not eager
    • finall_suspend first
    • the issue with eager initial_suspend when actually suspended later
• Trampoline
• Timers
• Structured concurency
  • sane principles
    • a child coroutine does not outlives its parent
    • a coroutine runs uninterrupted until a co_await
  • TODO: discuss the issue of detach/fire and forget
    • lifetime
      • discuss bad advice that uses detached models
      • https://isocpp.github.io/CppCoreGuidelines/CppCoreGuidelines#Rcoro-capture
      • more bad advice https://devblogs.microsoft.com/oldnewthing/20211103-00/?p=105870
      • though they really like detached in embedded environments, explain why
    • error propagation
  • TODO: discuss issue with blocking in bounded parallelism cases
  • TODO: discuss issue with destructors blocking
• Cancellation
  • hiding cancellation from function signature (e.g. see co_await get_cancellation_token()
• Nursery
• Threading models
• Windows Thread Pool

Bibliography

• spec N4775: relatively short, readable, but background info required
• Lewis Baker’s posts: long, not up to date, but really good background info required to understand coroutines
• Nathaniel J. Smith: Notes on structured concurrency, or: Go statement considered harmful
• C++ Coroutines at Scale - Implementation Choices at Google - Aaron Jacobs - C++Now 2024
• C++ Coroutines and Structured Concurrency in Practice - Dmitry Prokoptsev - C++Now 2024
• Structured Concurrency: Writing Safer Concurrent Code with Coroutines… - Lewis Baker - CppCon 2019
• CppCon 2018: G. Nishanov “Nano-coroutines to the Rescue! (Using Coroutines TS, of Course)