1// run
2
3// Copyright 2011 The Go Authors. All rights reserved.
4// Use of this source code is governed by a BSD-style
5// license that can be found in the LICENSE file.
6
7// Test that goroutines and garbage collection run during init.
8
9package main
10
11import "runtime"
12
13var x []byte
14
15func init() {
16	c := make(chan int)
17	go send(c)
18	<-c
19
20	const N = 1000
21	const MB = 1 << 20
22	b := make([]byte, MB)
23	for i := range b {
24		b[i] = byte(i%10 + '0')
25	}
26	s := string(b)
27
28	memstats := new(runtime.MemStats)
29	runtime.ReadMemStats(memstats)
30	sys, numGC := memstats.Sys, memstats.NumGC
31
32	// Generate 1,000 MB of garbage, only retaining 1 MB total.
33	for i := 0; i < N; i++ {
34		x = []byte(s)
35	}
36
37	// Verify that the garbage collector ran by seeing if we
38	// allocated fewer than N*MB bytes from the system.
39	runtime.ReadMemStats(memstats)
40	sys1, numGC1 := memstats.Sys, memstats.NumGC
41	if sys1-sys >= N*MB || numGC1 == numGC {
42		println("allocated 1000 chunks of", MB, "and used ", sys1-sys, "memory")
43		println("numGC went", numGC, "to", numGC1)
44		panic("init1")
45	}
46}
47
48func send(c chan int) {
49	c <- 1
50}
51
52func main() {
53}
54