Go Premium for a chance to win a PS4. Enter to Win

x
?
Solved

What is the Compiler Doing?

Posted on 2000-02-25
2
Medium Priority
?
206 Views
Last Modified: 2010-08-05
I am using VC++ 6.0.  What happens when a file such as #include<iostream> is inserted into several different files all within the same project?  Obviously, it is not necessary to include a file more than once but it seems to be done quite often.   Does this hinder the performance of the executable?  What exactly is happening?  Just wondering...
0
Comment
Question by:guile1
2 Comments
 
LVL 1

Accepted Solution

by:
Binder earned 400 total points
ID: 2559000
  No, it don´t hinder the performance of the executable, just
the performance of the compiler (a little bit). But there is a way
to minimize this effect. Looking at the start of iostream.h we found:

#ifndef _INC_IOSTREAM
#define _INC_IOSTREAM

....
#endif

   and of course several other lines of code. This means that
if the file wasn´t already included (if the symbol  _INC_IOSTREAM
wasn't defined yet) then the compiler includes it. If the symbol
was already defined, the compiler didn´t include it again.
0
 
LVL 22

Expert Comment

by:nietod
ID: 2559096
The use of #ifdef in that maner is very common.  It is necessary because C/C++ has rules against multiple definitions of the same "thing" in the same translation unit.  Without those #ifdef guards, the code would probably not compile.
0

Featured Post

Concerto Cloud for Software Providers & ISVs

Can Concerto Cloud Services help you focus on evolving your application offerings, while delivering the best cloud experience to your customers? From DevOps to revenue models and customer support, the answer is yes!

Learn how Concerto can help you.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

Templates For Beginners Or How To Encourage The Compiler To Work For You Introduction This tutorial is targeted at the reader who is, perhaps, familiar with the basics of C++ but would prefer a little slower introduction to the more ad…
IntroductionThis article is the second in a three part article series on the Visual Studio 2008 Debugger.  It provides tips in setting and using breakpoints. If not familiar with this debugger, you can find a basic introduction in the EE article loc…
The goal of the tutorial is to teach the user how to use functions in C++. The video will cover how to define functions, how to call functions and how to create functions prototypes. Microsoft Visual C++ 2010 Express will be used as a text editor an…
The goal of the video will be to teach the user the difference and consequence of passing data by value vs passing data by reference in C++. An example of passing data by value as well as an example of passing data by reference will be be given. Bot…

916 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question