Ways enhance C++ code to completely remove memory leaks

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memory

C++14

What type of things can I try to do with my existing code to fully return back memory to the operating system? Right as it stands there are 8 bytes of memory still in the heap. In addition, I am getting these errors when I run my code through Valgrind:

#ifndef LINKEDLIST
    #define LINKEDLIST  
    /** LinkedList Class Interface
    */
  //begining update  
 class CLinkedlist {
    private:
    struct node {
        node() : mData(0), mNext(nullptr) {}
        int mData;
        node* mNext;
	};
    typedef node *nodePtr;
        
    nodePtr mHead;
    // As already suggested these should be local variables
    nodePtr mCurr;
    nodePtr mTemp;
	public:
    CLinkedlist() : mHead(nullptr), mCurr(nullptr), mTemp(nullptr) {}
    /// end of update
    ~CLinkedlist();
    
        void AddNode( int);
        void DeleteNode( int );
        void Printlist();
    
    };
    
    #endif

    /** \file Linkedlist.cpp
    */

   
    /** Linkedlist Deconstructor
    */
    CLinkedlist::~CLinkedlist(){
      mCurr = mHead;
      mTemp = mHead;
      while (mCurr)
      {
    	mTemp = mCurr;
        mCurr = mCurr->mNext;
        cout << mTemp->mData << " was destroyed." <<endl;
        delete mTemp;
     
      }
      mHead = nullptr;
    }
    
    void CLinkedlist::AddNode( int datanode){
      nodePtr data = new node;
      data->mData = datanode;
    
      if (mHead)
      {
        /// starting from the head, walking down the list
        mCurr = mHead;
        while(mCurr->mNext != nullptr) {
          mCurr = mCurr->mNext;
        }
        mCurr->mNext = data;
      }
    
      else
      {
        mHead = data;
      }
    
    }
    
    void CLinkedlist:: DeleteNode(int deldata){
      nodePtr delptr = nullptr;
      mTemp = mHead;
      mCurr = mHead;
      /// The program either walked the entire list and found
      /// nothing or we found our data
      while (mCurr != nullptr && mCurr->mData !=deldata ){
        mTemp =mCurr;
        mCurr = mCurr->mNext;
      }
      if (!mCurr){
        cout << deldata << " was not in the list\n";
        delete delptr;
      }
      else {
        /// new code
        if (mHead == mCurr)
           mHead = nullptr;
        /// old code
        delptr = mCurr;
        mCurr = mCurr->mNext;
        mTemp ->mNext=mCurr;
        delete delptr;
        cout << "The value "<< deldata << " was deleted\n";
      }
    }
    /** Displays information about our current list
    */
    void CLinkedlist::Printlist(){
      mCurr = mHead;
      while (mCurr)
      {
        cout << mCurr->mData << " -> " << endl;
        mCurr = mCurr->mNext;
      }
    }

    /** 
     * \file main.cpp
     */
    #include <cstdlib>
    #include "Linklist.h"
    
    using namespace std;
    
    int main (){
      CLinkedlist John;
    
      John.AddNode(3);
      //John.DeleteNode(3);
      //John.AddNode(5);
      //John.AddNode(7);
      //John.Printlist();
    
    }

On top of that, I am getting various errors on Valgrind like the ones below. Based on uninitialised values

=24530== Use of uninitialised value of size 4
==24530==    at 0x4AFB934: free_mem (in /lib/arm-linux-gnueabihf/libc-2.19.so)
==24530==    by 0x4AFB3C3: __libc_freeres (in /lib/arm-linux-gnueabihf/libc-2.19.so)
==24530==    by 0x4023633: _vgnU_freeres (vg_preloaded.c:61)
==24530==    by 0x48C5ED7: std::ctype<char>::_M_widen_init() const (in /usr/lib/arm-linux-gnueabihf/libstdc++.so.6.0.20)
==24530== 
==24530== Conditional jump or move depends on uninitialised value(s)
==24530==    at 0x4AFB9B0: free_mem (in /lib/arm-linux-gnueabihf/libc-2.19.so)
==24530==    by 0x4AFB3C3: __libc_freeres (in /lib/arm-linux-gnueabihf/libc-2.19.so)
==24530==    by 0x4023633: _vgnU_freeres (vg_preloaded.c:61)
==24530==    by 0x48C5ED7: std::ctype<char>::_M_widen_init() const (in /usr/lib/arm-linux-gnueabihf/libstdc++.so.6.0.20)
==24530== 
==24530== 
==24530== HEAP SUMMARY:
==24530==     in use at exit: 8 bytes in 1 blocks
==24530==   total heap usage: 1 allocs, 0 frees, 8 bytes allocated
==24530== 
==24530== LEAK SUMMARY:
==24530==    definitely lost: 0 bytes in 0 blocks
==24530==    indirectly lost: 0 bytes in 0 blocks
==24530==      possibly lost: 0 bytes in 0 blocks
==24530==    still reachable: 8 bytes in 1 blocks
==24530==         suppressed: 0 bytes in 0 blocks

What type of things can I try to do with my existing code to fully return back memory to the operating system?
For testing purposes, I used a Blueberry Pi on a Linux operating system. In addition, I used a g++ compiler and included -std=c++11 flags if that helps.

What I have tried:

I have done thorough research on my deciphering my memory leaks, but either the things I found was programmed through c or not applicable in my situation. One of the issues I found that I potentially was I didn't initialize my values which are why I was getting those errors. However, after careful inspection, I initialize all my in my class declarations. I was able to trace the problem to my destructor, apparently, it isn't deallocating the memory properly. However, it could be a deeper issue. My DeleteNode () method when called in the main, is able to deallocate the memory, but I don't how or why it can do that but not my destructor.

Update
I tried various methods suggested on this forum, but unfortunately, that didn't work. I connected to various Raspberry Pies, including Blueberry, raspberry, and pennutbutter to test on my virtual Linux machine but whenever I use Valgrind to test my application, in addition to the error message that I already showed I also get an illegal instruction,(not shown). Also, I used Putty, but it had the same effect. However, I have sort of given up, Visual Studio it doesn't report I have any leaks and neither do you guys so I honestly don't know and you guys don't seem to find anything wrong with how I handle the memory allocation and deallocation, so I don't know.