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Source file test/stack.go

Documentation: test

  // run
  
  // Copyright 2009 The Go Authors. All rights reserved.
  // Use of this source code is governed by a BSD-style
  // license that can be found in the LICENSE file.
  
  // Test stack splitting code.
  // Try to tickle stack splitting bugs by doing
  // go, defer, and closure calls at different stack depths.
  
  package main
  
  type T [20]int
  
  func g(c chan int, t T) {
  	s := 0
  	for i := 0; i < len(t); i++ {
  		s += t[i]
  	}
  	c <- s
  }
  
  func d(t T) {
  	s := 0
  	for i := 0; i < len(t); i++ {
  		s += t[i]
  	}
  	if s != len(t) {
  		println("bad defer", s)
  		panic("fail")
  	}
  }
  
  func f0() {
  	// likely to make a new stack for f0,
  	// because the call to f1 puts 3000 bytes
  	// in our frame.
  	f1()
  }
  
  func f1() [3000]byte {
  	// likely to make a new stack for f1,
  	// because 3000 bytes were used by f0
  	// and we need 3000 more for the call
  	// to f2.  if the call to morestack in f1
  	// does not pass the frame size, the new
  	// stack (default size 5k) will not be big
  	// enough for the frame, and the morestack
  	// check in f2 will die, if we get that far 
  	// without faulting.
  	f2()
  	return [3000]byte{}
  }
  
  func f2() [3000]byte {
  	// just take up space
  	return [3000]byte{}
  }
  
  var c = make(chan int)
  var t T
  var b = []byte{1, 2, 3, 4, 5, 6, 7, 8, 9, 10}
  
  func recur(n int) {
  	ss := string(b)
  	if len(ss) != len(b) {
  		panic("bad []byte -> string")
  	}
  	go g(c, t)
  	f0()
  	s := <-c
  	if s != len(t) {
  		println("bad go", s)
  		panic("fail")
  	}
  	f := func(t T) int {
  		s := 0
  		for i := 0; i < len(t); i++ {
  			s += t[i]
  		}
  		s += n
  		return s
  	}
  	s = f(t)
  	if s != len(t)+n {
  		println("bad func", s, "at level", n)
  		panic("fail")
  	}
  	if n > 0 {
  		recur(n - 1)
  	}
  	defer d(t)
  }
  
  func main() {
  	for i := 0; i < len(t); i++ {
  		t[i] = 1
  	}
  	recur(8000)
  }
  

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