How to get memory size of variable?

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You can use the unsafe.Sizeof function for this.
It returns the size in bytes, occupied by the value you pass into it.
Here’s a working example:

package main

import "fmt"
import "unsafe"

func main() {
    a := int(123)
    b := int64(123)
    c := "foo"
    d := struct {
        FieldA float32
        FieldB string
    }{0, "bar"}

    fmt.Printf("a: %T, %d\n", a, unsafe.Sizeof(a))
    fmt.Printf("b: %T, %d\n", b, unsafe.Sizeof(b))
    fmt.Printf("c: %T, %d\n", c, unsafe.Sizeof(c))
    fmt.Printf("d: %T, %d\n", d, unsafe.Sizeof(d))
}

Take note that some platforms explicitly disallow the use of unsafe, because it is.. well, unsafe. This used to include AppEngine. Not sure if that is still the case today, but I imagine so.

As @Timur Fayzrakhmanov notes, reflect.TypeOf(variable).Size() will give you the same information. For the reflect package, the same restriction goes as for the unsafe package. I.e.: some platforms may not allow its use.

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