From 3cd85c0ca6bd4c29195e71fae4015b2ad89b555b Mon Sep 17 00:00:00 2001
From: Josh Bleecher Snyder <josh@tailscale.com>
Date: Fri, 17 Sep 2021 11:29:17 -0700
Subject: [PATCH] util/codegen: add ContainsPointers

And use it in cmd/cloner.

Signed-off-by: Josh Bleecher Snyder <josh@tailscale.com>
---
 cmd/cloner/cloner.go    | 41 +++++------------------------------------
 util/codegen/codegen.go | 35 +++++++++++++++++++++++++++++++++++
 2 files changed, 40 insertions(+), 36 deletions(-)

diff --git a/cmd/cloner/cloner.go b/cmd/cloner/cloner.go
index 421f0e69c..123529f95 100644
--- a/cmd/cloner/cloner.go
+++ b/cmd/cloner/cloner.go
@@ -156,7 +156,7 @@ func gen(buf *bytes.Buffer, imports map[string]struct{}, typ *types.Named, thisP
 	for i := 0; i < t.NumFields(); i++ {
 		fname := t.Field(i).Name()
 		ft := t.Field(i).Type()
-		if !containsPointers(ft) {
+		if !codegen.ContainsPointers(ft) {
 			continue
 		}
 		if named, _ := ft.(*types.Named); named != nil && !hasBasicUnderlying(ft) {
@@ -165,7 +165,7 @@ func gen(buf *bytes.Buffer, imports map[string]struct{}, typ *types.Named, thisP
 		}
 		switch ft := ft.Underlying().(type) {
 		case *types.Slice:
-			if containsPointers(ft.Elem()) {
+			if codegen.ContainsPointers(ft.Elem()) {
 				n := importedName(ft.Elem())
 				writef("dst.%s = make([]%s, len(src.%s))", fname, n, fname)
 				writef("for i := range dst.%s {", fname)
@@ -179,7 +179,7 @@ func gen(buf *bytes.Buffer, imports map[string]struct{}, typ *types.Named, thisP
 				writef("dst.%s = append(src.%s[:0:0], src.%s...)", fname, fname, fname)
 			}
 		case *types.Pointer:
-			if named, _ := ft.Elem().(*types.Named); named != nil && containsPointers(ft.Elem()) {
+			if named, _ := ft.Elem().(*types.Named); named != nil && codegen.ContainsPointers(ft.Elem()) {
 				writef("dst.%s = src.%s.Clone()", fname, fname)
 				continue
 			}
@@ -187,7 +187,7 @@ func gen(buf *bytes.Buffer, imports map[string]struct{}, typ *types.Named, thisP
 			writef("if dst.%s != nil {", fname)
 			writef("\tdst.%s = new(%s)", fname, n)
 			writef("\t*dst.%s = *src.%s", fname, fname)
-			if containsPointers(ft.Elem()) {
+			if codegen.ContainsPointers(ft.Elem()) {
 				writef("\t" + `panic("TODO pointers in pointers")`)
 			}
 			writef("}")
@@ -201,7 +201,7 @@ func gen(buf *bytes.Buffer, imports map[string]struct{}, typ *types.Named, thisP
 				// the key is always copied.
 				writef("\t\tdst.%s[k] = append([]%s{}, src.%s[k]...)", fname, n, fname)
 				writef("\t}")
-			} else if containsPointers(ft.Elem()) {
+			} else if codegen.ContainsPointers(ft.Elem()) {
 				writef("\tfor k, v := range src.%s {", fname)
 				writef("\t\tdst.%s[k] = v.Clone()", fname)
 				writef("\t}")
@@ -229,34 +229,3 @@ func hasBasicUnderlying(typ types.Type) bool {
 		return false
 	}
 }
-
-func containsPointers(typ types.Type) bool {
-	switch typ.String() {
-	case "time.Time":
-		// time.Time contains a pointer that does not need copying
-		return false
-	case "inet.af/netaddr.IP":
-		return false
-	}
-	switch ft := typ.Underlying().(type) {
-	case *types.Array:
-		return containsPointers(ft.Elem())
-	case *types.Chan:
-		return true
-	case *types.Interface:
-		return true // a little too broad
-	case *types.Map:
-		return true
-	case *types.Pointer:
-		return true
-	case *types.Slice:
-		return true
-	case *types.Struct:
-		for i := 0; i < ft.NumFields(); i++ {
-			if containsPointers(ft.Field(i).Type()) {
-				return true
-			}
-		}
-	}
-	return false
-}
diff --git a/util/codegen/codegen.go b/util/codegen/codegen.go
index 013170735..2df6c9b25 100644
--- a/util/codegen/codegen.go
+++ b/util/codegen/codegen.go
@@ -109,3 +109,38 @@ func importedName(t types.Type, thisPkg *types.Package) (qualifiedName, importPk
 	}
 	return types.TypeString(t, qual), importPkg
 }
+
+// ContainsPointers reports whether typ contains any pointers,
+// either explicitly or implicitly.
+// It has special handling for some types that contain pointers
+// that we know are free from memory aliasing/mutation concerns.
+func ContainsPointers(typ types.Type) bool {
+	switch typ.String() {
+	case "time.Time":
+		// time.Time contains a pointer that does not need copying
+		return false
+	case "inet.af/netaddr.IP":
+		return false
+	}
+	switch ft := typ.Underlying().(type) {
+	case *types.Array:
+		return ContainsPointers(ft.Elem())
+	case *types.Chan:
+		return true
+	case *types.Interface:
+		return true // a little too broad
+	case *types.Map:
+		return true
+	case *types.Pointer:
+		return true
+	case *types.Slice:
+		return true
+	case *types.Struct:
+		for i := 0; i < ft.NumFields(); i++ {
+			if ContainsPointers(ft.Field(i).Type()) {
+				return true
+			}
+		}
+	}
+	return false
+}