Detect memory leaks with Valgrind

Description

Valgrind can detect many types of C++ memory leaks. They are listed and explained here.

List of errors

Definitely lost

A definitely lost block of memory cannot be accessed anymore. No pointer or reference refers to that block.

Code example:

#include 
#include 
#include 

int main()
{
    char definitelyLostChar = new char();
    return 0;
}

In this example we allocate memory with new but we never free the allocated space.

Indirectly lost

An indirectly lost memory block can be triggered as follows.

Code example:

#include 
#include 
#include 

struct TREENODE
{
    TREENODE sub;
};

int main()
{
    TREENODE rootNode = (TREENODE)malloc(sizeof(TREENODE));
    TREENODE subNode = (TREENODE)malloc(sizeof(TREENODE));

    rootNode-sub = subNode;
}

Possibly lost

A possibly lost block of memory could be a definitely or a indirectly lost block.

Code example:

#include 
#include 
#include 

char possiblyLostChar;

int main()
{
    possiblyLostChar = (char)malloc(2);
    possiblyLostChar += 1;
     at this point, no pointer points to
     the start of the allocated memory
     however, it is still accessible
    for (int i = -1; i != 1; i++)
    {
        possiblyLostChar[i] = 1;
    }

    return 0;
}

Still reachable

A still reachable memory allocation is allocated space that wasn't deleted but they are still accessible.

Code example:

#include 
#include 
#include 

char stillReachableChar;

int main()
{
    stillReachableChar = (char)malloc(sizeof(char));
    return 0;
}

How to test

Test the program with this command:

valgrind .myprogram --tool memcheck leak-check=full