TITLE: Syntax for delete on an array of objects

PROBLEM: What is the correct syntax for using delete on an array of objects?

    char* s = new char [40];
    delete s;
 
    int *p = new int [40];
    delete 40 p;
 

RESPONSE: Anil A. Pal (pal@wpd.sgi.com)

Actually, both of these examples are incorrect as of the latest draft
of the C++ standard.  The correct way (for both cases) is:

    mumble* x = new mumble[40];
    delete [] x;

Earlier implementations of C++ (for example, those based on cfront 2.0 or
before) required the programmer to explicitly supply the count (40) in the
delete.

    delete [40] x;

What happens if you forget and do a simple delete x; ?  Well, for the
examples quoted (int and char) usually nothing dramatic.  The full
storage will probably be returned to the free pool (in typical
malloc/free based implementations).  

If the type mumble is a class with a destructor, however, forgetting the
array form of the delete will result in a SINGLE DESTRUCTOR being called,
for the 0-th element in the array. 

Using the array syntax (delete [] x;) will correctly call the destructor
for all elements of the array.