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Stack Frames

Think back to the warnings I gave you about working with void* data types. It's easy to push the wrong kinds of data onto our stack_t because, like Starbucks Wi-Fi, it will let anything in.

So, to prevent us from shooting ourselves in the foot, we will create some functions that are more type safe and make it much more difficult to do the wrong thing when interacting with our vm_t. Wrong things like:

// The C compiler won't stop us :'(
stack_push(vm->frames, (void *)7);
stack_push(vm->frames, (void *)"uh oh");

But we want to make it easier on ourselves to only push frame_t * types onto vm->frames, so we'll write some wrapper functions to help us out.

Assignment

Take a look at the frame_t type in vm.h. It's a simple struct that holds a stack_t of snek_object_t * pointers that represent the object references in the frame.

Complete the vm_frame_push function in vm.c. It should stack_push a frame_t * onto the vm->frames stack.
Complete the vm_new_frame function in vm.c. It should:
1. Allocate a new frame_t on the heap.
2. Initialize the frame's references with a stack_new of capacity 8.
3. Push the newly allocated frame onto the vm->frames stack.
4. Return the newly allocated frame.
Complete the frame_free function in vm.c. It should:
1. Free the frame_t's references stack (we have a special function for this)
2. Free the frame_t struct.