Hi all,
I'm currently observing a behavior in the package initialization that looks
incompatible with the Go language specification.
Let's consider the following two .go files which are in the same package
*f1.go*
package main
var A int = 3
var B int = A + 1
var C int = A
*f2.go*
package main
import "fmt"
var D = f()
func f() int {
A = 1
return 1
}
func main() {
fmt.Println(A, " ", B, " ", C)
}
According to the Go language specification, "package-level variable
initialization proceeds stepwise, with each step selecting the variable
earliest in *declaration order* which has no dependencies on uninitialized
variables".
As such, I would expect two possible orders in which the global variables
can be initialized:
1. A < B < C < D - happens when you compile the project by passing f1.go
first to the compiler, followed by f2.go . In this case, the output is "1 4
3"
2. A < D < B < C - happens when f2.go is passed first to the compiler. In
this case, the *expected output *would be "1 2 1". However, the *actual
output* is "1 2 3".
Adding to this, I observed that if we rewrite f1.go to the following, the
program now has the expected behavior when we pass f2.go first to the
compiler.
*rewritten f1.go*
package main
import "fmt"
var A int = initA()
var B int = initB()
var C int = initC()
func initA() int {
fmt.Println("Init A")
return 3
}
func initB() int {
fmt.Println("Init B")
return A + 1
}
func initC() int {
fmt.Println("Init C")
return A
}
*Output*
Init A
Init B
Init C
1 2 1
I observed this behavior in multiple versions of Go, including:
- go1.16.4 darwin/amd64
- go1.17.2 linux/amd64
- go1.18 linux/amd64
Is this the expected behavior? Am I overlooking any details in the Go
language specification or in the Go memory model? Or is this a bug in the
compiler?
Thanks in advance for any helpful comments!
--
You received this message because you are subscribed to the Google Groups
"golang-nuts" group.
To unsubscribe from this group and stop receiving emails from it, send an email
to golang-nuts+unsubscr...@googlegroups.com.
To view this discussion on the web visit
https://groups.google.com/d/msgid/golang-nuts/952f6d0a-72ba-4643-9014-d665365aa89dn%40googlegroups.com.
