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// Copyright 2014 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
// callgraph: a tool for reporting the call graph of a Go program.
// See Usage for details, or run with -help.
package main // import "golang.org/x/tools/cmd/callgraph"
// TODO(adonovan):
//
// Features:
// - restrict graph to a single package
// - output
// - functions reachable from root (use digraph tool?)
// - unreachable functions (use digraph tool?)
// - dynamic (runtime) types
// - indexed output (numbered nodes)
// - JSON output
// - additional template fields:
// callee file/line/col
import (
"bufio"
"bytes"
"flag"
"fmt"
"go/build"
"go/token"
"io"
"log"
"os"
"runtime"
"text/template"
"golang.org/x/tools/go/buildutil"
"golang.org/x/tools/go/callgraph"
"golang.org/x/tools/go/callgraph/cha"
"golang.org/x/tools/go/callgraph/rta"
"golang.org/x/tools/go/callgraph/static"
"golang.org/x/tools/go/loader"
"golang.org/x/tools/go/pointer"
"golang.org/x/tools/go/ssa"
"golang.org/x/tools/go/ssa/ssautil"
)
// flags
var (
algoFlag = flag.String("algo", "rta",
`Call graph construction algorithm (static, cha, rta, pta)`)
testFlag = flag.Bool("test", false,
"Loads test code (*_test.go) for imported packages")
formatFlag = flag.String("format",
"{{.Caller}}\t--{{.Dynamic}}-{{.Line}}:{{.Column}}-->\t{{.Callee}}",
"A template expression specifying how to format an edge")
ptalogFlag = flag.String("ptalog", "",
"Location of the points-to analysis log file, or empty to disable logging.")
)
func init() {
flag.Var((*buildutil.TagsFlag)(&build.Default.BuildTags), "tags", buildutil.TagsFlagDoc)
}
const Usage = `callgraph: display the the call graph of a Go program.
Usage:
callgraph [-algo=static|cha|rta|pta] [-test] [-format=...] <args>...
Flags:
-algo Specifies the call-graph construction algorithm, one of:
static static calls only (unsound)
cha Class Hierarchy Analysis
rta Rapid Type Analysis
pta inclusion-based Points-To Analysis
The algorithms are ordered by increasing precision in their
treatment of dynamic calls (and thus also computational cost).
RTA and PTA require a whole program (main or test), and
include only functions reachable from main.
-test Include the package's tests in the analysis.
-format Specifies the format in which each call graph edge is displayed.
One of:
digraph output suitable for input to
golang.org/x/tools/cmd/digraph.
graphviz output in AT&T GraphViz (.dot) format.
All other values are interpreted using text/template syntax.
The default value is:
{{.Caller}}\t--{{.Dynamic}}-{{.Line}}:{{.Column}}-->\t{{.Callee}}
The structure passed to the template is (effectively):
type Edge struct {
Caller *ssa.Function // calling function
Callee *ssa.Function // called function
// Call site:
Filename string // containing file
Offset int // offset within file of '('
Line int // line number
Column int // column number of call
Dynamic string // "static" or "dynamic"
Description string // e.g. "static method call"
}
Caller and Callee are *ssa.Function values, which print as
"(*sync/atomic.Mutex).Lock", but other attributes may be
derived from them, e.g. Caller.Pkg.Object.Path yields the
import path of the enclosing package. Consult the go/ssa
API documentation for details.
` + loader.FromArgsUsage + `
Examples:
Show the call graph of the trivial web server application:
callgraph -format digraph $GOROOT/src/net/http/triv.go
Same, but show only the packages of each function:
callgraph -format '{{.Caller.Pkg.Object.Path}} -> {{.Callee.Pkg.Object.Path}}' \
$GOROOT/src/net/http/triv.go | sort | uniq
Show functions that make dynamic calls into the 'fmt' test package,
using the pointer analysis algorithm:
callgraph -format='{{.Caller}} -{{.Dynamic}}-> {{.Callee}}' -test -algo=pta fmt |
sed -ne 's/-dynamic-/--/p' |
sed -ne 's/-->.*fmt_test.*$//p' | sort | uniq
Show all functions directly called by the callgraph tool's main function:
callgraph -format=digraph golang.org/x/tools/cmd/callgraph |
digraph succs golang.org/x/tools/cmd/callgraph.main
`
func init() {
// If $GOMAXPROCS isn't set, use the full capacity of the machine.
// For small machines, use at least 4 threads.
if os.Getenv("GOMAXPROCS") == "" {
n := runtime.NumCPU()
if n < 4 {
n = 4
}
runtime.GOMAXPROCS(n)
}
}
func main() {
flag.Parse()
if err := doCallgraph(&build.Default, *algoFlag, *formatFlag, *testFlag, flag.Args()); err != nil {
fmt.Fprintf(os.Stderr, "callgraph: %s\n", err)
os.Exit(1)
}
}
var stdout io.Writer = os.Stdout
func doCallgraph(ctxt *build.Context, algo, format string, tests bool, args []string) error {
conf := loader.Config{Build: ctxt}
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 := ssautil.CreateProgram(iprog, 0)
prog.Build()
// -- call graph construction ------------------------------------------
var cg *callgraph.Graph
switch algo {
case "static":
cg = static.CallGraph(prog)
case "cha":
cg = cha.CallGraph(prog)
case "pta":
// Set up points-to analysis log file.
var ptalog io.Writer
if *ptalogFlag != "" {
if f, err := os.Create(*ptalogFlag); err != nil {
log.Fatalf("Failed to create PTA log file: %s", err)
} else {
buf := bufio.NewWriter(f)
ptalog = buf
defer func() {
if err := buf.Flush(); err != nil {
log.Printf("flush: %s", err)
}
if err := f.Close(); err != nil {
log.Printf("close: %s", err)
}
}()
}
}
main, err := mainPackage(prog, tests)
if err != nil {
return err
}
config := &pointer.Config{
Mains: []*ssa.Package{main},
BuildCallGraph: true,
Log: ptalog,
}
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
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
}
// mainPackage returns the main package to analyze.
// The resulting package has a main() function.
func mainPackage(prog *ssa.Program, tests bool) (*ssa.Package, error) {
pkgs := prog.AllPackages()
// TODO(adonovan): allow independent control over tests, mains and libraries.
// TODO(adonovan): put this logic in a library; we keep reinventing it.
if tests {
// If -test, use all packages' tests.
if len(pkgs) > 0 {
if main := prog.CreateTestMainPackage(pkgs...); main != nil {
return main, nil
}
}
return nil, fmt.Errorf("no tests")
}
// Otherwise, use the first package named main.
for _, pkg := range pkgs {
if pkg.Pkg.Name() == "main" {
if pkg.Func("main") == nil {
return nil, fmt.Errorf("no func main() in main package")
}
return pkg, nil
}
}
return nil, fmt.Errorf("no main package")
}
type Edge struct {
Caller *ssa.Function
Callee *ssa.Function
edge *callgraph.Edge
fset *token.FileSet
position token.Position // initialized lazily
}
func (e *Edge) pos() *token.Position {
if e.position.Offset == -1 {
e.position = e.fset.Position(e.edge.Pos()) // called lazily
}
return &e.position
}
func (e *Edge) Filename() string { return e.pos().Filename }
func (e *Edge) Column() int { return e.pos().Column }
func (e *Edge) Line() int { return e.pos().Line }
func (e *Edge) Offset() int { return e.pos().Offset }
func (e *Edge) Dynamic() string {
if e.edge.Site != nil && e.edge.Site.Common().StaticCallee() == nil {
return "dynamic"
}
return "static"
}
func (e *Edge) Description() string { return e.edge.Description() }