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Unwind is a lightweight exceptions library for C.

Usage
=====

It has 2 constructs. The first should be fairly familiar:

TRY {
    /* Do something here that might throw an exception */
} EXCEPT(exc) {
    /* An exception occured, it is placed into the variable exc. Any exceptions 
       that occur here are handled in the next TRY construct upward. */
} END_TRY

The second may seem a little quirky:

AFTER {
    /* Do something here that might throw an exception. */
} THEN {
    /* Do some cleanup that should occur whether an exception is thrown or
       not. After this code is run, the exception is propagated. */
} END_AFTER

These can be nested (even through function calls). Exceptions are thrown with:

THROW(some_exception);

Where some_exception is a void *. It is undefined as to the outcome of throwing 
an exception from outside a TRY construct. Currently it is only possible to use 
unwind with single threaded code, but all that is needed for multithreaded 
usage is that the variables in unwind.c become thread local.

From within the except clause of a try block you can rethrow the previous 
exception with:

RETHROW;