pointers stack

[jackel7777]

assuming stack interface: where data is a pointer to some value and next is the next pointer.

void *Stack::pop() {
    Element *popElement = head;
    void *mydata;

    /* Assume StackError exception class is defined elsewhere */
    if( head == NULL )
        throw StackError( E_EMPTY );

    mydata = head->data;//will this be a problem
    head = head->next;
    delete popElement;
    return mydata;
}

1. Since myData is a pointer created locally would my return myData go out of scope.

2. Since i delete the node where head is and myData points to that isn't that a problem since that memory is lost.

Tell me on the issues of this code. Thanks

[sasanet]

mydata will go out of scope cos it's staticaly alocated and return address will point to strange value .. so you shoult create it dynamicaly
void* myData = new void;

delete popElement; you can't delete pointer to stack
when defined like: Element *popElement = new Element now you can delete.

[3hM2Nwbp]

Templates are often a better alternative than void pointers, just thought I'd mention that. The standard template library also has a stack implementation if you want to check that out. http://cplusplus.com/reference/stl/stack/

[firedraco]

@sasanet:

1) It would be fine, because you are only losing the address (mydata), which you are returning, not the pointed to data.

2) No, because just contains a pointer to the data. If the data was dynamically allocated, then you would have to delete it later however.

[rocketboy9000]

Templates don't allow a stack of non-homogenous types.

[jackel7777]

@firedraco

Since there is a call on delete popElement; and mydata = head->data; points to a segment that is deleted(head->data is a node that is deleted ), technically this is a case of undefined behavior.


assuming if data has been declared as int data; and not a pointer; then what happens, assuming the casting is done on the void pointer. So now it will point to garbage right>

[sasanet]

@firedraco
1) It would be fine, because you are only losing the address (mydata), which you are returning, not the pointed to data.

heh you're wright zzzz learning :)

[firedraco]

No, head->data is a pointer, so the actual data is still there.

[jackel7777]

crystal clear...thanks...just needed feedback...