Idempotent Header Files - Oracle® Solaris Studio 12.4: C++ User's Guide

Oracle® Solaris Studio 12.4: C++ User's Guide

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Updated: March 2015

Oracle^® Solaris Studio 12.4: C++ User's Guide

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Using This Documentation

Part I C++ Compiler

Part II Writing C++ Programs

Chapter 4 Language Extensions

4.1 Linker Scoping

4.2 Thread-Local Storage

4.3 Overriding With Less Restrictive Virtual Functions

4.4 Making Forward Declarations of enum Types and Variables

4.5 Using Incomplete enum Types

4.6 Using an enum Name as a Scope Qualifier

4.7 Using Anonymous struct Declarations

4.8 Passing the Address of an Anonymous Class Instance

4.9 Declaring a Static Namespace-Scope Function as a Class Friend

4.10 Using the Predefined __func__ Symbol for Function Name

4.11 Supported Attributes

4.12 Compiler Support for Intel MMX and Extended x86 Platform Intrinsics

Chapter 5 Program Organization

5.1 Header Files

5.1.1 Language-Adaptable Header Files

5.1.2 Idempotent Header Files

5.2 Template Definitions

Chapter 6 Creating and Using Templates

6.1 Function Templates

6.2 Class Templates

6.3 Template Instantiation

6.4 Template Composition

6.5 Default Template Parameters

6.6 Template Specialization

6.7 Template Problem Areas

Chapter 7 Compiling Templates

Chapter 8 Exception Handling

8.1 Synchronous and Asynchronous Exceptions

8.2 Specifying Runtime Errors

8.3 Disabling Exceptions

8.4 Using Runtime Functions and Predefined Exceptions

8.5 Mixing Exceptions With Signals and Setjmp/Longjmp

8.6 Building Shared Libraries That Have Exceptions

Chapter 9 Improving Program Performance

9.1 Avoiding Temporary Objects

9.2 Using Inline Functions

9.3 Using Default Operators

9.4 Using Value Classes

9.5 Cache Member Variables

Chapter 10 Building Multithreaded Programs

10.1 Building Multithreaded Programs

10.2 Using Exceptions in a Multithreaded Program

10.3 Sharing C++ Standard Library Objects Between Threads

10.4 Memory Barrier Intrinsics

Part III Libraries

Part IV Appendixes

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5.1.2 Idempotent Header Files

Your header files should be idempotent, that is, the effect of including a header file many times should be exactly the same as including the header file only once. This property is especially important for templates. You can best accomplish idempotency by setting preprocessor conditions that prevent the body of your header file from appearing more than once.

#ifndef HEADER_H
#define HEADER_H
/* contents of header file */
#endif

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