mirror of
https://github.com/golang/go
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109 lines
2.4 KiB
Go
109 lines
2.4 KiB
Go
// 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_test
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import (
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"fmt"
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"go/build"
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"go/parser"
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"sort"
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"code.google.com/p/go.tools/importer"
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"code.google.com/p/go.tools/pointer"
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"code.google.com/p/go.tools/ssa"
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)
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// This program demonstrates how to use the pointer analysis to
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// obtain a conservative call-graph of a Go program.
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//
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func Example() {
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const myprog = `
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package main
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import "fmt"
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type I interface {
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f()
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}
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type C struct{}
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func (C) f() {
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fmt.Println("C.f()")
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}
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func main() {
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var i I = C{}
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i.f() // dynamic method call
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}
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`
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// Construct an importer.
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// Imports will be loaded as if by 'go build'.
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imp := importer.New(&importer.Config{Build: &build.Default})
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// Parse the input file.
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file, err := parser.ParseFile(imp.Fset, "myprog.go", myprog, parser.DeclarationErrors)
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if err != nil {
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fmt.Print(err) // parse error
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return
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}
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// Create a "main" package containing one file.
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mainInfo := imp.LoadMainPackage(file)
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// Create SSA-form program representation.
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var mode ssa.BuilderMode
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prog := ssa.NewProgram(imp.Fset, mode)
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if err := prog.CreatePackages(imp); err != nil {
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fmt.Print(err) // type error in some package
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return
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}
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mainPkg := prog.Package(mainInfo.Pkg)
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// Build SSA code for bodies of all functions in the whole program.
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prog.BuildAll()
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// Run the pointer analysis and build the complete callgraph.
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callgraph := make(pointer.CallGraph)
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config := &pointer.Config{
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Mains: []*ssa.Package{mainPkg},
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Call: callgraph.AddEdge,
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}
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root := pointer.Analyze(config)
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// Visit callgraph in depth-first order.
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//
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// There may be multiple nodes for the
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// same function due to context sensitivity.
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var edges []string // call edges originating from the main package.
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seen := make(map[pointer.CallGraphNode]bool)
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var visit func(cgn pointer.CallGraphNode)
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visit = func(cgn pointer.CallGraphNode) {
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if seen[cgn] {
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return // already seen
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}
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seen[cgn] = true
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caller := cgn.Func()
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for callee := range callgraph[cgn] {
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if caller.Pkg == mainPkg {
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edges = append(edges, fmt.Sprint(caller, " --> ", callee.Func()))
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}
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visit(callee)
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}
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}
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visit(root)
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// Print the edges in sorted order.
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sort.Strings(edges)
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for _, edge := range edges {
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fmt.Println(edge)
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}
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// Output:
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// (main.C).f --> fmt.Println
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// main.init --> fmt.init
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// main.main --> (main.C).f
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}
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