Re: Add structure to vector
Jeff Dunlap wrote:
I am experimenting with STL containers and have successfully created
pointers to dynamically created structures and added those pointers to a
vector. Doing this has worked just as expected and this is how I intend to
work with structures contained in vectors.
Isn't that too much work taking care of all the new/delete calls?
Although I have no intention of storing locally created structures in a
vector, I wanted to know what happens when you try doing so and I did run
into some problems.
vector only manages pointers, it doesn't care what they point to.
Technically, even copying a pointer that does not point to the according
object (a so-called singular value) does constitute undefined behaviour, so
you better take care of removing the pointer to the local from the vector
before it goes out of scope.
In the code below, I create a local structure and add it to a vector but I
can't figure out why the structures destructor is called 3 times
struct myStruc
{
myStruc();
~myStruc();
};
myStruc::myStruc()
{
cout << "Constructor Called" << endl;
}
myStruc::~myStruc()
{
cout << "Destructor Called" << endl;
}
The compiler generates a copy constructor and assignment operator, those
might be used, too. Do a web-search for the so-called "Law of Three".
void staticTest()
{
std::vector <myStruc> vStructs;
vStructs.push_back(myStruc());
}
// the output is:
Constructor Called
Destructor Called
Destructor Called
Destructor Called
Nothing surprising here.
Uli
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