C++ API Reference

The greenlet class

The greenlet class is a wrapper around the greenlet_t structure from the cgreenlet C API. Before reading this section, make sure you have read the C API first.

Two constructors and a destructor are provided for the greenlet class:

class greenlet
    greenlet(greenlet_start_func_t start_func=0L,
                   greenlet *parent=0L, long stacksize=OL);
    greenlet(greenet_t *greenlet);

The first constructor creates a new greenlet instance from scratch. All arguments are optional and have the same measing as in the C API. The second form creates a greenlet instance from a greenlet_t struct from the C API. This allows C and C++ greenlets to exist in the same program. The destructor peforms the same thing as greenlet_destory() in the C API.

Main function

The greenlet’s main function is always its virtual run() method:

    virtual void *run(void *arg);

The default implementation of run() executes the start_func argument that was passed to the constructor. You can override run() to embed your main function in a derived class.

Greenlet methods

Many functions that exist in the C API exist as method on the greenlet class in the C++ API:

    void *switch_to(void *arg);
    void inject(greenlet_inject_func_t inject_func);
    void reset();

    bool isstarted();
    bool isdead();


Exceptions that are not caught in a greenlet will exit the greenlet’s main function and move it to the “DEAD” state. When this happens, the exception is then re-raised in the greenlet’s parent, and the parent’s parent, and so on, until either it is caught or until the root greenlet is reached. If the root greenlet does not catch the exception, the C++ program will terminate.