action.go

     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  	"cmd/internal/par"
    14  	"container/heap"
    15  	"context"
    16  	"debug/elf"
    17  	"encoding/json"
    18  	"fmt"
    19  	"internal/platform"
    20  	"os"
    21  	"path/filepath"
    22  	"slices"
    23  	"strings"
    24  	"sync"
    25  	"time"
    26  
    27  	"cmd/go/internal/base"
    28  	"cmd/go/internal/cache"
    29  	"cmd/go/internal/cfg"
    30  	"cmd/go/internal/load"
    31  	"cmd/go/internal/modload"
    32  	"cmd/go/internal/str"
    33  	"cmd/go/internal/trace"
    34  	"cmd/internal/buildid"
    35  	"cmd/internal/robustio"
    36  )
    37  
    38  // A Builder holds global state about a build.
    39  // It does not hold per-package state, because we
    40  // build packages in parallel, and the builder is shared.
    41  type Builder struct {
    42  	WorkDir            string                    // the temporary work directory (ends in filepath.Separator)
    43  	actionCache        map[cacheKey]*Action      // a cache of already-constructed actions
    44  	flagCache          map[[2]string]bool        // a cache of supported compiler flags
    45  	gccCompilerIDCache map[string]cache.ActionID // cache for gccCompilerID
    46  
    47  	IsCmdList           bool // running as part of go list; set p.Stale and additional fields below
    48  	NeedError           bool // list needs p.Error
    49  	NeedExport          bool // list needs p.Export
    50  	NeedCompiledGoFiles bool // list needs p.CompiledGoFiles
    51  	AllowErrors         bool // errors don't immediately exit the program
    52  
    53  	objdirSeq int // counter for NewObjdir
    54  	pkgSeq    int
    55  
    56  	backgroundSh *Shell // Shell that per-Action Shells are derived from
    57  
    58  	exec      sync.Mutex
    59  	readySema chan bool
    60  	ready     actionQueue
    61  
    62  	id             sync.Mutex
    63  	toolIDCache    par.Cache[string, string] // tool name -> tool ID
    64  	gccToolIDCache map[string]string         // tool name -> tool ID
    65  	buildIDCache   map[string]string         // file name -> build ID
    66  }
    67  
    68  // NOTE: Much of Action would not need to be exported if not for test.
    69  // Maybe test functionality should move into this package too?
    70  
    71  // An Actor runs an action.
    72  type Actor interface {
    73  	Act(*Builder, context.Context, *Action) error
    74  }
    75  
    76  // An ActorFunc is an Actor that calls the function.
    77  type ActorFunc func(*Builder, context.Context, *Action) error
    78  
    79  func (f ActorFunc) Act(b *Builder, ctx context.Context, a *Action) error {
    80  	return f(b, ctx, a)
    81  }
    82  
    83  // An Action represents a single action in the action graph.
    84  type Action struct {
    85  	Mode       string        // description of action operation
    86  	Package    *load.Package // the package this action works on
    87  	Deps       []*Action     // actions that must happen before this one
    88  	Actor      Actor         // the action itself (nil = no-op)
    89  	IgnoreFail bool          // whether to run f even if dependencies fail
    90  	TestOutput *bytes.Buffer // test output buffer
    91  	Args       []string      // additional args for runProgram
    92  
    93  	Provider any // Additional information to be passed to successive actions. Similar to a Bazel provider.
    94  
    95  	triggers []*Action // inverse of deps
    96  
    97  	buggyInstall bool // is this a buggy install (see -linkshared)?
    98  
    99  	TryCache func(*Builder, *Action, *Action) bool // callback for cache bypass
   100  
   101  	CacheExecutable bool // Whether to cache executables produced by link steps
   102  
   103  	// Generated files, directories.
   104  	Objdir           string         // directory for intermediate objects
   105  	Target           string         // goal of the action: the created package or executable
   106  	built            string         // the actual created package or executable
   107  	cachedExecutable string         // the cached executable, if CacheExecutable was set
   108  	actionID         cache.ActionID // cache ID of action input
   109  	buildID          string         // build ID of action output
   110  
   111  	VetxOnly  bool       // Mode=="vet": only being called to supply info about dependencies
   112  	needVet   bool       // Mode=="build": need to fill in vet config
   113  	needBuild bool       // Mode=="build": need to do actual build (can be false if needVet is true)
   114  	vetCfg    *vetConfig // vet config
   115  	output    []byte     // output redirect buffer (nil means use b.Print)
   116  
   117  	sh *Shell // lazily created per-Action shell; see Builder.Shell
   118  
   119  	// Execution state.
   120  	pending      int               // number of deps yet to complete
   121  	priority     int               // relative execution priority
   122  	Failed       *Action           // set to root cause if the action failed
   123  	json         *actionJSON       // action graph information
   124  	nonGoOverlay map[string]string // map from non-.go source files to copied files in objdir. Nil if no overlay is used.
   125  	traceSpan    *trace.Span
   126  }
   127  
   128  // BuildActionID returns the action ID section of a's build ID.
   129  func (a *Action) BuildActionID() string { return actionID(a.buildID) }
   130  
   131  // BuildContentID returns the content ID section of a's build ID.
   132  func (a *Action) BuildContentID() string { return contentID(a.buildID) }
   133  
   134  // BuildID returns a's build ID.
   135  func (a *Action) BuildID() string { return a.buildID }
   136  
   137  // BuiltTarget returns the actual file that was built. This differs
   138  // from Target when the result was cached.
   139  func (a *Action) BuiltTarget() string { return a.built }
   140  
   141  // CachedExecutable returns the cached executable, if CacheExecutable
   142  // was set and the executable could be cached, and "" otherwise.
   143  func (a *Action) CachedExecutable() string { return a.cachedExecutable }
   144  
   145  // An actionQueue is a priority queue of actions.
   146  type actionQueue []*Action
   147  
   148  // Implement heap.Interface
   149  func (q *actionQueue) Len() int           { return len(*q) }
   150  func (q *actionQueue) Swap(i, j int)      { (*q)[i], (*q)[j] = (*q)[j], (*q)[i] }
   151  func (q *actionQueue) Less(i, j int) bool { return (*q)[i].priority < (*q)[j].priority }
   152  func (q *actionQueue) Push(x any)         { *q = append(*q, x.(*Action)) }
   153  func (q *actionQueue) Pop() any {
   154  	n := len(*q) - 1
   155  	x := (*q)[n]
   156  	*q = (*q)[:n]
   157  	return x
   158  }
   159  
   160  func (q *actionQueue) push(a *Action) {
   161  	if a.json != nil {
   162  		a.json.TimeReady = time.Now()
   163  	}
   164  	heap.Push(q, a)
   165  }
   166  
   167  func (q *actionQueue) pop() *Action {
   168  	return heap.Pop(q).(*Action)
   169  }
   170  
   171  type actionJSON struct {
   172  	ID         int
   173  	Mode       string
   174  	Package    string
   175  	Deps       []int     `json:",omitempty"`
   176  	IgnoreFail bool      `json:",omitempty"`
   177  	Args       []string  `json:",omitempty"`
   178  	Link       bool      `json:",omitempty"`
   179  	Objdir     string    `json:",omitempty"`
   180  	Target     string    `json:",omitempty"`
   181  	Priority   int       `json:",omitempty"`
   182  	Failed     bool      `json:",omitempty"`
   183  	Built      string    `json:",omitempty"`
   184  	VetxOnly   bool      `json:",omitempty"`
   185  	NeedVet    bool      `json:",omitempty"`
   186  	NeedBuild  bool      `json:",omitempty"`
   187  	ActionID   string    `json:",omitempty"`
   188  	BuildID    string    `json:",omitempty"`
   189  	TimeReady  time.Time `json:",omitempty"`
   190  	TimeStart  time.Time `json:",omitempty"`
   191  	TimeDone   time.Time `json:",omitempty"`
   192  
   193  	Cmd     []string      // `json:",omitempty"`
   194  	CmdReal time.Duration `json:",omitempty"`
   195  	CmdUser time.Duration `json:",omitempty"`
   196  	CmdSys  time.Duration `json:",omitempty"`
   197  }
   198  
   199  // cacheKey is the key for the action cache.
   200  type cacheKey struct {
   201  	mode string
   202  	p    *load.Package
   203  }
   204  
   205  func actionGraphJSON(a *Action) string {
   206  	var workq []*Action
   207  	var inWorkq = make(map[*Action]int)
   208  
   209  	add := func(a *Action) {
   210  		if _, ok := inWorkq[a]; ok {
   211  			return
   212  		}
   213  		inWorkq[a] = len(workq)
   214  		workq = append(workq, a)
   215  	}
   216  	add(a)
   217  
   218  	for i := 0; i < len(workq); i++ {
   219  		for _, dep := range workq[i].Deps {
   220  			add(dep)
   221  		}
   222  	}
   223  
   224  	list := make([]*actionJSON, 0, len(workq))
   225  	for id, a := range workq {
   226  		if a.json == nil {
   227  			a.json = &actionJSON{
   228  				Mode:       a.Mode,
   229  				ID:         id,
   230  				IgnoreFail: a.IgnoreFail,
   231  				Args:       a.Args,
   232  				Objdir:     a.Objdir,
   233  				Target:     a.Target,
   234  				Failed:     a.Failed != nil,
   235  				Priority:   a.priority,
   236  				Built:      a.built,
   237  				VetxOnly:   a.VetxOnly,
   238  				NeedBuild:  a.needBuild,
   239  				NeedVet:    a.needVet,
   240  			}
   241  			if a.Package != nil {
   242  				// TODO(rsc): Make this a unique key for a.Package somehow.
   243  				a.json.Package = a.Package.ImportPath
   244  			}
   245  			for _, a1 := range a.Deps {
   246  				a.json.Deps = append(a.json.Deps, inWorkq[a1])
   247  			}
   248  		}
   249  		list = append(list, a.json)
   250  	}
   251  
   252  	js, err := json.MarshalIndent(list, "", "\t")
   253  	if err != nil {
   254  		fmt.Fprintf(os.Stderr, "go: writing debug action graph: %v\n", err)
   255  		return ""
   256  	}
   257  	return string(js)
   258  }
   259  
   260  // BuildMode specifies the build mode:
   261  // are we just building things or also installing the results?
   262  type BuildMode int
   263  
   264  const (
   265  	ModeBuild BuildMode = iota
   266  	ModeInstall
   267  	ModeBuggyInstall
   268  
   269  	ModeVetOnly = 1 << 8
   270  )
   271  
   272  // NewBuilder returns a new Builder ready for use.
   273  //
   274  // If workDir is the empty string, NewBuilder creates a WorkDir if needed
   275  // and arranges for it to be removed in case of an unclean exit.
   276  // The caller must Close the builder explicitly to clean up the WorkDir
   277  // before a clean exit.
   278  func NewBuilder(workDir string) *Builder {
   279  	b := new(Builder)
   280  
   281  	b.actionCache = make(map[cacheKey]*Action)
   282  	b.gccToolIDCache = make(map[string]string)
   283  	b.buildIDCache = make(map[string]string)
   284  
   285  	printWorkDir := false
   286  	if workDir != "" {
   287  		b.WorkDir = workDir
   288  	} else if cfg.BuildN {
   289  		b.WorkDir = "$WORK"
   290  	} else {
   291  		if !buildInitStarted {
   292  			panic("internal error: NewBuilder called before BuildInit")
   293  		}
   294  		tmp, err := os.MkdirTemp(cfg.Getenv("GOTMPDIR"), "go-build")
   295  		if err != nil {
   296  			base.Fatalf("go: creating work dir: %v", err)
   297  		}
   298  		if !filepath.IsAbs(tmp) {
   299  			abs, err := filepath.Abs(tmp)
   300  			if err != nil {
   301  				os.RemoveAll(tmp)
   302  				base.Fatalf("go: creating work dir: %v", err)
   303  			}
   304  			tmp = abs
   305  		}
   306  		b.WorkDir = tmp
   307  		builderWorkDirs.Store(b, b.WorkDir)
   308  		printWorkDir = cfg.BuildX || cfg.BuildWork
   309  	}
   310  
   311  	b.backgroundSh = NewShell(b.WorkDir, nil)
   312  
   313  	if printWorkDir {
   314  		b.BackgroundShell().Printf("WORK=%s\n", b.WorkDir)
   315  	}
   316  
   317  	if err := CheckGOOSARCHPair(cfg.Goos, cfg.Goarch); err != nil {
   318  		fmt.Fprintf(os.Stderr, "go: %v\n", err)
   319  		base.SetExitStatus(2)
   320  		base.Exit()
   321  	}
   322  
   323  	for _, tag := range cfg.BuildContext.BuildTags {
   324  		if strings.Contains(tag, ",") {
   325  			fmt.Fprintf(os.Stderr, "go: -tags space-separated list contains comma\n")
   326  			base.SetExitStatus(2)
   327  			base.Exit()
   328  		}
   329  	}
   330  
   331  	return b
   332  }
   333  
   334  var builderWorkDirs sync.Map // *Builder → WorkDir
   335  
   336  func (b *Builder) Close() error {
   337  	wd, ok := builderWorkDirs.Load(b)
   338  	if !ok {
   339  		return nil
   340  	}
   341  	defer builderWorkDirs.Delete(b)
   342  
   343  	if b.WorkDir != wd.(string) {
   344  		base.Errorf("go: internal error: Builder WorkDir unexpectedly changed from %s to %s", wd, b.WorkDir)
   345  	}
   346  
   347  	if !cfg.BuildWork {
   348  		if err := robustio.RemoveAll(b.WorkDir); err != nil {
   349  			return err
   350  		}
   351  	}
   352  	b.WorkDir = ""
   353  	return nil
   354  }
   355  
   356  func closeBuilders() {
   357  	leakedBuilders := 0
   358  	builderWorkDirs.Range(func(bi, _ any) bool {
   359  		leakedBuilders++
   360  		if err := bi.(*Builder).Close(); err != nil {
   361  			base.Error(err)
   362  		}
   363  		return true
   364  	})
   365  
   366  	if leakedBuilders > 0 && base.GetExitStatus() == 0 {
   367  		fmt.Fprintf(os.Stderr, "go: internal error: Builder leaked on successful exit\n")
   368  		base.SetExitStatus(1)
   369  	}
   370  }
   371  
   372  func CheckGOOSARCHPair(goos, goarch string) error {
   373  	if !platform.BuildModeSupported(cfg.BuildContext.Compiler, "default", goos, goarch) {
   374  		return fmt.Errorf("unsupported GOOS/GOARCH pair %s/%s", goos, goarch)
   375  	}
   376  	return nil
   377  }
   378  
   379  // NewObjdir returns the name of a fresh object directory under b.WorkDir.
   380  // It is up to the caller to call b.Mkdir on the result at an appropriate time.
   381  // The result ends in a slash, so that file names in that directory
   382  // can be constructed with direct string addition.
   383  //
   384  // NewObjdir must be called only from a single goroutine at a time,
   385  // so it is safe to call during action graph construction, but it must not
   386  // be called during action graph execution.
   387  func (b *Builder) NewObjdir() string {
   388  	b.objdirSeq++
   389  	return str.WithFilePathSeparator(filepath.Join(b.WorkDir, fmt.Sprintf("b%03d", b.objdirSeq)))
   390  }
   391  
   392  // readpkglist returns the list of packages that were built into the shared library
   393  // at shlibpath. For the native toolchain this list is stored, newline separated, in
   394  // an ELF note with name "Go\x00\x00" and type 1. For GCCGO it is extracted from the
   395  // .go_export section.
   396  func readpkglist(loaderstate *modload.State, shlibpath string) (pkgs []*load.Package) {
   397  	var stk load.ImportStack
   398  	if cfg.BuildToolchainName == "gccgo" {
   399  		f, err := elf.Open(shlibpath)
   400  		if err != nil {
   401  			base.Fatal(fmt.Errorf("failed to open shared library: %v", err))
   402  		}
   403  		defer f.Close()
   404  		sect := f.Section(".go_export")
   405  		if sect == nil {
   406  			base.Fatal(fmt.Errorf("%s: missing .go_export section", shlibpath))
   407  		}
   408  		data, err := sect.Data()
   409  		if err != nil {
   410  			base.Fatal(fmt.Errorf("%s: failed to read .go_export section: %v", shlibpath, err))
   411  		}
   412  		pkgpath := []byte("pkgpath ")
   413  		for _, line := range bytes.Split(data, []byte{'\n'}) {
   414  			if path, found := bytes.CutPrefix(line, pkgpath); found {
   415  				path = bytes.TrimSuffix(path, []byte{';'})
   416  				pkgs = append(pkgs, load.LoadPackageWithFlags(loaderstate, string(path), base.Cwd(), &stk, nil, 0))
   417  			}
   418  		}
   419  	} else {
   420  		pkglistbytes, err := buildid.ReadELFNote(shlibpath, "Go\x00\x00", 1)
   421  		if err != nil {
   422  			base.Fatalf("readELFNote failed: %v", err)
   423  		}
   424  		scanner := bufio.NewScanner(bytes.NewBuffer(pkglistbytes))
   425  		for scanner.Scan() {
   426  			t := scanner.Text()
   427  			pkgs = append(pkgs, load.LoadPackageWithFlags(loaderstate, t, base.Cwd(), &stk, nil, 0))
   428  		}
   429  	}
   430  	return
   431  }
   432  
   433  // cacheAction looks up {mode, p} in the cache and returns the resulting action.
   434  // If the cache has no such action, f() is recorded and returned.
   435  // TODO(rsc): Change the second key from *load.Package to interface{},
   436  // to make the caching in linkShared less awkward?
   437  func (b *Builder) cacheAction(mode string, p *load.Package, f func() *Action) *Action {
   438  	a := b.actionCache[cacheKey{mode, p}]
   439  	if a == nil {
   440  		a = f()
   441  		b.actionCache[cacheKey{mode, p}] = a
   442  	}
   443  	return a
   444  }
   445  
   446  // AutoAction returns the "right" action for go build or go install of p.
   447  func (b *Builder) AutoAction(loaderstate *modload.State, mode, depMode BuildMode, p *load.Package) *Action {
   448  	if p.Name == "main" {
   449  		return b.LinkAction(loaderstate, mode, depMode, p)
   450  	}
   451  	return b.CompileAction(mode, depMode, p)
   452  }
   453  
   454  // buildActor implements the Actor interface for package build
   455  // actions. For most package builds this simply means invoking the
   456  // *Builder.build method.
   457  type buildActor struct{}
   458  
   459  func (ba *buildActor) Act(b *Builder, ctx context.Context, a *Action) error {
   460  	return b.build(ctx, a)
   461  }
   462  
   463  // pgoActionID computes the action ID for a preprocess PGO action.
   464  func (b *Builder) pgoActionID(input string) cache.ActionID {
   465  	h := cache.NewHash("preprocess PGO profile " + input)
   466  
   467  	fmt.Fprintf(h, "preprocess PGO profile\n")
   468  	fmt.Fprintf(h, "preprofile %s\n", b.toolID("preprofile"))
   469  	fmt.Fprintf(h, "input %q\n", b.fileHash(input))
   470  
   471  	return h.Sum()
   472  }
   473  
   474  // pgoActor implements the Actor interface for preprocessing PGO profiles.
   475  type pgoActor struct {
   476  	// input is the path to the original pprof profile.
   477  	input string
   478  }
   479  
   480  func (p *pgoActor) Act(b *Builder, ctx context.Context, a *Action) error {
   481  	if b.useCache(a, b.pgoActionID(p.input), a.Target, !b.IsCmdList) || b.IsCmdList {
   482  		return nil
   483  	}
   484  	defer b.flushOutput(a)
   485  
   486  	sh := b.Shell(a)
   487  
   488  	if err := sh.Mkdir(a.Objdir); err != nil {
   489  		return err
   490  	}
   491  
   492  	if err := sh.run(".", p.input, nil, cfg.BuildToolexec, base.Tool("preprofile"), "-o", a.Target, "-i", p.input); err != nil {
   493  		return err
   494  	}
   495  
   496  	// N.B. Builder.build looks for the out in a.built, regardless of
   497  	// whether this came from cache.
   498  	a.built = a.Target
   499  
   500  	if !cfg.BuildN {
   501  		// Cache the output.
   502  		//
   503  		// N.B. We don't use updateBuildID here, as preprocessed PGO profiles
   504  		// do not contain a build ID. updateBuildID is typically responsible
   505  		// for adding to the cache, thus we must do so ourselves instead.
   506  
   507  		r, err := os.Open(a.Target)
   508  		if err != nil {
   509  			return fmt.Errorf("error opening target for caching: %w", err)
   510  		}
   511  
   512  		c := cache.Default()
   513  		outputID, _, err := c.Put(a.actionID, r)
   514  		r.Close()
   515  		if err != nil {
   516  			return fmt.Errorf("error adding target to cache: %w", err)
   517  		}
   518  		if cfg.BuildX {
   519  			sh.ShowCmd("", "%s # internal", joinUnambiguously(str.StringList("cp", a.Target, c.OutputFile(outputID))))
   520  		}
   521  	}
   522  
   523  	return nil
   524  }
   525  
   526  type checkCacheProvider struct {
   527  	need uint32 // What work do successive actions within this package's build need to do? Combination of need bits used in build actions.
   528  }
   529  
   530  // The actor to check the cache to determine what work needs to be done for the action.
   531  // It checks the cache and sets the need bits depending on the build mode and what's available
   532  // in the cache, so the cover and compile actions know what to do.
   533  // Currently, we don't cache the outputs of the individual actions composing the build
   534  // for a single package (such as the output of the cover actor) separately from the
   535  // output of the final build, but if we start doing so, we could schedule the run cgo
   536  // and cgo compile actions earlier because they wouldn't depend on the builds of the
   537  // dependencies of the package they belong to.
   538  type checkCacheActor struct {
   539  	covMetaFileName string
   540  	buildAction     *Action
   541  }
   542  
   543  func (cca *checkCacheActor) Act(b *Builder, ctx context.Context, a *Action) error {
   544  	buildAction := cca.buildAction
   545  	if buildAction.Mode == "build-install" {
   546  		// (*Builder).installAction can rewrite the build action with its install action,
   547  		// making the true build action its dependency. Fetch the build action in that case.
   548  		buildAction = buildAction.Deps[0]
   549  	}
   550  	pr, err := b.checkCacheForBuild(a, buildAction, cca.covMetaFileName)
   551  	if err != nil {
   552  		return err
   553  	}
   554  	a.Provider = pr
   555  	return nil
   556  }
   557  
   558  type coverProvider struct {
   559  	goSources, cgoSources []string // The go and cgo sources generated by the cover tool, which should be used instead of the raw sources on the package.
   560  }
   561  
   562  // The actor to run the cover tool to produce instrumented source files for cover
   563  // builds. In the case of a package with no test files, we store some additional state
   564  // information in the build actor to help with reporting.
   565  type coverActor struct {
   566  	// name of static meta-data file fragment emitted by the cover
   567  	// tool as part of the package cover action, for selected
   568  	// "go test -cover" runs.
   569  	covMetaFileName string
   570  
   571  	buildAction *Action
   572  }
   573  
   574  func (ca *coverActor) Act(b *Builder, ctx context.Context, a *Action) error {
   575  	pr, err := b.runCover(a, ca.buildAction, a.Objdir, a.Package.GoFiles, a.Package.CgoFiles)
   576  	if err != nil {
   577  		return err
   578  	}
   579  	a.Provider = pr
   580  	return nil
   581  }
   582  
   583  // runCgoActor implements the Actor interface for running the cgo command for the package.
   584  type runCgoActor struct {
   585  }
   586  
   587  func (c runCgoActor) Act(b *Builder, ctx context.Context, a *Action) error {
   588  	var cacheProvider *checkCacheProvider
   589  	for _, a1 := range a.Deps {
   590  		if pr, ok := a1.Provider.(*checkCacheProvider); ok {
   591  			cacheProvider = pr
   592  			break
   593  		}
   594  	}
   595  	need := cacheProvider.need
   596  	need &^= needCovMetaFile // handled by cover action
   597  	if need == 0 {
   598  		return nil
   599  	}
   600  	return b.runCgo(ctx, a)
   601  }
   602  
   603  type cgoCompileActor struct {
   604  	file string
   605  
   606  	compileFunc  func(*Action, string, string, []string, string) error
   607  	getFlagsFunc func(*runCgoProvider) []string
   608  
   609  	flags *[]string
   610  }
   611  
   612  func (c cgoCompileActor) Act(b *Builder, ctx context.Context, a *Action) error {
   613  	pr, ok := a.Deps[0].Provider.(*runCgoProvider)
   614  	if !ok {
   615  		return nil // cgo was not needed. do nothing.
   616  	}
   617  	a.nonGoOverlay = pr.nonGoOverlay
   618  	buildAction := a.triggers[0].triggers[0] // cgo compile -> cgo collect -> build
   619  
   620  	a.actionID = cache.Subkey(buildAction.actionID, "cgo compile "+c.file) // buildAction's action id was computed by the check cache action.
   621  	return c.compileFunc(a, a.Objdir, a.Target, c.getFlagsFunc(pr), c.file)
   622  }
   623  
   624  // CompileAction returns the action for compiling and possibly installing
   625  // (according to mode) the given package. The resulting action is only
   626  // for building packages (archives), never for linking executables.
   627  // depMode is the action (build or install) to use when building dependencies.
   628  // To turn package main into an executable, call b.Link instead.
   629  func (b *Builder) CompileAction(mode, depMode BuildMode, p *load.Package) *Action {
   630  	vetOnly := mode&ModeVetOnly != 0
   631  	mode &^= ModeVetOnly
   632  
   633  	if mode != ModeBuild && p.Target == "" {
   634  		// No permanent target.
   635  		mode = ModeBuild
   636  	}
   637  	if mode != ModeBuild && p.Name == "main" {
   638  		// We never install the .a file for a main package.
   639  		mode = ModeBuild
   640  	}
   641  
   642  	// Construct package build action.
   643  	a := b.cacheAction("build", p, func() *Action {
   644  		a := &Action{
   645  			Mode:    "build",
   646  			Package: p,
   647  			Actor:   &buildActor{},
   648  			Objdir:  b.NewObjdir(),
   649  		}
   650  
   651  		if p.Error == nil || !p.Error.IsImportCycle {
   652  			for _, p1 := range p.Internal.Imports {
   653  				a.Deps = append(a.Deps, b.CompileAction(depMode, depMode, p1))
   654  			}
   655  		}
   656  
   657  		if p.Internal.PGOProfile != "" {
   658  			pgoAction := b.cacheAction("preprocess PGO profile "+p.Internal.PGOProfile, nil, func() *Action {
   659  				a := &Action{
   660  					Mode:   "preprocess PGO profile",
   661  					Actor:  &pgoActor{input: p.Internal.PGOProfile},
   662  					Objdir: b.NewObjdir(),
   663  				}
   664  				a.Target = filepath.Join(a.Objdir, "pgo.preprofile")
   665  
   666  				return a
   667  			})
   668  			a.Deps = append(a.Deps, pgoAction)
   669  		}
   670  
   671  		if p.Standard {
   672  			switch p.ImportPath {
   673  			case "builtin", "unsafe":
   674  				// Fake packages - nothing to build.
   675  				a.Mode = "built-in package"
   676  				a.Actor = nil
   677  				return a
   678  			}
   679  
   680  			// gccgo standard library is "fake" too.
   681  			if cfg.BuildToolchainName == "gccgo" {
   682  				// the target name is needed for cgo.
   683  				a.Mode = "gccgo stdlib"
   684  				a.Target = p.Target
   685  				a.Actor = nil
   686  				return a
   687  			}
   688  		}
   689  
   690  		// Determine the covmeta file name.
   691  		var covMetaFileName string
   692  		if p.Internal.Cover.GenMeta {
   693  			covMetaFileName = covcmd.MetaFileForPackage(p.ImportPath)
   694  		}
   695  
   696  		// Create a cache action.
   697  		cacheAction := &Action{
   698  			Mode:    "build check cache",
   699  			Package: p,
   700  			Actor:   &checkCacheActor{buildAction: a, covMetaFileName: covMetaFileName},
   701  			Objdir:  a.Objdir,
   702  			Deps:    a.Deps, // Need outputs of dependency build actions to generate action id.
   703  		}
   704  		a.Deps = append(a.Deps, cacheAction)
   705  
   706  		// Create a cover action if we need to instrument the code for coverage.
   707  		// The cover action always runs in the same go build invocation as the build,
   708  		// and is not cached separately, so it can use the same objdir.
   709  		var coverAction *Action
   710  		if p.Internal.Cover.Mode != "" {
   711  			coverAction = b.cacheAction("cover", p, func() *Action {
   712  				return &Action{
   713  					Mode:    "cover",
   714  					Package: p,
   715  					Actor:   &coverActor{buildAction: a, covMetaFileName: covMetaFileName},
   716  					Objdir:  a.Objdir,
   717  					Deps:    []*Action{cacheAction},
   718  				}
   719  			})
   720  			a.Deps = append(a.Deps, coverAction)
   721  		}
   722  
   723  		// Create actions to run swig and cgo if needed. These actions always run in the
   724  		// same go build invocation as the build action and their actions are not cached
   725  		// separately, so they can use the same objdir.
   726  		if p.UsesCgo() || p.UsesSwig() {
   727  			deps := []*Action{cacheAction}
   728  			if coverAction != nil {
   729  				deps = append(deps, coverAction)
   730  			}
   731  			a.Deps = append(a.Deps, b.cgoAction(p, a.Objdir, deps, coverAction != nil))
   732  		}
   733  
   734  		return a
   735  	})
   736  
   737  	// Find the build action; the cache entry may have been replaced
   738  	// by the install action during (*Builder).installAction.
   739  	buildAction := a
   740  	switch buildAction.Mode {
   741  	case "build", "built-in package", "gccgo stdlib":
   742  		// ok
   743  	case "build-install":
   744  		buildAction = a.Deps[0]
   745  	default:
   746  		panic("lost build action: " + buildAction.Mode)
   747  	}
   748  	buildAction.needBuild = buildAction.needBuild || !vetOnly
   749  
   750  	// Construct install action.
   751  	if mode == ModeInstall || mode == ModeBuggyInstall {
   752  		a = b.installAction(a, mode)
   753  	}
   754  
   755  	return a
   756  }
   757  
   758  func (b *Builder) cgoAction(p *load.Package, objdir string, deps []*Action, hasCover bool) *Action {
   759  	cgoCollectAction := b.cacheAction("cgo collect", p, func() *Action {
   760  		// Run cgo
   761  		runCgo := b.cacheAction("cgo run", p, func() *Action {
   762  			return &Action{
   763  				Package: p,
   764  				Mode:    "cgo run",
   765  				Actor:   &runCgoActor{},
   766  				Objdir:  objdir,
   767  				Deps:    deps,
   768  			}
   769  		})
   770  
   771  		// Determine which files swig will produce in the cgo run action. We'll need to create
   772  		// actions to compile the C and C++ files produced by swig, as well as the C file
   773  		// produced by cgo processing swig's Go file outputs.
   774  		swigGo, swigC, swigCXX := b.swigOutputs(p, objdir)
   775  
   776  		oseq := 0
   777  		nextOfile := func() string {
   778  			oseq++
   779  			return objdir + fmt.Sprintf("_x%03d.o", oseq)
   780  		}
   781  		compileAction := func(file string, getFlagsFunc func(*runCgoProvider) []string, compileFunc func(*Action, string, string, []string, string) error) *Action {
   782  			mode := "cgo compile " + file
   783  			return b.cacheAction(mode, p, func() *Action {
   784  				return &Action{
   785  					Package: p,
   786  					Mode:    mode,
   787  					Actor:   &cgoCompileActor{file: file, getFlagsFunc: getFlagsFunc, compileFunc: compileFunc},
   788  					Deps:    []*Action{runCgo},
   789  					Objdir:  objdir,
   790  					Target:  nextOfile(),
   791  				}
   792  			})
   793  		}
   794  
   795  		var collectDeps []*Action
   796  
   797  		// Add compile actions for C files generated by cgo.
   798  		cgoFiles := p.CgoFiles
   799  		if hasCover {
   800  			cgoFiles = slices.Clone(cgoFiles)
   801  			for i := range cgoFiles {
   802  				cgoFiles[i] = strings.TrimSuffix(cgoFiles[i], ".go") + ".cover.go"
   803  			}
   804  		}
   805  		cfiles := []string{"_cgo_export.c"}
   806  		for _, fn := range slices.Concat(cgoFiles, swigGo) {
   807  			cfiles = append(cfiles, strings.TrimSuffix(filepath.Base(fn), ".go")+".cgo2.c")
   808  		}
   809  		for _, f := range cfiles {
   810  			collectDeps = append(collectDeps, compileAction(objdir+f, (*runCgoProvider).cflags, b.gcc))
   811  		}
   812  
   813  		// Add compile actions for S files.
   814  		var sfiles []string
   815  		// In a package using cgo, cgo compiles the C, C++ and assembly files with gcc.
   816  		// There is one exception: runtime/cgo's job is to bridge the
   817  		// cgo and non-cgo worlds, so it necessarily has files in both.
   818  		// In that case gcc only gets the gcc_* files.
   819  		if p.Standard && p.ImportPath == "runtime/cgo" {
   820  			for _, f := range p.SFiles {
   821  				if strings.HasPrefix(f, "gcc_") {
   822  					sfiles = append(sfiles, f)
   823  				}
   824  			}
   825  		} else {
   826  			sfiles = p.SFiles
   827  		}
   828  		for _, f := range sfiles {
   829  			collectDeps = append(collectDeps, compileAction(f, (*runCgoProvider).cflags, b.gas))
   830  		}
   831  
   832  		// Add compile actions for C files in the package, M files, and those generated by swig.
   833  		for _, f := range slices.Concat(p.CFiles, p.MFiles, swigC) {
   834  			collectDeps = append(collectDeps, compileAction(f, (*runCgoProvider).cflags, b.gcc))
   835  		}
   836  
   837  		// Add compile actions for C++ files in the package, and those generated by swig.
   838  		for _, f := range slices.Concat(p.CXXFiles, swigCXX) {
   839  			collectDeps = append(collectDeps, compileAction(f, (*runCgoProvider).cxxflags, b.gxx))
   840  		}
   841  
   842  		// Add compile actions for Fortran files in the package.
   843  		for _, f := range p.FFiles {
   844  			collectDeps = append(collectDeps, compileAction(f, (*runCgoProvider).fflags, b.gfortran))
   845  		}
   846  
   847  		// Add a single convenience action that does nothing to join the previous action,
   848  		// and better separate the cgo action dependencies of the build action from the
   849  		// build actions for its package dependencies.
   850  		return &Action{
   851  			Mode: "collect cgo",
   852  			Actor: ActorFunc(func(b *Builder, ctx context.Context, a *Action) error {
   853  				// Use the cgo run action's provider as our provider output,
   854  				// so it can be easily accessed by the build action.
   855  				a.Provider = a.Deps[0].Deps[0].Provider
   856  				return nil
   857  			}),
   858  			Deps:   collectDeps,
   859  			Objdir: objdir,
   860  		}
   861  	})
   862  
   863  	return cgoCollectAction
   864  }
   865  
   866  // VetAction returns the action for running go vet on package p.
   867  // It depends on the action for compiling p.
   868  // If the caller may be causing p to be installed, it is up to the caller
   869  // to make sure that the install depends on (runs after) vet.
   870  func (b *Builder) VetAction(loaderstate *modload.State, mode, depMode BuildMode, p *load.Package) *Action {
   871  	a := b.vetAction(loaderstate, mode, depMode, p)
   872  	a.VetxOnly = false
   873  	return a
   874  }
   875  
   876  func (b *Builder) vetAction(loaderstate *modload.State, mode, depMode BuildMode, p *load.Package) *Action {
   877  	// Construct vet action.
   878  	a := b.cacheAction("vet", p, func() *Action {
   879  		a1 := b.CompileAction(mode|ModeVetOnly, depMode, p)
   880  
   881  		var deps []*Action
   882  		if a1.buggyInstall {
   883  			// (*Builder).vet expects deps[0] to be the package.
   884  			// If we see buggyInstall
   885  			// here then a1 is an install of a shared library,
   886  			// and the real package is a1.Deps[0].
   887  			deps = []*Action{a1.Deps[0], a1}
   888  		} else {
   889  			deps = []*Action{a1}
   890  		}
   891  		for _, p1 := range p.Internal.Imports {
   892  			deps = append(deps, b.vetAction(loaderstate, mode, depMode, p1))
   893  		}
   894  
   895  		a := &Action{
   896  			Mode:       "vet",
   897  			Package:    p,
   898  			Deps:       deps,
   899  			Objdir:     a1.Objdir,
   900  			VetxOnly:   true,
   901  			IgnoreFail: true, // it's OK if vet of dependencies "fails" (reports problems)
   902  		}
   903  		if a1.Actor == nil {
   904  			// Built-in packages like unsafe.
   905  			return a
   906  		}
   907  		deps[0].needVet = true
   908  		a.Actor = ActorFunc((*Builder).vet)
   909  		return a
   910  	})
   911  	return a
   912  }
   913  
   914  // LinkAction returns the action for linking p into an executable
   915  // and possibly installing the result (according to mode).
   916  // depMode is the action (build or install) to use when compiling dependencies.
   917  func (b *Builder) LinkAction(loaderstate *modload.State, mode, depMode BuildMode, p *load.Package) *Action {
   918  	// Construct link action.
   919  	a := b.cacheAction("link", p, func() *Action {
   920  		a := &Action{
   921  			Mode:    "link",
   922  			Package: p,
   923  		}
   924  
   925  		a1 := b.CompileAction(ModeBuild, depMode, p)
   926  		a.Actor = ActorFunc((*Builder).link)
   927  		a.Deps = []*Action{a1}
   928  		a.Objdir = a1.Objdir
   929  
   930  		// An executable file. (This is the name of a temporary file.)
   931  		// Because we run the temporary file in 'go run' and 'go test',
   932  		// the name will show up in ps listings. If the caller has specified
   933  		// a name, use that instead of a.out. The binary is generated
   934  		// in an otherwise empty subdirectory named exe to avoid
   935  		// naming conflicts. The only possible conflict is if we were
   936  		// to create a top-level package named exe.
   937  		name := "a.out"
   938  		if p.Internal.ExeName != "" {
   939  			name = p.Internal.ExeName
   940  		} else if (cfg.Goos == "darwin" || cfg.Goos == "windows") && cfg.BuildBuildmode == "c-shared" && p.Target != "" {
   941  			// On OS X, the linker output name gets recorded in the
   942  			// shared library's LC_ID_DYLIB load command.
   943  			// The code invoking the linker knows to pass only the final
   944  			// path element. Arrange that the path element matches what
   945  			// we'll install it as; otherwise the library is only loadable as "a.out".
   946  			// On Windows, DLL file name is recorded in PE file
   947  			// export section, so do like on OS X.
   948  			_, name = filepath.Split(p.Target)
   949  		}
   950  		a.Target = a.Objdir + filepath.Join("exe", name) + cfg.ExeSuffix
   951  		a.built = a.Target
   952  		b.addTransitiveLinkDeps(loaderstate, a, a1, "")
   953  
   954  		// Sequence the build of the main package (a1) strictly after the build
   955  		// of all other dependencies that go into the link. It is likely to be after
   956  		// them anyway, but just make sure. This is required by the build ID-based
   957  		// shortcut in (*Builder).useCache(a1), which will call b.linkActionID(a).
   958  		// In order for that linkActionID call to compute the right action ID, all the
   959  		// dependencies of a (except a1) must have completed building and have
   960  		// recorded their build IDs.
   961  		a1.Deps = append(a1.Deps, &Action{Mode: "nop", Deps: a.Deps[1:]})
   962  		return a
   963  	})
   964  
   965  	if mode == ModeInstall || mode == ModeBuggyInstall {
   966  		a = b.installAction(a, mode)
   967  	}
   968  
   969  	return a
   970  }
   971  
   972  // installAction returns the action for installing the result of a1.
   973  func (b *Builder) installAction(a1 *Action, mode BuildMode) *Action {
   974  	// Because we overwrite the build action with the install action below,
   975  	// a1 may already be an install action fetched from the "build" cache key,
   976  	// and the caller just doesn't realize.
   977  	if strings.HasSuffix(a1.Mode, "-install") {
   978  		if a1.buggyInstall && mode == ModeInstall {
   979  			//  Congratulations! The buggy install is now a proper install.
   980  			a1.buggyInstall = false
   981  		}
   982  		return a1
   983  	}
   984  
   985  	// If there's no actual action to build a1,
   986  	// there's nothing to install either.
   987  	// This happens if a1 corresponds to reusing an already-built object.
   988  	if a1.Actor == nil {
   989  		return a1
   990  	}
   991  
   992  	p := a1.Package
   993  	return b.cacheAction(a1.Mode+"-install", p, func() *Action {
   994  		// The install deletes the temporary build result,
   995  		// so we need all other actions, both past and future,
   996  		// that attempt to depend on the build to depend instead
   997  		// on the install.
   998  
   999  		// Make a private copy of a1 (the build action),
  1000  		// no longer accessible to any other rules.
  1001  		buildAction := new(Action)
  1002  		*buildAction = *a1
  1003  
  1004  		// Overwrite a1 with the install action.
  1005  		// This takes care of updating past actions that
  1006  		// point at a1 for the build action; now they will
  1007  		// point at a1 and get the install action.
  1008  		// We also leave a1 in the action cache as the result
  1009  		// for "build", so that actions not yet created that
  1010  		// try to depend on the build will instead depend
  1011  		// on the install.
  1012  		*a1 = Action{
  1013  			Mode:    buildAction.Mode + "-install",
  1014  			Actor:   ActorFunc(BuildInstallFunc),
  1015  			Package: p,
  1016  			Objdir:  buildAction.Objdir,
  1017  			Deps:    []*Action{buildAction},
  1018  			Target:  p.Target,
  1019  			built:   p.Target,
  1020  
  1021  			buggyInstall: mode == ModeBuggyInstall,
  1022  		}
  1023  
  1024  		b.addInstallHeaderAction(a1)
  1025  		return a1
  1026  	})
  1027  }
  1028  
  1029  // addTransitiveLinkDeps adds to the link action a all packages
  1030  // that are transitive dependencies of a1.Deps.
  1031  // That is, if a is a link of package main, a1 is the compile of package main
  1032  // and a1.Deps is the actions for building packages directly imported by
  1033  // package main (what the compiler needs). The linker needs all packages
  1034  // transitively imported by the whole program; addTransitiveLinkDeps
  1035  // makes sure those are present in a.Deps.
  1036  // If shlib is non-empty, then a corresponds to the build and installation of shlib,
  1037  // so any rebuild of shlib should not be added as a dependency.
  1038  func (b *Builder) addTransitiveLinkDeps(loaderstate *modload.State, a, a1 *Action, shlib string) {
  1039  	// Expand Deps to include all built packages, for the linker.
  1040  	// Use breadth-first search to find rebuilt-for-test packages
  1041  	// before the standard ones.
  1042  	// TODO(rsc): Eliminate the standard ones from the action graph,
  1043  	// which will require doing a little bit more rebuilding.
  1044  	workq := []*Action{a1}
  1045  	haveDep := map[string]bool{}
  1046  	if a1.Package != nil {
  1047  		haveDep[a1.Package.ImportPath] = true
  1048  	}
  1049  	for i := 0; i < len(workq); i++ {
  1050  		a1 := workq[i]
  1051  		for _, a2 := range a1.Deps {
  1052  			// TODO(rsc): Find a better discriminator than the Mode strings, once the dust settles.
  1053  			if a2.Package == nil || (a2.Mode != "build-install" && a2.Mode != "build") || haveDep[a2.Package.ImportPath] {
  1054  				continue
  1055  			}
  1056  			haveDep[a2.Package.ImportPath] = true
  1057  			a.Deps = append(a.Deps, a2)
  1058  			if a2.Mode == "build-install" {
  1059  				a2 = a2.Deps[0] // walk children of "build" action
  1060  			}
  1061  			workq = append(workq, a2)
  1062  		}
  1063  	}
  1064  
  1065  	// If this is go build -linkshared, then the link depends on the shared libraries
  1066  	// in addition to the packages themselves. (The compile steps do not.)
  1067  	if cfg.BuildLinkshared {
  1068  		haveShlib := map[string]bool{shlib: true}
  1069  		for _, a1 := range a.Deps {
  1070  			p1 := a1.Package
  1071  			if p1 == nil || p1.Shlib == "" || haveShlib[filepath.Base(p1.Shlib)] {
  1072  				continue
  1073  			}
  1074  			haveShlib[filepath.Base(p1.Shlib)] = true
  1075  			// TODO(rsc): The use of ModeInstall here is suspect, but if we only do ModeBuild,
  1076  			// we'll end up building an overall library or executable that depends at runtime
  1077  			// on other libraries that are out-of-date, which is clearly not good either.
  1078  			// We call it ModeBuggyInstall to make clear that this is not right.
  1079  			a.Deps = append(a.Deps, b.linkSharedAction(loaderstate, ModeBuggyInstall, ModeBuggyInstall, p1.Shlib, nil))
  1080  		}
  1081  	}
  1082  }
  1083  
  1084  // addInstallHeaderAction adds an install header action to a, if needed.
  1085  // The action a should be an install action as generated by either
  1086  // b.CompileAction or b.LinkAction with mode=ModeInstall,
  1087  // and so a.Deps[0] is the corresponding build action.
  1088  func (b *Builder) addInstallHeaderAction(a *Action) {
  1089  	// Install header for cgo in c-archive and c-shared modes.
  1090  	p := a.Package
  1091  	if p.UsesCgo() && (cfg.BuildBuildmode == "c-archive" || cfg.BuildBuildmode == "c-shared") {
  1092  		hdrTarget := a.Target[:len(a.Target)-len(filepath.Ext(a.Target))] + ".h"
  1093  		if cfg.BuildContext.Compiler == "gccgo" && cfg.BuildO == "" {
  1094  			// For the header file, remove the "lib"
  1095  			// added by go/build, so we generate pkg.h
  1096  			// rather than libpkg.h.
  1097  			dir, file := filepath.Split(hdrTarget)
  1098  			file = strings.TrimPrefix(file, "lib")
  1099  			hdrTarget = filepath.Join(dir, file)
  1100  		}
  1101  		ah := &Action{
  1102  			Mode:    "install header",
  1103  			Package: a.Package,
  1104  			Deps:    []*Action{a.Deps[0]},
  1105  			Actor:   ActorFunc((*Builder).installHeader),
  1106  			Objdir:  a.Deps[0].Objdir,
  1107  			Target:  hdrTarget,
  1108  		}
  1109  		a.Deps = append(a.Deps, ah)
  1110  	}
  1111  }
  1112  
  1113  // buildmodeShared takes the "go build" action a1 into the building of a shared library of a1.Deps.
  1114  // That is, the input a1 represents "go build pkgs" and the result represents "go build -buildmode=shared pkgs".
  1115  func (b *Builder) buildmodeShared(loaderstate *modload.State, mode, depMode BuildMode, args []string, pkgs []*load.Package, a1 *Action) *Action {
  1116  	name, err := libname(args, pkgs)
  1117  	if err != nil {
  1118  		base.Fatalf("%v", err)
  1119  	}
  1120  	return b.linkSharedAction(loaderstate, mode, depMode, name, a1)
  1121  }
  1122  
  1123  // linkSharedAction takes a grouping action a1 corresponding to a list of built packages
  1124  // and returns an action that links them together into a shared library with the name shlib.
  1125  // If a1 is nil, shlib should be an absolute path to an existing shared library,
  1126  // and then linkSharedAction reads that library to find out the package list.
  1127  func (b *Builder) linkSharedAction(loaderstate *modload.State, mode, depMode BuildMode, shlib string, a1 *Action) *Action {
  1128  	fullShlib := shlib
  1129  	shlib = filepath.Base(shlib)
  1130  	a := b.cacheAction("build-shlib "+shlib, nil, func() *Action {
  1131  		if a1 == nil {
  1132  			// TODO(rsc): Need to find some other place to store config,
  1133  			// not in pkg directory. See golang.org/issue/22196.
  1134  			pkgs := readpkglist(loaderstate, fullShlib)
  1135  			a1 = &Action{
  1136  				Mode: "shlib packages",
  1137  			}
  1138  			for _, p := range pkgs {
  1139  				a1.Deps = append(a1.Deps, b.CompileAction(mode, depMode, p))
  1140  			}
  1141  		}
  1142  
  1143  		// Fake package to hold ldflags.
  1144  		// As usual shared libraries are a kludgy, abstraction-violating special case:
  1145  		// we let them use the flags specified for the command-line arguments.
  1146  		p := &load.Package{}
  1147  		p.Internal.CmdlinePkg = true
  1148  		p.Internal.Ldflags = load.BuildLdflags.For(p)
  1149  		p.Internal.Gccgoflags = load.BuildGccgoflags.For(p)
  1150  
  1151  		// Add implicit dependencies to pkgs list.
  1152  		// Currently buildmode=shared forces external linking mode, and
  1153  		// external linking mode forces an import of runtime/cgo (and
  1154  		// math on arm). So if it was not passed on the command line and
  1155  		// it is not present in another shared library, add it here.
  1156  		// TODO(rsc): Maybe this should only happen if "runtime" is in the original package set.
  1157  		// TODO(rsc): This should probably be changed to use load.LinkerDeps(p).
  1158  		// TODO(rsc): We don't add standard library imports for gccgo
  1159  		// because they are all always linked in anyhow.
  1160  		// Maybe load.LinkerDeps should be used and updated.
  1161  		a := &Action{
  1162  			Mode:    "go build -buildmode=shared",
  1163  			Package: p,
  1164  			Objdir:  b.NewObjdir(),
  1165  			Actor:   ActorFunc((*Builder).linkShared),
  1166  			Deps:    []*Action{a1},
  1167  		}
  1168  		a.Target = filepath.Join(a.Objdir, shlib)
  1169  		if cfg.BuildToolchainName != "gccgo" {
  1170  			add := func(a1 *Action, pkg string, force bool) {
  1171  				for _, a2 := range a1.Deps {
  1172  					if a2.Package != nil && a2.Package.ImportPath == pkg {
  1173  						return
  1174  					}
  1175  				}
  1176  				var stk load.ImportStack
  1177  				p := load.LoadPackageWithFlags(loaderstate, pkg, base.Cwd(), &stk, nil, 0)
  1178  				if p.Error != nil {
  1179  					base.Fatalf("load %s: %v", pkg, p.Error)
  1180  				}
  1181  				// Assume that if pkg (runtime/cgo or math)
  1182  				// is already accounted for in a different shared library,
  1183  				// then that shared library also contains runtime,
  1184  				// so that anything we do will depend on that library,
  1185  				// so we don't need to include pkg in our shared library.
  1186  				if force || p.Shlib == "" || filepath.Base(p.Shlib) == pkg {
  1187  					a1.Deps = append(a1.Deps, b.CompileAction(depMode, depMode, p))
  1188  				}
  1189  			}
  1190  			add(a1, "runtime/cgo", false)
  1191  			if cfg.Goarch == "arm" {
  1192  				add(a1, "math", false)
  1193  			}
  1194  
  1195  			// The linker step still needs all the usual linker deps.
  1196  			// (For example, the linker always opens runtime.a.)
  1197  			ldDeps, err := load.LinkerDeps(nil)
  1198  			if err != nil {
  1199  				base.Error(err)
  1200  			}
  1201  			for _, dep := range ldDeps {
  1202  				add(a, dep, true)
  1203  			}
  1204  		}
  1205  		b.addTransitiveLinkDeps(loaderstate, a, a1, shlib)
  1206  		return a
  1207  	})
  1208  
  1209  	// Install result.
  1210  	if (mode == ModeInstall || mode == ModeBuggyInstall) && a.Actor != nil {
  1211  		buildAction := a
  1212  
  1213  		a = b.cacheAction("install-shlib "+shlib, nil, func() *Action {
  1214  			// Determine the eventual install target.
  1215  			// The install target is root/pkg/shlib, where root is the source root
  1216  			// in which all the packages lie.
  1217  			// TODO(rsc): Perhaps this cross-root check should apply to the full
  1218  			// transitive package dependency list, not just the ones named
  1219  			// on the command line?
  1220  			pkgDir := a1.Deps[0].Package.Internal.Build.PkgTargetRoot
  1221  			for _, a2 := range a1.Deps {
  1222  				if dir := a2.Package.Internal.Build.PkgTargetRoot; dir != pkgDir {
  1223  					base.Fatalf("installing shared library: cannot use packages %s and %s from different roots %s and %s",
  1224  						a1.Deps[0].Package.ImportPath,
  1225  						a2.Package.ImportPath,
  1226  						pkgDir,
  1227  						dir)
  1228  				}
  1229  			}
  1230  			// TODO(rsc): Find out and explain here why gccgo is different.
  1231  			if cfg.BuildToolchainName == "gccgo" {
  1232  				pkgDir = filepath.Join(pkgDir, "shlibs")
  1233  			}
  1234  			target := filepath.Join(pkgDir, shlib)
  1235  
  1236  			a := &Action{
  1237  				Mode:   "go install -buildmode=shared",
  1238  				Objdir: buildAction.Objdir,
  1239  				Actor:  ActorFunc(BuildInstallFunc),
  1240  				Deps:   []*Action{buildAction},
  1241  				Target: target,
  1242  			}
  1243  			for _, a2 := range buildAction.Deps[0].Deps {
  1244  				p := a2.Package
  1245  				pkgTargetRoot := p.Internal.Build.PkgTargetRoot
  1246  				if pkgTargetRoot == "" {
  1247  					continue
  1248  				}
  1249  				a.Deps = append(a.Deps, &Action{
  1250  					Mode:    "shlibname",
  1251  					Package: p,
  1252  					Actor:   ActorFunc((*Builder).installShlibname),
  1253  					Target:  filepath.Join(pkgTargetRoot, p.ImportPath+".shlibname"),
  1254  					Deps:    []*Action{a.Deps[0]},
  1255  				})
  1256  			}
  1257  			return a
  1258  		})
  1259  	}
  1260  
  1261  	return a
  1262  }
  1263
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