C++ Coding Standards: 101 Rules, Guidelines, and Best Practices

99. Don’t use invalid objects. Don’t use unsafe functions

Summary

Don’t use expired medicines: Both invalid objects and historical but unsafe functions wreak havoc on your program’s health.

Discussion

There are three major kinds of invalid objects:

• Destroyed objects: Typical examples are automatic objects that have gone out of scope and deleted heap-based objects. After you call an object’s destructor, its lifetime is over and it is undefined and generally unsafe to do anything with it.

• Semantically invalidated objects: Typical examples include dangling pointers to deleted objects (e.g., a pointer p after a delete p;) and invalidated iterators (e.g., a vector<T>::iterator i after an insertion at the beginning of the container the iterator ...