C++: Boost and STL list of pointers

Example: Boost ptr_list:

01#include <boost/ptr_container/ptr_list.hpp>
02#include <iostream>
03 
04using namespace std;
05 
06class ABC
07{
08public:
09   int i;
10   float j;
11};
12 
13main()
14{
15   boost::ptr_list<ABC> intList;
16   boost::ptr_list<ABC>::iterator iterIntList;
17 
18   ABC *a= new ABC;
19   ABC *b= new ABC;
20   ABC *c= new ABC;
21 
22   a->i = 1;
23   b->i = 2;
24   c->i = 3;
25 
26   intList.push_back(a);
27   intList.push_back(b);
28   intList.push_back(c);
29 
30   for (iterIntList = intList.begin();
31        iterIntList != intList.end();
32        iterIntList++)
33   {
34      cout << iterIntList->i << endl;
35   }
36 
37   intList.clear(); // All pointers held in list are deleted.
38 
39}

Compile: g++ testBoostPtrList.cpp
Run: ./a.out

1
2
3

See http://www.boost.org/libs/ptr_container/doc/ptr_list.html

Red Hat RPM packages: boost, boost-devel Newer Linux releases like Red Hat Enterprise 5/CentOS 5 include boost "ptr_list". RHEL4 included boost libraries but did not include "ptr_list".

Ubuntu installation: apt-get install libboost-dev libboost-doc

Example: STL list of pointers:

01// g++ -g  testStlPtrList.cpp
02#include <iostream>
03#include <list>
04 
05using namespace std;
06 
07class ABC
08{
09public:
10   int i;
11   float j;
12};
13 
14main()
15{
16   list<ABC*> intList;
17   list<ABC*>::iterator iterIntList;
18 
19   ABC *a= new ABC;
20   ABC *b= new ABC;
21   ABC *c= new ABC;
22 
23   a->i = 1;
24   b->i = 2;
25   c->i = 3;
26 
27   intList.push_back(a);
28   intList.push_back(b);
29   intList.push_back(c);
30 
31   for (iterIntList = intList.begin();
32        iterIntList != intList.end();
33        iterIntList++)
34   {
35      cout << (*iterIntList)->i << endl;
36   }
37 
38   // Free pointers
39   for (iterIntList = intList.begin();
40        iterIntList != intList.end();
41        iterIntList++)
42   {
43      delete *iterIntList;
44   }
45 
46   intList.clear(); // List is deleted.
47 
48}

This example shows how one must delete each pointer individually.

For more information on STL list, see the YoLinux.com STL vector and STL list tutorial

GDB: pointers and memory investigation

You can test the above programs and investigate their respective memory clean-up in GDB.

See the YoLinux.com GDB tutorial.

Using GDB:

Compile with debugging enabled: g++ -g -o testStlPtrList testStlPtrList.cpp
Start GDB: gdb testStlPtrList
Show listing with line numbers: list
Set break point: break 30
Run program till break point: run

Find memory location of variable in GDB: print &(c->i)
```
(gdb) p &(c->i)
$4 = (int *) 0x503050
    
```
Dereference memory location: p (*0x503050)
```
(gdb) p (*0x503050)
$5 = 3
    
```
Dereference memory location after memory is freed: p (*0x503050)
```
(gdb) p (*0x503050)
$7 = 0
    
```
Using RHEL5. Note older systems may give you a nonsense value.

Books:

	The C++ Standard Library: A Tutorial Reference Nicolai M. Josuttis ISBN #0201379260, Addison Wesley Longman This book is the only book I have seen which covers string classes as implemented by current Linux distributions. It also offers a fairly complete coverage of the C++ Standard Template Library (STL). Good reference book.
	STL for C++ programmers Leen Ammeraal ISBN #0 471 97181 2, John Wiley & Sons Ltd. Short book which teaches C++ Standard Template Library (STL) by example. Not as great as a reference but is the best at introducing all the concepts necessary to grasp STL completely and good if you want to learn STL quickly. This book is easy to read and follow.
	Data Structures with C++ Using STL William Ford, Willaim Topp ISBN #0130858501, Prentice Hall
	STL Tutorial and Reference Guide: C++ Programming with the Standard Template Library David R. Musser, Gillmer J. Derge, Atul Saini ISBN #0201379236, Addison-Wesley Publications
	The C++ Templates: The complete guide. David Vandevoorde, Nicolai Josuttis ISBN #0201734842, Addison Wesley Pub Co. Covers complex use of C++ Templates.
	C++ How to Program by Harvey M. Deitel, Paul J. Deitel ISBN #0131857576, Prentice Hall Fifth edition. The first edition of this book (and Professor Sheely at UTA) taught me to program C++. It is complete and covers all the nuances of the C++ language. It also has good code examples. Good for both learning and reference.

C++ boost and STL template list of pointers: