cxxhazard

A small C++17 hazard pointer implementation written as a learning project.

The goal of this project is to study how hazard pointers can be used for safe memory reclamation in lock-free data structures. It includes a basic hazard pointer interface, retired-object reclamation, and a simple stack example.

Example

A simplified usage pattern:

bool pop(T& dest)
{
    auto hazard = make_hazard();

    node* old_head;
    do {
        old_head = hazard.protect(_head);

        if (old_head == nullptr)
            return false;

    } while (!_head.compare_exchange_strong(old_head, old_head->_next));

    hazard.unprotect();

    dest = *old_head->_data;

    retire(old_head, [old_head]() {
        delete old_head->_data;
        delete old_head;
    });

    return true;
}

For a complete example, see test/test01.cpp.

Project Structure

File	Purpose
hazard.hpp	Main public header
ptr.hpp	Hazard pointer interface
resource.hpp	Internal hazard pointer storage
reclaim.hpp	Retired object reclamation
domain.hpp	Domain/base class support
fwd.hpp	Forward declarations

Status

This project is mainly for studying lock-free memory reclamation. It is not intended to be a production-ready library.

TODO

• Add more tests
• Add more examples
• Improve the internal hazard pointer lookup structure