setjmp / longjmp

setjmp and longjmp, declared in <setjmp.h>, implement a non-local jump that lets a program save an execution point with setjmp and later jump back to it with longjmp, potentially unwinding several function calls at once. This is sometimes used as a rough substitute for exception handling, for example to recover from an error deep in a call stack. Because it skips normal function cleanup, like calling destructors in C++, it must be used carefully, and it does not exist to make error handling elegant, only possible.