Use of setjmp/longjmp

Basically these were calls that are used to recover from exceptional situations for a C program running on UNIX. It works as follows:

Suppose you have a long call sequence and when some exceptional condition is detected deep in the call chain you want to handle the situation somewhere high up in the call chain (ignoring all the intermediate call sites and the stack frames). It can be done as follows:

(1) First, call setjmp at the place in the higher position in the call chain with a global environment variable. It saves the program state (pc, sp, gen. purpose regs etc) onto the environment and returns to the current program point (returning a 0). Execution continues

(2) When a exceptional situation occurs deep in the call chain , call longjmp with the environment variable. This just restores the values of the registers from the environment and returns from the point where setjmp was called originally (with a 1 now).

Update from Chaitu: As can be seen from above, jumping from somwhere deep down the call chain to some point way higher up can be a recipe for memory leaks, since it is no way to deallocate any heap objects that create in the intermediate functions, unless a custom memory manager is used and some hack (or technique ?) is put in place to identify all the objects created by functions that were called by the handling function.
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