The primary goal of this project is to define a portable and efficient C programming interface (API) to determine the call-chain of a program. The API additionally provides the means to manipulate the preserved (callee-saved) state of each call-frame and to resume execution at any point in the call-chain (non-local goto). The API supports both local (same-process) and remote (across-process) operation. As such, the API is useful in a number of applications. Some examples include: exception handling, debuggers, introspection and efficient setjmp().