On 2007-12-28 20:32, Diwa wrote:
On Dec 28, 2:15 pm, "Victor Bazarov" <v.Abaza...@comAcast.net> wrote:
Diwa wrote:
// -----------------------------------
class Column
{
public:
string name;
vector<int> values;
};
// -----------------------------------
void loadValues()
{
Column *p = new Column();
p->values.push_back(55); // <--- Line 1
p->values.push_back(66); // <--- Line 2
delete p; // <--- Line 3
}
// -----------------------------------
Are the values inserted (Line 1 and 2) on
the stack or on the heap ?
Values that the container
'p->values' stores are _always_ in the free store, the vector
allocates all its values there, unless you provide some kind
of custom allocator, which you didn't.
Is there a memory leak for the two inserted
values inspite of the "delete p" at line 3 ?
No.
I suspect there is a memory leak. Here is my reasoning.
When "Column *p = new Column( )" is done it allocates,
lets say, 20 bytes. Just before the memory address
returned by "new", maybe it stores the num of bytes.
The "push_back()" done later at line 1 and line 2 may
results in some more "new" but still it will not
change the value (num of bytes) just before addr "p"
So at line 3, when "delete p" executes, it sees the
velue "20" just before p and then deletes only 20
bytes.
Am I missing something ?
Yes, when you push back the numbers on line 1 and 2 those are stored in
memory managed by the vector 'values'. When you, on line 3, delete p it
will call the destructor of the Column class pointed to by p. When this
happens it will call the destructors of its members 'name' and 'value'.
When the vector's destructor is run it will free whatever memory was
used by the vector, including that used to store the elements that you
pushed back on line 1 and 2. You only have to worry about the memory you
explicitly allocated using new, nothing else.
Ah, now I feel stupid. Obviously, when 'delete p' is done it
memory deletion is taken care of automatically. I don't why
behaviour of "free p". Thanks anyways, Erik and Victor.