PoC of function hooking in Swift

Due to compiler optimizations, some class methods and functions are inlined/removed, so we're unable to get their addresses to route.
rd_get_func_imp() returns some value for these ones though, but it's invalid and points outside a target memory region.

So the following code generates a compiler error

Error: Partial application of struct method is not allowed

var err = SwiftRoute.replace(function: String().substringFromIndex, with: {
                                        ^^^^^^^^^^^^^^^^^^^^^^^^^^
    (index : Int) -> String in
        return "routed"
})

because String is a struct, not a real class.

For now, we don't pass a third argument original_ptr to the rd_route() call:

rd_route(rd_get_func_impl(targetMethod), rd_get_func_impl(replacement), nil)

so we lose an original implementation — that's a big problem, e.g. when we need to call it from new implementation (see issue #3).

Is there a way we can consume original_ptr in Swift?

AFAIK, setters and getters are shared between all instances of a class in Swift. They seem to have the following structure:

const int foo_offset = 0x48;

int getFoo(void *self)
{
    return *(uinptr_t *)(self + foo_offset);
}


void setFoo(int new_value, void *self)
{
    // there will be release/retain for non-scalar types 
    // ...
   *(uintptr_t *)(self + foo_offset) = new_value;
}

So it's impossible (?) to hook a getter/setter for the only instance of a class.
Needs some research, though.