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Developing applications using the Eclipse C/C++
Development Toolkit
Creating a C++ application using the Standard Template Library and
the CDT
Michael Galpin
Developer
Ludi Labs
10 July 2007
When most people think "Eclipse," they think "Java™ IDE." Eclipse is much more. With the
proper plug-ins, one can use Eclipse to work with PHP, Ruby, and Groovy, C, and C++. In
this article, you get started with the the Eclipse C/C++ Development Toolkit (CDT). We build
a simple application in C++ using the CDT and the C++ Standard Template Library (STL) to
streamline the process and take advantage of some of the powerful features of C++.
This article, which is a follow-up to "C/C++ development with the Eclipse Platform," is intended
for C++ developers who want to learn C++ development using the Eclipse CDT. A simple C++
application is developed in the article. The application makes use of the C++ STL. Readers should
be familiar with the STL, as well as with basic object-oriented programming principles such as
inheritance and polymorphism. A familiarity with Eclipse will be helpful, but is not required.
Before we start
You need to install the following:
• Eclipse
We're using the CDT, which is a plug-in to Eclipse, so of course you need Eclipse. The article
uses Eclipse V3.2.
• Java Runtime Environment
We're building a C++ application, but we're using Eclipse. Eclipse is a Java application itself,
so it needs a Java Runtime Environment (JRE). The article uses Eclipse V3.2, which requires
a JRE of V1.4 or higher. If you want to also use Eclipse for Java development, you'll need a
Java Development Kit (JDK).
• Eclipse C/C++ Development Toolkit (CDT)
© Copyright IBM Corporation 2007
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This article is about the CDT, so you'll need it, of course. For instructions on installing
the CDT on early versions of Eclipse, read a "C/C++ Development with the Eclipse
Platform" (developerWorks 2003) .
• Cygwin
If you're using Microsoft Windows®, you will find Cygwin — which provides a Linux®-like
environment on Windows — helpful.
• GNU C/C++ Development Tools
The CDT uses the standard GNU C/C++ tools for compiling your code, building your project,
and debugging the applications. These tools are GNU Compiler Collection (GCC) for C++
(g++), make, and the GNU Project Debugger (GDB). If you're a programmer using Linux or
Mac OS X, there's a pretty good chance these tools are installed on your machine. The article
contains instructions for setting up these tools for Windows.
The Eclipse CDT
The Eclipse CDT is an Eclipse plug-in that transforms Eclipse into a powerful C/C++ IDE. It
was designed to bring many of the great features Eclipse enjoyed by Java developers to C/C
++ developers, such as project management, integrated debugging, class wizards, automated
builds, syntax coloring, and code completion. When Eclipse is used as a Java IDE, it leverages
and integrates with the JDK. Similarly, the CDT leverages and integrates with standard C/C++
tools, such as g++, make, and GDB. This has lead to it becoming very popular on Linux, where
those tools are readily available and used for most C++ development. The CDT can be set up
on Windows to use the same tools. There is also an ongoing effort to get the CDT to work with
Microsoft's C++ tools to make it even more attractive to Windows C++ developers.
Installing the CDT
We start by assuming you installed Eclipse and can run it. If not, consult Eclipse's Web site for
getting up and running. Let's install the CDT. The CDT is an Eclipse plug-in, so it uses Eclipse's
Software Updates feature. Select Help > Software Updates > Find and Install.
Figure 1. Eclipse Software Updates
Next, you'll want to choose Search for new features to install.
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Figure 2. Search for new features
If you're using a newer version of Eclipse, the Callisto or Europa discovery sites should be
included. (Editor's note: Since this was written in April 2007, the Europa release was still in the
planning stages. However, installing Europa is expected to be similar to Callisto.) Simply select it
and click Finish.
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Figure 3. Callisto Discovery Site
Eclipse might ask you to choose from a list of mirror sites for the Callisto Discovery Site. Pick
whatever one seems closest to you. You should see a list of plug-ins from the Callisto Discovery
Site. You'll want to select C and C++ Development and click Next.
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Figure 4. Available Callisto plug-ins
You'll be asked to accept the license for the CDT. Once you've done that, you can click Next. You'll
see a summary of what's going to be downloaded and installed. Simply click Finish.
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Figure 5. Download and installation summary
Eclipse's Update Manager will then download the CDT plug-in from the mirror site you selected
earlier. The CDT is about 11 MB total, so this could take a few minutes, depending on your Internet
connection speed. Once everything is downloaded, you'll be asked to confirm that you want to
install the new features. Click Install All.
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Figure 6. Confirm installation
After you finish installing CDT, you'll be asked to restart Eclipse. Go ahead and do that. Once
Eclipse restarts, the CDT will be ready to go.
Windows configuration
If you're running Eclipse on Linux or Mac OS X, you're ready to start using the CDT to develop a C
++ application. If you're on Windows, there might be a few more steps. As mentioned, CDT relies
on the standard GNU C++ development tools: g++, make, and GDB. These are usually included
on Linux or Mac OS X. They're usually not included with Windows. But don't worry. These tools
can be easily installed on Windows. Perhaps the easiest way is to install Cygwin. Cygwin provides
Linux-like environment on Windows (see Resources). When installing Cygwin, you'll be asked to
pick the packages you want to install. Make sure to go into the development section and select
gcc: g++, make, and GDB. This will cause their prerequisites to be installed, too.
Once you're done installing Cygwin, you'll need to add g++, make, and GDB to your path. The
easiest way to do this is to add Cygwin's bin directory to your path, since that's where g++, make,
and GDB can be found. Once that's done, restart Eclipse.
Playing the lottery
At this point, we should be ready to start developing our application with CDT. Let's pause to
figure out what we want to develop. The sample application is a simple command-line program for
generating lottery numbers. Many states have lotteries, and the rules vary quite a bit. We'll allow
the user to pick which state lottery he wants to generate numbers for. This will provide us a good
way to use C++'s support for polymorphic behavior.
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Creating the project
Eclipse uses the concepts of perspectives to allow for various plug-ins to customize their
commands and views. Eclipse starts off by default in the Java perspective. CDT includes its own
perspective, so we'll want to switch to that. To do that, select Window > Open Perspective >
Other. You should see a list of perspectives available to you. Select the C/C++ perspective and
click OK.
Figure 7. Select C/C++ perspective
Eclipse should now look something like Figure 8.
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Figure 8. The C/C++ perspective
Eclipse organizes your code into projects, so we'll want to create a new project. Select File > New
> Managed Make C++ Project.
Figure 9. New C++ project
You might have noticed there were several different options for the project. We wanted a C++
project. We selected a "Managed Make," since that will allow Eclipse to create the make file for us.
You could select a "Standard Make" flavor and write your own make file. We should now be in the
New Project wizard, where we'll name our project Lottery and click Finish.
This will create an empty project, which you should see in the C/C++ Projects window. Rightclick on the project and select New > Source Folder. This will bring up the "New Source Folder"
wizard, where we'll name our folder src and click Finish.
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Basic lottery
We're ready to start creating some code. We'll start by creating the executable of our application.
Right-click on the source folder we just created and selected New > Source File, as shown in
Figure 10.
Let's create an empty main method for now. This is just a placeholder; we'll add more to this after
we've created the rest of our project.
int main()
{
return 0;
}
Save your project, and Eclipse will make it for you automatically. You should see some output in
the console indicating that it compiled successfully.
We're ready to create our first class. Right-click on the source folder we just created and select
New > Class.
Figure 10. New class
This should bring up the New Class wizard. We'll give our class a namespace lotto, and we'll call
our class Lottery.
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Figure 11. Lottery class
Eclipse will now create stubs for your class. CDT does a lot of nice things for you. It generates
the appropriate compiler directives in the header file. It encourages best practices by generating
separate interface (Lottery.h) and implementation (Lottery.cpp) files. It encourages another best
practice by making your class' destructor virtual. We can enter the source code for these classes
as seen in Listings 1 and 2.
Listing 1. Lottery.h
#ifndef LOTTERY_H_
#define LOTTERY_H_
#include <string>
#include <sstream>
#include <cstdlib>
#include <time.h>
using namespace std;
namespace lotto
{
class Lottery
{
protected:
int ticketSize, maxNum;
int* generateNumbers();
public:
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Lottery(int,int);
virtual ~Lottery();
virtual string printTicket();
};
}
#endif /*LOTTERY_H_*/
Listing 2 shows the implementation file for the Lottery class.
Listing 2. Lottery.cpp
#include "Lottery.h"
namespace lotto
{
Lottery::Lottery(int size, int num)
{
this->ticketSize = size;
this->maxNum = num;
}
Lottery::~Lottery()
{
}
int* Lottery::generateNumbers()
{
int* allNums = new int[this->maxNum +1];
for (int i=0; i <= this->maxNum ; i++)
{
allNums[i] = 0;
}
int* nums = new int[this->ticketSize];
for (int i=0; i < this->ticketSize; i++)
{
int val = 1 + rand() % (this->maxNum);
if (allNums[val])
{
i--;
}
else
{
nums[i] = val;
allNums[val] =1;
}
}
return nums;
}
string Lottery::printTicket()
{
ostringstream str;
int* nums = this->generateNumbers();
for (int i=0;i< this->ticketSize; i++)
{
str << *nums << ' ';
nums++;
}
return str.str();
}
}
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What's this code doing? Well, our Lottery class has two attributes. The ticketSize attribute is the
number of numbers on the lottery ticket. The maxNum is the maximum number on the ticket. Later,
we'll use the Florida state lottery as an example. There, you pick six numbers from 1 to 53, so
ticketSize would be 6 and maxNum would be 53.
The generateNumbers method generates an array of numbers corresponding to the numbers on a
lottery ticket. It uses the STL function rand() to generate numbers randomly. The allNums array is
used to keep track of what numbers have been generated so far, so we can make sure we don't
get a duplicate number on our ticket. Finally, the printTicket() creates a string representation of
our ticket.
When you save the files, Eclipse builds your project automatically. Again, if you save the project, it
should be compiled and you should see compilation messages in the console, as shown in Listing
3.
Listing 3. Compiler output in console
**** Build of configuration Debug for project Lottery ****
make -k all
Building file: ../src/Main.cpp
Invoking: GCC C++ Compiler
g++ -O0 -g3 -Wall -c -fmessage-length=0 -MMD -MP -MF"src/Main.d" -MT"src/Main.d"
-o"src/Main.o" "../src/Main.cpp"
Finished building: ../src/Main.cpp
Building target: Lottery
Invoking: MacOS X C++ Linker
g++ -o "Lottery" ./src/Lottery.o ./src/Main.o
Finished building target: Lottery
Build complete for project Lottery
MegaLottery class
You might have noticed that we made the printTicket() method virtual when it was declared in
the header file. That will allow us to subclass Lottery and override this method. We wanted to do
that because some states have a lottery with a "mega" number. This is a separately drawn number
that any ticket must match in addition to the other numbers drawn. Let's create a MegaLottery
class for these states that will subclass Lottery.
Once again, right-click on our source folder and select New > Class, as we did earlier. This time in
the New Class wizard, we'll declare our new class in the same namespace, but call it MegaLottery.
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Figure 12. MegaLottery class
To subclass Lottery, select the Add button next to the Base Classes section. This will bring up the
Choose Base Class dialog. You can start typing the name of the class, and Eclipse will narrow the
list of base class candidates quickly. You'll want to select Lottery and click OK.
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Figure 13. Choose base classes
We can enter the code for MegaLottery, as shown in Listings 4 and 5.
Listing 4. MegaLottery.h
#ifndef MEGALOTTERY_H_
#define MEGALOTTERY_H_
#include "Lottery.h"
using std::string;
namespace lotto
{
class MegaLottery : public lotto::Lottery
{
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protected:
int maxMegaNum;
public:
MegaLottery(int,int,int);
virtual ~MegaLottery();
string printTicket();
};
}
#endif /*MEGALOTTERY_H_*/
Listing 5 shows the implementation file for the MegaLottery class.
Listing 5. MegaLottery.cpp
#include "MegaLottery.h"
using namespace std;
namespace lotto
{
MegaLottery::MegaLottery(int ticketSize, int maxNum, int maxMegaNum) :
Lottery(ticketSize,maxNum)
{
this->maxMegaNum = maxMegaNum;
}
MegaLottery::~MegaLottery()
{
}
string MegaLottery::printTicket()
{
ostringstream tick;
tick << Lottery::printTicket() << " Mega: ";
int mega = 1 + rand() % this->maxMegaNum;
tick << mega;
return tick.str();
}
}
The main difference between Lottery and MegaLottery is that MegaLottery has an extra attribute
maxMegaNum. This is the max value that the mega number can take. It overrides the printTicket()
method. It uses the base class to generate the first part of the ticket, then it generates the mega
number and appends it to the string representation of the ticket.
We just need a way to create the various lotteries. We'll use a class Factory Pattern to do this.
We'll do this by adding a LotteryFactory class. We want all Lotteries to come from the same
factory, so we'll make LotteryFactory a singleton. The code for it is in Listings 6 and 7.
Listing 6. #ifndef LOTTERYFACTORY_H_
#define LOTTERYFACTORY_H_
#include "Lottery.h"
namespace lotto
{
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class LotteryFactory
{
public:
enum State { California, Florida };
static LotteryFactory* getInstance();
Lottery* getLottery(State);
private:
LotteryFactory();
};
}
#endif /*LOTTERYFACTORY_H_*/
Listing 7 shows the implementation file for the LotteryFactory class.
Listing 7. LotteryFactory.cpp
#include "LotteryFactory.h"
#include "MegaLottery.h"
namespace lotto
{
LotteryFactory::LotteryFactory()
{
srand(time(NULL));
}
Lottery* LotteryFactory::getLottery(State s)
{
if (s == LotteryFactory::California)
{
Lottery* lotto = new MegaLottery(5,47,27);
return lotto;
}
else
{
Lottery* lotto = new Lottery(6,53);
return lotto;
}
}
LotteryFactory* LotteryFactory::getInstance()
{
static LotteryFactory instance;
return &instance;
}
}
The LotteryFactory has an enum of the different types of lotteries. We've only put in Florida
and California in the example, but it shouldn't be hard to add as many as you want. The
LotteryFactory's constructor seeds the rand() function used by our lottery classes. We just need
to implement our executable's main method.
Listing 8. Main.cpp
#include <iostream>
#include "LotteryFactory.h"
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using namespace lotto;
int main()
{
LotteryFactory* factory = LotteryFactory::getInstance();
cout << "What lottery do you want to play?" << endl;
cout << "(1) California, (2) Florida" << endl;
int cmd;
scanf("%d", &cmd);
Lottery* lotto = 0;
switch (cmd)
{
case 1 :
lotto = factory->getLottery(LotteryFactory::California);
break;
case 2 :
lotto = factory->getLottery(LotteryFactory::Florida);
break;
default :
cout << "Sorry didn't understand that" << endl;
}
cout << "Ticket: " << lotto->printTicket() << endl;
delete lotto;
return 0;
}
Running the program
We're ready to run our program. Select Run > Run.
Figure 14. Choose base classes
Select C/C++ Local Application and click the New button.
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Figure 15. New C/C++ run profile
This will bring up the Create run configuration interface for the Lottery project. You'll need to select
its executable by clicking the Search Project button.
Figure 16. Search project for executable
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You can select the binary that Eclipse created for you and click OK.
Figure 17. Search project for executable
Just click Run, and the program should run in your console. The code below shows some sample
output.
What lottery do you want to play?
(1) California, (2) Florida
2
Ticket: 12 28 24 15 35 22
Debugging the program
Our program should run fine, but let's take a look at debugging the application. First, create a
breakpoint in our code. Pick a line and right-click next to it and select Toggle Breakpoint.
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Figure 18. Create breakpoint
We need to create a debug configuration, much like we created a run configuration. Select Run >
Debug.
Figure 19. Create debug configuration
This should bring up the Debug configuration. This is based on the Run configuration, and you
shouldn't need to change anything. Just click Debug.
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Figure 20. Debug configuration
Once the debugger starts, it will prompt you to switch to the Debugger perspective. Do so. Notice
that in the configuration we set things to break automatically at the startup of our main method.
Thus, the debugger should break immediately and you should see a screen something like Figure
21.
Figure 21. The debugger
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Summary
We've built and debugged our lottery application. You can easily add more lottery schemes to it.
Some of these could involve additional subclasses. CDT makes it easier than ever to create these
classes and class hierarchies, and to run and debug the application to test it.
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Resources
Learn
• Integrate an external code checker into Eclipse CDT (Alex Ruiz, developerWorks): Learn how
to execute C/C++ code analysis tools with Codan in Eclipse.
• Get an overview of the CDT in "C/C++ development with the Eclipse Platform."
• See a video on setting up Eclipse in the developerWorks demo The Eclipse development
platform: Introduction, download, and installation.
• Dig deep into the CDT's architecture in the five-part series titled "Building a CDT-based
editor."
• Windows developers can learn about migrating to the CDT in "Migrate Visual Studio C and C
++ projects to Eclipse CDT."
• Windows developers can also check out the CDT-MSVC project, a project for incorporating
Microsoft's compiler and debugger with CDT.
• Check out the "Recommended Eclipse reading list."
• Browse all the Eclipse content on developerWorks.
• Expand your Eclipse skills by checking out IBM developerWorks' Eclipse project resources.
• To listen to interesting interviews and discussions for software developers, check out
developerWorks podcasts.
• For an introduction to the Eclipse platform, see "Getting started with the Eclipse Platform."
• Stay current with developerWorks' Technical events and webcasts.
• Watch and learn about IBM and open source technologies and product functions with the nocost developerWorks On demand demos.
• Check out upcoming conferences, trade shows, webcasts, and other Events around the world
that are of interest to IBM open source developers.
• Visit the developerWorks Open source zone for extensive how-to information, tools, and
project updates to help you develop with open source technologies and use them with IBM's
products.
Get products and technologies
• As someone interested in C/C++ development, you might want to check out a trial of IBM's
XL C/C++ compiler for Linux or AIX®.
• Learn about MinGW, the GNU C/C++ tools for Windows included with Cygwin.
• Download Cygwin a Linux-like environment for Windows. It consists of two parts: A DLL
that acts as a Linux API emulation layer providing substantial Linux API functionality and a
collection of tools that provide a Linux look and feel.
• The Eclipse C/C++ Development Toolkit (CDT) download information contains the latest
information about the available versions of CDT.
• Innovate your next open source development project with IBM trial software.
Discuss
• Doug Schaefer is the CDT's lead developer. Check out Doug on the Eclipse CDT for the
latest news on the CDT.
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• The Eclipse Platform newsgroups should be your first stop to discuss questions regarding
Eclipse. (Selecting this will launch your default Usenet news reader application and open
eclipse.platform.)
• The Eclipse forums have many resources for people interested in using and extending
Eclipse.
• Get involved in the developerWorks community. Connect with other developerWorks users
while exploring dW's developer-driven blogs, forums, groups, and wikis.
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About the author
Michael Galpin
Michael Galpin holds a degree in mathematics from the California Institute of
Technology. He has been a Java developer since the late 1990s and is a software
engineer for Vitria Technology, in Sunnyvale, CA.
© Copyright IBM Corporation 2007
(www.ibm.com/legal/copytrade.shtml)
Trademarks
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