func checkCallsExpectation(prog *ssa.Program, e *expectation, cg *callgraph.Graph) bool {
	found := make(map[string]int)
	err := callgraph.GraphVisitEdges(cg, func(edge *callgraph.Edge) error {
		// Name-based matching is inefficient but it allows us to
		// match functions whose names that would not appear in an
		// index ("<root>") or which are not unique ("[email protected]").
		if edge.Caller.Func.String() == e.args[0] {
			calleeStr := edge.Callee.Func.String()
			if calleeStr == e.args[1] {
				return errOK // expectation satisified; stop the search
			}
			found[calleeStr]++
		}
		return nil
	})
	if err == errOK {
		return true
	}
	if len(found) == 0 {
		e.errorf("didn't find any calls from %s", e.args[0])
	}
	e.errorf("found no call from %s to %s, but only to %s",
		e.args[0], e.args[1], join(found))
	return false
}

func visitGraph(ptrResult *pointer.Result, globals map[ssa.Value]usage, typemap map[*types.Named]usage) error {
	n := runtime.NumCPU()
	q := make(chan *callgraph.Edge, n)
	var vgwg sync.WaitGroup
	vgwg.Add(n)
	for i := 0; i < n; i++ {
		go func() {
			for edge := range q {
				for _, blk := range edge.Callee.Func.Blocks {
					for _, ins := range blk.Instrs {
						for _, rand := range ins.Operands(nil) {
							if rand != nil && *rand != nil {
								visitRand(edge, rand, globals, typemap)
							}
						}
					}
				}
			}
			vgwg.Done()
		}()
	}
	err := callgraph.GraphVisitEdges(ptrResult.CallGraph, func(edge *callgraph.Edge) error {
		if edge.Callee != nil {
			q <- edge
		}
		return nil
	})
	close(q)
	vgwg.Wait()
	return err
}

func printGraph(cg *callgraph.Graph, from *types.Package) string {
	var edges []string
	callgraph.GraphVisitEdges(cg, func(e *callgraph.Edge) error {
		if strings.Contains(e.Description(), "dynamic") {
			edges = append(edges, fmt.Sprintf("%s --> %s",
				e.Caller.Func.RelString(from),
				e.Callee.Func.RelString(from)))
		}
		return nil
	})
	sort.Strings(edges)

	var buf bytes.Buffer
	buf.WriteString("Dynamic calls\n")
	for _, edge := range edges {
		fmt.Fprintf(&buf, "  %s\n", edge)
	}
	return strings.TrimSpace(buf.String())
}

func printResult(res *rta.Result, from *types.Package) string {
	var buf bytes.Buffer

	writeSorted := func(ss []string) {
		sort.Strings(ss)
		for _, s := range ss {
			fmt.Fprintf(&buf, "  %s\n", s)
		}
	}

	buf.WriteString("Dynamic calls\n")
	var edges []string
	callgraph.GraphVisitEdges(res.CallGraph, func(e *callgraph.Edge) error {
		if strings.Contains(e.Description(), "dynamic") {
			edges = append(edges, fmt.Sprintf("%s --> %s",
				e.Caller.Func.RelString(from),
				e.Callee.Func.RelString(from)))
		}
		return nil
	})
	writeSorted(edges)

	buf.WriteString("Reachable functions\n")
	var reachable []string
	for f := range res.Reachable {
		reachable = append(reachable, f.RelString(from))
	}
	writeSorted(reachable)

	buf.WriteString("Reflect types\n")
	var rtypes []string
	res.RuntimeTypes.Iterate(func(key types.Type, value interface{}) {
		if value == false { // accessible to reflection
			rtypes = append(rtypes, types.TypeString(from, key))
		}
	})
	writeSorted(rtypes)

	return strings.TrimSpace(buf.String())
}

func TestStatic(t *testing.T) {
	conf := loader.Config{ParserMode: parser.ParseComments}
	f, err := conf.ParseFile("P.go", input)
	if err != nil {
		t.Fatal(err)
	}

	conf.CreateFromFiles("P", f)
	iprog, err := conf.Load()
	if err != nil {
		t.Fatal(err)
	}

	P := iprog.Created[0].Pkg

	prog := ssautil.CreateProgram(iprog, 0)
	prog.BuildAll()

	cg := static.CallGraph(prog)

	var edges []string
	callgraph.GraphVisitEdges(cg, func(e *callgraph.Edge) error {
		edges = append(edges, fmt.Sprintf("%s -> %s",
			e.Caller.Func.RelString(P),
			e.Callee.Func.RelString(P)))
		return nil
	})
	sort.Strings(edges)

	want := []string{
		"(*C).f -> (C).f",
		"f -> (C).f",
		"f -> f$1",
		"f -> g",
	}
	if !reflect.DeepEqual(edges, want) {
		t.Errorf("Got edges %v, want %v", edges, want)
	}
}

// This program demonstrates how to use the pointer analysis to
// obtain a conservative call-graph of a Go program.
// It also shows how to compute the points-to set of a variable,
// in this case, (C).f's ch parameter.
//
func Example() {
	const myprog = `
package main

import "fmt"

type I interface {
	f(map[string]int)
}

type C struct{}

func (C) f(m map[string]int) {
	fmt.Println("C.f()")
}

func main() {
	var i I = C{}
	x := map[string]int{"one":1}
	i.f(x) // dynamic method call
}
`
	var conf loader.Config

	// Parse the input file, a string.
	// (Command-line tools should use conf.FromArgs.)
	file, err := conf.ParseFile("myprog.go", myprog)
	if err != nil {
		fmt.Print(err) // parse error
		return
	}

	// Create single-file main package and import its dependencies.
	conf.CreateFromFiles("main", file)

	iprog, err := conf.Load()
	if err != nil {
		fmt.Print(err) // type error in some package
		return
	}

	// Create SSA-form program representation.
	prog := ssautil.CreateProgram(iprog, 0)
	mainPkg := prog.Package(iprog.Created[0].Pkg)

	// Build SSA code for bodies of all functions in the whole program.
	prog.Build()

	// Configure the pointer analysis to build a call-graph.
	config := &pointer.Config{
		Mains:          []*ssa.Package{mainPkg},
		BuildCallGraph: true,
	}

	// Query points-to set of (C).f's parameter m, a map.
	C := mainPkg.Type("C").Type()
	Cfm := prog.LookupMethod(C, mainPkg.Pkg, "f").Params[1]
	config.AddQuery(Cfm)

	// Run the pointer analysis.
	result, err := pointer.Analyze(config)
	if err != nil {
		panic(err) // internal error in pointer analysis
	}

	// Find edges originating from the main package.
	// By converting to strings, we de-duplicate nodes
	// representing the same function due to context sensitivity.
	var edges []string
	callgraph.GraphVisitEdges(result.CallGraph, func(edge *callgraph.Edge) error {
		caller := edge.Caller.Func
		if caller.Pkg == mainPkg {
			edges = append(edges, fmt.Sprint(caller, " --> ", edge.Callee.Func))
		}
		return nil
	})

	// Print the edges in sorted order.
	sort.Strings(edges)
	for _, edge := range edges {
		fmt.Println(edge)
	}
	fmt.Println()

	// Print the labels of (C).f(m)'s points-to set.
	fmt.Println("m may point to:")
	var labels []string
	for _, l := range result.Queries[Cfm].PointsTo().Labels() {
		label := fmt.Sprintf("  %s: %s", prog.Fset.Position(l.Pos()), l)
		labels = append(labels, label)
	}
	sort.Strings(labels)
	for _, label := range labels {
		fmt.Println(label)
	}
//.........这里部分代码省略.........

func doCallgraph(ctxt *build.Context, algo, format string, tests bool, args []string) error {
	conf := loader.Config{
		Build:         ctxt,
		SourceImports: true,
	}

	if len(args) == 0 {
		fmt.Fprintln(os.Stderr, Usage)
		return nil
	}

	// Use the initial packages from the command line.
	args, err := conf.FromArgs(args, tests)
	if err != nil {
		return err
	}

	// Load, parse and type-check the whole program.
	iprog, err := conf.Load()
	if err != nil {
		return err
	}

	// Create and build SSA-form program representation.
	prog := ssa.Create(iprog, 0)
	prog.BuildAll()

	// -- call graph construction ------------------------------------------

	var cg *callgraph.Graph

	switch algo {
	case "static":
		cg = static.CallGraph(prog)

	case "cha":
		cg = cha.CallGraph(prog)

	case "pta":
		main, err := mainPackage(prog, tests)
		if err != nil {
			return err
		}
		config := &pointer.Config{
			Mains:          []*ssa.Package{main},
			BuildCallGraph: true,
		}
		ptares, err := pointer.Analyze(config)
		if err != nil {
			return err // internal error in pointer analysis
		}
		cg = ptares.CallGraph

	case "rta":
		main, err := mainPackage(prog, tests)
		if err != nil {
			return err
		}
		roots := []*ssa.Function{
			main.Func("init"),
			main.Func("main"),
		}
		rtares := rta.Analyze(roots, true)
		cg = rtares.CallGraph

		// NB: RTA gives us Reachable and RuntimeTypes too.

	default:
		return fmt.Errorf("unknown algorithm: %s", algo)
	}

	cg.DeleteSyntheticNodes()

	// -- output------------------------------------------------------------

	var before, after string

	// Pre-canned formats.
	switch format {
	case "digraph":
		format = `{{printf "%q %q" .Caller .Callee}}`

	case "graphviz":
		before = "digraph callgraph {\n"
		after = "}\n"
		format = `  {{printf "%q" .Caller}} -> {{printf "%q" .Callee}}"`
	}

	tmpl, err := template.New("-format").Parse(format)
	if err != nil {
		return fmt.Errorf("invalid -format template: %v", err)
	}

	// Allocate these once, outside the traversal.
	var buf bytes.Buffer
	data := Edge{fset: prog.Fset}

	fmt.Fprint(stdout, before)
	if err := callgraph.GraphVisitEdges(cg, func(edge *callgraph.Edge) error {
		data.position.Offset = -1
//.........这里部分代码省略.........

//.........这里部分代码省略.........
		}
		if main == nil {
			return fmt.Errorf("no tests")
		}
	} else {
		// Otherwise, use main.main.
		for _, pkg := range pkgs {
			if pkg.Object.Name() == "main" {
				main = pkg
				if main.Func("main") == nil {
					return fmt.Errorf("no func main() in main package")
				}
				break
			}
		}
		if main == nil {
			return fmt.Errorf("no main package")
		}
	}

	// Invariant: main package has a main() function.

	// -- call graph construction ------------------------------------------

	var cg *callgraph.Graph

	switch algo {
	case "pta":
		config := &pointer.Config{
			Mains:          []*ssa.Package{main},
			BuildCallGraph: true,
		}
		ptares, err := pointer.Analyze(config)
		if err != nil {
			return err // internal error in pointer analysis
		}
		cg = ptares.CallGraph

	case "rta":
		roots := []*ssa.Function{
			main.Func("init"),
			main.Func("main"),
		}
		rtares := rta.Analyze(roots, true)
		cg = rtares.CallGraph

		// NB: RTA gives us Reachable and RuntimeTypes too.

	default:
		return fmt.Errorf("unknown algorithm: %s", algo)
	}

	cg.DeleteSyntheticNodes()

	// -- output------------------------------------------------------------

	var before, after string

	// Pre-canned formats.
	switch format {
	case "digraph":
		format = `{{printf "%q %q" .Caller .Callee}}`

	case "graphviz":
		before = "digraph callgraph {\n"
		after = "}\n"
		format = `  {{printf "%q" .Caller}} -> {{printf "%q" .Callee}}"`
	}

	tmpl, err := template.New("-format").Parse(format)
	if err != nil {
		return fmt.Errorf("invalid -format template: %v", err)
	}

	// Allocate these once, outside the traversal.
	var buf bytes.Buffer
	data := Edge{fset: prog.Fset}

	fmt.Fprint(stdout, before)
	if err := callgraph.GraphVisitEdges(cg, func(edge *callgraph.Edge) error {
		data.position.Offset = -1
		data.edge = edge
		data.Caller = edge.Caller.Func
		data.Callee = edge.Callee.Func

		buf.Reset()
		if err := tmpl.Execute(&buf, &data); err != nil {
			return err
		}
		stdout.Write(buf.Bytes())
		if len := buf.Len(); len == 0 || buf.Bytes()[len-1] != '\n' {
			fmt.Fprintln(stdout)
		}
		return nil
	}); err != nil {
		return err
	}
	fmt.Fprint(stdout, after)
	return nil
}