Include Guards

#including a file more than once during the same compilation session will most likely cause the compiler to issue error messages since definitions and declarations of the file are repeated. However, in many cases, the same file may be #included in different source file that are compiled together:

 #include "Time.h" //file Time.h itself contains #include "chrono.h"  directive#include "Date.h" //file date.h also contains #include "chrono.h"  directivevoid main() {Date d;Time t; }

In order to avoid compile time errors, every header file should have an #include guard to ensure it is scanned only once in a single compilation session:

 //file Chrono.h#ifndef CHRONO_H //is this file #included the first time during this compilation?#define CHRONO_H	true//declarations, namespace definitions, typedefs and any other stuff goes here:class Chrono { /*_*/ };#endif

If CHRONO_H is defined, the compiler ignores the contents of Chrono.h between #ifndef and #endif. The first time Chrono.h is scanned during compilation, its contents are read and CHRONO_H is defined. Any subsequent inclusion thereafter is harmless since the file contents will be ignored. Bear in mind that all standard headers have #include guards.

Share the Post:
Share on facebook
Share on twitter
Share on linkedin


The Latest

microsoft careers

Top Careers at Microsoft

Microsoft has gained its position as one of the top companies in the world, and Microsoft careers are flourishing. This multinational company is efficiently developing popular software and computers with other consumer electronics. It is a dream come true for so many people to acquire a high paid, high-prestige job

your company's audio

4 Areas of Your Company Where Your Audio Really Matters

Your company probably relies on audio more than you realize. Whether you’re creating a spoken text message to a colleague or giving a speech, you want your audio to shine. Otherwise, you could cause avoidable friction points and potentially hurt your brand reputation. For example, let’s say you create a

chrome os developer mode

How to Turn on Chrome OS Developer Mode

Google’s Chrome OS is a popular operating system that is widely used on Chromebooks and other devices. While it is designed to be simple and user-friendly, there are times when users may want to access additional features and functionality. One way to do this is by turning on Chrome OS