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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.
package main
// TODO(adonovan): new queries
// - show all statements that may update the selected lvalue
// (local, global, field, etc).
// - show all places where an object of type T is created
// (&T{}, var t T, new(T), new(struct{array [3]T}), etc.
import (
type printfFunc func(pos interface{}, format string, args ...interface{})
// A QueryResult is an item of output. Each query produces a stream of
// query results, calling Query.Output for each one.
type QueryResult interface {
// JSON returns the QueryResult in JSON form.
JSON(fset *token.FileSet) []byte
// PrintPlain prints the QueryResult in plain text form.
// The implementation calls printfFunc to print each line of output.
PrintPlain(printf printfFunc)
// A QueryPos represents the position provided as input to a query:
// a textual extent in the program's source code, the AST node it
// corresponds to, and the package to which it belongs.
// Instances are created by parseQueryPos.
type queryPos struct {
fset *token.FileSet
start, end token.Pos // source extent of query
path []ast.Node // AST path from query node to root of ast.File
exact bool // 2nd result of PathEnclosingInterval
info *loader.PackageInfo // type info for the queried package (nil for fastQueryPos)
// TypeString prints type T relative to the query position.
func (qpos *queryPos) typeString(T types.Type) string {
return types.TypeString(T, types.RelativeTo(
// ObjectString prints object obj relative to the query position.
func (qpos *queryPos) objectString(obj types.Object) string {
return types.ObjectString(obj, types.RelativeTo(
// A Query specifies a single guru query.
type Query struct {
Pos string // query position
Build *build.Context // package loading configuration
// pointer analysis options
Scope []string // main packages in (*loader.Config).FromArgs syntax
PTALog io.Writer // (optional) pointer-analysis log file
Reflection bool // model reflection soundly (currently slow).
// result-printing function, safe for concurrent use
Output func(*token.FileSet, QueryResult)
// Run runs an guru query and populates its Fset and Result.
func Run(mode string, q *Query) error {
switch mode {
case "callees":
return callees(q)
case "callers":
return callers(q)
case "callstack":
return callstack(q)
case "peers":
return peers(q)
case "pointsto":
return pointsto(q)
case "whicherrs":
return whicherrs(q)
case "definition":
return definition(q)
case "describe":
return describe(q)
case "freevars":
return freevars(q)
case "implements":
return implements(q)
case "referrers":
return referrers(q)
case "what":
return what(q)
return fmt.Errorf("invalid mode: %q", mode)
func setPTAScope(lconf *loader.Config, scope []string) error {
pkgs := buildutil.ExpandPatterns(lconf.Build, scope)
if len(pkgs) == 0 {
return fmt.Errorf("no packages specified for pointer analysis scope")
// The value of each entry in pkgs is true,
// giving ImportWithTests (not Import) semantics.
lconf.ImportPkgs = pkgs
return nil
// Create a pointer.Config whose scope is the initial packages of lprog
// and their dependencies.
func setupPTA(prog *ssa.Program, lprog *loader.Program, ptaLog io.Writer, reflection bool) (*pointer.Config, error) {
// For each initial package (specified on the command line),
// analyze the package if it has a main function.
var mains []*ssa.Package
for _, info := range lprog.InitialPackages() {
p := prog.Package(info.Pkg)
// Add package to the pointer analysis scope.
if p.Pkg.Name() == "main" && p.Func("main") != nil {
mains = append(mains, p)
if mains == nil {
return nil, fmt.Errorf("analysis scope has no main and no tests")
return &pointer.Config{
Log: ptaLog,
Reflection: reflection,
Mains: mains,
}, nil
// importQueryPackage finds the package P containing the
// query position and tells conf to import it.
// It returns the package's path.
func importQueryPackage(pos string, conf *loader.Config) (string, error) {
fqpos, err := fastQueryPos(conf.Build, pos)
if err != nil {
return "", err // bad query
filename := fqpos.fset.File(fqpos.start).Name()
_, importPath, err := guessImportPath(filename, conf.Build)
if err != nil {
// Can't find GOPATH dir.
// Treat the query file as its own package.
importPath = "command-line-arguments"
conf.CreateFromFilenames(importPath, filename)
} else {
// Check that it's possible to load the queried package.
// (e.g. guru tests contain different 'package' decls in same dir.)
// Keep consistent with logic in loader/util.go!
cfg2 := *conf.Build
cfg2.CgoEnabled = false
bp, err := cfg2.Import(importPath, "", 0)
if err != nil {
return "", err // no files for package
switch pkgContainsFile(bp, filename) {
case 'T':
case 'X':
importPath += "_test" // for TypeCheckFuncBodies
case 'G':
// This happens for ad-hoc packages like
// $GOROOT/src/net/http/triv.go.
return "", fmt.Errorf("package %q doesn't contain file %s",
importPath, filename)
conf.TypeCheckFuncBodies = func(p string) bool { return p == importPath }
return importPath, nil
// pkgContainsFile reports whether file was among the packages Go
// files, Test files, eXternal test files, or not found.
func pkgContainsFile(bp *build.Package, filename string) byte {
for i, files := range [][]string{bp.GoFiles, bp.TestGoFiles, bp.XTestGoFiles} {
for _, file := range files {
if sameFile(filepath.Join(bp.Dir, file), filename) {
return "GTX"[i]
return 0 // not found
// ParseQueryPos parses the source query position pos and returns the
// AST node of the loaded program lprog that it identifies.
// If needExact, it must identify a single AST subtree;
// this is appropriate for queries that allow fairly arbitrary syntax,
// e.g. "describe".
func parseQueryPos(lprog *loader.Program, pos string, needExact bool) (*queryPos, error) {
filename, startOffset, endOffset, err := parsePos(pos)
if err != nil {
return nil, err
// Find the named file among those in the loaded program.
var file *token.File
lprog.Fset.Iterate(func(f *token.File) bool {
if sameFile(filename, f.Name()) {
file = f
return false // done
return true // continue
if file == nil {
return nil, fmt.Errorf("file %s not found in loaded program", filename)
start, end, err := fileOffsetToPos(file, startOffset, endOffset)
if err != nil {
return nil, err
info, path, exact := lprog.PathEnclosingInterval(start, end)
if path == nil {
return nil, fmt.Errorf("no syntax here")
if needExact && !exact {
return nil, fmt.Errorf("ambiguous selection within %s", astutil.NodeDescription(path[0]))
return &queryPos{lprog.Fset, start, end, path, exact, info}, nil
// ---------- Utilities ----------
// loadWithSoftErrors calls lconf.Load, suppressing "soft" errors. (See Go issue 16530.)
// TODO(adonovan): Once the loader has an option to allow soft errors,
// replace calls to loadWithSoftErrors with loader calls with that parameter.
func loadWithSoftErrors(lconf *loader.Config) (*loader.Program, error) {
lconf.AllowErrors = true
// Ideally we would just return conf.Load() here, but go/types
// reports certain "soft" errors that gc does not (Go issue 14596).
// As a workaround, we set AllowErrors=true and then duplicate
// the loader's error checking but allow soft errors.
// It would be nice if the loader API permitted "AllowErrors: soft".
prog, err := lconf.Load()
if err != nil {
return nil, err
var errpkgs []string
// Report hard errors in indirectly imported packages.
for _, info := range prog.AllPackages {
if containsHardErrors(info.Errors) {
errpkgs = append(errpkgs, info.Pkg.Path())
} else {
// Enable SSA construction for packages containing only soft errors.
info.TransitivelyErrorFree = true
if errpkgs != nil {
var more string
if len(errpkgs) > 3 {
more = fmt.Sprintf(" and %d more", len(errpkgs)-3)
errpkgs = errpkgs[:3]
return nil, fmt.Errorf("couldn't load packages due to errors: %s%s",
strings.Join(errpkgs, ", "), more)
return prog, err
func containsHardErrors(errors []error) bool {
for _, err := range errors {
if err, ok := err.(types.Error); ok && err.Soft {
return true
return false
// allowErrors causes type errors to be silently ignored.
// (Not suitable if SSA construction follows.)
func allowErrors(lconf *loader.Config) {
ctxt := *lconf.Build // copy
ctxt.CgoEnabled = false
lconf.Build = &ctxt
lconf.AllowErrors = true
// AllErrors makes the parser always return an AST instead of
// bailing out after 10 errors and returning an empty ast.File.
lconf.ParserMode = parser.AllErrors
lconf.TypeChecker.Error = func(err error) {}
// ptrAnalysis runs the pointer analysis and returns its result.
func ptrAnalysis(conf *pointer.Config) *pointer.Result {
result, err := pointer.Analyze(conf)
if err != nil {
panic(err) // pointer analysis internal error
return result
func unparen(e ast.Expr) ast.Expr { return astutil.Unparen(e) }
// deref returns a pointer's element type; otherwise it returns typ.
func deref(typ types.Type) types.Type {
if p, ok := typ.Underlying().(*types.Pointer); ok {
return p.Elem()
return typ
// fprintf prints to w a message of the form "location: message\n"
// where location is derived from pos.
// pos must be one of:
// - a token.Pos, denoting a position
// - an ast.Node, denoting an interval
// - anything with a Pos() method:
// ssa.Member, ssa.Value, ssa.Instruction, types.Object, pointer.Label, etc.
// - a QueryPos, denoting the extent of the user's query.
// - nil, meaning no position at all.
// The output format is is compatible with the 'gnu'
// compilation-error-regexp in Emacs' compilation mode.
func fprintf(w io.Writer, fset *token.FileSet, pos interface{}, format string, args ...interface{}) {
var start, end token.Pos
switch pos := pos.(type) {
case ast.Node:
start = pos.Pos()
end = pos.End()
case token.Pos:
start = pos
end = start
case *types.PkgName:
// The Pos of most PkgName objects does not coincide with an identifier,
// so we suppress the usual start+len(name) heuristic for types.Objects.
start = pos.Pos()
end = start
case types.Object:
start = pos.Pos()
end = start + token.Pos(len(pos.Name())) // heuristic
case interface {
Pos() token.Pos
start = pos.Pos()
end = start
case *queryPos:
start = pos.start
end = pos.end
case nil:
// no-op
panic(fmt.Sprintf("invalid pos: %T", pos))
if sp := fset.Position(start); start == end {
// (prints "-: " for token.NoPos)
fmt.Fprintf(w, "%s: ", sp)
} else {
ep := fset.Position(end)
// The -1 below is a concession to Emacs's broken use of
// inclusive (not half-open) intervals.
// Other editors may not want it.
// TODO(adonovan): add an -editor=vim|emacs|acme|auto
// flag; auto uses EMACS=t / VIM=... / etc env vars.
fmt.Fprintf(w, "%s:%d.%d-%d.%d: ",
sp.Filename, sp.Line, sp.Column, ep.Line, ep.Column-1)
fmt.Fprintf(w, format, args...)
io.WriteString(w, "\n")
func toJSON(x interface{}) []byte {
b, err := json.MarshalIndent(x, "", "\t")
if err != nil {
log.Fatalf("JSON error: %v", err)
return b