Several pointer concepts: dangling pointers and smart pointers as well as dumb pointers and wild pointers

Dangling pointer: a pointer originally allocated and used after it has been released. Known as dangling pointers

Smart pointers: This is a pointer usage mechanism that allows an allocated space to be used repeatedly, reducing the amount of space opened and released, which not only increases efficiency but also reduces the probability of errors ( If you release a piece of space twice, the program is likely to get stuck)

Dumb pointers: traditional pointers, which are malloc and free pointers, completely operated by programmers, fool pointers

Wild pointer: refers to a pointer that has not been allocated or deleted.