ps :)

1. struct padded_string final { . . . }; final is opportunity for optimization. And it is indeed used for that. One can use godbolt to check.

2. size_t length {} --- Why the empty parentheses? That is the value initialization ; value initialized object might be called as "zeroed". the object is given determinate value: zero, null, etc ...

   1. size_t length is the default initialization -- object is given an indeterminate value.

Example:

int my_array[10] {}; // all elements 0 in C++, not allowed in C

Merging.