good good study, day day up!

vendor/gopl.io/ch5/defer2/defer.go

@@ -0,0 +1,51 @@
+// Copyright © 2016 Alan A. A. Donovan & Brian W. Kernighan.
+// License: https://creativecommons.org/licenses/by-nc-sa/4.0/
+
+// See page 151.
+
+// Defer2 demonstrates a deferred call to runtime.Stack during a panic.
+package main
+
+import (
+	"fmt"
+	"os"
+	"runtime"
+)
+
+//!+
+func main() {
+	defer printStack()
+	f(3)
+}
+
+func printStack() {
+	var buf [4096]byte
+	n := runtime.Stack(buf[:], false)
+	os.Stdout.Write(buf[:n])
+}
+
+//!-
+
+func f(x int) {
+	fmt.Printf("f(%d)\n", x+0/x) // panics if x == 0
+	defer fmt.Printf("defer %d\n", x)
+	f(x - 1)
+}
+
+/*
+//!+printstack
+goroutine 1 [running]:
+main.printStack()
+	src/gopl.io/ch5/defer2/defer.go:20
+main.f(0)
+	src/gopl.io/ch5/defer2/defer.go:27
+main.f(1)
+	src/gopl.io/ch5/defer2/defer.go:29
+main.f(2)
+	src/gopl.io/ch5/defer2/defer.go:29
+main.f(3)
+	src/gopl.io/ch5/defer2/defer.go:29
+main.main()
+	src/gopl.io/ch5/defer2/defer.go:15
+//!-printstack
+*/