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Source file test/escape_array.go

Documentation: test

  // errorcheck -0 -m -l
  
  // Copyright 2015 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 escape analysis for arrays and some large things
  
  package foo
  
  var Ssink *string
  
  type U [2]*string
  
  func bar(a, b *string) U { // ERROR "leaking param: a to result ~r2 level=0$" "leaking param: b to result ~r2 level=0$"
  	return U{a, b}
  }
  
  func foo(x U) U { // ERROR "leaking param: x to result ~r1 level=0$"
  	return U{x[1], x[0]}
  }
  
  func bff(a, b *string) U { // ERROR "leaking param: a to result ~r2 level=0$" "leaking param: b to result ~r2 level=0$"
  	return foo(foo(bar(a, b)))
  }
  
  func tbff1() *string {
  	a := "cat"
  	b := "dog"       // ERROR "moved to heap: b$"
  	u := bff(&a, &b) // ERROR "tbff1 &a does not escape$" "tbff1 &b does not escape$"
  	_ = u[0]
  	return &b // ERROR "&b escapes to heap$"
  }
  
  // BAD: need fine-grained analysis to track u[0] and u[1] differently.
  func tbff2() *string {
  	a := "cat"       // ERROR "moved to heap: a$"
  	b := "dog"       // ERROR "moved to heap: b$"
  	u := bff(&a, &b) // ERROR "&a escapes to heap$" "&b escapes to heap$"
  	_ = u[0]
  	return u[1]
  }
  
  func car(x U) *string { // ERROR "leaking param: x to result ~r1 level=0$"
  	return x[0]
  }
  
  // BAD: need fine-grained analysis to track x[0] and x[1] differently.
  func fun(x U, y *string) *string { // ERROR "leaking param: x to result ~r2 level=0$" "leaking param: y to result ~r2 level=0$"
  	x[0] = y
  	return x[1]
  }
  
  func fup(x *U, y *string) *string { // ERROR "leaking param: x to result ~r2 level=1$" "leaking param: y$"
  	x[0] = y // leaking y to heap is intended
  	return x[1]
  }
  
  func fum(x *U, y **string) *string { // ERROR "leaking param: x to result ~r2 level=1$" "leaking param content: y$"
  	x[0] = *y
  	return x[1]
  }
  
  func fuo(x *U, y *U) *string { // ERROR "leaking param: x to result ~r2 level=1$" "leaking param content: y$"
  	x[0] = y[0]
  	return x[1]
  }
  
  // These two tests verify that:
  // small array literals are stack allocated;
  // pointers stored in small array literals do not escape;
  // large array literals are heap allocated;
  // pointers stored in large array literals escape.
  func hugeLeaks1(x **string, y **string) { // ERROR "leaking param content: x" "hugeLeaks1 y does not escape" "mark escaped content: x"
  	a := [10]*string{*y}
  	_ = a
  	// 4 x 4,000,000 exceeds MaxStackVarSize, therefore it must be heap allocated if pointers are 4 bytes or larger.
  	b := [4000000]*string{*x} // ERROR "moved to heap: b"
  	_ = b
  }
  
  func hugeLeaks2(x *string, y *string) { // ERROR "leaking param: x" "hugeLeaks2 y does not escape"
  	a := [10]*string{y}
  	_ = a
  	// 4 x 4,000,000 exceeds MaxStackVarSize, therefore it must be heap allocated if pointers are 4 bytes or larger.
  	b := [4000000]*string{x} // ERROR "moved to heap: b"
  	_ = b
  }
  
  // BAD: x need not leak.
  func doesNew1(x *string, y *string) { // ERROR "leaking param: x" "leaking param: y"
  	a := new([10]*string) // ERROR "new\(\[10\]\*string\) does not escape"
  	a[0] = x
  	b := new([65537]*string) // ERROR "new\(\[65537\]\*string\) escapes to heap"
  	b[0] = y
  }
  
  type a10 struct {
  	s *string
  	i [10]int32
  }
  
  type a65537 struct {
  	s *string
  	i [65537]int32
  }
  
  // BAD: x need not leak.
  func doesNew2(x *string, y *string) { // ERROR "leaking param: x" "leaking param: y"
  	a := new(a10) // ERROR "new\(a10\) does not escape"
  	a.s = x
  	b := new(a65537) // ERROR "new\(a65537\) escapes to heap"
  	b.s = y
  }
  
  // BAD: x need not leak.
  func doesMakeSlice(x *string, y *string) { // ERROR "leaking param: x" "leaking param: y"
  	a := make([]*string, 10) // ERROR "make\(\[\]\*string, 10\) does not escape"
  	a[0] = x
  	b := make([]*string, 65537) // ERROR "make\(\[\]\*string, 65537\) escapes to heap"
  	b[0] = y
  }
  

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