inline keyword (C++)

inline function

If a function is inline, the compiler places a copy of the code of that function at each point where the function is called at compile time. One of the important advantages of using an inline function is that it eliminates the function calling overhead of a traditional function.

inline variable

https://www.geeksforgeeks.org/cpp-17-inline-variables/

https://stackoverflow.com/questions/38043442/how-do-inline-variables-work