replace existing object on the stack with default constructed one

I would like to know the best/correct way to get back to the initial values of an object without playing with delete and new (everything must stay on the stack)

With this 2 classes:

static const int defaultValue{15};
class Foo
{
  private: 
     int val1{defaultValue};
     short val2{4};
} 
class LongStandingObject
{
   public:
     void resetFoo(int index);
   private:
     Foo foos[100];
}

If I need to reset some foos to their default values, what is the best way?

1. Create reset method in Foo

   void Foo::reset()
   {
      val1 = defaultValue;
      val2 = 4;
   }
   
   

   I don't really like the idea to have the values coming from 2 differents places and I do like to have the defaults values in the header next to the variable declaration.

2. Replace by a locally created Foo

   void LongStandingObject::resetFoo(int index)
   {
      foos[index] = Foo();
   }
   
   

   Am I heading to trouble when the local variable is destroyed?

3. Use memcpy

   void LongStandingObject::resetFoo(int index)
   {
      Foo foo;
      memcpy(foos[index], &foo, sizeof(Foo));
   }
   
   

   Maybe less readable...

4. Any other method?