Question

What is the difference between: double deletion, memory leak, and deletion of stack memory? What are the conditions that cause each of these errors? I ask this in reference to question 5 on this test. I’m not too familiar with what is good practice vs. bad practice when it comes to this stuff, so any guidelines/tips are appreciated!

Answer 1

The referenced link has a test with answers already on it, so I don’t think further clarifying the test’s answers will be helping to cheat.

A correct program will always execute exactly one call to delete for each call to new. All of these things are violations of this rule.

A double deletion calls delete more than once.

A* p = new A;
if ( someOption )
    delete p;

... more code ...
delete p;    // p is double freed if someOption is true
return;

A memory leak doesn’t call delete at all.

A* p = new A;
if ( someOption )
    delete p;    // p leaked if someOption is not true
return;

And deletion of stack memory calls delete on memory that was not returned from new.

A a;

A* p;
if ( someOption )
    p = &a;
else
    p = new A;

delete p;    // p is deletion of stack memory if someOption is true