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Oracle Solaris Studio 12.3: C++ User's Guide     Oracle Solaris Studio 12.3 Information Library
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Part I C++ Compiler

1.  The C++ Compiler

2.  Using the C++ Compiler

3.  Using the C++ Compiler Options

Part II Writing C++ Programs

4.  Language Extensions

5.  Program Organization

6.  Creating and Using Templates

7.  Compiling Templates

8.  Exception Handling

9.  Improving Program Performance

9.1 Avoiding Temporary Objects

9.2 Using Inline Functions

9.3 Using Default Operators

9.4 Using Value Classes

9.4.1 Choosing to Pass Classes Directly

9.4.2 Passing Classes Directly on Various Processors

9.5 Cache Member Variables

10.  Building Multithreaded Programs

Part III Libraries

11.  Using Libraries

12.  Using the C++ Standard Library

13.  Using the Classic iostream Library

14.  Building Libraries

Part IV Appendixes

A.  C++ Compiler Options

B.  Pragmas



9.3 Using Default Operators

If a class definition does not declare a parameterless constructor, a copy constructor, a copy assignment operator, or a destructor, the compiler will implicitly declare them. These are called default operators. A C-like struct has these default operators. When the compiler builds a default operator, it knows a great deal about the work that needs to be done and can produce very good code. This code is often much faster than user-written code because the compiler can take advantage of assembly-level facilities while the programmer usually cannot. So, when the default operators do what is needed, the program should not declare user-defined versions of these operators.

Default operators are inline functions, so do not use default operators when inline functions are inappropriate (see the previous section). Otherwise, default operators are appropriate in the following situations:

Some C++ programming texts suggest that class programmers always define all operators so that any reader of the code will know that the class programmer did not forget to consider the semantics of the default operators. Obviously, this advice interferes with the optimization discussed above. The resolution of the conflict is to place a comment in the code stating that the class is using the default operator.