cmd/compile: update escape analysis tests for newescape

The new escape analysis implementation tries to emit debugging
diagnostics that are compatible with the existing implementation, but
there's a handful of cases that are easier to handle by updating the
test expectations instead.

For regress tests that need updating, the original file is copied to
oldescapeXXX.go.go with -newescape=false added to the //errorcheck
line, while the file is updated in place with -newescape=true and new
test requirements.

Notable test changes:

1) escape_because.go looks for a lot of detailed internal debugging
messages that are fairly particular to how esc.go works and that I
haven't attempted to port over to escape.go yet.

2) There are a lot of "leaking param: x to result ~r1 level=-1"
messages for code like

    func(p *int) *T { return &T{p} }

that were simply wrong. Here &T must be heap allocated unconditionally
(because it's being returned); and since p is stored into it, p
escapes unconditionally too. esc.go incorrectly reports that p escapes
conditionally only if the returned pointer escaped.

3) esc.go used to print each "leaking param" analysis result as it
discovered them, which could lead to redundant messages (e.g., that a
param leaks at level=0 and level=1). escape.go instead prints
everything at the end, once it knows the shortest path to each sink.

4) esc.go didn't precisely model direct-interface types, resulting in
some values unnecessarily escaping to the heap when stored into
non-escaping interface values.

5) For functions written in assembly, esc.go only printed "does not
escape" messages, whereas escape.go prints "does not escape" or
"leaking param" as appropriate, consistent with the behavior for
functions written in Go.

6) 12 tests included "BAD" annotations identifying cases where esc.go
was unnecessarily heap allocating something. These are all fixed by
escape.go.

Updates #23109.

Change-Id: Iabc9eb14c94c9cadde3b183478d1fd54f013502f
Reviewed-on: https://go-review.googlesource.com/c/go/+/170447
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: David Chase <drchase@google.com>

test/escape2.go

-// errorcheck -0 -m -l
+// errorcheck -0 -m -l -newescape=true
 
 // Copyright 2010 The Go Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style
@@ -121,7 +121,7 @@ func NewBar() *Bar {
 	return &Bar{42, nil} // ERROR "&Bar literal escapes to heap$"
 }
 
-func NewBarp(x *int) *Bar { // ERROR "leaking param: x to result ~r1 level=-1$"
+func NewBarp(x *int) *Bar { // ERROR "leaking param: x$"
 	return &Bar{42, x} // ERROR "&Bar literal escapes to heap$"
 }
 
@@ -758,7 +758,7 @@ type LimitedFooer struct {
 	N int64
 }
 
-func LimitFooer(r Fooer, n int64) Fooer { // ERROR "leaking param: r to result ~r2 level=-1$"
+func LimitFooer(r Fooer, n int64) Fooer { // ERROR "leaking param: r$"
 	return &LimitedFooer{r, n} // ERROR "&LimitedFooer literal escapes to heap$"
 }
 
@@ -1360,7 +1360,7 @@ func F2([]byte)
 
 func F3(x []byte) // ERROR "F3 x does not escape$"
 
-func F4(x []byte)
+func F4(x []byte) // ERROR "leaking param: x$"
 
 func G() {
 	var buf1 [10]byte
@@ -1529,8 +1529,7 @@ type V struct {
 	s *string
 }
 
-// BAD -- level of leak ought to be 0
-func NewV(u U) *V { // ERROR "leaking param: u to result ~r1 level=-1"
+func NewV(u U) *V { // ERROR "leaking param: u$"
 	return &V{u.String()} // ERROR "&V literal escapes to heap$"
 }
 
@@ -1543,7 +1542,7 @@ func foo152() {
 
 // issue 8176 - &x in type switch body not marked as escaping
 
-func foo153(v interface{}) *int { // ERROR "leaking param: v to result ~r1 level=-1$"
+func foo153(v interface{}) *int { // ERROR "foo153 v does not escape"
 	switch x := v.(type) {
 	case int: // ERROR "moved to heap: x$"
 		return &x
@@ -1806,7 +1805,7 @@ func issue10353() {
 	issue10353a(x)()
 }
 
-func issue10353a(x *int) func() { // ERROR "leaking param: x to result ~r1 level=-1$"
+func issue10353a(x *int) func() { // ERROR "leaking param: x$"
 	return func() { // ERROR "func literal escapes to heap$"
 		println(*x)
 	}

test/escape2n.go

-// errorcheck -0 -N -m -l
+// errorcheck -0 -N -m -l -newescape=true
 
 // Copyright 2010 The Go Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style
@@ -121,7 +121,7 @@ func NewBar() *Bar {
 	return &Bar{42, nil} // ERROR "&Bar literal escapes to heap$"
 }
 
-func NewBarp(x *int) *Bar { // ERROR "leaking param: x to result ~r1 level=-1$"
+func NewBarp(x *int) *Bar { // ERROR "leaking param: x$"
 	return &Bar{42, x} // ERROR "&Bar literal escapes to heap$"
 }
 
@@ -758,7 +758,7 @@ type LimitedFooer struct {
 	N int64
 }
 
-func LimitFooer(r Fooer, n int64) Fooer { // ERROR "leaking param: r to result ~r2 level=-1$"
+func LimitFooer(r Fooer, n int64) Fooer { // ERROR "leaking param: r$"
 	return &LimitedFooer{r, n} // ERROR "&LimitedFooer literal escapes to heap$"
 }
 
@@ -1360,7 +1360,7 @@ func F2([]byte)
 
 func F3(x []byte) // ERROR "F3 x does not escape$"
 
-func F4(x []byte)
+func F4(x []byte) // ERROR "leaking param: x$"
 
 func G() {
 	var buf1 [10]byte
@@ -1529,8 +1529,7 @@ type V struct {
 	s *string
 }
 
-// BAD -- level of leak ought to be 0
-func NewV(u U) *V { // ERROR "leaking param: u to result ~r1 level=-1"
+func NewV(u U) *V { // ERROR "leaking param: u$"
 	return &V{u.String()} // ERROR "&V literal escapes to heap$"
 }
 
@@ -1543,7 +1542,7 @@ func foo152() {
 
 // issue 8176 - &x in type switch body not marked as escaping
 
-func foo153(v interface{}) *int { // ERROR "leaking param: v to result ~r1 level=-1$"
+func foo153(v interface{}) *int { // ERROR "foo153 v does not escape"
 	switch x := v.(type) {
 	case int: // ERROR "moved to heap: x$"
 		return &x
@@ -1806,7 +1805,7 @@ func issue10353() {
 	issue10353a(x)()
 }
 
-func issue10353a(x *int) func() { // ERROR "leaking param: x to result ~r1 level=-1$"
+func issue10353a(x *int) func() { // ERROR "leaking param: x$"
 	return func() { // ERROR "func literal escapes to heap$"
 		println(*x)
 	}

test/escape5.go

-// errorcheck -0 -m -l
+// errorcheck -0 -m -l -newescape=true
 
 // Copyright 2012 The Go Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style
@@ -129,7 +129,7 @@ type T2 struct {
 	Y *T1
 }
 
-func f8(p *T1) (k T2) { // ERROR "leaking param: p to result k" "leaking param: p"
+func f8(p *T1) (k T2) { // ERROR "leaking param: p$"
 	if p == nil {
 		k = T2{}
 		return

test/escape_because.go

-// errorcheck -0 -m -m -l
+// errorcheck -0 -m -m -l -newescape=false
 
 // Copyright 2015 The Go Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style

test/escape_calls.go

-// errorcheck -0 -m -l
+// errorcheck -0 -m -l -newescape=true
 
 // Copyright 2015 The Go Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style
@@ -36,7 +36,7 @@ func walk(np **Node) int { // ERROR "leaking param content: np"
 	wl := walk(&n.left)
 	wr := walk(&n.right)
 	if wl < wr {
-		n.left, n.right = n.right, n.left
+		n.left, n.right = n.right, n.left // ERROR "ignoring self-assignment"
 		wl, wr = wr, wl
 	}
 	*np = n

test/escape_closure.go

-// errorcheck -0 -m -l
+// errorcheck -0 -m -l -newescape=true
 
 // Copyright 2015 The Go Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style
@@ -11,27 +11,24 @@ package escape
 var sink interface{}
 
 func ClosureCallArgs0() {
-	x := 0         // ERROR "moved to heap: x"
+	x := 0
 	func(p *int) { // ERROR "p does not escape" "func literal does not escape"
 		*p = 1
-		// BAD: x should not escape to heap here
 	}(&x)
 }
 
 func ClosureCallArgs1() {
-	x := 0 // ERROR "moved to heap: x"
+	x := 0
 	for {
 		func(p *int) { // ERROR "p does not escape" "func literal does not escape"
 			*p = 1
-			// BAD: x should not escape to heap here
 		}(&x)
 	}
 }
 
 func ClosureCallArgs2() {
 	for {
-		// BAD: x should not escape here
-		x := 0         // ERROR "moved to heap: x"
+		x := 0
 		func(p *int) { // ERROR "p does not escape" "func literal does not escape"
 			*p = 1
 		}(&x)
@@ -46,8 +43,7 @@ func ClosureCallArgs3() {
 }
 
 func ClosureCallArgs4() {
-	// BAD: x should not leak here
-	x := 0                  // ERROR "moved to heap: x"
+	x := 0
 	_ = func(p *int) *int { // ERROR "leaking param: p to result ~r1" "func literal does not escape"
 		return p
 	}(&x)
@@ -55,7 +51,9 @@ func ClosureCallArgs4() {
 
 func ClosureCallArgs5() {
 	x := 0                     // ERROR "moved to heap: x"
-	sink = func(p *int) *int { // ERROR "leaking param: p to result ~r1" "func literal does not escape" "\(func literal\)\(&x\) escapes to heap"
+	// TODO(mdempsky): We get "leaking param: p" here because the new escape analysis pass
+	// can tell that p flows directly to sink, but it's a little weird. Re-evaluate.
+	sink = func(p *int) *int { // ERROR "leaking param: p" "func literal does not escape" "\(func literal\)\(&x\) escapes to heap"
 		return p
 	}(&x)
 }
@@ -79,10 +77,9 @@ func ClosureCallArgs7() {
 }
 
 func ClosureCallArgs8() {
-	x := 0               // ERROR "moved to heap: x"
+	x := 0
 	defer func(p *int) { // ERROR "p does not escape" "func literal does not escape"
 		*p = 1
-		// BAD: x should not escape to heap here
 	}(&x)
 }
 
@@ -113,8 +110,7 @@ func ClosureCallArgs11() {
 }
 
 func ClosureCallArgs12() {
-	// BAD: x should not leak
-	x := 0                    // ERROR "moved to heap: x"
+	x := 0
 	defer func(p *int) *int { // ERROR "leaking param: p to result ~r1" "func literal does not escape"
 		return p
 	}(&x)
@@ -128,21 +124,18 @@ func ClosureCallArgs13() {
 }
 
 func ClosureCallArgs14() {
-	x := 0 // ERROR "moved to heap: x"
-	// BAD: &x should not escape here
-	p := &x                  // ERROR "moved to heap: p"
+	x := 0
+	p := &x
 	_ = func(p **int) *int { // ERROR "leaking param: p to result ~r1 level=1" "func literal does not escape"
 		return *p
-		// BAD: p should not escape here
 	}(&p)
 }
 
 func ClosureCallArgs15() {
 	x := 0                      // ERROR "moved to heap: x"
-	p := &x                     // ERROR "moved to heap: p"
-	sink = func(p **int) *int { // ERROR "leaking param: p to result ~r1 level=1" "func literal does not escape" "\(func literal\)\(&p\) escapes to heap"
+	p := &x
+	sink = func(p **int) *int { // ERROR "leaking param content: p" "func literal does not escape" "\(func literal\)\(&p\) escapes to heap"
 		return *p
-		// BAD: p should not escape here
 	}(&p)
 }
 
@@ -152,7 +145,7 @@ func ClosureLeak1(s string) string { // ERROR "ClosureLeak1 s does not escape"
 }
 
 // See #14409 -- returning part of captured var leaks it.
-func ClosureLeak1a(a ...string) string { // ERROR "leaking param: a to result ~r1 level=1"
+func ClosureLeak1a(a ...string) string { // ERROR "leaking param: a to result ~r1 level=1$"
 	return func() string { // ERROR "ClosureLeak1a func literal does not escape"
 		return a[0]
 	}()
@@ -163,11 +156,11 @@ func ClosureLeak2(s string) string { // ERROR "ClosureLeak2 s does not escape"
 	c := ClosureLeak2a(t) // ERROR "ClosureLeak2 ... argument does not escape"
 	return c
 }
-func ClosureLeak2a(a ...string) string { // ERROR "leaking param: a to result ~r1 level=1"
+func ClosureLeak2a(a ...string) string { // ERROR "leaking param content: a"
 	return ClosureLeak2b(func() string { // ERROR "ClosureLeak2a func literal does not escape"
 		return a[0]
 	})
 }
-func ClosureLeak2b(f func() string) string { // ERROR "leaking param: f to result ~r1 level=1"
+func ClosureLeak2b(f func() string) string { // ERROR "ClosureLeak2b f does not escape"
 	return f()
 }

test/escape_field.go

-// errorcheck -0 -m -l
+// errorcheck -0 -m -l -newescape=true
 
 // Copyright 2015 The Go Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style
@@ -149,7 +149,7 @@ func field16() {
 	var x X
 	// BAD: &i should not escape
 	x.p1 = &i
-	var iface interface{} = x // ERROR "x escapes to heap"
+	var iface interface{} = x // ERROR "field16 x does not escape"
 	x1 := iface.(X)
 	sink = x1.p2 // ERROR "x1\.p2 escapes to heap"
 }
@@ -158,7 +158,7 @@ func field17() {
 	i := 0 // ERROR "moved to heap: i$"
 	var x X
 	x.p1 = &i
-	var iface interface{} = x // ERROR "x escapes to heap"
+	var iface interface{} = x // ERROR "field17 x does not escape"
 	x1 := iface.(X)
 	sink = x1.p1 // ERROR "x1\.p1 escapes to heap"
 }
@@ -168,7 +168,7 @@ func field18() {
 	var x X
 	// BAD: &i should not escape
 	x.p1 = &i
-	var iface interface{} = x // ERROR "x escapes to heap"
+	var iface interface{} = x // ERROR "field18 x does not escape"
 	y, _ := iface.(Y)         // Put X, but extracted Y. The cast will fail, so y is zero initialized.
 	sink = y                  // ERROR "y escapes to heap"
 }

test/escape_iface.go

-// errorcheck -0 -m -l
+// errorcheck -0 -m -l -newescape=true
 
 // Copyright 2015 The Go Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style
@@ -110,8 +110,7 @@ func efaceEscape1() {
 	{
 		i := 0         // ERROR "moved to heap: i"
 		v := M1{&i, 0}
-		// BAD: v does not escape to heap here
-		var x M = v // ERROR "v escapes to heap"
+		var x M = v // ERROR "efaceEscape1 v does not escape"
 		v1 := x.(M1)
 		sink = v1 // ERROR "v1 escapes to heap"
 	}

test/escape_param.go

-// errorcheck -0 -m -l
+// errorcheck -0 -m -l -newescape=true
 
 // Copyright 2015 The Go Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style
@@ -415,7 +415,7 @@ func f(x *Node) { // ERROR "leaking param content: x"
 	Sink = &Node{x.p} // ERROR "&Node literal escapes to heap"
 }
 
-func g(x *Node) *Node { // ERROR "leaking param: x to result ~r1 level=0"
+func g(x *Node) *Node { // ERROR "leaking param content: x"
 	return &Node{x.p} // ERROR "&Node literal escapes to heap"
 }
 

test/escape_struct_return.go

-// errorcheck -0 -m -l
+// errorcheck -0 -m -l -newescape=true
 
 // Copyright 2015 The Go Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style
@@ -19,7 +19,7 @@ func A(sp *string, spp **string) U { // ERROR "leaking param: sp to result ~r2 l
 	return U{sp, spp}
 }
 
-func B(spp **string) U { // ERROR "leaking param: spp to result ~r1 level=0$" "leaking param: spp to result ~r1 level=1$"
+func B(spp **string) U { // ERROR "leaking param: spp to result ~r1 level=0$"
 	return U{*spp, spp}
 }
 

test/fixedbugs/issue12006.go

-// errorcheck -0 -m -l
+// errorcheck -0 -m -l -newescape=true
 
 // Copyright 2015 The Go Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style
@@ -23,7 +23,7 @@ func FooNx(x *int, vals ...*int) (s int) { // ERROR "leaking param: x" "leaking
 
 var sink []*int
 
-func FooNy(x *int, vals ...*int) (s int) { // ERROR "leaking param: x" "leaking param: vals" "leaking param content: vals"
+func FooNy(x *int, vals ...*int) (s int) { // ERROR "leaking param: x" "leaking param: vals"
 	vals = append(vals, x)
 	sink = vals
 	return FooN(vals...)

test/fixedbugs/issue17318.go

-// errorcheck -0 -N -m -l
+// errorcheck -0 -N -m -l -newescape=true
 
 // Copyright 2016 The Go Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style
@@ -26,8 +26,8 @@ func (e ent) String() string {
 }
 
 //go:noinline
-func foo(ops closure, j int) (err fmt.Stringer) { // ERROR "leaking param: ops$" "leaking param: ops to result err level=0$"
-	enqueue := func(i int) fmt.Stringer { // ERROR "func literal escapes to heap$"
+func foo(ops closure, j int) (err fmt.Stringer) { // ERROR "foo ops does not escape"
+	enqueue := func(i int) fmt.Stringer { // ERROR "foo func literal does not escape"
 		return ops(i, j) // ERROR "ops\(i, j\) escapes to heap$"
 	}
 	err = enqueue(4)
@@ -39,7 +39,7 @@ func foo(ops closure, j int) (err fmt.Stringer) { // ERROR "leaking param: ops$"
 
 func main() {
 	// 3 identical functions, to get different escape behavior.
-	f := func(i, j int) ent { // ERROR "func literal escapes to heap$"
+	f := func(i, j int) ent { // ERROR "main func literal does not escape"
 		return ent(i + j)
 	}
 	i := foo(f, 3).(ent)

test/fixedbugs/oldescape_issue12006.go

+// errorcheck -0 -m -l -newescape=false
+
+// 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 through ... parameters.
+
+package foo
+
+func FooN(vals ...*int) (s int) { // ERROR "FooN vals does not escape"
+	for _, v := range vals {
+		s += *v
+	}
+	return s
+}
+
+// Append forces heap allocation and copies entries in vals to heap, therefore they escape to heap.
+func FooNx(x *int, vals ...*int) (s int) { // ERROR "leaking param: x" "leaking param content: vals"
+	vals = append(vals, x)
+	return FooN(vals...)
+}
+
+var sink []*int
+
+func FooNy(x *int, vals ...*int) (s int) { // ERROR "leaking param: x" "leaking param: vals" "leaking param content: vals"
+	vals = append(vals, x)
+	sink = vals
+	return FooN(vals...)
+}
+
+func FooNz(vals ...*int) (s int) { // ERROR "leaking param: vals"
+	sink = vals
+	return FooN(vals...)
+}
+
+func TFooN() {
+	for i := 0; i < 1000; i++ {
+		var i, j int
+		FooN(&i, &j) // ERROR "TFooN ... argument does not escape"
+	}
+}
+
+func TFooNx() {
+	for i := 0; i < 1000; i++ {
+		var i, j, k int   // ERROR "moved to heap: i" "moved to heap: j" "moved to heap: k"
+		FooNx(&k, &i, &j) // ERROR "TFooNx ... argument does not escape"
+	}
+}
+
+func TFooNy() {
+	for i := 0; i < 1000; i++ {
+		var i, j, k int   // ERROR "moved to heap: i" "moved to heap: j" "moved to heap: k"
+		FooNy(&k, &i, &j) // ERROR "... argument escapes to heap"
+	}
+}
+
+func TFooNz() {
+	for i := 0; i < 1000; i++ {
+		var i, j int  // ERROR "moved to heap: i" "moved to heap: j"
+		FooNz(&i, &j) // ERROR "... argument escapes to heap"
+	}
+}
+
+var isink *int32
+
+func FooI(args ...interface{}) { // ERROR "leaking param content: args"
+	for i := 0; i < len(args); i++ {
+		switch x := args[i].(type) {
+		case nil:
+			println("is nil")
+		case int32:
+			println("is int32")
+		case *int32:
+			println("is *int32")
+			isink = x
+		case string:
+			println("is string")
+		}
+	}
+}
+
+func TFooI() {
+	a := int32(1) // ERROR "moved to heap: a"
+	b := "cat"
+	c := &a
+	FooI(a, b, c) // ERROR "a escapes to heap" "b escapes to heap" "c escapes to heap" "TFooI ... argument does not escape"
+}
+
+func FooJ(args ...interface{}) *int32 { // ERROR "leaking param: args to result ~r1 level=1"
+	for i := 0; i < len(args); i++ {
+		switch x := args[i].(type) {
+		case nil:
+			println("is nil")
+		case int32:
+			println("is int32")
+		case *int32:
+			println("is *int32")
+			return x
+		case string:
+			println("is string")
+		}
+	}
+	return nil
+}
+
+func TFooJ1() {
+	a := int32(1)
+	b := "cat"
+	c := &a
+	FooJ(a, b, c) // ERROR "TFooJ1 a does not escape" "TFooJ1 b does not escape" "TFooJ1 c does not escape" "TFooJ1 ... argument does not escape"
+}
+
+func TFooJ2() {
+	a := int32(1) // ERROR "moved to heap: a"
+	b := "cat"
+	c := &a
+	isink = FooJ(a, b, c) // ERROR "a escapes to heap" "b escapes to heap" "c escapes to heap" "TFooJ2 ... argument does not escape"
+}
+
+type fakeSlice struct {
+	l int
+	a *[4]interface{}
+}
+
+func FooK(args fakeSlice) *int32 { // ERROR "leaking param: args to result ~r1 level=1"
+	for i := 0; i < args.l; i++ {
+		switch x := (*args.a)[i].(type) {
+		case nil:
+			println("is nil")
+		case int32:
+			println("is int32")
+		case *int32:
+			println("is *int32")
+			return x
+		case string:
+			println("is string")
+		}
+	}
+	return nil
+}
+
+func TFooK2() {
+	a := int32(1) // ERROR "moved to heap: a"
+	b := "cat"
+	c := &a
+	fs := fakeSlice{3, &[4]interface{}{a, b, c, nil}} // ERROR "a escapes to heap" "b escapes to heap" "c escapes to heap" "TFooK2 &\[4\]interface {} literal does not escape"
+	isink = FooK(fs)
+}
+
+func FooL(args []interface{}) *int32 { // ERROR "leaking param: args to result ~r1 level=1"
+	for i := 0; i < len(args); i++ {
+		switch x := args[i].(type) {
+		case nil:
+			println("is nil")
+		case int32:
+			println("is int32")
+		case *int32:
+			println("is *int32")
+			return x
+		case string:
+			println("is string")
+		}
+	}
+	return nil
+}
+
+func TFooL2() {
+	a := int32(1) // ERROR "moved to heap: a"
+	b := "cat"
+	c := &a
+	s := []interface{}{a, b, c} // ERROR "a escapes to heap" "b escapes to heap" "c escapes to heap" "TFooL2 \[\]interface {} literal does not escape"
+	isink = FooL(s)
+}

test/fixedbugs/oldescape_issue17318.go

+// errorcheck -0 -N -m -l -newescape=false
+
+// Copyright 2016 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.
+
+// The escape analyzer needs to run till its root set settles
+// (this is not that often, it turns out).
+// This test is likely to become stale because the leak depends
+// on a spurious-escape bug -- return an interface as a named
+// output parameter appears to cause the called closure to escape,
+// where returning it as a regular type does not.
+
+package main
+
+import (
+	"fmt"
+)
+
+type closure func(i, j int) ent
+
+type ent int
+
+func (e ent) String() string {
+	return fmt.Sprintf("%d", int(e)) // ERROR "ent.String ... argument does not escape$" "int\(e\) escapes to heap$"
+}
+
+//go:noinline
+func foo(ops closure, j int) (err fmt.Stringer) { // ERROR "leaking param: ops$" "leaking param: ops to result err level=0$"
+	enqueue := func(i int) fmt.Stringer { // ERROR "func literal escapes to heap$"
+		return ops(i, j) // ERROR "ops\(i, j\) escapes to heap$"
+	}
+	err = enqueue(4)
+	if err != nil {
+		return err
+	}
+	return // return result of enqueue, a fmt.Stringer
+}
+
+func main() {
+	// 3 identical functions, to get different escape behavior.
+	f := func(i, j int) ent { // ERROR "func literal escapes to heap$"
+		return ent(i + j)
+	}
+	i := foo(f, 3).(ent)
+	fmt.Printf("foo(f,3)=%d\n", int(i)) // ERROR "int\(i\) escapes to heap$" "main ... argument does not escape$"
+}

test/linkname.dir/linkname2.go

@@ -3,7 +3,7 @@ package y
 import _ "unsafe"
 
 //go:linkname byteIndex linkname1.indexByte
-func byteIndex(xs []byte, b byte) int
+func byteIndex(xs []byte, b byte) int // ERROR "leaking param: xs"
 
 func ContainsSlash(data []byte) bool { // ERROR "leaking param: data" "can inline ContainsSlash"
 	if byteIndex(data, '/') != -1 {

test/linkname.go

-// errorcheckandrundir -0 -m -l=4
+// errorcheckandrundir -0 -m -l=4 -newescape=true
 
 // Copyright 2010 The Go Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style

test/oldescape5.go

+// errorcheck -0 -m -l -newescape=false
+
+// Copyright 2012 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, using compiler diagnostic flags, that the escape analysis is working.
+// Compiles but does not run.  Inlining is disabled.
+
+package foo
+
+import "runtime"
+
+func noleak(p *int) int { // ERROR "p does not escape"
+	return *p
+}
+
+func leaktoret(p *int) *int { // ERROR "leaking param: p to result"
+	return p
+}
+
+func leaktoret2(p *int) (*int, *int) { // ERROR "leaking param: p to result ~r1" "leaking param: p to result ~r2"
+	return p, p
+}
+
+func leaktoret22(p, q *int) (*int, *int) { // ERROR "leaking param: p to result ~r2" "leaking param: q to result ~r3"
+	return p, q
+}
+
+func leaktoret22b(p, q *int) (*int, *int) { // ERROR "leaking param: p to result ~r3" "leaking param: q to result ~r2"
+	return leaktoret22(q, p)
+}
+
+func leaktoret22c(p, q *int) (*int, *int) { // ERROR "leaking param: p to result ~r3" "leaking param: q to result ~r2"
+	r, s := leaktoret22(q, p)
+	return r, s
+}
+
+func leaktoret22d(p, q *int) (r, s *int) { // ERROR "leaking param: p to result s" "leaking param: q to result r"
+	r, s = leaktoret22(q, p)
+	return
+}
+
+func leaktoret22e(p, q *int) (r, s *int) { // ERROR "leaking param: p to result s" "leaking param: q to result r"
+	r, s = leaktoret22(q, p)
+	return r, s
+}
+
+func leaktoret22f(p, q *int) (r, s *int) { // ERROR "leaking param: p to result s" "leaking param: q to result r"
+	rr, ss := leaktoret22(q, p)
+	return rr, ss
+}
+
+var gp *int
+
+func leaktosink(p *int) *int { // ERROR "leaking param: p"
+	gp = p
+	return p
+}
+
+func f1() {
+	var x int
+	p := noleak(&x)
+	_ = p
+}
+
+func f2() {
+	var x int
+	p := leaktoret(&x)
+	_ = p
+}
+
+func f3() {
+	var x int          // ERROR "moved to heap: x"
+	p := leaktoret(&x)
+	gp = p
+}
+
+func f4() {
+	var x int              // ERROR "moved to heap: x"
+	p, q := leaktoret2(&x)
+	gp = p
+	gp = q
+}
+
+func f5() {
+	var x int
+	leaktoret22(leaktoret2(&x))
+}
+
+func f6() {
+	var x int                               // ERROR "moved to heap: x"
+	px1, px2 := leaktoret22(leaktoret2(&x))
+	gp = px1
+	_ = px2
+}
+
+type T struct{ x int }
+
+func (t *T) Foo(u int) (*T, bool) { // ERROR "leaking param: t to result"
+	t.x += u
+	return t, true
+}
+
+func f7() *T {
+	r, _ := new(T).Foo(42) // ERROR "new.T. escapes to heap"
+	return r
+}
+
+func leakrecursive1(p, q *int) (*int, *int) { // ERROR "leaking param: p" "leaking param: q"
+	return leakrecursive2(q, p)
+}
+
+func leakrecursive2(p, q *int) (*int, *int) { // ERROR "leaking param: p" "leaking param: q"
+	if *p > *q {
+		return leakrecursive1(q, p)
+	}
+	// without this, leakrecursive? are safe for p and q, b/c in fact their graph does not have leaking edges.
+	return p, q
+}
+
+var global interface{}
+
+type T1 struct {
+	X *int
+}
+
+type T2 struct {
+	Y *T1
+}
+
+func f8(p *T1) (k T2) { // ERROR "leaking param: p to result k" "leaking param: p"
+	if p == nil {
+		k = T2{}
+		return
+	}
+
+	// should make p leak always
+	global = p // ERROR "p escapes to heap"
+	return T2{p}
+}
+
+func f9() {
+	var j T1 // ERROR "moved to heap: j"
+	f8(&j)
+}
+
+func f10() {
+	// These don't escape but are too big for the stack
+	var x [1 << 30]byte         // ERROR "moved to heap: x"
+	var y = make([]byte, 1<<30) // ERROR "make\(\[\]byte, 1 << 30\) escapes to heap"
+	_ = x[0] + y[0]
+}
+
+// Test for issue 19687 (passing to unnamed parameters does not escape).
+func f11(**int) {
+}
+func f12(_ **int) {
+}
+func f13() {
+	var x *int
+	f11(&x)
+	f12(&x)
+	runtime.KeepAlive(&x) // ERROR "&x does not escape"
+}
+
+// Test for issue 24305 (passing to unnamed receivers does not escape).
+type U int
+
+func (*U) M()   {}
+func (_ *U) N() {}
+
+func _() {
+	var u U
+	u.M()
+	u.N()
+}
+
+// Issue 24730: taking address in a loop causes unnecessary escape
+type T24730 struct {
+	x [64]byte
+}
+
+func (t *T24730) g() { // ERROR "t does not escape"
+	y := t.x[:]
+	for i := range t.x[:] {
+		y = t.x[:]
+		y[i] = 1
+	}
+
+	var z *byte
+	for i := range t.x[:] {
+		z = &t.x[i]
+		*z = 2
+	}
+}
+
+// Issue 15730: copy causes unnecessary escape
+
+var sink []byte
+var sink2 []int
+var sink3 []*int
+
+func f15730a(args ...interface{}) { // ERROR "args does not escape"
+	for _, arg := range args {
+		switch a := arg.(type) {
+		case string:
+			copy(sink, a)
+		}
+	}
+}
+
+func f15730b(args ...interface{}) { // ERROR "args does not escape"
+	for _, arg := range args {
+		switch a := arg.(type) {
+		case []int:
+			copy(sink2, a)
+		}
+	}
+}
+
+func f15730c(args ...interface{}) { // ERROR "leaking param content: args"
+	for _, arg := range args {
+		switch a := arg.(type) {
+		case []*int:
+			// copy pointerful data should cause escape
+			copy(sink3, a)
+		}
+	}
+}
+
+// Issue 29000: unnamed parameter is not handled correctly
+
+var sink4 interface{}
+var alwaysFalse = false
+
+func f29000(_ int, x interface{}) { // ERROR "leaking param: x"
+	sink4 = x
+	if alwaysFalse {
+		g29000()
+	}
+}
+
+func g29000() {
+	x := 1
+	f29000(2, x) // ERROR "x escapes to heap"
+}

test/oldescape_calls.go

+// errorcheck -0 -m -l -newescape=false
+
+// 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 function parameters.
+
+// In this test almost everything is BAD except the simplest cases
+// where input directly flows to output.
+
+package foo
+
+func f(buf []byte) []byte { // ERROR "leaking param: buf to result ~r1 level=0$"
+	return buf
+}
+
+func g(*byte) string
+
+func h(e int) {
+	var x [32]byte // ERROR "moved to heap: x$"
+	g(&f(x[:])[0])
+}
+
+type Node struct {
+	s           string
+	left, right *Node
+}
+
+func walk(np **Node) int { // ERROR "leaking param content: np"
+	n := *np
+	w := len(n.s)
+	if n == nil {
+		return 0
+	}
+	wl := walk(&n.left)
+	wr := walk(&n.right)
+	if wl < wr {
+		n.left, n.right = n.right, n.left
+		wl, wr = wr, wl
+	}
+	*np = n
+	return w + wl + wr
+}
+
+// Test for bug where func var f used prototype's escape analysis results.
+func prototype(xyz []string) {} // ERROR "prototype xyz does not escape"
+func bar() {
+	var got [][]string
+	f := prototype
+	f = func(ss []string) { got = append(got, ss) } // ERROR "leaking param: ss" "func literal does not escape"
+	s := "string"
+	f([]string{s}) // ERROR "\[\]string literal escapes to heap"
+}

test/oldescape_closure.go

+// errorcheck -0 -m -l -newescape=false
+
+// 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 closure arguments.
+
+package escape
+
+var sink interface{}
+
+func ClosureCallArgs0() {
+	x := 0         // ERROR "moved to heap: x"
+	func(p *int) { // ERROR "p does not escape" "func literal does not escape"
+		*p = 1
+		// BAD: x should not escape to heap here
+	}(&x)
+}
+
+func ClosureCallArgs1() {
+	x := 0 // ERROR "moved to heap: x"
+	for {
+		func(p *int) { // ERROR "p does not escape" "func literal does not escape"
+			*p = 1
+			// BAD: x should not escape to heap here
+		}(&x)
+	}
+}
+
+func ClosureCallArgs2() {
+	for {
+		// BAD: x should not escape here
+		x := 0         // ERROR "moved to heap: x"
+		func(p *int) { // ERROR "p does not escape" "func literal does not escape"
+			*p = 1
+		}(&x)
+	}
+}
+
+func ClosureCallArgs3() {
+	x := 0         // ERROR "moved to heap: x"
+	func(p *int) { // ERROR "leaking param: p" "func literal does not escape"
+		sink = p // ERROR "p escapes to heap"
+	}(&x)
+}
+
+func ClosureCallArgs4() {
+	// BAD: x should not leak here
+	x := 0                  // ERROR "moved to heap: x"
+	_ = func(p *int) *int { // ERROR "leaking param: p to result ~r1" "func literal does not escape"
+		return p
+	}(&x)
+}
+
+func ClosureCallArgs5() {
+	x := 0                     // ERROR "moved to heap: x"
+	sink = func(p *int) *int { // ERROR "leaking param: p to result ~r1" "func literal does not escape" "\(func literal\)\(&x\) escapes to heap"
+		return p
+	}(&x)
+}
+
+func ClosureCallArgs6() {
+	x := 0         // ERROR "moved to heap: x"
+	func(p *int) { // ERROR "moved to heap: p" "func literal does not escape"
+		sink = &p // ERROR "&p escapes to heap"
+	}(&x)
+}
+
+func ClosureCallArgs7() {
+	var pp *int
+	for {
+		x := 0         // ERROR "moved to heap: x"
+		func(p *int) { // ERROR "leaking param: p" "func literal does not escape"
+			pp = p
+		}(&x)
+	}
+	_ = pp
+}
+
+func ClosureCallArgs8() {
+	x := 0               // ERROR "moved to heap: x"
+	defer func(p *int) { // ERROR "p does not escape" "func literal does not escape"
+		*p = 1
+		// BAD: x should not escape to heap here
+	}(&x)
+}
+
+func ClosureCallArgs9() {
+	// BAD: x should not leak
+	x := 0 // ERROR "moved to heap: x"
+	for {
+		defer func(p *int) { // ERROR "func literal escapes to heap" "p does not escape"
+			*p = 1
+		}(&x)
+	}
+}
+
+func ClosureCallArgs10() {
+	for {
+		x := 0               // ERROR "moved to heap: x"
+		defer func(p *int) { // ERROR "func literal escapes to heap" "p does not escape"
+			*p = 1
+		}(&x)
+	}
+}
+
+func ClosureCallArgs11() {
+	x := 0               // ERROR "moved to heap: x"
+	defer func(p *int) { // ERROR "leaking param: p" "func literal does not escape"
+		sink = p // ERROR "p escapes to heap"
+	}(&x)
+}
+
+func ClosureCallArgs12() {
+	// BAD: x should not leak
+	x := 0                    // ERROR "moved to heap: x"
+	defer func(p *int) *int { // ERROR "leaking param: p to result ~r1" "func literal does not escape"
+		return p
+	}(&x)
+}
+
+func ClosureCallArgs13() {
+	x := 0               // ERROR "moved to heap: x"
+	defer func(p *int) { // ERROR "moved to heap: p" "func literal does not escape"
+		sink = &p // ERROR "&p escapes to heap"
+	}(&x)
+}
+
+func ClosureCallArgs14() {
+	x := 0 // ERROR "moved to heap: x"
+	// BAD: &x should not escape here
+	p := &x                  // ERROR "moved to heap: p"
+	_ = func(p **int) *int { // ERROR "leaking param: p to result ~r1 level=1" "func literal does not escape"
+		return *p
+		// BAD: p should not escape here
+	}(&p)
+}
+
+func ClosureCallArgs15() {
+	x := 0                      // ERROR "moved to heap: x"
+	p := &x                     // ERROR "moved to heap: p"
+	sink = func(p **int) *int { // ERROR "leaking param: p to result ~r1 level=1" "func literal does not escape" "\(func literal\)\(&p\) escapes to heap"
+		return *p
+		// BAD: p should not escape here
+	}(&p)
+}
+
+func ClosureLeak1(s string) string { // ERROR "ClosureLeak1 s does not escape"
+	t := s + "YYYY"         // ERROR "escapes to heap"
+	return ClosureLeak1a(t) // ERROR "ClosureLeak1 ... argument does not escape"
+}
+
+// See #14409 -- returning part of captured var leaks it.
+func ClosureLeak1a(a ...string) string { // ERROR "leaking param: a to result ~r1 level=1"
+	return func() string { // ERROR "ClosureLeak1a func literal does not escape"
+		return a[0]
+	}()
+}
+
+func ClosureLeak2(s string) string { // ERROR "ClosureLeak2 s does not escape"
+	t := s + "YYYY"       // ERROR "escapes to heap"
+	c := ClosureLeak2a(t) // ERROR "ClosureLeak2 ... argument does not escape"
+	return c
+}
+func ClosureLeak2a(a ...string) string { // ERROR "leaking param: a to result ~r1 level=1"
+	return ClosureLeak2b(func() string { // ERROR "ClosureLeak2a func literal does not escape"
+		return a[0]
+	})
+}
+func ClosureLeak2b(f func() string) string { // ERROR "leaking param: f to result ~r1 level=1"
+	return f()
+}

test/oldescape_field.go

+// errorcheck -0 -m -l -newescape=false
+
+// 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 with respect to field assignments.
+
+package escape
+
+var sink interface{}
+
+type X struct {
+	p1 *int
+	p2 *int
+	a  [2]*int
+}
+
+type Y struct {
+	x X
+}
+
+func field0() {
+	i := 0 // ERROR "moved to heap: i$"
+	var x X
+	x.p1 = &i
+	sink = x.p1 // ERROR "x\.p1 escapes to heap"
+}
+
+func field1() {
+	i := 0 // ERROR "moved to heap: i$"
+	var x X
+	// BAD: &i should not escape
+	x.p1 = &i
+	sink = x.p2 // ERROR "x\.p2 escapes to heap"
+}
+
+func field3() {
+	i := 0 // ERROR "moved to heap: i$"
+	var x X
+	x.p1 = &i
+	sink = x  // ERROR "x escapes to heap"
+}
+
+func field4() {
+	i := 0 // ERROR "moved to heap: i$"
+	var y Y
+	y.x.p1 = &i
+	x := y.x
+	sink = x // ERROR "x escapes to heap"
+}
+
+func field5() {
+	i := 0 // ERROR "moved to heap: i$"
+	var x X
+	// BAD: &i should not escape here
+	x.a[0] = &i
+	sink = x.a[1] // ERROR "x\.a\[1\] escapes to heap"
+}
+
+// BAD: we are not leaking param x, only x.p2
+func field6(x *X) { // ERROR "leaking param content: x$"
+	sink = x.p2 // ERROR "x\.p2 escapes to heap"
+}
+
+func field6a() {
+	i := 0 // ERROR "moved to heap: i$"
+	var x X
+	// BAD: &i should not escape
+	x.p1 = &i
+	field6(&x)
+}
+
+func field7() {
+	i := 0
+	var y Y
+	y.x.p1 = &i
+	x := y.x
+	var y1 Y
+	y1.x = x
+	_ = y1.x.p1
+}
+
+func field8() {
+	i := 0 // ERROR "moved to heap: i$"
+	var y Y
+	y.x.p1 = &i
+	x := y.x
+	var y1 Y
+	y1.x = x
+	sink = y1.x.p1 // ERROR "y1\.x\.p1 escapes to heap"
+}
+
+func field9() {
+	i := 0 // ERROR "moved to heap: i$"
+	var y Y
+	y.x.p1 = &i
+	x := y.x
+	var y1 Y
+	y1.x = x
+	sink = y1.x // ERROR "y1\.x escapes to heap"
+}
+
+func field10() {
+	i := 0 // ERROR "moved to heap: i$"
+	var y Y
+	// BAD: &i should not escape
+	y.x.p1 = &i
+	x := y.x
+	var y1 Y
+	y1.x = x
+	sink = y1.x.p2 // ERROR "y1\.x\.p2 escapes to heap"
+}
+
+func field11() {
+	i := 0         // ERROR "moved to heap: i$"
+	x := X{p1: &i}
+	sink = x.p1    // ERROR "x\.p1 escapes to heap"
+}
+
+func field12() {
+	i := 0 // ERROR "moved to heap: i$"
+	// BAD: &i should not escape
+	x := X{p1: &i}
+	sink = x.p2    // ERROR "x\.p2 escapes to heap"
+}
+
+func field13() {
+	i := 0          // ERROR "moved to heap: i$"
+	x := &X{p1: &i} // ERROR "field13 &X literal does not escape$"
+	sink = x.p1     // ERROR "x\.p1 escapes to heap"
+}
+
+func field14() {
+	i := 0 // ERROR "moved to heap: i$"
+	// BAD: &i should not escape
+	x := &X{p1: &i} // ERROR "field14 &X literal does not escape$"
+	sink = x.p2     // ERROR "x\.p2 escapes to heap"
+}
+
+func field15() {
+	i := 0          // ERROR "moved to heap: i$"
+	x := &X{p1: &i} // ERROR "&X literal escapes to heap$"
+	sink = x        // ERROR "x escapes to heap"
+}
+
+func field16() {
+	i := 0 // ERROR "moved to heap: i$"
+	var x X
+	// BAD: &i should not escape
+	x.p1 = &i
+	var iface interface{} = x // ERROR "x escapes to heap"
+	x1 := iface.(X)
+	sink = x1.p2 // ERROR "x1\.p2 escapes to heap"
+}
+
+func field17() {
+	i := 0 // ERROR "moved to heap: i$"
+	var x X
+	x.p1 = &i
+	var iface interface{} = x // ERROR "x escapes to heap"
+	x1 := iface.(X)
+	sink = x1.p1 // ERROR "x1\.p1 escapes to heap"
+}
+
+func field18() {
+	i := 0 // ERROR "moved to heap: i$"
+	var x X
+	// BAD: &i should not escape
+	x.p1 = &i
+	var iface interface{} = x // ERROR "x escapes to heap"
+	y, _ := iface.(Y)         // Put X, but extracted Y. The cast will fail, so y is zero initialized.
+	sink = y                  // ERROR "y escapes to heap"
+}

test/oldescape_linkname.dir/linkname1.go

+package x
+
+func indexByte(xs []byte, b byte) int { // ERROR "indexByte xs does not escape"
+	for i, x := range xs {
+		if x == b {
+			return i
+		}
+	}
+	return -1
+}

test/oldescape_linkname.dir/linkname2.go

+package y
+
+import _ "unsafe"
+
+//go:linkname byteIndex linkname1.indexByte
+func byteIndex(xs []byte, b byte) int
+
+func ContainsSlash(data []byte) bool { // ERROR "leaking param: data" "can inline ContainsSlash"
+	if byteIndex(data, '/') != -1 {
+		return true
+	}
+	return false
+}

test/oldescape_linkname.dir/linkname3.go

+package main
+
+import _ "./linkname1"
+import "./linkname2"
+
+func main() { // ERROR "can inline main"
+	str := "hello/world"
+	bs := []byte(str)        // ERROR "\(\[\]byte\)\(str\) escapes to heap"
+	if y.ContainsSlash(bs) { // ERROR "inlining call to y.ContainsSlash"
+	}
+}

test/oldescape_linkname.go

+// errorcheckandrundir -0 -m -l=4 -newescape=false
+
+// Copyright 2010 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.
+
+// Tests that linknames are included in export data (issue 18167).
+package ignored
+
+/*
+Without CL 33911, this test would fail with the following error:
+
+main.main: relocation target linkname2.byteIndex not defined
+main.main: undefined: "linkname2.byteIndex"
+*/