  Coroutines and events are two common abstractions for writing concurrent
programs. Because coroutines are often more convenient, but events more
portable and efficient, it is natural to want to translate the former into the
latter. CPC is such a source-to-source translator for C programs, based on a
partial conversion into continuation-passing style (CPS conversion) of
functions annotated as cooperative.
  In this article, we study the application of the CPC translator to QEMU, an
open-source machine emulator which also uses annotated coroutine functions for
concurrency. We first propose a new type of annotations to identify functions
which never cooperate, and we introduce CoroCheck, a tool for the static
analysis and inference of cooperation annotations. Then, we improve the CPC
translator, defining CPS conversion as a calling convention for the C language,
with support for indirect calls to CPS-converted function through function
pointers. Finally, we apply CoroCheck and CPC to QEMU (750 000 lines of C
code), fixing hundreds of missing annotations and comparing performance of the
translated code with existing implementations of coroutines in QEMU.
  Our work shows the importance of static annotation checking to prevent actual
concurrency bugs, and demonstrates that CPS conversion is a flexible, portable,
and efficient compilation technique, even for very large programs written in an
imperative language.
