Golang High-Performance Programming EP1: Empty Struct

The secret and application of the empty struct with a size of 0

huizhou92

4 min read

·

Jun 18, 2024

--

1

Listen

Share

Press enter or click to view image in full size

The Mystery of the Empty Struct in Go: Understanding its Usage and Optimization

In Go, a regular struct typically occupies a block of memory. However, there’s a particular case: if it’s an empty struct, its size is zero. How is this possible, and what is the use of an empty struct?

type Test struct {
     A int
     B string
 }
 ​
 func main() {
     fmt.Println(unsafe.Sizeof(Test{}))
     fmt.Println(unsafe.Sizeof(struct{}{}))
 }
 ​
 /*
 24
 0
 */

The Secret of the Empty Struct

Special Variable: zerobase

An empty struct is a struct with no memory size. This statement is correct, but to be more precise, it has a special starting point: the zerobase variable. This is a uintptr global variable that occupies 8 bytes. Whenever countless struct {} variables are defined, the compiler assigns the address of this zerobase variable. In other words, in Go, any memory allocation with a size of 0 uses the same address, &zerobase.

Example

package main
 ​
 import "fmt"
 ​
 type emptyStruct struct…