Goの(&[5]int{})[:]の実験

1.go

package main

import "fmt"

func main() {
	a := [5]int{}
	b := a[:]
	fmt.Println(b)
}

2.go

package main

import "fmt"

func main() {
	a := (&[5]int{})[:]
	fmt.Println(a)
}

README.md

Goの(&[5]int{})[:]の実験

実行例

$ make diff
cat -n 1.go
     1  package main
     2
     3  import "fmt"
     4
     5  func main() {
     6          a := [5]int{}
     7          b := a[:]
     8          fmt.Println(b)
     9  }
go build -trimpath -o 1 ./1.go
go tool objdump -gnu -s main.main 1 | sed 's/1.go//g' | cut -f2- > 1.dump
cat -n 2.go
     1  package main
     2
     3  import "fmt"
     4
     5  func main() {
     6          a := (&[5]int{})[:]
     7          fmt.Println(a)
     8  }
go build -trimpath -o 2 ./2.go
go tool objdump -gnu -s main.main 2 | sed 's/2.go//g' | cut -f2- > 2.dump
diff 1.dump 2.dump

関連

• Array/slicing rules : golang
• go/complit1.go at 21ec72c2ca5168f3f10b4594a553b3a038c8df29 · golang/go

Makefile

.DEFAULT_GOAL := help

.PHONY: help diff

help: ## show this message
	@grep -E '^[a-zA-Z0-9_-]+:.*?## .*$$' $(MAKEFILE_LIST) | awk 'BEGIN {FS = ":.*?## "}; {printf "\033[36m%-8s\033[0m %s\n", $$1, $$2}'

diff: ## 1 と 2 の go tool objdump の差分を表示する
diff: 1.dump 2.dump
	diff $^

1.dump: 1
	go tool objdump -gnu -s main.main 1 | sed 's/1.go/0.go/g' | cut -f2- > 1.dump

2.dump: 2
	go tool objdump -gnu -s main.main 2 | sed 's/2.go/0.go/g' | cut -f2- > 2.dump

1:
	cat -n 1.go
	go build -trimpath -o 1 ./1.go

2:
	cat -n 2.go
	go build -trimpath -o 2 ./2.go

clean: ## clean
	-rm 1 2 1.dump 2.dump