Are there related documents about function address offset?

[DDOG]

Stubber/Sources/Stubber/Stubber.swift

Line 102 in 9f18335

 let offset = MemoryLayout<Int>.size == 8 ? 16 : 12 

[Suyeol Jeon]

I did refer https://github.com/rodionovd/SWRoute/wiki/Function-hooking-in-Swift . But the memory address keeps changing in Xcode 12 everytime I access to the function :(