How to Use unsafe.Sizeof, Alignof, and Offsetof

Use unsafe.Sizeof, unsafe.Alignof, and unsafe.Offsetof as compile-time functions to inspect the memory layout of Go types. unsafe.Sizeof returns the size in bytes, unsafe.Alignof returns the alignment requirement, and unsafe.Offsetof returns the byte offset of a field within a struct.

package main

import (
	"fmt"
	"unsafe"
)

type Point struct {
	X int
	Y int
}

func main() {
	var p Point
	fmt.Println("Size:", unsafe.Sizeof(p))
	fmt.Println("Align:", unsafe.Alignof(p))
	fmt.Println("Offset of Y:", unsafe.Offsetof(p.Y))
}

These functions let you measure how much memory a variable takes up and how it is arranged inside a struct. Think of Sizeof as measuring the total footprint of a box, Alignof as checking how strictly the box must be placed on a grid, and Offsetof as finding the exact distance from the start of the box to a specific item inside it. You use them when writing low-level code that needs to interact with memory directly.