Why can't you name a function in Go "init"?
Yes, the function init()
is special. It is automatically executed when a package is loaded. Even the package main
may contain one or more init()
functions that are executed before the actual program begins: http://golang.org/doc/effective_go.html#init
It is part of the package initialization, as explained in the language specification: http://golang.org/ref/spec#Package_initialization
It is commonly used to initialize package variables, etc.
You can also see the different errors you can get when using init
in golang/test/init.go
// Verify that erroneous use of init is detected.
// Does not compile.
package main
import "runtime"
func init() {
}
func main() {
init() // ERROR "undefined.*init"
runtime.init() // ERROR "unexported.*runtime\.init"
var _ = init // ERROR "undefined.*init"
}
init
itself is managed by golang/cmd/gc/init.c
:
Now in cmd/compile/internal/gc/init.go
:
/*
* a function named init is a special case.
* it is called by the initialization before
* main is run. to make it unique within a
* package and also uncallable, the name,
* normally "pkg.init", is altered to "pkg.init·1".
*/
Its use is illustrated in "When is the init()
function in go (golang) run?"