Old (~2007) fun project implementing sync-looking libev async code using continuation passing. The implementation (ab)uses (GC)C macros and computed gotos, in the spirit of Duff's device.

See the SM_CALL implementation and how it is used:

if(SM_CALL(evaio_recv_peek, fd, s->buf+100, 1000-103, childco) < 0) {
  ...
}