Calling a method for memory allocation c++

Question

Does doing the following, create memory problems (new allocations without proper deletes) Assuming an object named "object"

class aClass
 { 
private:
    object* myobject;
public:
    aClass() : myobject(NULL) {};
    ~aClass() 
         {
            if(myobject)
               delete myobject;
             myobject = NULL;
         }
    void myfuction() 
       {
          if(myobject)
             myobject = new object();
       }
 }

does calling myfunction() often create memory which is never released, or the fact that i create the variable and copy it to myobject is safe, because at the end the myobject gets deleted ?

In it's current form, myfunction will never allocate any memory. — SergeyA, Mar 24 '16 at 18:34
Why ? above i said, assuming object is defined. Which means once its constructor is called , it is created. — Sam Gomari, Mar 24 '16 at 18:39
Because `if(myobject)` won't ever become `true` and should actually be `if(!myobject)`. — πάντα ῥεῖ, Mar 24 '16 at 18:41
Good point, but there is a leak ? yet in the bottom you asserted there is none. ??? thnks — Sam Gomari, Mar 24 '16 at 19:10
@πάνταῥεῖ i see, you're saying in its current form, there is no leak, but if `if(!myobject)` is written then, there will be a leak. correct ? — Sam Gomari, Mar 24 '16 at 19:19
@SamGomari no, because once called, myobject will no longer be `NULL` so `if (!myobject)` will always evaluate to `false`. — robsn, Mar 24 '16 at 19:20

score 2 · Accepted Answer · edited May 23 '17 at 10:33

does calling myfunction() often create memory which is never released,

Currently as this function is written, it would never allocate any memory at all, since you have (correctly) initialized the pointer in your constructor:

aClass() : myobject(NULL) {};
                 // ^^^^

so the condition in myfunction()

if(myobject)

will never be met, supposed the only code where memory allocation is done for myobject is in myfunction().

or the fact that i create the variable and copy it to myobject is safe, because at the end the myobject gets deleted ?

Well, calling delete for a NULL pointer is transparent and won't ever fail.

Actually I think you want to write myfunction() like this:

void myfuction() {
    if(!myobject)
    // ^ Check if myobject is NULL
         myobject = new object();
}

The destructor will correctly delete the allocated memory as soon the aClass instance goes out of scope.

But be aware of the Rule of Three and other operations that would affect assignments to the myobject member.

thanks , Is `if(myobect == NULL)` the same as `if(myobject)` or opposite ? , — Sam Gomari, Mar 24 '16 at 19:38
@SamGomari These are opposite actually, `if(myobject)` is equivalent to `if(myobject != NULL)`. — πάντα ῥεῖ, Mar 24 '16 at 19:41

Calling a method for memory allocation c++

1 Answers1