My task was to implement a garbage collector for a basic Scheme interpreter implemented in C. All the files here were already complete except alloc.c, which was where I completed the implementation of the function collect_garbage(). More details below.
This garbage collection was done in a mark-and-sweep way. For the marking phase, I implemented the functions mark_environment(Environment *env), mark_value(Value *v), and mark_lambda(Lambda *f). These functions recursively call each other to handle various relationships between the data structures. mark_eval_stack was also implemented to handle the evaluation stack.
Next is the sweep phase. Three helper functions were created for this phase. They are sweep_values(), sweep_lambdas(), and sweep_environments(). These functions unmark objects if they are marked for the next garbage collection. If objects are unmarked, they are deleted.
See examples.scm for instructions on testing the garbage collector.