314 lines
8.2 KiB
Go
314 lines
8.2 KiB
Go
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// Copyright 2013 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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package pointer
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import (
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"bytes"
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"fmt"
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"go/types"
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"log"
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"os"
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"os/exec"
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"runtime"
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"time"
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"golang.org/x/tools/container/intsets"
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)
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// CanPoint reports whether the type T is pointerlike,
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// for the purposes of this analysis.
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func CanPoint(T types.Type) bool {
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switch T := T.(type) {
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case *types.Named:
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if obj := T.Obj(); obj.Name() == "Value" && obj.Pkg().Path() == "reflect" {
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return true // treat reflect.Value like interface{}
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}
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return CanPoint(T.Underlying())
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case *types.Pointer, *types.Interface, *types.Map, *types.Chan, *types.Signature, *types.Slice:
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return true
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}
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return false // array struct tuple builtin basic
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}
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// CanHaveDynamicTypes reports whether the type T can "hold" dynamic types,
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// i.e. is an interface (incl. reflect.Type) or a reflect.Value.
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//
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func CanHaveDynamicTypes(T types.Type) bool {
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switch T := T.(type) {
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case *types.Named:
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if obj := T.Obj(); obj.Name() == "Value" && obj.Pkg().Path() == "reflect" {
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return true // reflect.Value
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}
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return CanHaveDynamicTypes(T.Underlying())
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case *types.Interface:
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return true
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}
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return false
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}
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func isInterface(T types.Type) bool { return types.IsInterface(T) }
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// mustDeref returns the element type of its argument, which must be a
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// pointer; panic ensues otherwise.
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func mustDeref(typ types.Type) types.Type {
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return typ.Underlying().(*types.Pointer).Elem()
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}
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// deref returns a pointer's element type; otherwise it returns typ.
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func deref(typ types.Type) types.Type {
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if p, ok := typ.Underlying().(*types.Pointer); ok {
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return p.Elem()
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}
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return typ
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}
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// A fieldInfo describes one subelement (node) of the flattening-out
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// of a type T: the subelement's type and its path from the root of T.
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//
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// For example, for this type:
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// type line struct{ points []struct{x, y int} }
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// flatten() of the inner struct yields the following []fieldInfo:
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// struct{ x, y int } ""
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// int ".x"
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// int ".y"
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// and flatten(line) yields:
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// struct{ points []struct{x, y int} } ""
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// struct{ x, y int } ".points[*]"
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// int ".points[*].x
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// int ".points[*].y"
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//
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type fieldInfo struct {
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typ types.Type
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// op and tail describe the path to the element (e.g. ".a#2.b[*].c").
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op interface{} // *Array: true; *Tuple: int; *Struct: *types.Var; *Named: nil
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tail *fieldInfo
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}
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// path returns a user-friendly string describing the subelement path.
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//
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func (fi *fieldInfo) path() string {
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var buf bytes.Buffer
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for p := fi; p != nil; p = p.tail {
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switch op := p.op.(type) {
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case bool:
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fmt.Fprintf(&buf, "[*]")
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case int:
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fmt.Fprintf(&buf, "#%d", op)
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case *types.Var:
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fmt.Fprintf(&buf, ".%s", op.Name())
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}
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}
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return buf.String()
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}
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// flatten returns a list of directly contained fields in the preorder
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// traversal of the type tree of t. The resulting elements are all
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// scalars (basic types or pointerlike types), except for struct/array
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// "identity" nodes, whose type is that of the aggregate.
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//
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// reflect.Value is considered pointerlike, similar to interface{}.
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//
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// Callers must not mutate the result.
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//
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func (a *analysis) flatten(t types.Type) []*fieldInfo {
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fl, ok := a.flattenMemo[t]
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if !ok {
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switch t := t.(type) {
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case *types.Named:
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u := t.Underlying()
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if isInterface(u) {
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// Debuggability hack: don't remove
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// the named type from interfaces as
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// they're very verbose.
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fl = append(fl, &fieldInfo{typ: t})
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} else {
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fl = a.flatten(u)
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}
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case *types.Basic,
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*types.Signature,
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*types.Chan,
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*types.Map,
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*types.Interface,
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*types.Slice,
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*types.Pointer:
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fl = append(fl, &fieldInfo{typ: t})
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case *types.Array:
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fl = append(fl, &fieldInfo{typ: t}) // identity node
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for _, fi := range a.flatten(t.Elem()) {
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fl = append(fl, &fieldInfo{typ: fi.typ, op: true, tail: fi})
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}
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case *types.Struct:
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fl = append(fl, &fieldInfo{typ: t}) // identity node
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for i, n := 0, t.NumFields(); i < n; i++ {
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f := t.Field(i)
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for _, fi := range a.flatten(f.Type()) {
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fl = append(fl, &fieldInfo{typ: fi.typ, op: f, tail: fi})
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}
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}
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case *types.Tuple:
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// No identity node: tuples are never address-taken.
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n := t.Len()
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if n == 1 {
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// Don't add a fieldInfo link for singletons,
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// e.g. in params/results.
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fl = append(fl, a.flatten(t.At(0).Type())...)
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} else {
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for i := 0; i < n; i++ {
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f := t.At(i)
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for _, fi := range a.flatten(f.Type()) {
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fl = append(fl, &fieldInfo{typ: fi.typ, op: i, tail: fi})
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}
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}
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}
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default:
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panic(fmt.Sprintf("cannot flatten unsupported type %T", t))
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}
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a.flattenMemo[t] = fl
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}
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return fl
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}
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// sizeof returns the number of pointerlike abstractions (nodes) in the type t.
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func (a *analysis) sizeof(t types.Type) uint32 {
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return uint32(len(a.flatten(t)))
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}
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// shouldTrack reports whether object type T contains (recursively)
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// any fields whose addresses should be tracked.
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func (a *analysis) shouldTrack(T types.Type) bool {
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if a.track == trackAll {
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return true // fast path
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}
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track, ok := a.trackTypes[T]
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if !ok {
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a.trackTypes[T] = true // break cycles conservatively
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// NB: reflect.Value, reflect.Type are pre-populated to true.
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for _, fi := range a.flatten(T) {
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switch ft := fi.typ.Underlying().(type) {
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case *types.Interface, *types.Signature:
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track = true // needed for callgraph
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case *types.Basic:
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// no-op
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case *types.Chan:
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track = a.track&trackChan != 0 || a.shouldTrack(ft.Elem())
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case *types.Map:
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track = a.track&trackMap != 0 || a.shouldTrack(ft.Key()) || a.shouldTrack(ft.Elem())
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case *types.Slice:
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track = a.track&trackSlice != 0 || a.shouldTrack(ft.Elem())
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case *types.Pointer:
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track = a.track&trackPtr != 0 || a.shouldTrack(ft.Elem())
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case *types.Array, *types.Struct:
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// No need to look at field types since they will follow (flattened).
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default:
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// Includes *types.Tuple, which are never address-taken.
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panic(ft)
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}
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if track {
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break
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}
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}
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a.trackTypes[T] = track
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if !track && a.log != nil {
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fmt.Fprintf(a.log, "\ttype not tracked: %s\n", T)
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}
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}
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return track
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}
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// offsetOf returns the (abstract) offset of field index within struct
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// or tuple typ.
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func (a *analysis) offsetOf(typ types.Type, index int) uint32 {
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var offset uint32
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switch t := typ.Underlying().(type) {
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case *types.Tuple:
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for i := 0; i < index; i++ {
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offset += a.sizeof(t.At(i).Type())
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}
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case *types.Struct:
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offset++ // the node for the struct itself
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for i := 0; i < index; i++ {
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offset += a.sizeof(t.Field(i).Type())
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}
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default:
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panic(fmt.Sprintf("offsetOf(%s : %T)", typ, typ))
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}
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return offset
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}
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// sliceToArray returns the type representing the arrays to which
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// slice type slice points.
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func sliceToArray(slice types.Type) *types.Array {
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return types.NewArray(slice.Underlying().(*types.Slice).Elem(), 1)
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}
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// Node set -------------------------------------------------------------------
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type nodeset struct {
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intsets.Sparse
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}
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func (ns *nodeset) String() string {
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var buf bytes.Buffer
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buf.WriteRune('{')
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var space [50]int
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for i, n := range ns.AppendTo(space[:0]) {
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if i > 0 {
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buf.WriteString(", ")
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}
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buf.WriteRune('n')
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fmt.Fprintf(&buf, "%d", n)
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}
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buf.WriteRune('}')
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return buf.String()
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}
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func (ns *nodeset) add(n nodeid) bool {
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return ns.Sparse.Insert(int(n))
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}
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func (x *nodeset) addAll(y *nodeset) bool {
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return x.UnionWith(&y.Sparse)
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}
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// Profiling & debugging -------------------------------------------------------
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var timers = make(map[string]time.Time)
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func start(name string) {
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if debugTimers {
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timers[name] = time.Now()
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log.Printf("%s...\n", name)
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}
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}
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func stop(name string) {
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if debugTimers {
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log.Printf("%s took %s\n", name, time.Since(timers[name]))
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}
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}
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// diff runs the command "diff a b" and reports its success.
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func diff(a, b string) bool {
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var cmd *exec.Cmd
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switch runtime.GOOS {
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case "plan9":
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cmd = exec.Command("/bin/diff", "-c", a, b)
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default:
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cmd = exec.Command("/usr/bin/diff", "-u", a, b)
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}
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cmd.Stdout = os.Stderr
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cmd.Stderr = os.Stderr
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return cmd.Run() == nil
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}
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