Should we take care of the safe bool problem?

[chirsz-ever]

Currently shared_ptr and unique_ptr use implicit operator bool to be convertible to a bool value.

This causes some problems, such as:

shared_ptr<int> p(new int(10));
// ...
int x = p;

In this case p would be converted to a bool value and than converted to a int value, 0 or 1.

A better way is to define operator! and operator void*.

See: https://en.cppreference.com/w/cpp/language/implicit_conversion