The "bare minimum" is actually not at all

Using Arduino Programming Questions
1

Inspired by: The "bare minimum" sketch isn't the bare minimum ... - Programming Questions - Arduino Forum

Anyway, most is clear, except:this will produce 260 bytes executable on MEGA. What can be expected is just few bytes of executable for endless loop.

int main(){  
}

This code will initial MEGA properly for default Arduino setting, but it use 644bytes of flash memory and 9 bytes for RAM,

int main()
{
  init();

  while(1) {}  
}

What for is actually such difference in both cases? What and why is added?

If nothing is used, there is no point to add any library useless code. I believed all not used code functions are excluded from executable automatically.

2

What is your point ?

3

UKHeliBob:
What is your point ?

There is no point, just trying to understand why is inserted code actually never used.

4

Useful tool

5

the compiler can't optimize away the setting of MCU registers. it doesn't understand the registers and what they do and if the setting of registers is useful or not