Rule 8-5-1 Must a non-static class member variable also explicitly initialized in constructor?

[ProgCPlusPlus]

The main statement of rule 8-5-1 is:

Each class constructor shall initialize all non-static members of its class.

The example shows a compliant and a non compliant constructor of a class having only member variables of basic numerical type int32_t. It is clear that a member variable of a basic type must be initialized before first read access to avoid an undefined behavior.

But what about non-static members of a class being of type class.

Must a constructor of the class member variable explicitly called in the constructor to be compliant to this rule?

Example:

Code:

class A
{
   public:
      A ( ) : m_a( false )
      {
      }
      bool GetmA ( void )
      {
         return ( m_a );
      }
   private:
      bool m_a;
};


class B
{
   public:
      B ( ) : m_a( false )  // Compliant or non-compliant because of
      {                     // not explicitly calling constructor of m_b?
      }
      B ( const bool a ) : m_a( a ), m_b()  // Definitely compliant
      {
      }
      bool GetmA ( void )
      {
         return ( m_a );
      }
      bool GetmB (void )
      {
          return m_b.GetmA();
      }
   private:
      bool m_a;
      A    m_b;
};

int main ( void )
{
   B b;
   if ( b.GetmB() )
   {
   }
}

The default constructor of class A for member variable m_b is in both constructors of class B called, but in default constructor of class B only implicit according to C++ standard.

Is the default constructor of class B not explicitly calling default constructor of class A for member variable m_b compliant to rule 8-5-1?