There is one huge struct in our code, and its being passed around everywhere as a value. I would like to be able to know the size(amount of memory in bytes, go will allocate for a variable of this struct), without incurring the overhead of initialising a dummy value.
Is there a way to do that in golang?
In C we have the sizeof compile-time unary operator, that can do this.
Note : This is not the duplicate of Sizeof struct in Go, because in my case I cant use unsafe.Sizeof(<variable>) or reflect.ValueOf(<variable>).Type().Size() because they need a variable or a literal to be initialised
Use answers in Sizeof struct in Go, but start with a nil pointer to the type:
type Coord3d struct {
X, Y, Z int64
}
// Option 1:
ptrType := reflect.TypeFor[*Coord3d]()
valueType := ptrType.Elem()
size := valueType.Size()
fmt.Println(size) // prints 24
// Option 2:
size = unsafe.Sizeof(*(*Coord3d)(nil))
fmt.Println(size) // prints 24
https://play.golang.com/p/Bj8hvQ3aPeP
The simplest and most efficient approach is to rely on compiler optimizations.
size = unsafe.Sizeof(Coord3d{})
fmt.Println(size) // prints 24
Because the value of Coord3d{} is not used, the compiler does not allocate it.