| 1 | // Copyright 2013 The Go Authors. All rights reserved. |
|---|---|
| 2 | // Use of this source code is governed by a BSD-style |
| 3 | // license that can be found in the LICENSE file. |
| 4 | |
| 5 | package pointer_test |
| 6 | |
| 7 | import ( |
| 8 | "fmt" |
| 9 | "sort" |
| 10 | |
| 11 | "golang.org/x/tools/go/callgraph" |
| 12 | "golang.org/x/tools/go/loader" |
| 13 | "golang.org/x/tools/go/pointer" |
| 14 | "golang.org/x/tools/go/ssa" |
| 15 | "golang.org/x/tools/go/ssa/ssautil" |
| 16 | ) |
| 17 | |
| 18 | // This program demonstrates how to use the pointer analysis to |
| 19 | // obtain a conservative call-graph of a Go program. |
| 20 | // It also shows how to compute the points-to set of a variable, |
| 21 | // in this case, (C).f's ch parameter. |
| 22 | func Example() { |
| 23 | const myprog = ` |
| 24 | package main |
| 25 | |
| 26 | import "fmt" |
| 27 | |
| 28 | type I interface { |
| 29 | f(map[string]int) |
| 30 | } |
| 31 | |
| 32 | type C struct{} |
| 33 | |
| 34 | func (C) f(m map[string]int) { |
| 35 | fmt.Println("C.f()") |
| 36 | } |
| 37 | |
| 38 | func main() { |
| 39 | var i I = C{} |
| 40 | x := map[string]int{"one":1} |
| 41 | i.f(x) // dynamic method call |
| 42 | } |
| 43 | ` |
| 44 | var conf loader.Config |
| 45 | |
| 46 | // Parse the input file, a string. |
| 47 | // (Command-line tools should use conf.FromArgs.) |
| 48 | file, err := conf.ParseFile("myprog.go", myprog) |
| 49 | if err != nil { |
| 50 | fmt.Print(err) // parse error |
| 51 | return |
| 52 | } |
| 53 | |
| 54 | // Create single-file main package and import its dependencies. |
| 55 | conf.CreateFromFiles("main", file) |
| 56 | |
| 57 | iprog, err := conf.Load() |
| 58 | if err != nil { |
| 59 | fmt.Print(err) // type error in some package |
| 60 | return |
| 61 | } |
| 62 | |
| 63 | // Create SSA-form program representation. |
| 64 | prog := ssautil.CreateProgram(iprog, ssa.InstantiateGenerics) |
| 65 | mainPkg := prog.Package(iprog.Created[0].Pkg) |
| 66 | |
| 67 | // Build SSA code for bodies of all functions in the whole program. |
| 68 | prog.Build() |
| 69 | |
| 70 | // Configure the pointer analysis to build a call-graph. |
| 71 | config := &pointer.Config{ |
| 72 | Mains: []*ssa.Package{mainPkg}, |
| 73 | BuildCallGraph: true, |
| 74 | } |
| 75 | |
| 76 | // Query points-to set of (C).f's parameter m, a map. |
| 77 | C := mainPkg.Type("C").Type() |
| 78 | Cfm := prog.LookupMethod(C, mainPkg.Pkg, "f").Params[1] |
| 79 | config.AddQuery(Cfm) |
| 80 | |
| 81 | // Run the pointer analysis. |
| 82 | result, err := pointer.Analyze(config) |
| 83 | if err != nil { |
| 84 | panic(err) // internal error in pointer analysis |
| 85 | } |
| 86 | |
| 87 | // Find edges originating from the main package. |
| 88 | // By converting to strings, we de-duplicate nodes |
| 89 | // representing the same function due to context sensitivity. |
| 90 | var edges []string |
| 91 | callgraph.GraphVisitEdges(result.CallGraph, func(edge *callgraph.Edge) error { |
| 92 | caller := edge.Caller.Func |
| 93 | if caller.Pkg == mainPkg { |
| 94 | edges = append(edges, fmt.Sprint(caller, " --> ", edge.Callee.Func)) |
| 95 | } |
| 96 | return nil |
| 97 | }) |
| 98 | |
| 99 | // Print the edges in sorted order. |
| 100 | sort.Strings(edges) |
| 101 | for _, edge := range edges { |
| 102 | fmt.Println(edge) |
| 103 | } |
| 104 | fmt.Println() |
| 105 | |
| 106 | // Print the labels of (C).f(m)'s points-to set. |
| 107 | fmt.Println("m may point to:") |
| 108 | var labels []string |
| 109 | for _, l := range result.Queries[Cfm].PointsTo().Labels() { |
| 110 | label := fmt.Sprintf(" %s: %s", prog.Fset.Position(l.Pos()), l) |
| 111 | labels = append(labels, label) |
| 112 | } |
| 113 | sort.Strings(labels) |
| 114 | for _, label := range labels { |
| 115 | fmt.Println(label) |
| 116 | } |
| 117 | |
| 118 | // Output: |
| 119 | // (main.C).f --> fmt.Println |
| 120 | // main.init --> fmt.init |
| 121 | // main.main --> (main.C).f |
| 122 | // |
| 123 | // m may point to: |
| 124 | // myprog.go:18:21: makemap |
| 125 | } |
| 126 |
Members