Source file src/cmd/go/internal/work/action.go

Documentation: cmd/go/internal/work

     1  // Copyright 2011 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  // Action graph creation (planning).
     6  
     7  package work
     8  
     9  import (
    10  	"bufio"
    11  	"bytes"
    12  	"cmd/internal/cov/covcmd"
    13  	"container/heap"
    14  	"context"
    15  	"debug/elf"
    16  	"encoding/json"
    17  	"fmt"
    18  	"internal/platform"
    19  	"os"
    20  	"path/filepath"
    21  	"strings"
    22  	"sync"
    23  	"time"
    24  
    25  	"cmd/go/internal/base"
    26  	"cmd/go/internal/cache"
    27  	"cmd/go/internal/cfg"
    28  	"cmd/go/internal/load"
    29  	"cmd/go/internal/robustio"
    30  	"cmd/go/internal/str"
    31  	"cmd/go/internal/trace"
    32  	"cmd/internal/buildid"
    33  )
    34  
    35  // A Builder holds global state about a build.
    36  // It does not hold per-package state, because we
    37  // build packages in parallel, and the builder is shared.
    38  type Builder struct {
    39  	WorkDir            string                    // the temporary work directory (ends in filepath.Separator)
    40  	actionCache        map[cacheKey]*Action      // a cache of already-constructed actions
    41  	flagCache          map[[2]string]bool        // a cache of supported compiler flags
    42  	gccCompilerIDCache map[string]cache.ActionID // cache for gccCompilerID
    43  
    44  	IsCmdList           bool // running as part of go list; set p.Stale and additional fields below
    45  	NeedError           bool // list needs p.Error
    46  	NeedExport          bool // list needs p.Export
    47  	NeedCompiledGoFiles bool // list needs p.CompiledGoFiles
    48  	AllowErrors         bool // errors don't immediately exit the program
    49  
    50  	objdirSeq int // counter for NewObjdir
    51  	pkgSeq    int
    52  
    53  	backgroundSh *Shell // Shell that per-Action Shells are derived from
    54  
    55  	exec      sync.Mutex
    56  	readySema chan bool
    57  	ready     actionQueue
    58  
    59  	id           sync.Mutex
    60  	toolIDCache  map[string]string // tool name -> tool ID
    61  	buildIDCache map[string]string // file name -> build ID
    62  }
    63  
    64  // NOTE: Much of Action would not need to be exported if not for test.
    65  // Maybe test functionality should move into this package too?
    66  
    67  // An Actor runs an action.
    68  type Actor interface {
    69  	Act(*Builder, context.Context, *Action) error
    70  }
    71  
    72  // An ActorFunc is an Actor that calls the function.
    73  type ActorFunc func(*Builder, context.Context, *Action) error
    74  
    75  func (f ActorFunc) Act(b *Builder, ctx context.Context, a *Action) error {
    76  	return f(b, ctx, a)
    77  }
    78  
    79  // An Action represents a single action in the action graph.
    80  type Action struct {
    81  	Mode       string        // description of action operation
    82  	Package    *load.Package // the package this action works on
    83  	Deps       []*Action     // actions that must happen before this one
    84  	Actor      Actor         // the action itself (nil = no-op)
    85  	IgnoreFail bool          // whether to run f even if dependencies fail
    86  	TestOutput *bytes.Buffer // test output buffer
    87  	Args       []string      // additional args for runProgram
    88  
    89  	triggers []*Action // inverse of deps
    90  
    91  	buggyInstall bool // is this a buggy install (see -linkshared)?
    92  
    93  	TryCache func(*Builder, *Action) bool // callback for cache bypass
    94  
    95  	// Generated files, directories.
    96  	Objdir   string         // directory for intermediate objects
    97  	Target   string         // goal of the action: the created package or executable
    98  	built    string         // the actual created package or executable
    99  	actionID cache.ActionID // cache ID of action input
   100  	buildID  string         // build ID of action output
   101  
   102  	VetxOnly  bool       // Mode=="vet": only being called to supply info about dependencies
   103  	needVet   bool       // Mode=="build": need to fill in vet config
   104  	needBuild bool       // Mode=="build": need to do actual build (can be false if needVet is true)
   105  	vetCfg    *vetConfig // vet config
   106  	output    []byte     // output redirect buffer (nil means use b.Print)
   107  
   108  	sh *Shell // lazily created per-Action shell; see Builder.Shell
   109  
   110  	// Execution state.
   111  	pending      int               // number of deps yet to complete
   112  	priority     int               // relative execution priority
   113  	Failed       bool              // whether the action failed
   114  	json         *actionJSON       // action graph information
   115  	nonGoOverlay map[string]string // map from non-.go source files to copied files in objdir. Nil if no overlay is used.
   116  	traceSpan    *trace.Span
   117  }
   118  
   119  // BuildActionID returns the action ID section of a's build ID.
   120  func (a *Action) BuildActionID() string { return actionID(a.buildID) }
   121  
   122  // BuildContentID returns the content ID section of a's build ID.
   123  func (a *Action) BuildContentID() string { return contentID(a.buildID) }
   124  
   125  // BuildID returns a's build ID.
   126  func (a *Action) BuildID() string { return a.buildID }
   127  
   128  // BuiltTarget returns the actual file that was built. This differs
   129  // from Target when the result was cached.
   130  func (a *Action) BuiltTarget() string { return a.built }
   131  
   132  // An actionQueue is a priority queue of actions.
   133  type actionQueue []*Action
   134  
   135  // Implement heap.Interface
   136  func (q *actionQueue) Len() int           { return len(*q) }
   137  func (q *actionQueue) Swap(i, j int)      { (*q)[i], (*q)[j] = (*q)[j], (*q)[i] }
   138  func (q *actionQueue) Less(i, j int) bool { return (*q)[i].priority < (*q)[j].priority }
   139  func (q *actionQueue) Push(x any)         { *q = append(*q, x.(*Action)) }
   140  func (q *actionQueue) Pop() any {
   141  	n := len(*q) - 1
   142  	x := (*q)[n]
   143  	*q = (*q)[:n]
   144  	return x
   145  }
   146  
   147  func (q *actionQueue) push(a *Action) {
   148  	if a.json != nil {
   149  		a.json.TimeReady = time.Now()
   150  	}
   151  	heap.Push(q, a)
   152  }
   153  
   154  func (q *actionQueue) pop() *Action {
   155  	return heap.Pop(q).(*Action)
   156  }
   157  
   158  type actionJSON struct {
   159  	ID         int
   160  	Mode       string
   161  	Package    string
   162  	Deps       []int     `json:",omitempty"`
   163  	IgnoreFail bool      `json:",omitempty"`
   164  	Args       []string  `json:",omitempty"`
   165  	Link       bool      `json:",omitempty"`
   166  	Objdir     string    `json:",omitempty"`
   167  	Target     string    `json:",omitempty"`
   168  	Priority   int       `json:",omitempty"`
   169  	Failed     bool      `json:",omitempty"`
   170  	Built      string    `json:",omitempty"`
   171  	VetxOnly   bool      `json:",omitempty"`
   172  	NeedVet    bool      `json:",omitempty"`
   173  	NeedBuild  bool      `json:",omitempty"`
   174  	ActionID   string    `json:",omitempty"`
   175  	BuildID    string    `json:",omitempty"`
   176  	TimeReady  time.Time `json:",omitempty"`
   177  	TimeStart  time.Time `json:",omitempty"`
   178  	TimeDone   time.Time `json:",omitempty"`
   179  
   180  	Cmd     []string      // `json:",omitempty"`
   181  	CmdReal time.Duration `json:",omitempty"`
   182  	CmdUser time.Duration `json:",omitempty"`
   183  	CmdSys  time.Duration `json:",omitempty"`
   184  }
   185  
   186  // cacheKey is the key for the action cache.
   187  type cacheKey struct {
   188  	mode string
   189  	p    *load.Package
   190  }
   191  
   192  func actionGraphJSON(a *Action) string {
   193  	var workq []*Action
   194  	var inWorkq = make(map[*Action]int)
   195  
   196  	add := func(a *Action) {
   197  		if _, ok := inWorkq[a]; ok {
   198  			return
   199  		}
   200  		inWorkq[a] = len(workq)
   201  		workq = append(workq, a)
   202  	}
   203  	add(a)
   204  
   205  	for i := 0; i < len(workq); i++ {
   206  		for _, dep := range workq[i].Deps {
   207  			add(dep)
   208  		}
   209  	}
   210  
   211  	var list []*actionJSON
   212  	for id, a := range workq {
   213  		if a.json == nil {
   214  			a.json = &actionJSON{
   215  				Mode:       a.Mode,
   216  				ID:         id,
   217  				IgnoreFail: a.IgnoreFail,
   218  				Args:       a.Args,
   219  				Objdir:     a.Objdir,
   220  				Target:     a.Target,
   221  				Failed:     a.Failed,
   222  				Priority:   a.priority,
   223  				Built:      a.built,
   224  				VetxOnly:   a.VetxOnly,
   225  				NeedBuild:  a.needBuild,
   226  				NeedVet:    a.needVet,
   227  			}
   228  			if a.Package != nil {
   229  				// TODO(rsc): Make this a unique key for a.Package somehow.
   230  				a.json.Package = a.Package.ImportPath
   231  			}
   232  			for _, a1 := range a.Deps {
   233  				a.json.Deps = append(a.json.Deps, inWorkq[a1])
   234  			}
   235  		}
   236  		list = append(list, a.json)
   237  	}
   238  
   239  	js, err := json.MarshalIndent(list, "", "\t")
   240  	if err != nil {
   241  		fmt.Fprintf(os.Stderr, "go: writing debug action graph: %v\n", err)
   242  		return ""
   243  	}
   244  	return string(js)
   245  }
   246  
   247  // BuildMode specifies the build mode:
   248  // are we just building things or also installing the results?
   249  type BuildMode int
   250  
   251  const (
   252  	ModeBuild BuildMode = iota
   253  	ModeInstall
   254  	ModeBuggyInstall
   255  
   256  	ModeVetOnly = 1 << 8
   257  )
   258  
   259  // NewBuilder returns a new Builder ready for use.
   260  //
   261  // If workDir is the empty string, NewBuilder creates a WorkDir if needed
   262  // and arranges for it to be removed in case of an unclean exit.
   263  // The caller must Close the builder explicitly to clean up the WorkDir
   264  // before a clean exit.
   265  func NewBuilder(workDir string) *Builder {
   266  	b := new(Builder)
   267  
   268  	b.actionCache = make(map[cacheKey]*Action)
   269  	b.toolIDCache = make(map[string]string)
   270  	b.buildIDCache = make(map[string]string)
   271  
   272  	if workDir != "" {
   273  		b.WorkDir = workDir
   274  	} else if cfg.BuildN {
   275  		b.WorkDir = "$WORK"
   276  	} else {
   277  		if !buildInitStarted {
   278  			panic("internal error: NewBuilder called before BuildInit")
   279  		}
   280  		tmp, err := os.MkdirTemp(cfg.Getenv("GOTMPDIR"), "go-build")
   281  		if err != nil {
   282  			base.Fatalf("go: creating work dir: %v", err)
   283  		}
   284  		if !filepath.IsAbs(tmp) {
   285  			abs, err := filepath.Abs(tmp)
   286  			if err != nil {
   287  				os.RemoveAll(tmp)
   288  				base.Fatalf("go: creating work dir: %v", err)
   289  			}
   290  			tmp = abs
   291  		}
   292  		b.WorkDir = tmp
   293  		builderWorkDirs.Store(b, b.WorkDir)
   294  		if cfg.BuildX || cfg.BuildWork {
   295  			fmt.Fprintf(os.Stderr, "WORK=%s\n", b.WorkDir)
   296  		}
   297  	}
   298  
   299  	b.backgroundSh = NewShell(b.WorkDir, nil)
   300  
   301  	if err := CheckGOOSARCHPair(cfg.Goos, cfg.Goarch); err != nil {
   302  		fmt.Fprintf(os.Stderr, "go: %v\n", err)
   303  		base.SetExitStatus(2)
   304  		base.Exit()
   305  	}
   306  
   307  	for _, tag := range cfg.BuildContext.BuildTags {
   308  		if strings.Contains(tag, ",") {
   309  			fmt.Fprintf(os.Stderr, "go: -tags space-separated list contains comma\n")
   310  			base.SetExitStatus(2)
   311  			base.Exit()
   312  		}
   313  	}
   314  
   315  	return b
   316  }
   317  
   318  var builderWorkDirs sync.Map // *Builder → WorkDir
   319  
   320  func (b *Builder) Close() error {
   321  	wd, ok := builderWorkDirs.Load(b)
   322  	if !ok {
   323  		return nil
   324  	}
   325  	defer builderWorkDirs.Delete(b)
   326  
   327  	if b.WorkDir != wd.(string) {
   328  		base.Errorf("go: internal error: Builder WorkDir unexpectedly changed from %s to %s", wd, b.WorkDir)
   329  	}
   330  
   331  	if !cfg.BuildWork {
   332  		if err := robustio.RemoveAll(b.WorkDir); err != nil {
   333  			return err
   334  		}
   335  	}
   336  	b.WorkDir = ""
   337  	return nil
   338  }
   339  
   340  func closeBuilders() {
   341  	leakedBuilders := 0
   342  	builderWorkDirs.Range(func(bi, _ any) bool {
   343  		leakedBuilders++
   344  		if err := bi.(*Builder).Close(); err != nil {
   345  			base.Error(err)
   346  		}
   347  		return true
   348  	})
   349  
   350  	if leakedBuilders > 0 && base.GetExitStatus() == 0 {
   351  		fmt.Fprintf(os.Stderr, "go: internal error: Builder leaked on successful exit\n")
   352  		base.SetExitStatus(1)
   353  	}
   354  }
   355  
   356  func CheckGOOSARCHPair(goos, goarch string) error {
   357  	if !platform.BuildModeSupported(cfg.BuildContext.Compiler, "default", goos, goarch) {
   358  		return fmt.Errorf("unsupported GOOS/GOARCH pair %s/%s", goos, goarch)
   359  	}
   360  	return nil
   361  }
   362  
   363  // NewObjdir returns the name of a fresh object directory under b.WorkDir.
   364  // It is up to the caller to call b.Mkdir on the result at an appropriate time.
   365  // The result ends in a slash, so that file names in that directory
   366  // can be constructed with direct string addition.
   367  //
   368  // NewObjdir must be called only from a single goroutine at a time,
   369  // so it is safe to call during action graph construction, but it must not
   370  // be called during action graph execution.
   371  func (b *Builder) NewObjdir() string {
   372  	b.objdirSeq++
   373  	return str.WithFilePathSeparator(filepath.Join(b.WorkDir, fmt.Sprintf("b%03d", b.objdirSeq)))
   374  }
   375  
   376  // readpkglist returns the list of packages that were built into the shared library
   377  // at shlibpath. For the native toolchain this list is stored, newline separated, in
   378  // an ELF note with name "Go\x00\x00" and type 1. For GCCGO it is extracted from the
   379  // .go_export section.
   380  func readpkglist(shlibpath string) (pkgs []*load.Package) {
   381  	var stk load.ImportStack
   382  	if cfg.BuildToolchainName == "gccgo" {
   383  		f, err := elf.Open(shlibpath)
   384  		if err != nil {
   385  			base.Fatal(fmt.Errorf("failed to open shared library: %v", err))
   386  		}
   387  		defer f.Close()
   388  		sect := f.Section(".go_export")
   389  		if sect == nil {
   390  			base.Fatal(fmt.Errorf("%s: missing .go_export section", shlibpath))
   391  		}
   392  		data, err := sect.Data()
   393  		if err != nil {
   394  			base.Fatal(fmt.Errorf("%s: failed to read .go_export section: %v", shlibpath, err))
   395  		}
   396  		pkgpath := []byte("pkgpath ")
   397  		for _, line := range bytes.Split(data, []byte{'\n'}) {
   398  			if path, found := bytes.CutPrefix(line, pkgpath); found {
   399  				path = bytes.TrimSuffix(path, []byte{';'})
   400  				pkgs = append(pkgs, load.LoadPackageWithFlags(string(path), base.Cwd(), &stk, nil, 0))
   401  			}
   402  		}
   403  	} else {
   404  		pkglistbytes, err := buildid.ReadELFNote(shlibpath, "Go\x00\x00", 1)
   405  		if err != nil {
   406  			base.Fatalf("readELFNote failed: %v", err)
   407  		}
   408  		scanner := bufio.NewScanner(bytes.NewBuffer(pkglistbytes))
   409  		for scanner.Scan() {
   410  			t := scanner.Text()
   411  			pkgs = append(pkgs, load.LoadPackageWithFlags(t, base.Cwd(), &stk, nil, 0))
   412  		}
   413  	}
   414  	return
   415  }
   416  
   417  // cacheAction looks up {mode, p} in the cache and returns the resulting action.
   418  // If the cache has no such action, f() is recorded and returned.
   419  // TODO(rsc): Change the second key from *load.Package to interface{},
   420  // to make the caching in linkShared less awkward?
   421  func (b *Builder) cacheAction(mode string, p *load.Package, f func() *Action) *Action {
   422  	a := b.actionCache[cacheKey{mode, p}]
   423  	if a == nil {
   424  		a = f()
   425  		b.actionCache[cacheKey{mode, p}] = a
   426  	}
   427  	return a
   428  }
   429  
   430  // AutoAction returns the "right" action for go build or go install of p.
   431  func (b *Builder) AutoAction(mode, depMode BuildMode, p *load.Package) *Action {
   432  	if p.Name == "main" {
   433  		return b.LinkAction(mode, depMode, p)
   434  	}
   435  	return b.CompileAction(mode, depMode, p)
   436  }
   437  
   438  // buildActor implements the Actor interface for package build
   439  // actions. For most package builds this simply means invoking th
   440  // *Builder.build method; in the case of "go test -cover" for
   441  // a package with no test files, we stores some additional state
   442  // information in the build actor to help with reporting.
   443  type buildActor struct {
   444  	// name of static meta-data file fragment emitted by the cover
   445  	// tool as part of the package build action, for selected
   446  	// "go test -cover" runs.
   447  	covMetaFileName string
   448  }
   449  
   450  // newBuildActor returns a new buildActor object, setting up the
   451  // covMetaFileName field if 'genCoverMeta' flag is set.
   452  func newBuildActor(p *load.Package, genCoverMeta bool) *buildActor {
   453  	ba := &buildActor{}
   454  	if genCoverMeta {
   455  		ba.covMetaFileName = covcmd.MetaFileForPackage(p.ImportPath)
   456  	}
   457  	return ba
   458  }
   459  
   460  func (ba *buildActor) Act(b *Builder, ctx context.Context, a *Action) error {
   461  	return b.build(ctx, a)
   462  }
   463  
   464  // pgoActionID computes the action ID for a preprocess PGO action.
   465  func (b *Builder) pgoActionID(input string) cache.ActionID {
   466  	h := cache.NewHash("preprocess PGO profile " + input)
   467  
   468  	fmt.Fprintf(h, "preprocess PGO profile\n")
   469  	fmt.Fprintf(h, "preprofile %s\n", b.toolID("preprofile"))
   470  	fmt.Fprintf(h, "input %q\n", b.fileHash(input))
   471  
   472  	return h.Sum()
   473  }
   474  
   475  // pgoActor implements the Actor interface for preprocessing PGO profiles.
   476  type pgoActor struct {
   477  	// input is the path to the original pprof profile.
   478  	input string
   479  }
   480  
   481  func (p *pgoActor) Act(b *Builder, ctx context.Context, a *Action) error {
   482  	if b.useCache(a, b.pgoActionID(p.input), a.Target, !b.IsCmdList) || b.IsCmdList {
   483  		return nil
   484  	}
   485  	defer b.flushOutput(a)
   486  
   487  	sh := b.Shell(a)
   488  
   489  	if err := sh.Mkdir(a.Objdir); err != nil {
   490  		return err
   491  	}
   492  
   493  	if err := sh.run(".", p.input, nil, cfg.BuildToolexec, base.Tool("preprofile"), "-o", a.Target, "-i", p.input); err != nil {
   494  		return err
   495  	}
   496  
   497  	// N.B. Builder.build looks for the out in a.built, regardless of
   498  	// whether this came from cache.
   499  	a.built = a.Target
   500  
   501  	if !cfg.BuildN {
   502  		// Cache the output.
   503  		//
   504  		// N.B. We don't use updateBuildID here, as preprocessed PGO profiles
   505  		// do not contain a build ID. updateBuildID is typically responsible
   506  		// for adding to the cache, thus we must do so ourselves instead.
   507  
   508  		r, err := os.Open(a.Target)
   509  		if err != nil {
   510  			return fmt.Errorf("error opening target for caching: %w", err)
   511  		}
   512  
   513  		c := cache.Default()
   514  		outputID, _, err := c.Put(a.actionID, r)
   515  		r.Close()
   516  		if err != nil {
   517  			return fmt.Errorf("error adding target to cache: %w", err)
   518  		}
   519  		if cfg.BuildX {
   520  			sh.ShowCmd("", "%s # internal", joinUnambiguously(str.StringList("cp", a.Target, c.OutputFile(outputID))))
   521  		}
   522  	}
   523  
   524  	return nil
   525  }
   526  
   527  // CompileAction returns the action for compiling and possibly installing
   528  // (according to mode) the given package. The resulting action is only
   529  // for building packages (archives), never for linking executables.
   530  // depMode is the action (build or install) to use when building dependencies.
   531  // To turn package main into an executable, call b.Link instead.
   532  func (b *Builder) CompileAction(mode, depMode BuildMode, p *load.Package) *Action {
   533  	vetOnly := mode&ModeVetOnly != 0
   534  	mode &^= ModeVetOnly
   535  
   536  	if mode != ModeBuild && p.Target == "" {
   537  		// No permanent target.
   538  		mode = ModeBuild
   539  	}
   540  	if mode != ModeBuild && p.Name == "main" {
   541  		// We never install the .a file for a main package.
   542  		mode = ModeBuild
   543  	}
   544  
   545  	// Construct package build action.
   546  	a := b.cacheAction("build", p, func() *Action {
   547  		a := &Action{
   548  			Mode:    "build",
   549  			Package: p,
   550  			Actor:   newBuildActor(p, p.Internal.Cover.GenMeta),
   551  			Objdir:  b.NewObjdir(),
   552  		}
   553  
   554  		if p.Error == nil || !p.Error.IsImportCycle {
   555  			for _, p1 := range p.Internal.Imports {
   556  				a.Deps = append(a.Deps, b.CompileAction(depMode, depMode, p1))
   557  			}
   558  		}
   559  
   560  		if p.Internal.PGOProfile != "" {
   561  			pgoAction := b.cacheAction("preprocess PGO profile "+p.Internal.PGOProfile, nil, func() *Action {
   562  				a := &Action{
   563  					Mode:    "preprocess PGO profile",
   564  					Actor:   &pgoActor{input: p.Internal.PGOProfile},
   565  					Objdir:  b.NewObjdir(),
   566  				}
   567  				a.Target = filepath.Join(a.Objdir, "pgo.preprofile")
   568  
   569  				return a
   570  			})
   571  			a.Deps = append(a.Deps, pgoAction)
   572  		}
   573  
   574  		if p.Standard {
   575  			switch p.ImportPath {
   576  			case "builtin", "unsafe":
   577  				// Fake packages - nothing to build.
   578  				a.Mode = "built-in package"
   579  				a.Actor = nil
   580  				return a
   581  			}
   582  
   583  			// gccgo standard library is "fake" too.
   584  			if cfg.BuildToolchainName == "gccgo" {
   585  				// the target name is needed for cgo.
   586  				a.Mode = "gccgo stdlib"
   587  				a.Target = p.Target
   588  				a.Actor = nil
   589  				return a
   590  			}
   591  		}
   592  
   593  		return a
   594  	})
   595  
   596  	// Find the build action; the cache entry may have been replaced
   597  	// by the install action during (*Builder).installAction.
   598  	buildAction := a
   599  	switch buildAction.Mode {
   600  	case "build", "built-in package", "gccgo stdlib":
   601  		// ok
   602  	case "build-install":
   603  		buildAction = a.Deps[0]
   604  	default:
   605  		panic("lost build action: " + buildAction.Mode)
   606  	}
   607  	buildAction.needBuild = buildAction.needBuild || !vetOnly
   608  
   609  	// Construct install action.
   610  	if mode == ModeInstall || mode == ModeBuggyInstall {
   611  		a = b.installAction(a, mode)
   612  	}
   613  
   614  	return a
   615  }
   616  
   617  // VetAction returns the action for running go vet on package p.
   618  // It depends on the action for compiling p.
   619  // If the caller may be causing p to be installed, it is up to the caller
   620  // to make sure that the install depends on (runs after) vet.
   621  func (b *Builder) VetAction(mode, depMode BuildMode, p *load.Package) *Action {
   622  	a := b.vetAction(mode, depMode, p)
   623  	a.VetxOnly = false
   624  	return a
   625  }
   626  
   627  func (b *Builder) vetAction(mode, depMode BuildMode, p *load.Package) *Action {
   628  	// Construct vet action.
   629  	a := b.cacheAction("vet", p, func() *Action {
   630  		a1 := b.CompileAction(mode|ModeVetOnly, depMode, p)
   631  
   632  		// vet expects to be able to import "fmt".
   633  		var stk load.ImportStack
   634  		stk.Push("vet")
   635  		p1, err := load.LoadImportWithFlags("fmt", p.Dir, p, &stk, nil, 0)
   636  		if err != nil {
   637  			base.Fatalf("unexpected error loading fmt package from package %s: %v", p.ImportPath, err)
   638  		}
   639  		stk.Pop()
   640  		aFmt := b.CompileAction(ModeBuild, depMode, p1)
   641  
   642  		var deps []*Action
   643  		if a1.buggyInstall {
   644  			// (*Builder).vet expects deps[0] to be the package
   645  			// and deps[1] to be "fmt". If we see buggyInstall
   646  			// here then a1 is an install of a shared library,
   647  			// and the real package is a1.Deps[0].
   648  			deps = []*Action{a1.Deps[0], aFmt, a1}
   649  		} else {
   650  			deps = []*Action{a1, aFmt}
   651  		}
   652  		for _, p1 := range p.Internal.Imports {
   653  			deps = append(deps, b.vetAction(mode, depMode, p1))
   654  		}
   655  
   656  		a := &Action{
   657  			Mode:       "vet",
   658  			Package:    p,
   659  			Deps:       deps,
   660  			Objdir:     a1.Objdir,
   661  			VetxOnly:   true,
   662  			IgnoreFail: true, // it's OK if vet of dependencies "fails" (reports problems)
   663  		}
   664  		if a1.Actor == nil {
   665  			// Built-in packages like unsafe.
   666  			return a
   667  		}
   668  		deps[0].needVet = true
   669  		a.Actor = ActorFunc((*Builder).vet)
   670  		return a
   671  	})
   672  	return a
   673  }
   674  
   675  // LinkAction returns the action for linking p into an executable
   676  // and possibly installing the result (according to mode).
   677  // depMode is the action (build or install) to use when compiling dependencies.
   678  func (b *Builder) LinkAction(mode, depMode BuildMode, p *load.Package) *Action {
   679  	// Construct link action.
   680  	a := b.cacheAction("link", p, func() *Action {
   681  		a := &Action{
   682  			Mode:    "link",
   683  			Package: p,
   684  		}
   685  
   686  		a1 := b.CompileAction(ModeBuild, depMode, p)
   687  		a.Actor = ActorFunc((*Builder).link)
   688  		a.Deps = []*Action{a1}
   689  		a.Objdir = a1.Objdir
   690  
   691  		// An executable file. (This is the name of a temporary file.)
   692  		// Because we run the temporary file in 'go run' and 'go test',
   693  		// the name will show up in ps listings. If the caller has specified
   694  		// a name, use that instead of a.out. The binary is generated
   695  		// in an otherwise empty subdirectory named exe to avoid
   696  		// naming conflicts. The only possible conflict is if we were
   697  		// to create a top-level package named exe.
   698  		name := "a.out"
   699  		if p.Internal.ExeName != "" {
   700  			name = p.Internal.ExeName
   701  		} else if (cfg.Goos == "darwin" || cfg.Goos == "windows") && cfg.BuildBuildmode == "c-shared" && p.Target != "" {
   702  			// On OS X, the linker output name gets recorded in the
   703  			// shared library's LC_ID_DYLIB load command.
   704  			// The code invoking the linker knows to pass only the final
   705  			// path element. Arrange that the path element matches what
   706  			// we'll install it as; otherwise the library is only loadable as "a.out".
   707  			// On Windows, DLL file name is recorded in PE file
   708  			// export section, so do like on OS X.
   709  			_, name = filepath.Split(p.Target)
   710  		}
   711  		a.Target = a.Objdir + filepath.Join("exe", name) + cfg.ExeSuffix
   712  		a.built = a.Target
   713  		b.addTransitiveLinkDeps(a, a1, "")
   714  
   715  		// Sequence the build of the main package (a1) strictly after the build
   716  		// of all other dependencies that go into the link. It is likely to be after
   717  		// them anyway, but just make sure. This is required by the build ID-based
   718  		// shortcut in (*Builder).useCache(a1), which will call b.linkActionID(a).
   719  		// In order for that linkActionID call to compute the right action ID, all the
   720  		// dependencies of a (except a1) must have completed building and have
   721  		// recorded their build IDs.
   722  		a1.Deps = append(a1.Deps, &Action{Mode: "nop", Deps: a.Deps[1:]})
   723  		return a
   724  	})
   725  
   726  	if mode == ModeInstall || mode == ModeBuggyInstall {
   727  		a = b.installAction(a, mode)
   728  	}
   729  
   730  	return a
   731  }
   732  
   733  // installAction returns the action for installing the result of a1.
   734  func (b *Builder) installAction(a1 *Action, mode BuildMode) *Action {
   735  	// Because we overwrite the build action with the install action below,
   736  	// a1 may already be an install action fetched from the "build" cache key,
   737  	// and the caller just doesn't realize.
   738  	if strings.HasSuffix(a1.Mode, "-install") {
   739  		if a1.buggyInstall && mode == ModeInstall {
   740  			//  Congratulations! The buggy install is now a proper install.
   741  			a1.buggyInstall = false
   742  		}
   743  		return a1
   744  	}
   745  
   746  	// If there's no actual action to build a1,
   747  	// there's nothing to install either.
   748  	// This happens if a1 corresponds to reusing an already-built object.
   749  	if a1.Actor == nil {
   750  		return a1
   751  	}
   752  
   753  	p := a1.Package
   754  	return b.cacheAction(a1.Mode+"-install", p, func() *Action {
   755  		// The install deletes the temporary build result,
   756  		// so we need all other actions, both past and future,
   757  		// that attempt to depend on the build to depend instead
   758  		// on the install.
   759  
   760  		// Make a private copy of a1 (the build action),
   761  		// no longer accessible to any other rules.
   762  		buildAction := new(Action)
   763  		*buildAction = *a1
   764  
   765  		// Overwrite a1 with the install action.
   766  		// This takes care of updating past actions that
   767  		// point at a1 for the build action; now they will
   768  		// point at a1 and get the install action.
   769  		// We also leave a1 in the action cache as the result
   770  		// for "build", so that actions not yet created that
   771  		// try to depend on the build will instead depend
   772  		// on the install.
   773  		*a1 = Action{
   774  			Mode:    buildAction.Mode + "-install",
   775  			Actor:   ActorFunc(BuildInstallFunc),
   776  			Package: p,
   777  			Objdir:  buildAction.Objdir,
   778  			Deps:    []*Action{buildAction},
   779  			Target:  p.Target,
   780  			built:   p.Target,
   781  
   782  			buggyInstall: mode == ModeBuggyInstall,
   783  		}
   784  
   785  		b.addInstallHeaderAction(a1)
   786  		return a1
   787  	})
   788  }
   789  
   790  // addTransitiveLinkDeps adds to the link action a all packages
   791  // that are transitive dependencies of a1.Deps.
   792  // That is, if a is a link of package main, a1 is the compile of package main
   793  // and a1.Deps is the actions for building packages directly imported by
   794  // package main (what the compiler needs). The linker needs all packages
   795  // transitively imported by the whole program; addTransitiveLinkDeps
   796  // makes sure those are present in a.Deps.
   797  // If shlib is non-empty, then a corresponds to the build and installation of shlib,
   798  // so any rebuild of shlib should not be added as a dependency.
   799  func (b *Builder) addTransitiveLinkDeps(a, a1 *Action, shlib string) {
   800  	// Expand Deps to include all built packages, for the linker.
   801  	// Use breadth-first search to find rebuilt-for-test packages
   802  	// before the standard ones.
   803  	// TODO(rsc): Eliminate the standard ones from the action graph,
   804  	// which will require doing a little bit more rebuilding.
   805  	workq := []*Action{a1}
   806  	haveDep := map[string]bool{}
   807  	if a1.Package != nil {
   808  		haveDep[a1.Package.ImportPath] = true
   809  	}
   810  	for i := 0; i < len(workq); i++ {
   811  		a1 := workq[i]
   812  		for _, a2 := range a1.Deps {
   813  			// TODO(rsc): Find a better discriminator than the Mode strings, once the dust settles.
   814  			if a2.Package == nil || (a2.Mode != "build-install" && a2.Mode != "build") || haveDep[a2.Package.ImportPath] {
   815  				continue
   816  			}
   817  			haveDep[a2.Package.ImportPath] = true
   818  			a.Deps = append(a.Deps, a2)
   819  			if a2.Mode == "build-install" {
   820  				a2 = a2.Deps[0] // walk children of "build" action
   821  			}
   822  			workq = append(workq, a2)
   823  		}
   824  	}
   825  
   826  	// If this is go build -linkshared, then the link depends on the shared libraries
   827  	// in addition to the packages themselves. (The compile steps do not.)
   828  	if cfg.BuildLinkshared {
   829  		haveShlib := map[string]bool{shlib: true}
   830  		for _, a1 := range a.Deps {
   831  			p1 := a1.Package
   832  			if p1 == nil || p1.Shlib == "" || haveShlib[filepath.Base(p1.Shlib)] {
   833  				continue
   834  			}
   835  			haveShlib[filepath.Base(p1.Shlib)] = true
   836  			// TODO(rsc): The use of ModeInstall here is suspect, but if we only do ModeBuild,
   837  			// we'll end up building an overall library or executable that depends at runtime
   838  			// on other libraries that are out-of-date, which is clearly not good either.
   839  			// We call it ModeBuggyInstall to make clear that this is not right.
   840  			a.Deps = append(a.Deps, b.linkSharedAction(ModeBuggyInstall, ModeBuggyInstall, p1.Shlib, nil))
   841  		}
   842  	}
   843  }
   844  
   845  // addInstallHeaderAction adds an install header action to a, if needed.
   846  // The action a should be an install action as generated by either
   847  // b.CompileAction or b.LinkAction with mode=ModeInstall,
   848  // and so a.Deps[0] is the corresponding build action.
   849  func (b *Builder) addInstallHeaderAction(a *Action) {
   850  	// Install header for cgo in c-archive and c-shared modes.
   851  	p := a.Package
   852  	if p.UsesCgo() && (cfg.BuildBuildmode == "c-archive" || cfg.BuildBuildmode == "c-shared") {
   853  		hdrTarget := a.Target[:len(a.Target)-len(filepath.Ext(a.Target))] + ".h"
   854  		if cfg.BuildContext.Compiler == "gccgo" && cfg.BuildO == "" {
   855  			// For the header file, remove the "lib"
   856  			// added by go/build, so we generate pkg.h
   857  			// rather than libpkg.h.
   858  			dir, file := filepath.Split(hdrTarget)
   859  			file = strings.TrimPrefix(file, "lib")
   860  			hdrTarget = filepath.Join(dir, file)
   861  		}
   862  		ah := &Action{
   863  			Mode:    "install header",
   864  			Package: a.Package,
   865  			Deps:    []*Action{a.Deps[0]},
   866  			Actor:   ActorFunc((*Builder).installHeader),
   867  			Objdir:  a.Deps[0].Objdir,
   868  			Target:  hdrTarget,
   869  		}
   870  		a.Deps = append(a.Deps, ah)
   871  	}
   872  }
   873  
   874  // buildmodeShared takes the "go build" action a1 into the building of a shared library of a1.Deps.
   875  // That is, the input a1 represents "go build pkgs" and the result represents "go build -buildmode=shared pkgs".
   876  func (b *Builder) buildmodeShared(mode, depMode BuildMode, args []string, pkgs []*load.Package, a1 *Action) *Action {
   877  	name, err := libname(args, pkgs)
   878  	if err != nil {
   879  		base.Fatalf("%v", err)
   880  	}
   881  	return b.linkSharedAction(mode, depMode, name, a1)
   882  }
   883  
   884  // linkSharedAction takes a grouping action a1 corresponding to a list of built packages
   885  // and returns an action that links them together into a shared library with the name shlib.
   886  // If a1 is nil, shlib should be an absolute path to an existing shared library,
   887  // and then linkSharedAction reads that library to find out the package list.
   888  func (b *Builder) linkSharedAction(mode, depMode BuildMode, shlib string, a1 *Action) *Action {
   889  	fullShlib := shlib
   890  	shlib = filepath.Base(shlib)
   891  	a := b.cacheAction("build-shlib "+shlib, nil, func() *Action {
   892  		if a1 == nil {
   893  			// TODO(rsc): Need to find some other place to store config,
   894  			// not in pkg directory. See golang.org/issue/22196.
   895  			pkgs := readpkglist(fullShlib)
   896  			a1 = &Action{
   897  				Mode: "shlib packages",
   898  			}
   899  			for _, p := range pkgs {
   900  				a1.Deps = append(a1.Deps, b.CompileAction(mode, depMode, p))
   901  			}
   902  		}
   903  
   904  		// Fake package to hold ldflags.
   905  		// As usual shared libraries are a kludgy, abstraction-violating special case:
   906  		// we let them use the flags specified for the command-line arguments.
   907  		p := &load.Package{}
   908  		p.Internal.CmdlinePkg = true
   909  		p.Internal.Ldflags = load.BuildLdflags.For(p)
   910  		p.Internal.Gccgoflags = load.BuildGccgoflags.For(p)
   911  
   912  		// Add implicit dependencies to pkgs list.
   913  		// Currently buildmode=shared forces external linking mode, and
   914  		// external linking mode forces an import of runtime/cgo (and
   915  		// math on arm). So if it was not passed on the command line and
   916  		// it is not present in another shared library, add it here.
   917  		// TODO(rsc): Maybe this should only happen if "runtime" is in the original package set.
   918  		// TODO(rsc): This should probably be changed to use load.LinkerDeps(p).
   919  		// TODO(rsc): We don't add standard library imports for gccgo
   920  		// because they are all always linked in anyhow.
   921  		// Maybe load.LinkerDeps should be used and updated.
   922  		a := &Action{
   923  			Mode:    "go build -buildmode=shared",
   924  			Package: p,
   925  			Objdir:  b.NewObjdir(),
   926  			Actor:   ActorFunc((*Builder).linkShared),
   927  			Deps:    []*Action{a1},
   928  		}
   929  		a.Target = filepath.Join(a.Objdir, shlib)
   930  		if cfg.BuildToolchainName != "gccgo" {
   931  			add := func(a1 *Action, pkg string, force bool) {
   932  				for _, a2 := range a1.Deps {
   933  					if a2.Package != nil && a2.Package.ImportPath == pkg {
   934  						return
   935  					}
   936  				}
   937  				var stk load.ImportStack
   938  				p := load.LoadPackageWithFlags(pkg, base.Cwd(), &stk, nil, 0)
   939  				if p.Error != nil {
   940  					base.Fatalf("load %s: %v", pkg, p.Error)
   941  				}
   942  				// Assume that if pkg (runtime/cgo or math)
   943  				// is already accounted for in a different shared library,
   944  				// then that shared library also contains runtime,
   945  				// so that anything we do will depend on that library,
   946  				// so we don't need to include pkg in our shared library.
   947  				if force || p.Shlib == "" || filepath.Base(p.Shlib) == pkg {
   948  					a1.Deps = append(a1.Deps, b.CompileAction(depMode, depMode, p))
   949  				}
   950  			}
   951  			add(a1, "runtime/cgo", false)
   952  			if cfg.Goarch == "arm" {
   953  				add(a1, "math", false)
   954  			}
   955  
   956  			// The linker step still needs all the usual linker deps.
   957  			// (For example, the linker always opens runtime.a.)
   958  			ldDeps, err := load.LinkerDeps(nil)
   959  			if err != nil {
   960  				base.Error(err)
   961  			}
   962  			for _, dep := range ldDeps {
   963  				add(a, dep, true)
   964  			}
   965  		}
   966  		b.addTransitiveLinkDeps(a, a1, shlib)
   967  		return a
   968  	})
   969  
   970  	// Install result.
   971  	if (mode == ModeInstall || mode == ModeBuggyInstall) && a.Actor != nil {
   972  		buildAction := a
   973  
   974  		a = b.cacheAction("install-shlib "+shlib, nil, func() *Action {
   975  			// Determine the eventual install target.
   976  			// The install target is root/pkg/shlib, where root is the source root
   977  			// in which all the packages lie.
   978  			// TODO(rsc): Perhaps this cross-root check should apply to the full
   979  			// transitive package dependency list, not just the ones named
   980  			// on the command line?
   981  			pkgDir := a1.Deps[0].Package.Internal.Build.PkgTargetRoot
   982  			for _, a2 := range a1.Deps {
   983  				if dir := a2.Package.Internal.Build.PkgTargetRoot; dir != pkgDir {
   984  					base.Fatalf("installing shared library: cannot use packages %s and %s from different roots %s and %s",
   985  						a1.Deps[0].Package.ImportPath,
   986  						a2.Package.ImportPath,
   987  						pkgDir,
   988  						dir)
   989  				}
   990  			}
   991  			// TODO(rsc): Find out and explain here why gccgo is different.
   992  			if cfg.BuildToolchainName == "gccgo" {
   993  				pkgDir = filepath.Join(pkgDir, "shlibs")
   994  			}
   995  			target := filepath.Join(pkgDir, shlib)
   996  
   997  			a := &Action{
   998  				Mode:   "go install -buildmode=shared",
   999  				Objdir: buildAction.Objdir,
  1000  				Actor:  ActorFunc(BuildInstallFunc),
  1001  				Deps:   []*Action{buildAction},
  1002  				Target: target,
  1003  			}
  1004  			for _, a2 := range buildAction.Deps[0].Deps {
  1005  				p := a2.Package
  1006  				pkgTargetRoot := p.Internal.Build.PkgTargetRoot
  1007  				if pkgTargetRoot == "" {
  1008  					continue
  1009  				}
  1010  				a.Deps = append(a.Deps, &Action{
  1011  					Mode:    "shlibname",
  1012  					Package: p,
  1013  					Actor:   ActorFunc((*Builder).installShlibname),
  1014  					Target:  filepath.Join(pkgTargetRoot, p.ImportPath+".shlibname"),
  1015  					Deps:    []*Action{a.Deps[0]},
  1016  				})
  1017  			}
  1018  			return a
  1019  		})
  1020  	}
  1021  
  1022  	return a
  1023  }
  1024  

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