// welcome supplement
Shared_ptr smart pointers can ensure that only a pointer to the destination address or retain a NULL
Function members:
| Member name | effect |
| get | Get the address of the target element |
| owner_before | // unknown role there is to know it thanks to supplement the under |
| reset |
Replace the target element |
| swap | Interactive two shared_ptr objects |
| unique | Check that the only target resource |
| use_count | How many computers owns the object (including myself) |