1.Initialization with parentheses and curly braces.
int *pi = new int(1024);
string *ps = new string(10, '9');
vector<int> *pv = new vector<int>{0,1,2,3,4,5,6,7,8,9};
</int></int>
2.Difference default initialization between int and string.
- pi points to a dynamically allocated, unamed, uninitialized int.
string *ps = new string; // default initialized to the empty string.
int *pi = new int; // default initialized; *pi is undefine.
3.We can use auto only with a single initializer inside parentheses.
auto p1 = new auto(obj); // p points to an object of the type of obj.
// that object is initialized from obj.
auto p2 = new auto{a, b, c}; // error:must use parentheses for the initializer.
4.use new to allocate const objects.
- A dynamically allocated const object must be initialized.
5.If new is unable to allocate the requested storage:
-
It throws an exception of type bad_alloc.
-
Using new (nothrow) to avod throwing an exception, and returns a null ptr.
int *p2 = new (nothrow) int; // if allocation fails, new returns a null ptr.
1.A delete expression takes a pointer to the object we want to free:
- must point to a dynamically allocated obj or be null.(otherwise undefined)
2.Although the value of a const obj cannot be modified, the obj itself can be destroyed.
const int *pi = new const int(1024);
delete pi; // ok: delete a const obj.
-
Set p to nullptr to provide only limited protections.
-
Avoiding dereference dangling ptr to make system crash.
int *p(new int(42)); // p points to dynamic memory.
auto q = p; // p and q point to the same memory.
delete p; // invalidates both p and q.
p = nullptr; // indicates that p is no longer bound to an obj.
Original: https://www.cnblogs.com/Dy2MoRaw/p/15861509.html
Author: Dy2MoRaw
Title: Using New and Delete to manage memory directly (new header)
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