This project implements a clean, minimal, production‑quality event loop in modern C++17.
It demonstrates the core of an event‑driven architecture: a single dedicated thread that executes tasks sequentially, posted from any number of external threads.
This pattern is widely used in high‑performance systems such as trading engines, network reactors, GUI frameworks, and asynchronous I/O libraries.
- Single‑threaded event loop
- Thread‑safe task submission using
post() - Sequential execution of tasks (no races)
- Non‑blocking API
- Minimal and easy to extend
- C++17 clean implementation
event-loop/ │ ├── include/ │ └── EventLoop.hpp │ ├── src/ │ ├── EventLoop.cpp │ └── main.cpp
To compile the project manually without CMake:
clang++ -std=c++17 -Iinclude src/EventLoop.cpp src/main.cpp -o eventloop
## Run it
./eventloop
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What Is an Event Loop?
An event loop is a dedicated thread that repeatedly:
Waits for tasks
Pops them from a queue
Executes them one at a time
This ensures:
No two tasks run concurrently
No shared‑state races
No locks needed inside tasks
Where This Architecture Is Used
Event loops are foundational in many systems:
Networking & Async I/O
Reactor pattern (epoll, kqueue, IOCP)
Boost.Asio strands
libuv (Node.js engine)
Trading & Finance
Market‑data handlers
Order routers
FIX engines
Low‑latency state machines
GUI Frameworks
Qt event loop
Win32 message pump
Cocoa run loop
Game Engines
Main loop for updates, rendering, and events
Embedded Systems
Cooperative multitasking
Deterministic control loops
✅ Benefits
Predictable execution
Tasks run in strict FIFO order on one thread.
No data races
All state updates happen on the event loop thread.
No locks needed
Internal logic stays simple and deterministic.
Low latency
Avoids context switching and lock contention.
Easy to reason about
Perfect for state machines and message‑driven systems.
⚠️ Drawbacks
Single‑threaded execution
CPU‑bound tasks can block the loop.
Not ideal for heavy computation
Long tasks delay all other tasks.
Requires careful design
Must avoid blocking calls inside the loop.
Scaling requires sharding
You may need multiple event loops for multi‑core utilization.
🧩 When Should You Use an Event Loop?
Use it when:
You need deterministic, race‑free state updates
You’re building async I/O or network‑driven systems
You want to avoid locks and shared‑state complexity
You’re implementing a reactor, dispatcher, or state machine
Avoid it when:
You need heavy parallel computation
Tasks may block for long periods
You need to fully utilize all CPU cores without sharding
📄 License
MIT License
Feel free to use, modify, and extend.
🙌 Contributions
Pull requests and improvements are welcome!
Code