everything but calling the destructor correctly is handled

.gitignore

@@ -1,2 +1,3 @@
 *.o
 test
+test_gdb

Makefile

@@ -1,3 +1,5 @@
 CXX=clang++
 test: SharedPtr_test.cpp SharedPtr.hpp
 	$(CXX) SharedPtr_test.cpp -Wall -fsanitize=address -g -o test
+test_gdb: SharedPtr_test.cpp SharedPtr.hpp
+	$(CXX) SharedPtr_test.cpp -Wall -g -o test_gdb

SharedPtr.hpp

@@ -28,8 +28,9 @@ public:
 template <typename T> class ControlImpl : public Control {
   T *val;
   void destroy() override {
-    delete val;
-    delete this;
+    // std::cerr << this << '\t' << val << std::endl;
+    //  delete val;
+    //  delete this;
   }
 
 public:
@@ -51,12 +52,16 @@ public:
   }
 
   SharedPtr(const SharedPtr &p) : raw{p.raw}, underlying{p.underlying} {
+    if (this->underlying != nullptr) {
       this->underlying->increment();
     }
+  }
   template <typename U>
   SharedPtr(const SharedPtr<U> &p) : raw{p.raw}, underlying{p.underlying} {
+    if (this->underlying != nullptr) {
       this->underlying->increment();
     }
+  }
 
   SharedPtr(SharedPtr &&p) : raw{p.raw}, underlying{p.underlying} {
     p.raw = nullptr;
@@ -74,9 +79,13 @@ public:
       return *this;
     }
     this->raw = rhs.raw;
+    if (this->underlying != nullptr) {
       this->underlying->decrement();
+    }
     this->underlying = rhs.underlying;
+    if (this->underlying != nullptr) {
       this->underlying->increment();
+    }
     return *this;
   }
   template <typename U> SharedPtr<T> &operator=(const SharedPtr<U> &rhs) {
@@ -84,9 +93,13 @@ public:
       return *this;
     }
     this->raw = rhs.raw;
+    if (this->underlying != nullptr) {
       this->underlying->decrement();
+    }
     this->underlying = rhs.underlying;
+    if (this->underlying != nullptr) {
       this->underlying->increment();
+    }
     return *this;
   }
 
@@ -95,7 +108,9 @@ public:
       return *this;
     }
     this->raw = rhs.raw;
+    if (this->underlying != nullptr) {
       this->underlying->decrement();
+    }
     this->underlying = rhs.underlying;
     rhs.raw = nullptr;
     rhs.underlying = nullptr;
@@ -105,12 +120,18 @@ public:
       return *this;
     }
     this->raw = rhs.raw;
+    if (this->underlying != nullptr) {
       this->underlying->decrement();
+    }
     this->underlying = rhs.underlying;
     rhs.raw = nullptr;
     rhs.underlying = nullptr;
   }
-  ~SharedPtr() { this->underlying->decrement(); }
+  ~SharedPtr() {
+    if (this->underlying != nullptr) {
+      this->underlying->decrement();
+    }
+  }
 
   void reset() {
     this->raw = nullptr;