The libunwind project

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
The libunwind API makes it trivial to implement the stack-manipulation aspects of exception handling.
The libunwind API makes it trivial for debuggers to generate the call-chain (backtrace) of the threads in a running program.
It is often useful for a running thread to determine its call-chain. For example, this is useful to display error messages (to show how the error came about) and for performance monitoring/analysis.
efficient setjmp()
With libunwind, it is possible to implement an extremely efficient version of setjmp(). Effectively, the only context that needs to be saved consists of the stack-pointer(s).