9.6. Destructors

A destructor is another type of special member function. The name of the destructor for a class is the tilde character (~) followed by the class name. This naming convention has intuitive appeal, because as we’ll see in a later chapter, the tilde operator is the bitwise complement operator, and, in a sense, the destructor is the complement of the constructor. A destructor may not specify parameters or a return type.

A class’s destructor is called implicitly when an object is destroyed. This occurs, for example, as an object is destroyed when program execution leaves the scope in which that object was instantiated. The destructor itself does not actually release the object’s memory—it performs termination housekeeping before the object’s memory is reclaimed, so the memory may be reused to hold new objects.

Even though destructors have not been defined for the classes presented so far, every class has one destructor. If you do not explicitly define a destructor, the compiler defines an “empty” destructor. [Note: We’ll see that such an implicitly created destructor does, in fact, perform important operations on class-type objects that are created through composition (Section 9.11) and inheritance (Chapter 11).] In Chapter 10, we’ll build destructors appropriate for classes whose objects contain dynamically allocated memory (e.g., for arrays and strings) or use other system resources (e.g., files on disk, which we study in Chapter 14). We discuss how to dynamically allocate and deallocate memory in Chapter 10.