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new is a "deep keyword"new is very different than in managed languages like C# and Java.new int will "ask" for the OS to find 4 bytes of contiguous memory, and it will return a pointer to that memory address. This process will have it's own overhead, even though the OS are optimized to do this kind of operation. Just keep in mind that we have this overhead.- Besides allocating the memory for us,
new also calls the default constructor, if anyone is called (different than in C#, that will return a null pointer).
new is an operator in C++, as +, -, or %; so it also can be overloaded.
- Usually,
new will call the c function `malloc, and then the default constructor
- if used
new[], we should use delete[] also
- We can pass explicitly a memory to
new
Entity e* = new(ptr) Entity();
// stack allocation
int a = 2;
// heap allocation (when using `new`)
int* b = new int;
int* c = new int[50]; // 200 bytes allocated
// parentheses are optional
Entity* e = new Entity();
// allocated 10 times the sizeof(entity)
Entity* eArray = new Entity[10];
// Entity occupies 28 bytes
std::cout << "size of one Entity object: " << sizeof(Entity) << std::endl;
Entity e* = new Entity();
// This is basically the same thing that the line above
// except that we have the default constructor called for us.
// This is more `c style`
Entity e = (Entity*)malloc(sizeof(Entity));
- Always remember to call the
delete keyword after using new
delete, calls free and the destructor
Entity e* = new Entity();
delete(e);
// the same as
free(e);
e.~Entity(e);