diff --git a/fuzzers/libfuzzer/compiler b/fuzzers/libfuzzer/compiler
index 13ff4dc299..056a86af34 100755
--- a/fuzzers/libfuzzer/compiler
+++ b/fuzzers/libfuzzer/compiler
@@ -32,6 +32,8 @@ def cc_mode():
     args = common_opts()
     args += sys.argv[1:]
     
+    args += ["-fsanitize-coverage=trace-pc-guard,trace-cmp"]
+    
     if os.getenv("AFL_USE_ASAN"):
         args += ["-fsanitize=address"]
     if os.getenv("AFL_USE_MSAN"):
@@ -53,6 +55,8 @@ def ld_mode():
       os.path.join(script_dir, "runtime", "rt.o"),
       os.path.join(script_dir, "target", "release", "liblibfuzzer.a"),
     ]
+    
+    args += ["-fsanitize-coverage=trace-pc-guard,trace-cmp"]
 
     if os.getenv("AFL_USE_ASAN"):
         args += ["-fsanitize=address"]
diff --git a/fuzzers/libfuzzer/runtime/rt.c b/fuzzers/libfuzzer/runtime/rt.c
index 32e5aa4890..1fa6ef9755 100644
--- a/fuzzers/libfuzzer/runtime/rt.c
+++ b/fuzzers/libfuzzer/runtime/rt.c
@@ -1,4 +1,123 @@
+#include <stdint.h>
 
+#define MAP_SIZE 65536
+
+uint8_t  __lafl_dummy_map[MAP_SIZE];
+
+uint8_t *__lafl_edges_map = __lafl_dummy_map;
+uint8_t *__lafl_cmp_map = __lafl_dummy_map;
+
+uint32_t __lafl_max_edges_size = 0;
+
+void __sanitizer_cov_trace_pc_guard(uint32_t *guard) {
+
+  __lafl_edges_map[*guard]++;
+
+}
+
+void __sanitizer_cov_trace_pc_guard_init(uint32_t *start, uint32_t *stop) {
+
+  if (start == stop || *start) return;
+
+  *(start++) = (++__lafl_max_edges_size) & (MAP_SIZE -1);
+
+  while (start < stop) {
+
+    *start = (++__lafl_max_edges_size) & (MAP_SIZE -1);
+    start++;
+
+  }
+
+}
+
+#define MAX(a, b)           \
+  ({                        \
+                            \
+    __typeof__(a) _a = (a); \
+    __typeof__(b) _b = (b); \
+    _a > _b ? _a : _b;      \
+                            \
+  })
+
+#if defined(__APPLE__)
+  #pragma weak __sanitizer_cov_trace_const_cmp1 = __sanitizer_cov_trace_cmp1
+  #pragma weak __sanitizer_cov_trace_const_cmp2 = __sanitizer_cov_trace_cmp2
+  #pragma weak __sanitizer_cov_trace_const_cmp4 = __sanitizer_cov_trace_cmp4
+  #pragma weak __sanitizer_cov_trace_const_cmp8 = __sanitizer_cov_trace_cmp8
+#else
+void __sanitizer_cov_trace_const_cmp1(uint8_t arg1, uint8_t arg2) __attribute__((alias("__sanitizer_cov_trace_cmp1")));
+void __sanitizer_cov_trace_const_cmp2(uint16_t arg1, uint16_t arg2)
+    __attribute__((alias("__sanitizer_cov_trace_cmp2")));
+void __sanitizer_cov_trace_const_cmp4(uint32_t arg1, uint32_t arg2)
+    __attribute__((alias("__sanitizer_cov_trace_cmp4")));
+void __sanitizer_cov_trace_const_cmp8(uint64_t arg1, uint64_t arg2)
+    __attribute__((alias("__sanitizer_cov_trace_cmp8")));
+#endif
+
+void __sanitizer_cov_trace_cmp1(uint8_t arg1, uint8_t arg2) {
+
+  uintptr_t k = (uintptr_t)__builtin_return_address(0);
+  k = (k >> 4) ^ (k << 8);
+  k &= MAP_SIZE - 1;
+  __lafl_cmp_map[k] = MAX(__lafl_cmp_map[k], (__builtin_popcount(~(arg1 ^ arg2))));
+
+}
+
+void __sanitizer_cov_trace_cmp2(uint16_t arg1, uint16_t arg2) {
+
+  uintptr_t k = (uintptr_t)__builtin_return_address(0);
+  k = (k >> 4) ^ (k << 8);
+  k &= MAP_SIZE - 1;
+  __lafl_cmp_map[k] = MAX(__lafl_cmp_map[k], (__builtin_popcount(~(arg1 ^ arg2))));
+
+}
+
+void __sanitizer_cov_trace_cmp4(uint32_t arg1, uint32_t arg2) {
+
+  uintptr_t k = (uintptr_t)__builtin_return_address(0);
+  k = (k >> 4) ^ (k << 8);
+  k &= MAP_SIZE - 1;
+  __lafl_cmp_map[k] = MAX(__lafl_cmp_map[k], (__builtin_popcount(~(arg1 ^ arg2))));
+
+}
+
+void __sanitizer_cov_trace_cmp8(uint64_t arg1, uint64_t arg2) {
+
+  uintptr_t k = (uintptr_t)__builtin_return_address(0);
+  k = (k >> 4) ^ (k << 8);
+  k &= MAP_SIZE - 1;
+  __lafl_cmp_map[k] = MAX(__lafl_cmp_map[k], (__builtin_popcountll(~(arg1 ^ arg2))));
+
+}
+
+void __sanitizer_cov_trace_switch(uint64_t val, uint64_t *cases) {
+
+  uintptr_t rt = (uintptr_t)__builtin_return_address(0);
+  if (cases[1] == 64) {
+
+    for (uint64_t i = 0; i < cases[0]; i++) {
+
+      uintptr_t k = rt + i;
+      k = (k >> 4) ^ (k << 8);
+      k &= MAP_SIZE - 1;
+      __lafl_cmp_map[k] = MAX(__lafl_cmp_map[k], (__builtin_popcountll(~(val ^ cases[i + 2]))));
+
+    }
+
+  } else {
+
+    for (uint64_t i = 0; i < cases[0]; i++) {
+
+      uintptr_t k = rt + i;
+      k = (k >> 4) ^ (k << 8);
+      k &= MAP_SIZE - 1;
+      __lafl_cmp_map[k] = MAX(__lafl_cmp_map[k], (__builtin_popcount(~(val ^ cases[i + 2]))));
+
+    }
+
+  }
+
+}
 
 __attribute__((weak)) int LLVMFuzzerInitialize(int *argc, char ***argv);
 
diff --git a/fuzzers/libfuzzer/src/lib.rs b/fuzzers/libfuzzer/src/lib.rs
index a6cf977b3c..8eafca0060 100644
--- a/fuzzers/libfuzzer/src/lib.rs
+++ b/fuzzers/libfuzzer/src/lib.rs
@@ -1,17 +1,28 @@
 use std::boxed::Box;
+use std::cell::RefCell;
+use std::rc::Rc;
 
 use afl::corpus::{Corpus, InMemoryCorpus, Testcase};
-use afl::engines::{DefaultEngine, DefaultState, Engine};
+use afl::engines::{DefaultEngine, DefaultState, Engine, State};
 use afl::executors::inmemory::InMemoryExecutor;
 use afl::executors::{Executor, ExitKind};
+use afl::feedbacks::{create_history_map, MaxMapFeedback};
 use afl::inputs::bytes::BytesInput;
 use afl::mutators::scheduled::{mutation_bitflip, ComposedByMutations, DefaultScheduledMutator};
+use afl::observers::DefaultMapObserver;
 use afl::stages::mutational::DefaultMutationalStage;
 use afl::utils::DefaultRand;
 
+const MAP_SIZE: usize = 65536;
+
+#[no_mangle]
 extern "C" {
     /// int LLVMFuzzerTestOneInput(const uint8_t *Data, size_t Size)
     fn LLVMFuzzerTestOneInput(data: *const u8, size: usize) -> i32;
+
+    static __lafl_edges_map: *mut u8;
+    static __lafl_cmp_map: *mut u8;
+    static __lafl_max_edges_size: u32;
 }
 
 fn harness<I>(_executor: &dyn Executor<I>, buf: &[u8]) -> ExitKind {
@@ -29,8 +40,17 @@ pub extern "C" fn afl_libfuzzer_main() {
     let testcase = Testcase::new(vec![0; 4]).into();
     corpus.add(testcase);
 
+    let edges_observer = Rc::new(RefCell::new(DefaultMapObserver::new_from_ptr(
+        unsafe { __lafl_edges_map },
+        unsafe { __lafl_max_edges_size as usize },
+    )));
+    let edges_history_map = create_history_map::<u8>(MAP_SIZE);
+    let edges_feedback = MaxMapFeedback::new(edges_observer.clone(), edges_history_map);
+
     let executor = InMemoryExecutor::<BytesInput>::new(harness);
     let mut state = DefaultState::new(corpus, executor);
+    state.add_observer(edges_observer);
+    state.add_feedback(Box::new(edges_feedback));
 
     let mut engine = DefaultEngine::new();
     let mut mutator = DefaultScheduledMutator::new(&rand);
diff --git a/src/engines/mod.rs b/src/engines/mod.rs
index da8528553a..d05eb759fc 100644
--- a/src/engines/mod.rs
+++ b/src/engines/mod.rs
@@ -20,29 +20,29 @@ where
     I: Input,
 {
     /// Get the linked observers
-    fn observers(&self) -> &[Box<dyn Observer>];
+    fn observers(&self) -> &[Rc<RefCell<dyn Observer>>];
 
     /// Get the linked observers
-    fn observers_mut(&mut self) -> &mut Vec<Box<dyn Observer>>;
+    fn observers_mut(&mut self) -> &mut Vec<Rc<RefCell<dyn Observer>>>;
 
     /// Add a linked observer
-    fn add_observer(&mut self, observer: Box<dyn Observer>) {
+    fn add_observer(&mut self, observer: Rc<RefCell<dyn Observer>>) {
         self.observers_mut().push(observer);
     }
 
     /// Reset the state of all the observes linked to this executor
     fn reset_observers(&mut self) -> Result<(), AflError> {
-        for observer in self.observers_mut() {
-            observer.reset()?;
+        for observer in self.observers() {
+            observer.borrow_mut().reset()?;
         }
         Ok(())
     }
 
     /// Run the post exec hook for all the observes linked to this executor
     fn post_exec_observers(&mut self) -> Result<(), AflError> {
-        self.observers_mut()
-            .iter_mut()
-            .map(|x| x.post_exec())
+        self.observers()
+            .iter()
+            .map(|x| x.borrow_mut().post_exec())
             .fold(Ok(()), |acc, x| if x.is_err() { x } else { acc })
     }
 
@@ -101,7 +101,7 @@ where
     E: Executor<I>,
     I: Input,
 {
-    observers: Vec<Box<dyn Observer>>,
+    observers: Vec<Rc<RefCell<dyn Observer>>>,
     feedbacks: Vec<Box<dyn Feedback<I>>>,
     corpus: C,
     executor: E,
@@ -113,11 +113,11 @@ where
     E: Executor<I>,
     I: Input,
 {
-    fn observers(&self) -> &[Box<dyn Observer>] {
+    fn observers(&self) -> &[Rc<RefCell<dyn Observer>>] {
         &self.observers
     }
 
-    fn observers_mut(&mut self) -> &mut Vec<Box<dyn Observer>> {
+    fn observers_mut(&mut self) -> &mut Vec<Rc<RefCell<dyn Observer>>> {
         &mut self.observers
     }
 
diff --git a/src/feedbacks/mod.rs b/src/feedbacks/mod.rs
index 810af1568a..07390bc141 100644
--- a/src/feedbacks/mod.rs
+++ b/src/feedbacks/mod.rs
@@ -78,21 +78,21 @@ where
 }
 
 /// The most common AFL-like feedback type
-pub struct MapFeedback<'a, T, R, O>
+pub struct MapFeedback<T, R, O>
 where
     T: Integer + Copy + 'static,
     R: Reducer<T>,
     O: MapObserver<T>,
 {
     /// Contains information about untouched entries
-    history_map: &'a RefCell<Vec<T>>,
+    history_map: Rc<RefCell<Vec<T>>>,
     /// The observer this feedback struct observes
-    map_observer: &'a RefCell<O>,
+    map_observer: Rc<RefCell<O>>,
     /// Phantom Data of Reducer
     phantom: PhantomData<R>,
 }
 
-impl<'a, T, R, O, I> Feedback<I> for MapFeedback<'a, T, R, O>
+impl<T, R, O, I> Feedback<I> for MapFeedback<T, R, O>
 where
     T: Integer + Copy + 'static,
     R: Reducer<T>,
@@ -122,7 +122,7 @@ where
     }
 }
 
-impl<'a, T, R, O> MapFeedback<'a, T, R, O>
+impl<T, R, O> MapFeedback<T, R, O>
 where
     T: Integer + Copy + 'static,
     R: Reducer<T>,
@@ -130,7 +130,7 @@ where
 {
     /// Create new MapFeedback using a map observer, and a map.
     /// The map can be shared.
-    pub fn new(map_observer: &'a RefCell<O>, history_map: &'a RefCell<Vec<T>>) -> Self {
+    pub fn new(map_observer: Rc<RefCell<O>>, history_map: Rc<RefCell<Vec<T>>>) -> Self {
         MapFeedback {
             map_observer: map_observer,
             history_map: history_map,
@@ -140,14 +140,14 @@ where
 }
 
 /// Returns a usable history map of the given size
-pub fn create_history_map<T>(map_size: usize) -> RefCell<Vec<T>>
+pub fn create_history_map<T>(map_size: usize) -> Rc<RefCell<Vec<T>>>
 where
     T: Default + Clone,
 {
     {
-        RefCell::new(vec![T::default(); map_size])
+        Rc::new(RefCell::new(vec![T::default(); map_size]))
     }
 }
 
-pub type MaxMapFeedback<'a, T, O> = MapFeedback<'a, T, MaxReducer<T>, O>;
-pub type MinMapFeedback<'a, T, O> = MapFeedback<'a, T, MinReducer<T>, O>;
+pub type MaxMapFeedback<T, O> = MapFeedback<T, MaxReducer<T>, O>;
+pub type MinMapFeedback<T, O> = MapFeedback<T, MinReducer<T>, O>;
diff --git a/src/observers/mod.rs b/src/observers/mod.rs
index 7f4917dd18..5df1e17edc 100644
--- a/src/observers/mod.rs
+++ b/src/observers/mod.rs
@@ -1,5 +1,7 @@
 extern crate num;
 
+use alloc::rc::Rc;
+use core::cell::RefCell;
 use core::slice::from_raw_parts_mut;
 use num::Integer;
 
@@ -57,13 +59,19 @@ where
     initial: T,
 }
 
-impl<'a, T: Integer + Copy> Observer for DefaultMapObserver<'a, T> {
+impl<'a, T> Observer for DefaultMapObserver<'a, T>
+where
+    T: Integer + Copy,
+{
     fn reset(&mut self) -> Result<(), AflError> {
         self.reset_map()
     }
 }
 
-impl<'a, T: Integer + Copy> MapObserver<T> for DefaultMapObserver<'a, T> {
+impl<'a, T> MapObserver<T> for DefaultMapObserver<'a, T>
+where
+    T: Integer + Copy,
+{
     fn map(&self) -> &[T] {
         &self.map
     }
@@ -85,7 +93,10 @@ impl<'a, T: Integer + Copy> MapObserver<T> for DefaultMapObserver<'a, T> {
     }
 }
 
-impl<'a, T: Integer + Copy> DefaultMapObserver<'a, T> {
+impl<'a, T> DefaultMapObserver<'a, T>
+where
+    T: Integer + Copy,
+{
     /// Creates a new MapObserver
     pub fn new(map: &'a mut [T]) -> Self {
         let initial = if map.len() > 0 { map[0] } else { T::zero() };
@@ -106,3 +117,12 @@ impl<'a, T: Integer + Copy> DefaultMapObserver<'a, T> {
         }
     }
 }
+
+impl<'a, T> Into<Rc<RefCell<Self>>> for DefaultMapObserver<'a, T>
+where
+    T: Integer + Copy,
+{
+    fn into(self) -> Rc<RefCell<Self>> {
+        Rc::new(RefCell::new(self))
+    }
+}