Question

I ran purify on my code which runs in Solaris and it shows lot of memory leaks.
But I checked the code and most of the leaks seem to be invalid.

For eg,

File1.cpp

Obj* getMyObj()
{
    Obj* obj = NULL;
    if(condition)
    {
        obj = new Obj();   //Purify is reporting leak here
        //Fill obj
    }

    ...
    return obj;
}

File2.cpp

void myfunc()
{
    Obj* myobj = getMyObj();

   if(myobj == NULL)
       return;
    ...
    ...

    delete myobj;    //The object is deleted here
}

Even though the object is destroyed properly in File2.cpp, why is purify reporting leak in File1.cpp?

EDIT

The NULL check was just a typo, I corrected it.

Answer 1

Even though the object is destroyed properly in File2.cpp, […]

This assumption is wrong.

Obj* myobj = getMyObj();

If getMyObj actually creates an object, it won’t return a null pointer. That means the condition in the following if is true, and then the function returns immediately.

if(myobj)
    return;

No further code executes in that function, so it’s never destroyed.

I recommend the use of smart pointers instead of this kind of manual management, as this kind of errors just goes away. With C++11 you can use std::unique_ptr, otherwise you can use std::auto_ptr if you’re careful.