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Source file src/go/build/build.go

Documentation: go/build

     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  package build
     6  
     7  import (
     8  	"bytes"
     9  	"errors"
    10  	"fmt"
    11  	"go/ast"
    12  	"go/doc"
    13  	"go/token"
    14  	exec "internal/execabs"
    15  	"internal/goroot"
    16  	"internal/goversion"
    17  	"io"
    18  	"io/fs"
    19  	"io/ioutil"
    20  	"os"
    21  	pathpkg "path"
    22  	"path/filepath"
    23  	"runtime"
    24  	"sort"
    25  	"strconv"
    26  	"strings"
    27  	"unicode"
    28  	"unicode/utf8"
    29  )
    30  
    31  // A Context specifies the supporting context for a build.
    32  type Context struct {
    33  	GOARCH string // target architecture
    34  	GOOS   string // target operating system
    35  	GOROOT string // Go root
    36  	GOPATH string // Go path
    37  
    38  	// Dir is the caller's working directory, or the empty string to use
    39  	// the current directory of the running process. In module mode, this is used
    40  	// to locate the main module.
    41  	//
    42  	// If Dir is non-empty, directories passed to Import and ImportDir must
    43  	// be absolute.
    44  	Dir string
    45  
    46  	CgoEnabled  bool   // whether cgo files are included
    47  	UseAllFiles bool   // use files regardless of +build lines, file names
    48  	Compiler    string // compiler to assume when computing target paths
    49  
    50  	// The build and release tags specify build constraints
    51  	// that should be considered satisfied when processing +build lines.
    52  	// Clients creating a new context may customize BuildTags, which
    53  	// defaults to empty, but it is usually an error to customize ReleaseTags,
    54  	// which defaults to the list of Go releases the current release is compatible with.
    55  	// BuildTags is not set for the Default build Context.
    56  	// In addition to the BuildTags and ReleaseTags, build constraints
    57  	// consider the values of GOARCH and GOOS as satisfied tags.
    58  	// The last element in ReleaseTags is assumed to be the current release.
    59  	BuildTags   []string
    60  	ReleaseTags []string
    61  
    62  	// The install suffix specifies a suffix to use in the name of the installation
    63  	// directory. By default it is empty, but custom builds that need to keep
    64  	// their outputs separate can set InstallSuffix to do so. For example, when
    65  	// using the race detector, the go command uses InstallSuffix = "race", so
    66  	// that on a Linux/386 system, packages are written to a directory named
    67  	// "linux_386_race" instead of the usual "linux_386".
    68  	InstallSuffix string
    69  
    70  	// By default, Import uses the operating system's file system calls
    71  	// to read directories and files. To read from other sources,
    72  	// callers can set the following functions. They all have default
    73  	// behaviors that use the local file system, so clients need only set
    74  	// the functions whose behaviors they wish to change.
    75  
    76  	// JoinPath joins the sequence of path fragments into a single path.
    77  	// If JoinPath is nil, Import uses filepath.Join.
    78  	JoinPath func(elem ...string) string
    79  
    80  	// SplitPathList splits the path list into a slice of individual paths.
    81  	// If SplitPathList is nil, Import uses filepath.SplitList.
    82  	SplitPathList func(list string) []string
    83  
    84  	// IsAbsPath reports whether path is an absolute path.
    85  	// If IsAbsPath is nil, Import uses filepath.IsAbs.
    86  	IsAbsPath func(path string) bool
    87  
    88  	// IsDir reports whether the path names a directory.
    89  	// If IsDir is nil, Import calls os.Stat and uses the result's IsDir method.
    90  	IsDir func(path string) bool
    91  
    92  	// HasSubdir reports whether dir is lexically a subdirectory of
    93  	// root, perhaps multiple levels below. It does not try to check
    94  	// whether dir exists.
    95  	// If so, HasSubdir sets rel to a slash-separated path that
    96  	// can be joined to root to produce a path equivalent to dir.
    97  	// If HasSubdir is nil, Import uses an implementation built on
    98  	// filepath.EvalSymlinks.
    99  	HasSubdir func(root, dir string) (rel string, ok bool)
   100  
   101  	// ReadDir returns a slice of fs.FileInfo, sorted by Name,
   102  	// describing the content of the named directory.
   103  	// If ReadDir is nil, Import uses ioutil.ReadDir.
   104  	ReadDir func(dir string) ([]fs.FileInfo, error)
   105  
   106  	// OpenFile opens a file (not a directory) for reading.
   107  	// If OpenFile is nil, Import uses os.Open.
   108  	OpenFile func(path string) (io.ReadCloser, error)
   109  }
   110  
   111  // joinPath calls ctxt.JoinPath (if not nil) or else filepath.Join.
   112  func (ctxt *Context) joinPath(elem ...string) string {
   113  	if f := ctxt.JoinPath; f != nil {
   114  		return f(elem...)
   115  	}
   116  	return filepath.Join(elem...)
   117  }
   118  
   119  // splitPathList calls ctxt.SplitPathList (if not nil) or else filepath.SplitList.
   120  func (ctxt *Context) splitPathList(s string) []string {
   121  	if f := ctxt.SplitPathList; f != nil {
   122  		return f(s)
   123  	}
   124  	return filepath.SplitList(s)
   125  }
   126  
   127  // isAbsPath calls ctxt.IsAbsPath (if not nil) or else filepath.IsAbs.
   128  func (ctxt *Context) isAbsPath(path string) bool {
   129  	if f := ctxt.IsAbsPath; f != nil {
   130  		return f(path)
   131  	}
   132  	return filepath.IsAbs(path)
   133  }
   134  
   135  // isDir calls ctxt.IsDir (if not nil) or else uses os.Stat.
   136  func (ctxt *Context) isDir(path string) bool {
   137  	if f := ctxt.IsDir; f != nil {
   138  		return f(path)
   139  	}
   140  	fi, err := os.Stat(path)
   141  	return err == nil && fi.IsDir()
   142  }
   143  
   144  // hasSubdir calls ctxt.HasSubdir (if not nil) or else uses
   145  // the local file system to answer the question.
   146  func (ctxt *Context) hasSubdir(root, dir string) (rel string, ok bool) {
   147  	if f := ctxt.HasSubdir; f != nil {
   148  		return f(root, dir)
   149  	}
   150  
   151  	// Try using paths we received.
   152  	if rel, ok = hasSubdir(root, dir); ok {
   153  		return
   154  	}
   155  
   156  	// Try expanding symlinks and comparing
   157  	// expanded against unexpanded and
   158  	// expanded against expanded.
   159  	rootSym, _ := filepath.EvalSymlinks(root)
   160  	dirSym, _ := filepath.EvalSymlinks(dir)
   161  
   162  	if rel, ok = hasSubdir(rootSym, dir); ok {
   163  		return
   164  	}
   165  	if rel, ok = hasSubdir(root, dirSym); ok {
   166  		return
   167  	}
   168  	return hasSubdir(rootSym, dirSym)
   169  }
   170  
   171  // hasSubdir reports if dir is within root by performing lexical analysis only.
   172  func hasSubdir(root, dir string) (rel string, ok bool) {
   173  	const sep = string(filepath.Separator)
   174  	root = filepath.Clean(root)
   175  	if !strings.HasSuffix(root, sep) {
   176  		root += sep
   177  	}
   178  	dir = filepath.Clean(dir)
   179  	if !strings.HasPrefix(dir, root) {
   180  		return "", false
   181  	}
   182  	return filepath.ToSlash(dir[len(root):]), true
   183  }
   184  
   185  // readDir calls ctxt.ReadDir (if not nil) or else ioutil.ReadDir.
   186  func (ctxt *Context) readDir(path string) ([]fs.FileInfo, error) {
   187  	if f := ctxt.ReadDir; f != nil {
   188  		return f(path)
   189  	}
   190  	return ioutil.ReadDir(path)
   191  }
   192  
   193  // openFile calls ctxt.OpenFile (if not nil) or else os.Open.
   194  func (ctxt *Context) openFile(path string) (io.ReadCloser, error) {
   195  	if fn := ctxt.OpenFile; fn != nil {
   196  		return fn(path)
   197  	}
   198  
   199  	f, err := os.Open(path)
   200  	if err != nil {
   201  		return nil, err // nil interface
   202  	}
   203  	return f, nil
   204  }
   205  
   206  // isFile determines whether path is a file by trying to open it.
   207  // It reuses openFile instead of adding another function to the
   208  // list in Context.
   209  func (ctxt *Context) isFile(path string) bool {
   210  	f, err := ctxt.openFile(path)
   211  	if err != nil {
   212  		return false
   213  	}
   214  	f.Close()
   215  	return true
   216  }
   217  
   218  // gopath returns the list of Go path directories.
   219  func (ctxt *Context) gopath() []string {
   220  	var all []string
   221  	for _, p := range ctxt.splitPathList(ctxt.GOPATH) {
   222  		if p == "" || p == ctxt.GOROOT {
   223  			// Empty paths are uninteresting.
   224  			// If the path is the GOROOT, ignore it.
   225  			// People sometimes set GOPATH=$GOROOT.
   226  			// Do not get confused by this common mistake.
   227  			continue
   228  		}
   229  		if strings.HasPrefix(p, "~") {
   230  			// Path segments starting with ~ on Unix are almost always
   231  			// users who have incorrectly quoted ~ while setting GOPATH,
   232  			// preventing it from expanding to $HOME.
   233  			// The situation is made more confusing by the fact that
   234  			// bash allows quoted ~ in $PATH (most shells do not).
   235  			// Do not get confused by this, and do not try to use the path.
   236  			// It does not exist, and printing errors about it confuses
   237  			// those users even more, because they think "sure ~ exists!".
   238  			// The go command diagnoses this situation and prints a
   239  			// useful error.
   240  			// On Windows, ~ is used in short names, such as c:\progra~1
   241  			// for c:\program files.
   242  			continue
   243  		}
   244  		all = append(all, p)
   245  	}
   246  	return all
   247  }
   248  
   249  // SrcDirs returns a list of package source root directories.
   250  // It draws from the current Go root and Go path but omits directories
   251  // that do not exist.
   252  func (ctxt *Context) SrcDirs() []string {
   253  	var all []string
   254  	if ctxt.GOROOT != "" && ctxt.Compiler != "gccgo" {
   255  		dir := ctxt.joinPath(ctxt.GOROOT, "src")
   256  		if ctxt.isDir(dir) {
   257  			all = append(all, dir)
   258  		}
   259  	}
   260  	for _, p := range ctxt.gopath() {
   261  		dir := ctxt.joinPath(p, "src")
   262  		if ctxt.isDir(dir) {
   263  			all = append(all, dir)
   264  		}
   265  	}
   266  	return all
   267  }
   268  
   269  // Default is the default Context for builds.
   270  // It uses the GOARCH, GOOS, GOROOT, and GOPATH environment variables
   271  // if set, or else the compiled code's GOARCH, GOOS, and GOROOT.
   272  var Default Context = defaultContext()
   273  
   274  func defaultGOPATH() string {
   275  	env := "HOME"
   276  	if runtime.GOOS == "windows" {
   277  		env = "USERPROFILE"
   278  	} else if runtime.GOOS == "plan9" {
   279  		env = "home"
   280  	}
   281  	if home := os.Getenv(env); home != "" {
   282  		def := filepath.Join(home, "go")
   283  		if filepath.Clean(def) == filepath.Clean(runtime.GOROOT()) {
   284  			// Don't set the default GOPATH to GOROOT,
   285  			// as that will trigger warnings from the go tool.
   286  			return ""
   287  		}
   288  		return def
   289  	}
   290  	return ""
   291  }
   292  
   293  var defaultReleaseTags []string
   294  
   295  func defaultContext() Context {
   296  	var c Context
   297  
   298  	c.GOARCH = envOr("GOARCH", runtime.GOARCH)
   299  	c.GOOS = envOr("GOOS", runtime.GOOS)
   300  	c.GOROOT = pathpkg.Clean(runtime.GOROOT())
   301  	c.GOPATH = envOr("GOPATH", defaultGOPATH())
   302  	c.Compiler = runtime.Compiler
   303  
   304  	// Each major Go release in the Go 1.x series adds a new
   305  	// "go1.x" release tag. That is, the go1.x tag is present in
   306  	// all releases >= Go 1.x. Code that requires Go 1.x or later
   307  	// should say "+build go1.x", and code that should only be
   308  	// built before Go 1.x (perhaps it is the stub to use in that
   309  	// case) should say "+build !go1.x".
   310  	// The last element in ReleaseTags is the current release.
   311  	for i := 1; i <= goversion.Version; i++ {
   312  		c.ReleaseTags = append(c.ReleaseTags, "go1."+strconv.Itoa(i))
   313  	}
   314  
   315  	defaultReleaseTags = append([]string{}, c.ReleaseTags...) // our own private copy
   316  
   317  	env := os.Getenv("CGO_ENABLED")
   318  	if env == "" {
   319  		env = defaultCGO_ENABLED
   320  	}
   321  	switch env {
   322  	case "1":
   323  		c.CgoEnabled = true
   324  	case "0":
   325  		c.CgoEnabled = false
   326  	default:
   327  		// cgo must be explicitly enabled for cross compilation builds
   328  		if runtime.GOARCH == c.GOARCH && runtime.GOOS == c.GOOS {
   329  			c.CgoEnabled = cgoEnabled[c.GOOS+"/"+c.GOARCH]
   330  			break
   331  		}
   332  		c.CgoEnabled = false
   333  	}
   334  
   335  	return c
   336  }
   337  
   338  func envOr(name, def string) string {
   339  	s := os.Getenv(name)
   340  	if s == "" {
   341  		return def
   342  	}
   343  	return s
   344  }
   345  
   346  // An ImportMode controls the behavior of the Import method.
   347  type ImportMode uint
   348  
   349  const (
   350  	// If FindOnly is set, Import stops after locating the directory
   351  	// that should contain the sources for a package. It does not
   352  	// read any files in the directory.
   353  	FindOnly ImportMode = 1 << iota
   354  
   355  	// If AllowBinary is set, Import can be satisfied by a compiled
   356  	// package object without corresponding sources.
   357  	//
   358  	// Deprecated:
   359  	// The supported way to create a compiled-only package is to
   360  	// write source code containing a //go:binary-only-package comment at
   361  	// the top of the file. Such a package will be recognized
   362  	// regardless of this flag setting (because it has source code)
   363  	// and will have BinaryOnly set to true in the returned Package.
   364  	AllowBinary
   365  
   366  	// If ImportComment is set, parse import comments on package statements.
   367  	// Import returns an error if it finds a comment it cannot understand
   368  	// or finds conflicting comments in multiple source files.
   369  	// See golang.org/s/go14customimport for more information.
   370  	ImportComment
   371  
   372  	// By default, Import searches vendor directories
   373  	// that apply in the given source directory before searching
   374  	// the GOROOT and GOPATH roots.
   375  	// If an Import finds and returns a package using a vendor
   376  	// directory, the resulting ImportPath is the complete path
   377  	// to the package, including the path elements leading up
   378  	// to and including "vendor".
   379  	// For example, if Import("y", "x/subdir", 0) finds
   380  	// "x/vendor/y", the returned package's ImportPath is "x/vendor/y",
   381  	// not plain "y".
   382  	// See golang.org/s/go15vendor for more information.
   383  	//
   384  	// Setting IgnoreVendor ignores vendor directories.
   385  	//
   386  	// In contrast to the package's ImportPath,
   387  	// the returned package's Imports, TestImports, and XTestImports
   388  	// are always the exact import paths from the source files:
   389  	// Import makes no attempt to resolve or check those paths.
   390  	IgnoreVendor
   391  )
   392  
   393  // A Package describes the Go package found in a directory.
   394  type Package struct {
   395  	Dir           string   // directory containing package sources
   396  	Name          string   // package name
   397  	ImportComment string   // path in import comment on package statement
   398  	Doc           string   // documentation synopsis
   399  	ImportPath    string   // import path of package ("" if unknown)
   400  	Root          string   // root of Go tree where this package lives
   401  	SrcRoot       string   // package source root directory ("" if unknown)
   402  	PkgRoot       string   // package install root directory ("" if unknown)
   403  	PkgTargetRoot string   // architecture dependent install root directory ("" if unknown)
   404  	BinDir        string   // command install directory ("" if unknown)
   405  	Goroot        bool     // package found in Go root
   406  	PkgObj        string   // installed .a file
   407  	AllTags       []string // tags that can influence file selection in this directory
   408  	ConflictDir   string   // this directory shadows Dir in $GOPATH
   409  	BinaryOnly    bool     // cannot be rebuilt from source (has //go:binary-only-package comment)
   410  
   411  	// Source files
   412  	GoFiles           []string // .go source files (excluding CgoFiles, TestGoFiles, XTestGoFiles)
   413  	CgoFiles          []string // .go source files that import "C"
   414  	IgnoredGoFiles    []string // .go source files ignored for this build (including ignored _test.go files)
   415  	InvalidGoFiles    []string // .go source files with detected problems (parse error, wrong package name, and so on)
   416  	IgnoredOtherFiles []string // non-.go source files ignored for this build
   417  	CFiles            []string // .c source files
   418  	CXXFiles          []string // .cc, .cpp and .cxx source files
   419  	MFiles            []string // .m (Objective-C) source files
   420  	HFiles            []string // .h, .hh, .hpp and .hxx source files
   421  	FFiles            []string // .f, .F, .for and .f90 Fortran source files
   422  	SFiles            []string // .s source files
   423  	SwigFiles         []string // .swig files
   424  	SwigCXXFiles      []string // .swigcxx files
   425  	SysoFiles         []string // .syso system object files to add to archive
   426  
   427  	// Cgo directives
   428  	CgoCFLAGS    []string // Cgo CFLAGS directives
   429  	CgoCPPFLAGS  []string // Cgo CPPFLAGS directives
   430  	CgoCXXFLAGS  []string // Cgo CXXFLAGS directives
   431  	CgoFFLAGS    []string // Cgo FFLAGS directives
   432  	CgoLDFLAGS   []string // Cgo LDFLAGS directives
   433  	CgoPkgConfig []string // Cgo pkg-config directives
   434  
   435  	// Test information
   436  	TestGoFiles  []string // _test.go files in package
   437  	XTestGoFiles []string // _test.go files outside package
   438  
   439  	// Dependency information
   440  	Imports        []string                    // import paths from GoFiles, CgoFiles
   441  	ImportPos      map[string][]token.Position // line information for Imports
   442  	TestImports    []string                    // import paths from TestGoFiles
   443  	TestImportPos  map[string][]token.Position // line information for TestImports
   444  	XTestImports   []string                    // import paths from XTestGoFiles
   445  	XTestImportPos map[string][]token.Position // line information for XTestImports
   446  
   447  	// //go:embed patterns found in Go source files
   448  	// For example, if a source file says
   449  	//	//go:embed a* b.c
   450  	// then the list will contain those two strings as separate entries.
   451  	// (See package embed for more details about //go:embed.)
   452  	EmbedPatterns        []string                    // patterns from GoFiles, CgoFiles
   453  	EmbedPatternPos      map[string][]token.Position // line information for EmbedPatterns
   454  	TestEmbedPatterns    []string                    // patterns from TestGoFiles
   455  	TestEmbedPatternPos  map[string][]token.Position // line information for TestEmbedPatterns
   456  	XTestEmbedPatterns   []string                    // patterns from XTestGoFiles
   457  	XTestEmbedPatternPos map[string][]token.Position // line information for XTestEmbedPatternPos
   458  }
   459  
   460  // IsCommand reports whether the package is considered a
   461  // command to be installed (not just a library).
   462  // Packages named "main" are treated as commands.
   463  func (p *Package) IsCommand() bool {
   464  	return p.Name == "main"
   465  }
   466  
   467  // ImportDir is like Import but processes the Go package found in
   468  // the named directory.
   469  func (ctxt *Context) ImportDir(dir string, mode ImportMode) (*Package, error) {
   470  	return ctxt.Import(".", dir, mode)
   471  }
   472  
   473  // NoGoError is the error used by Import to describe a directory
   474  // containing no buildable Go source files. (It may still contain
   475  // test files, files hidden by build tags, and so on.)
   476  type NoGoError struct {
   477  	Dir string
   478  }
   479  
   480  func (e *NoGoError) Error() string {
   481  	return "no buildable Go source files in " + e.Dir
   482  }
   483  
   484  // MultiplePackageError describes a directory containing
   485  // multiple buildable Go source files for multiple packages.
   486  type MultiplePackageError struct {
   487  	Dir      string   // directory containing files
   488  	Packages []string // package names found
   489  	Files    []string // corresponding files: Files[i] declares package Packages[i]
   490  }
   491  
   492  func (e *MultiplePackageError) Error() string {
   493  	// Error string limited to two entries for compatibility.
   494  	return fmt.Sprintf("found packages %s (%s) and %s (%s) in %s", e.Packages[0], e.Files[0], e.Packages[1], e.Files[1], e.Dir)
   495  }
   496  
   497  func nameExt(name string) string {
   498  	i := strings.LastIndex(name, ".")
   499  	if i < 0 {
   500  		return ""
   501  	}
   502  	return name[i:]
   503  }
   504  
   505  // Import returns details about the Go package named by the import path,
   506  // interpreting local import paths relative to the srcDir directory.
   507  // If the path is a local import path naming a package that can be imported
   508  // using a standard import path, the returned package will set p.ImportPath
   509  // to that path.
   510  //
   511  // In the directory containing the package, .go, .c, .h, and .s files are
   512  // considered part of the package except for:
   513  //
   514  //	- .go files in package documentation
   515  //	- files starting with _ or . (likely editor temporary files)
   516  //	- files with build constraints not satisfied by the context
   517  //
   518  // If an error occurs, Import returns a non-nil error and a non-nil
   519  // *Package containing partial information.
   520  //
   521  func (ctxt *Context) Import(path string, srcDir string, mode ImportMode) (*Package, error) {
   522  	p := &Package{
   523  		ImportPath: path,
   524  	}
   525  	if path == "" {
   526  		return p, fmt.Errorf("import %q: invalid import path", path)
   527  	}
   528  
   529  	var pkgtargetroot string
   530  	var pkga string
   531  	var pkgerr error
   532  	suffix := ""
   533  	if ctxt.InstallSuffix != "" {
   534  		suffix = "_" + ctxt.InstallSuffix
   535  	}
   536  	switch ctxt.Compiler {
   537  	case "gccgo":
   538  		pkgtargetroot = "pkg/gccgo_" + ctxt.GOOS + "_" + ctxt.GOARCH + suffix
   539  	case "gc":
   540  		pkgtargetroot = "pkg/" + ctxt.GOOS + "_" + ctxt.GOARCH + suffix
   541  	default:
   542  		// Save error for end of function.
   543  		pkgerr = fmt.Errorf("import %q: unknown compiler %q", path, ctxt.Compiler)
   544  	}
   545  	setPkga := func() {
   546  		switch ctxt.Compiler {
   547  		case "gccgo":
   548  			dir, elem := pathpkg.Split(p.ImportPath)
   549  			pkga = pkgtargetroot + "/" + dir + "lib" + elem + ".a"
   550  		case "gc":
   551  			pkga = pkgtargetroot + "/" + p.ImportPath + ".a"
   552  		}
   553  	}
   554  	setPkga()
   555  
   556  	binaryOnly := false
   557  	if IsLocalImport(path) {
   558  		pkga = "" // local imports have no installed path
   559  		if srcDir == "" {
   560  			return p, fmt.Errorf("import %q: import relative to unknown directory", path)
   561  		}
   562  		if !ctxt.isAbsPath(path) {
   563  			p.Dir = ctxt.joinPath(srcDir, path)
   564  		}
   565  		// p.Dir directory may or may not exist. Gather partial information first, check if it exists later.
   566  		// Determine canonical import path, if any.
   567  		// Exclude results where the import path would include /testdata/.
   568  		inTestdata := func(sub string) bool {
   569  			return strings.Contains(sub, "/testdata/") || strings.HasSuffix(sub, "/testdata") || strings.HasPrefix(sub, "testdata/") || sub == "testdata"
   570  		}
   571  		if ctxt.GOROOT != "" {
   572  			root := ctxt.joinPath(ctxt.GOROOT, "src")
   573  			if sub, ok := ctxt.hasSubdir(root, p.Dir); ok && !inTestdata(sub) {
   574  				p.Goroot = true
   575  				p.ImportPath = sub
   576  				p.Root = ctxt.GOROOT
   577  				setPkga() // p.ImportPath changed
   578  				goto Found
   579  			}
   580  		}
   581  		all := ctxt.gopath()
   582  		for i, root := range all {
   583  			rootsrc := ctxt.joinPath(root, "src")
   584  			if sub, ok := ctxt.hasSubdir(rootsrc, p.Dir); ok && !inTestdata(sub) {
   585  				// We found a potential import path for dir,
   586  				// but check that using it wouldn't find something
   587  				// else first.
   588  				if ctxt.GOROOT != "" && ctxt.Compiler != "gccgo" {
   589  					if dir := ctxt.joinPath(ctxt.GOROOT, "src", sub); ctxt.isDir(dir) {
   590  						p.ConflictDir = dir
   591  						goto Found
   592  					}
   593  				}
   594  				for _, earlyRoot := range all[:i] {
   595  					if dir := ctxt.joinPath(earlyRoot, "src", sub); ctxt.isDir(dir) {
   596  						p.ConflictDir = dir
   597  						goto Found
   598  					}
   599  				}
   600  
   601  				// sub would not name some other directory instead of this one.
   602  				// Record it.
   603  				p.ImportPath = sub
   604  				p.Root = root
   605  				setPkga() // p.ImportPath changed
   606  				goto Found
   607  			}
   608  		}
   609  		// It's okay that we didn't find a root containing dir.
   610  		// Keep going with the information we have.
   611  	} else {
   612  		if strings.HasPrefix(path, "/") {
   613  			return p, fmt.Errorf("import %q: cannot import absolute path", path)
   614  		}
   615  
   616  		if err := ctxt.importGo(p, path, srcDir, mode); err == nil {
   617  			goto Found
   618  		} else if err != errNoModules {
   619  			return p, err
   620  		}
   621  
   622  		gopath := ctxt.gopath() // needed twice below; avoid computing many times
   623  
   624  		// tried records the location of unsuccessful package lookups
   625  		var tried struct {
   626  			vendor []string
   627  			goroot string
   628  			gopath []string
   629  		}
   630  
   631  		// Vendor directories get first chance to satisfy import.
   632  		if mode&IgnoreVendor == 0 && srcDir != "" {
   633  			searchVendor := func(root string, isGoroot bool) bool {
   634  				sub, ok := ctxt.hasSubdir(root, srcDir)
   635  				if !ok || !strings.HasPrefix(sub, "src/") || strings.Contains(sub, "/testdata/") {
   636  					return false
   637  				}
   638  				for {
   639  					vendor := ctxt.joinPath(root, sub, "vendor")
   640  					if ctxt.isDir(vendor) {
   641  						dir := ctxt.joinPath(vendor, path)
   642  						if ctxt.isDir(dir) && hasGoFiles(ctxt, dir) {
   643  							p.Dir = dir
   644  							p.ImportPath = strings.TrimPrefix(pathpkg.Join(sub, "vendor", path), "src/")
   645  							p.Goroot = isGoroot
   646  							p.Root = root
   647  							setPkga() // p.ImportPath changed
   648  							return true
   649  						}
   650  						tried.vendor = append(tried.vendor, dir)
   651  					}
   652  					i := strings.LastIndex(sub, "/")
   653  					if i < 0 {
   654  						break
   655  					}
   656  					sub = sub[:i]
   657  				}
   658  				return false
   659  			}
   660  			if ctxt.Compiler != "gccgo" && searchVendor(ctxt.GOROOT, true) {
   661  				goto Found
   662  			}
   663  			for _, root := range gopath {
   664  				if searchVendor(root, false) {
   665  					goto Found
   666  				}
   667  			}
   668  		}
   669  
   670  		// Determine directory from import path.
   671  		if ctxt.GOROOT != "" {
   672  			// If the package path starts with "vendor/", only search GOROOT before
   673  			// GOPATH if the importer is also within GOROOT. That way, if the user has
   674  			// vendored in a package that is subsequently included in the standard
   675  			// distribution, they'll continue to pick up their own vendored copy.
   676  			gorootFirst := srcDir == "" || !strings.HasPrefix(path, "vendor/")
   677  			if !gorootFirst {
   678  				_, gorootFirst = ctxt.hasSubdir(ctxt.GOROOT, srcDir)
   679  			}
   680  			if gorootFirst {
   681  				dir := ctxt.joinPath(ctxt.GOROOT, "src", path)
   682  				if ctxt.Compiler != "gccgo" {
   683  					isDir := ctxt.isDir(dir)
   684  					binaryOnly = !isDir && mode&AllowBinary != 0 && pkga != "" && ctxt.isFile(ctxt.joinPath(ctxt.GOROOT, pkga))
   685  					if isDir || binaryOnly {
   686  						p.Dir = dir
   687  						p.Goroot = true
   688  						p.Root = ctxt.GOROOT
   689  						goto Found
   690  					}
   691  				}
   692  				tried.goroot = dir
   693  			}
   694  		}
   695  		if ctxt.Compiler == "gccgo" && goroot.IsStandardPackage(ctxt.GOROOT, ctxt.Compiler, path) {
   696  			p.Dir = ctxt.joinPath(ctxt.GOROOT, "src", path)
   697  			p.Goroot = true
   698  			p.Root = ctxt.GOROOT
   699  			goto Found
   700  		}
   701  		for _, root := range gopath {
   702  			dir := ctxt.joinPath(root, "src", path)
   703  			isDir := ctxt.isDir(dir)
   704  			binaryOnly = !isDir && mode&AllowBinary != 0 && pkga != "" && ctxt.isFile(ctxt.joinPath(root, pkga))
   705  			if isDir || binaryOnly {
   706  				p.Dir = dir
   707  				p.Root = root
   708  				goto Found
   709  			}
   710  			tried.gopath = append(tried.gopath, dir)
   711  		}
   712  
   713  		// If we tried GOPATH first due to a "vendor/" prefix, fall back to GOPATH.
   714  		// That way, the user can still get useful results from 'go list' for
   715  		// standard-vendored paths passed on the command line.
   716  		if ctxt.GOROOT != "" && tried.goroot == "" {
   717  			dir := ctxt.joinPath(ctxt.GOROOT, "src", path)
   718  			if ctxt.Compiler != "gccgo" {
   719  				isDir := ctxt.isDir(dir)
   720  				binaryOnly = !isDir && mode&AllowBinary != 0 && pkga != "" && ctxt.isFile(ctxt.joinPath(ctxt.GOROOT, pkga))
   721  				if isDir || binaryOnly {
   722  					p.Dir = dir
   723  					p.Goroot = true
   724  					p.Root = ctxt.GOROOT
   725  					goto Found
   726  				}
   727  			}
   728  			tried.goroot = dir
   729  		}
   730  
   731  		// package was not found
   732  		var paths []string
   733  		format := "\t%s (vendor tree)"
   734  		for _, dir := range tried.vendor {
   735  			paths = append(paths, fmt.Sprintf(format, dir))
   736  			format = "\t%s"
   737  		}
   738  		if tried.goroot != "" {
   739  			paths = append(paths, fmt.Sprintf("\t%s (from $GOROOT)", tried.goroot))
   740  		} else {
   741  			paths = append(paths, "\t($GOROOT not set)")
   742  		}
   743  		format = "\t%s (from $GOPATH)"
   744  		for _, dir := range tried.gopath {
   745  			paths = append(paths, fmt.Sprintf(format, dir))
   746  			format = "\t%s"
   747  		}
   748  		if len(tried.gopath) == 0 {
   749  			paths = append(paths, "\t($GOPATH not set. For more details see: 'go help gopath')")
   750  		}
   751  		return p, fmt.Errorf("cannot find package %q in any of:\n%s", path, strings.Join(paths, "\n"))
   752  	}
   753  
   754  Found:
   755  	if p.Root != "" {
   756  		p.SrcRoot = ctxt.joinPath(p.Root, "src")
   757  		p.PkgRoot = ctxt.joinPath(p.Root, "pkg")
   758  		p.BinDir = ctxt.joinPath(p.Root, "bin")
   759  		if pkga != "" {
   760  			p.PkgTargetRoot = ctxt.joinPath(p.Root, pkgtargetroot)
   761  			p.PkgObj = ctxt.joinPath(p.Root, pkga)
   762  		}
   763  	}
   764  
   765  	// If it's a local import path, by the time we get here, we still haven't checked
   766  	// that p.Dir directory exists. This is the right time to do that check.
   767  	// We can't do it earlier, because we want to gather partial information for the
   768  	// non-nil *Package returned when an error occurs.
   769  	// We need to do this before we return early on FindOnly flag.
   770  	if IsLocalImport(path) && !ctxt.isDir(p.Dir) {
   771  		if ctxt.Compiler == "gccgo" && p.Goroot {
   772  			// gccgo has no sources for GOROOT packages.
   773  			return p, nil
   774  		}
   775  
   776  		// package was not found
   777  		return p, fmt.Errorf("cannot find package %q in:\n\t%s", path, p.Dir)
   778  	}
   779  
   780  	if mode&FindOnly != 0 {
   781  		return p, pkgerr
   782  	}
   783  	if binaryOnly && (mode&AllowBinary) != 0 {
   784  		return p, pkgerr
   785  	}
   786  
   787  	if ctxt.Compiler == "gccgo" && p.Goroot {
   788  		// gccgo has no sources for GOROOT packages.
   789  		return p, nil
   790  	}
   791  
   792  	dirs, err := ctxt.readDir(p.Dir)
   793  	if err != nil {
   794  		return p, err
   795  	}
   796  
   797  	var badGoError error
   798  	var Sfiles []string // files with ".S"(capital S)/.sx(capital s equivalent for case insensitive filesystems)
   799  	var firstFile, firstCommentFile string
   800  	embedPos := make(map[string][]token.Position)
   801  	testEmbedPos := make(map[string][]token.Position)
   802  	xTestEmbedPos := make(map[string][]token.Position)
   803  	importPos := make(map[string][]token.Position)
   804  	testImportPos := make(map[string][]token.Position)
   805  	xTestImportPos := make(map[string][]token.Position)
   806  	allTags := make(map[string]bool)
   807  	fset := token.NewFileSet()
   808  	for _, d := range dirs {
   809  		if d.IsDir() {
   810  			continue
   811  		}
   812  		if d.Mode()&fs.ModeSymlink != 0 {
   813  			if ctxt.isDir(ctxt.joinPath(p.Dir, d.Name())) {
   814  				// Symlinks to directories are not source files.
   815  				continue
   816  			}
   817  		}
   818  
   819  		name := d.Name()
   820  		ext := nameExt(name)
   821  
   822  		badFile := func(err error) {
   823  			if badGoError == nil {
   824  				badGoError = err
   825  			}
   826  			p.InvalidGoFiles = append(p.InvalidGoFiles, name)
   827  		}
   828  
   829  		info, err := ctxt.matchFile(p.Dir, name, allTags, &p.BinaryOnly, fset)
   830  		if err != nil {
   831  			badFile(err)
   832  			continue
   833  		}
   834  		if info == nil {
   835  			if strings.HasPrefix(name, "_") || strings.HasPrefix(name, ".") {
   836  				// not due to build constraints - don't report
   837  			} else if ext == ".go" {
   838  				p.IgnoredGoFiles = append(p.IgnoredGoFiles, name)
   839  			} else if fileListForExt(p, ext) != nil {
   840  				p.IgnoredOtherFiles = append(p.IgnoredOtherFiles, name)
   841  			}
   842  			continue
   843  		}
   844  		data, filename := info.header, info.name
   845  
   846  		// Going to save the file. For non-Go files, can stop here.
   847  		switch ext {
   848  		case ".go":
   849  			// keep going
   850  		case ".S", ".sx":
   851  			// special case for cgo, handled at end
   852  			Sfiles = append(Sfiles, name)
   853  			continue
   854  		default:
   855  			if list := fileListForExt(p, ext); list != nil {
   856  				*list = append(*list, name)
   857  			}
   858  			continue
   859  		}
   860  
   861  		if info.parseErr != nil {
   862  			badFile(info.parseErr)
   863  			continue
   864  		}
   865  		pf := info.parsed
   866  
   867  		pkg := pf.Name.Name
   868  		if pkg == "documentation" {
   869  			p.IgnoredGoFiles = append(p.IgnoredGoFiles, name)
   870  			continue
   871  		}
   872  
   873  		isTest := strings.HasSuffix(name, "_test.go")
   874  		isXTest := false
   875  		if isTest && strings.HasSuffix(pkg, "_test") {
   876  			isXTest = true
   877  			pkg = pkg[:len(pkg)-len("_test")]
   878  		}
   879  
   880  		if p.Name == "" {
   881  			p.Name = pkg
   882  			firstFile = name
   883  		} else if pkg != p.Name {
   884  			badFile(&MultiplePackageError{
   885  				Dir:      p.Dir,
   886  				Packages: []string{p.Name, pkg},
   887  				Files:    []string{firstFile, name},
   888  			})
   889  			p.InvalidGoFiles = append(p.InvalidGoFiles, name)
   890  		}
   891  		// Grab the first package comment as docs, provided it is not from a test file.
   892  		if pf.Doc != nil && p.Doc == "" && !isTest && !isXTest {
   893  			p.Doc = doc.Synopsis(pf.Doc.Text())
   894  		}
   895  
   896  		if mode&ImportComment != 0 {
   897  			qcom, line := findImportComment(data)
   898  			if line != 0 {
   899  				com, err := strconv.Unquote(qcom)
   900  				if err != nil {
   901  					badFile(fmt.Errorf("%s:%d: cannot parse import comment", filename, line))
   902  				} else if p.ImportComment == "" {
   903  					p.ImportComment = com
   904  					firstCommentFile = name
   905  				} else if p.ImportComment != com {
   906  					badFile(fmt.Errorf("found import comments %q (%s) and %q (%s) in %s", p.ImportComment, firstCommentFile, com, name, p.Dir))
   907  				}
   908  			}
   909  		}
   910  
   911  		// Record imports and information about cgo.
   912  		isCgo := false
   913  		for _, imp := range info.imports {
   914  			if imp.path == "C" {
   915  				if isTest {
   916  					badFile(fmt.Errorf("use of cgo in test %s not supported", filename))
   917  					continue
   918  				}
   919  				isCgo = true
   920  				if imp.doc != nil {
   921  					if err := ctxt.saveCgo(filename, p, imp.doc); err != nil {
   922  						badFile(err)
   923  					}
   924  				}
   925  			}
   926  		}
   927  
   928  		var fileList *[]string
   929  		var importMap, embedMap map[string][]token.Position
   930  		switch {
   931  		case isCgo:
   932  			allTags["cgo"] = true
   933  			if ctxt.CgoEnabled {
   934  				fileList = &p.CgoFiles
   935  				importMap = importPos
   936  				embedMap = embedPos
   937  			} else {
   938  				// Ignore imports and embeds from cgo files if cgo is disabled.
   939  				fileList = &p.IgnoredGoFiles
   940  			}
   941  		case isXTest:
   942  			fileList = &p.XTestGoFiles
   943  			importMap = xTestImportPos
   944  			embedMap = xTestEmbedPos
   945  		case isTest:
   946  			fileList = &p.TestGoFiles
   947  			importMap = testImportPos
   948  			embedMap = testEmbedPos
   949  		default:
   950  			fileList = &p.GoFiles
   951  			importMap = importPos
   952  			embedMap = embedPos
   953  		}
   954  		*fileList = append(*fileList, name)
   955  		if importMap != nil {
   956  			for _, imp := range info.imports {
   957  				importMap[imp.path] = append(importMap[imp.path], fset.Position(imp.pos))
   958  			}
   959  		}
   960  		if embedMap != nil {
   961  			for _, emb := range info.embeds {
   962  				embedMap[emb.pattern] = append(embedMap[emb.pattern], emb.pos)
   963  			}
   964  		}
   965  	}
   966  
   967  	for tag := range allTags {
   968  		p.AllTags = append(p.AllTags, tag)
   969  	}
   970  	sort.Strings(p.AllTags)
   971  
   972  	p.EmbedPatterns, p.EmbedPatternPos = cleanDecls(embedPos)
   973  	p.TestEmbedPatterns, p.TestEmbedPatternPos = cleanDecls(testEmbedPos)
   974  	p.XTestEmbedPatterns, p.XTestEmbedPatternPos = cleanDecls(xTestEmbedPos)
   975  
   976  	p.Imports, p.ImportPos = cleanDecls(importPos)
   977  	p.TestImports, p.TestImportPos = cleanDecls(testImportPos)
   978  	p.XTestImports, p.XTestImportPos = cleanDecls(xTestImportPos)
   979  
   980  	// add the .S/.sx files only if we are using cgo
   981  	// (which means gcc will compile them).
   982  	// The standard assemblers expect .s files.
   983  	if len(p.CgoFiles) > 0 {
   984  		p.SFiles = append(p.SFiles, Sfiles...)
   985  		sort.Strings(p.SFiles)
   986  	} else {
   987  		p.IgnoredOtherFiles = append(p.IgnoredOtherFiles, Sfiles...)
   988  		sort.Strings(p.IgnoredOtherFiles)
   989  	}
   990  
   991  	if badGoError != nil {
   992  		return p, badGoError
   993  	}
   994  	if len(p.GoFiles)+len(p.CgoFiles)+len(p.TestGoFiles)+len(p.XTestGoFiles) == 0 {
   995  		return p, &NoGoError{p.Dir}
   996  	}
   997  	return p, pkgerr
   998  }
   999  
  1000  func fileListForExt(p *Package, ext string) *[]string {
  1001  	switch ext {
  1002  	case ".c":
  1003  		return &p.CFiles
  1004  	case ".cc", ".cpp", ".cxx":
  1005  		return &p.CXXFiles
  1006  	case ".m":
  1007  		return &p.MFiles
  1008  	case ".h", ".hh", ".hpp", ".hxx":
  1009  		return &p.HFiles
  1010  	case ".f", ".F", ".for", ".f90":
  1011  		return &p.FFiles
  1012  	case ".s", ".S", ".sx":
  1013  		return &p.SFiles
  1014  	case ".swig":
  1015  		return &p.SwigFiles
  1016  	case ".swigcxx":
  1017  		return &p.SwigCXXFiles
  1018  	case ".syso":
  1019  		return &p.SysoFiles
  1020  	}
  1021  	return nil
  1022  }
  1023  
  1024  func uniq(list []string) []string {
  1025  	if list == nil {
  1026  		return nil
  1027  	}
  1028  	out := make([]string, len(list))
  1029  	copy(out, list)
  1030  	sort.Strings(out)
  1031  	uniq := out[:0]
  1032  	for _, x := range out {
  1033  		if len(uniq) == 0 || uniq[len(uniq)-1] != x {
  1034  			uniq = append(uniq, x)
  1035  		}
  1036  	}
  1037  	return uniq
  1038  }
  1039  
  1040  var errNoModules = errors.New("not using modules")
  1041  
  1042  // importGo checks whether it can use the go command to find the directory for path.
  1043  // If using the go command is not appropriate, importGo returns errNoModules.
  1044  // Otherwise, importGo tries using the go command and reports whether that succeeded.
  1045  // Using the go command lets build.Import and build.Context.Import find code
  1046  // in Go modules. In the long term we want tools to use go/packages (currently golang.org/x/tools/go/packages),
  1047  // which will also use the go command.
  1048  // Invoking the go command here is not very efficient in that it computes information
  1049  // about the requested package and all dependencies and then only reports about the requested package.
  1050  // Then we reinvoke it for every dependency. But this is still better than not working at all.
  1051  // See golang.org/issue/26504.
  1052  func (ctxt *Context) importGo(p *Package, path, srcDir string, mode ImportMode) error {
  1053  	// To invoke the go command,
  1054  	// we must not being doing special things like AllowBinary or IgnoreVendor,
  1055  	// and all the file system callbacks must be nil (we're meant to use the local file system).
  1056  	if mode&AllowBinary != 0 || mode&IgnoreVendor != 0 ||
  1057  		ctxt.JoinPath != nil || ctxt.SplitPathList != nil || ctxt.IsAbsPath != nil || ctxt.IsDir != nil || ctxt.HasSubdir != nil || ctxt.ReadDir != nil || ctxt.OpenFile != nil || !equal(ctxt.ReleaseTags, defaultReleaseTags) {
  1058  		return errNoModules
  1059  	}
  1060  
  1061  	// Predict whether module aware mode is enabled by checking the value of
  1062  	// GO111MODULE and looking for a go.mod file in the source directory or
  1063  	// one of its parents. Running 'go env GOMOD' in the source directory would
  1064  	// give a canonical answer, but we'd prefer not to execute another command.
  1065  	go111Module := os.Getenv("GO111MODULE")
  1066  	switch go111Module {
  1067  	case "off":
  1068  		return errNoModules
  1069  	default: // "", "on", "auto", anything else
  1070  		// Maybe use modules.
  1071  	}
  1072  
  1073  	if srcDir != "" {
  1074  		var absSrcDir string
  1075  		if filepath.IsAbs(srcDir) {
  1076  			absSrcDir = srcDir
  1077  		} else if ctxt.Dir != "" {
  1078  			return fmt.Errorf("go/build: Dir is non-empty, so relative srcDir is not allowed: %v", srcDir)
  1079  		} else {
  1080  			// Find the absolute source directory. hasSubdir does not handle
  1081  			// relative paths (and can't because the callbacks don't support this).
  1082  			var err error
  1083  			absSrcDir, err = filepath.Abs(srcDir)
  1084  			if err != nil {
  1085  				return errNoModules
  1086  			}
  1087  		}
  1088  
  1089  		// If the source directory is in GOROOT, then the in-process code works fine
  1090  		// and we should keep using it. Moreover, the 'go list' approach below doesn't
  1091  		// take standard-library vendoring into account and will fail.
  1092  		if _, ok := ctxt.hasSubdir(filepath.Join(ctxt.GOROOT, "src"), absSrcDir); ok {
  1093  			return errNoModules
  1094  		}
  1095  	}
  1096  
  1097  	// For efficiency, if path is a standard library package, let the usual lookup code handle it.
  1098  	if ctxt.GOROOT != "" {
  1099  		dir := ctxt.joinPath(ctxt.GOROOT, "src", path)
  1100  		if ctxt.isDir(dir) {
  1101  			return errNoModules
  1102  		}
  1103  	}
  1104  
  1105  	// If GO111MODULE=auto, look to see if there is a go.mod.
  1106  	// Since go1.13, it doesn't matter if we're inside GOPATH.
  1107  	if go111Module == "auto" {
  1108  		var (
  1109  			parent string
  1110  			err    error
  1111  		)
  1112  		if ctxt.Dir == "" {
  1113  			parent, err = os.Getwd()
  1114  			if err != nil {
  1115  				// A nonexistent working directory can't be in a module.
  1116  				return errNoModules
  1117  			}
  1118  		} else {
  1119  			parent, err = filepath.Abs(ctxt.Dir)
  1120  			if err != nil {
  1121  				// If the caller passed a bogus Dir explicitly, that's materially
  1122  				// different from not having modules enabled.
  1123  				return err
  1124  			}
  1125  		}
  1126  		for {
  1127  			if f, err := ctxt.openFile(ctxt.joinPath(parent, "go.mod")); err == nil {
  1128  				buf := make([]byte, 100)
  1129  				_, err := f.Read(buf)
  1130  				f.Close()
  1131  				if err == nil || err == io.EOF {
  1132  					// go.mod exists and is readable (is a file, not a directory).
  1133  					break
  1134  				}
  1135  			}
  1136  			d := filepath.Dir(parent)
  1137  			if len(d) >= len(parent) {
  1138  				return errNoModules // reached top of file system, no go.mod
  1139  			}
  1140  			parent = d
  1141  		}
  1142  	}
  1143  
  1144  	cmd := exec.Command("go", "list", "-e", "-compiler="+ctxt.Compiler, "-tags="+strings.Join(ctxt.BuildTags, ","), "-installsuffix="+ctxt.InstallSuffix, "-f={{.Dir}}\n{{.ImportPath}}\n{{.Root}}\n{{.Goroot}}\n{{if .Error}}{{.Error}}{{end}}\n", "--", path)
  1145  
  1146  	if ctxt.Dir != "" {
  1147  		cmd.Dir = ctxt.Dir
  1148  	}
  1149  
  1150  	var stdout, stderr strings.Builder
  1151  	cmd.Stdout = &stdout
  1152  	cmd.Stderr = &stderr
  1153  
  1154  	cgo := "0"
  1155  	if ctxt.CgoEnabled {
  1156  		cgo = "1"
  1157  	}
  1158  	cmd.Env = append(os.Environ(),
  1159  		"GOOS="+ctxt.GOOS,
  1160  		"GOARCH="+ctxt.GOARCH,
  1161  		"GOROOT="+ctxt.GOROOT,
  1162  		"GOPATH="+ctxt.GOPATH,
  1163  		"CGO_ENABLED="+cgo,
  1164  	)
  1165  
  1166  	if err := cmd.Run(); err != nil {
  1167  		return fmt.Errorf("go/build: go list %s: %v\n%s\n", path, err, stderr.String())
  1168  	}
  1169  
  1170  	f := strings.SplitN(stdout.String(), "\n", 5)
  1171  	if len(f) != 5 {
  1172  		return fmt.Errorf("go/build: importGo %s: unexpected output:\n%s\n", path, stdout.String())
  1173  	}
  1174  	dir := f[0]
  1175  	errStr := strings.TrimSpace(f[4])
  1176  	if errStr != "" && dir == "" {
  1177  		// If 'go list' could not locate the package (dir is empty),
  1178  		// return the same error that 'go list' reported.
  1179  		return errors.New(errStr)
  1180  	}
  1181  
  1182  	// If 'go list' did locate the package, ignore the error.
  1183  	// It was probably related to loading source files, and we'll
  1184  	// encounter it ourselves shortly if the FindOnly flag isn't set.
  1185  	p.Dir = dir
  1186  	p.ImportPath = f[1]
  1187  	p.Root = f[2]
  1188  	p.Goroot = f[3] == "true"
  1189  	return nil
  1190  }
  1191  
  1192  func equal(x, y []string) bool {
  1193  	if len(x) != len(y) {
  1194  		return false
  1195  	}
  1196  	for i, xi := range x {
  1197  		if xi != y[i] {
  1198  			return false
  1199  		}
  1200  	}
  1201  	return true
  1202  }
  1203  
  1204  // hasGoFiles reports whether dir contains any files with names ending in .go.
  1205  // For a vendor check we must exclude directories that contain no .go files.
  1206  // Otherwise it is not possible to vendor just a/b/c and still import the
  1207  // non-vendored a/b. See golang.org/issue/13832.
  1208  func hasGoFiles(ctxt *Context, dir string) bool {
  1209  	ents, _ := ctxt.readDir(dir)
  1210  	for _, ent := range ents {
  1211  		if !ent.IsDir() && strings.HasSuffix(ent.Name(), ".go") {
  1212  			return true
  1213  		}
  1214  	}
  1215  	return false
  1216  }
  1217  
  1218  func findImportComment(data []byte) (s string, line int) {
  1219  	// expect keyword package
  1220  	word, data := parseWord(data)
  1221  	if string(word) != "package" {
  1222  		return "", 0
  1223  	}
  1224  
  1225  	// expect package name
  1226  	_, data = parseWord(data)
  1227  
  1228  	// now ready for import comment, a // or /* */ comment
  1229  	// beginning and ending on the current line.
  1230  	for len(data) > 0 && (data[0] == ' ' || data[0] == '\t' || data[0] == '\r') {
  1231  		data = data[1:]
  1232  	}
  1233  
  1234  	var comment []byte
  1235  	switch {
  1236  	case bytes.HasPrefix(data, slashSlash):
  1237  		i := bytes.Index(data, newline)
  1238  		if i < 0 {
  1239  			i = len(data)
  1240  		}
  1241  		comment = data[2:i]
  1242  	case bytes.HasPrefix(data, slashStar):
  1243  		data = data[2:]
  1244  		i := bytes.Index(data, starSlash)
  1245  		if i < 0 {
  1246  			// malformed comment
  1247  			return "", 0
  1248  		}
  1249  		comment = data[:i]
  1250  		if bytes.Contains(comment, newline) {
  1251  			return "", 0
  1252  		}
  1253  	}
  1254  	comment = bytes.TrimSpace(comment)
  1255  
  1256  	// split comment into `import`, `"pkg"`
  1257  	word, arg := parseWord(comment)
  1258  	if string(word) != "import" {
  1259  		return "", 0
  1260  	}
  1261  
  1262  	line = 1 + bytes.Count(data[:cap(data)-cap(arg)], newline)
  1263  	return strings.TrimSpace(string(arg)), line
  1264  }
  1265  
  1266  var (
  1267  	slashSlash = []byte("//")
  1268  	slashStar  = []byte("/*")
  1269  	starSlash  = []byte("*/")
  1270  	newline    = []byte("\n")
  1271  )
  1272  
  1273  // skipSpaceOrComment returns data with any leading spaces or comments removed.
  1274  func skipSpaceOrComment(data []byte) []byte {
  1275  	for len(data) > 0 {
  1276  		switch data[0] {
  1277  		case ' ', '\t', '\r', '\n':
  1278  			data = data[1:]
  1279  			continue
  1280  		case '/':
  1281  			if bytes.HasPrefix(data, slashSlash) {
  1282  				i := bytes.Index(data, newline)
  1283  				if i < 0 {
  1284  					return nil
  1285  				}
  1286  				data = data[i+1:]
  1287  				continue
  1288  			}
  1289  			if bytes.HasPrefix(data, slashStar) {
  1290  				data = data[2:]
  1291  				i := bytes.Index(data, starSlash)
  1292  				if i < 0 {
  1293  					return nil
  1294  				}
  1295  				data = data[i+2:]
  1296  				continue
  1297  			}
  1298  		}
  1299  		break
  1300  	}
  1301  	return data
  1302  }
  1303  
  1304  // parseWord skips any leading spaces or comments in data
  1305  // and then parses the beginning of data as an identifier or keyword,
  1306  // returning that word and what remains after the word.
  1307  func parseWord(data []byte) (word, rest []byte) {
  1308  	data = skipSpaceOrComment(data)
  1309  
  1310  	// Parse past leading word characters.
  1311  	rest = data
  1312  	for {
  1313  		r, size := utf8.DecodeRune(rest)
  1314  		if unicode.IsLetter(r) || '0' <= r && r <= '9' || r == '_' {
  1315  			rest = rest[size:]
  1316  			continue
  1317  		}
  1318  		break
  1319  	}
  1320  
  1321  	word = data[:len(data)-len(rest)]
  1322  	if len(word) == 0 {
  1323  		return nil, nil
  1324  	}
  1325  
  1326  	return word, rest
  1327  }
  1328  
  1329  // MatchFile reports whether the file with the given name in the given directory
  1330  // matches the context and would be included in a Package created by ImportDir
  1331  // of that directory.
  1332  //
  1333  // MatchFile considers the name of the file and may use ctxt.OpenFile to
  1334  // read some or all of the file's content.
  1335  func (ctxt *Context) MatchFile(dir, name string) (match bool, err error) {
  1336  	info, err := ctxt.matchFile(dir, name, nil, nil, nil)
  1337  	return info != nil, err
  1338  }
  1339  
  1340  var dummyPkg Package
  1341  
  1342  // fileInfo records information learned about a file included in a build.
  1343  type fileInfo struct {
  1344  	name     string // full name including dir
  1345  	header   []byte
  1346  	fset     *token.FileSet
  1347  	parsed   *ast.File
  1348  	parseErr error
  1349  	imports  []fileImport
  1350  	embeds   []fileEmbed
  1351  	embedErr error
  1352  }
  1353  
  1354  type fileImport struct {
  1355  	path string
  1356  	pos  token.Pos
  1357  	doc  *ast.CommentGroup
  1358  }
  1359  
  1360  type fileEmbed struct {
  1361  	pattern string
  1362  	pos     token.Position
  1363  }
  1364  
  1365  // matchFile determines whether the file with the given name in the given directory
  1366  // should be included in the package being constructed.
  1367  // If the file should be included, matchFile returns a non-nil *fileInfo (and a nil error).
  1368  // Non-nil errors are reserved for unexpected problems.
  1369  //
  1370  // If name denotes a Go program, matchFile reads until the end of the
  1371  // imports and returns that section of the file in the fileInfo's header field,
  1372  // even though it only considers text until the first non-comment
  1373  // for +build lines.
  1374  //
  1375  // If allTags is non-nil, matchFile records any encountered build tag
  1376  // by setting allTags[tag] = true.
  1377  func (ctxt *Context) matchFile(dir, name string, allTags map[string]bool, binaryOnly *bool, fset *token.FileSet) (*fileInfo, error) {
  1378  	if strings.HasPrefix(name, "_") ||
  1379  		strings.HasPrefix(name, ".") {
  1380  		return nil, nil
  1381  	}
  1382  
  1383  	i := strings.LastIndex(name, ".")
  1384  	if i < 0 {
  1385  		i = len(name)
  1386  	}
  1387  	ext := name[i:]
  1388  
  1389  	if !ctxt.goodOSArchFile(name, allTags) && !ctxt.UseAllFiles {
  1390  		return nil, nil
  1391  	}
  1392  
  1393  	if ext != ".go" && fileListForExt(&dummyPkg, ext) == nil {
  1394  		// skip
  1395  		return nil, nil
  1396  	}
  1397  
  1398  	info := &fileInfo{name: ctxt.joinPath(dir, name), fset: fset}
  1399  	if ext == ".syso" {
  1400  		// binary, no reading
  1401  		return info, nil
  1402  	}
  1403  
  1404  	f, err := ctxt.openFile(info.name)
  1405  	if err != nil {
  1406  		return nil, err
  1407  	}
  1408  
  1409  	if strings.HasSuffix(name, ".go") {
  1410  		err = readGoInfo(f, info)
  1411  		if strings.HasSuffix(name, "_test.go") {
  1412  			binaryOnly = nil // ignore //go:binary-only-package comments in _test.go files
  1413  		}
  1414  	} else {
  1415  		binaryOnly = nil // ignore //go:binary-only-package comments in non-Go sources
  1416  		info.header, err = readComments(f)
  1417  	}
  1418  	f.Close()
  1419  	if err != nil {
  1420  		return nil, fmt.Errorf("read %s: %v", info.name, err)
  1421  	}
  1422  
  1423  	// Look for +build comments to accept or reject the file.
  1424  	ok, sawBinaryOnly, err := ctxt.shouldBuild(info.header, allTags)
  1425  	if err != nil {
  1426  		return nil, err
  1427  	}
  1428  	if !ok && !ctxt.UseAllFiles {
  1429  		return nil, nil
  1430  	}
  1431  
  1432  	if binaryOnly != nil && sawBinaryOnly {
  1433  		*binaryOnly = true
  1434  	}
  1435  
  1436  	return info, nil
  1437  }
  1438  
  1439  func cleanDecls(m map[string][]token.Position) ([]string, map[string][]token.Position) {
  1440  	all := make([]string, 0, len(m))
  1441  	for path := range m {
  1442  		all = append(all, path)
  1443  	}
  1444  	sort.Strings(all)
  1445  	return all, m
  1446  }
  1447  
  1448  // Import is shorthand for Default.Import.
  1449  func Import(path, srcDir string, mode ImportMode) (*Package, error) {
  1450  	return Default.Import(path, srcDir, mode)
  1451  }
  1452  
  1453  // ImportDir is shorthand for Default.ImportDir.
  1454  func ImportDir(dir string, mode ImportMode) (*Package, error) {
  1455  	return Default.ImportDir(dir, mode)
  1456  }
  1457  
  1458  var (
  1459  	bSlashSlash = []byte(slashSlash)
  1460  	bStarSlash  = []byte(starSlash)
  1461  	bSlashStar  = []byte(slashStar)
  1462  
  1463  	goBuildComment = []byte("//go:build")
  1464  
  1465  	errGoBuildWithoutBuild = errors.New("//go:build comment without // +build comment")
  1466  	errMultipleGoBuild     = errors.New("multiple //go:build comments") // unused in Go 1.(N-1)
  1467  )
  1468  
  1469  func isGoBuildComment(line []byte) bool {
  1470  	if !bytes.HasPrefix(line, goBuildComment) {
  1471  		return false
  1472  	}
  1473  	line = bytes.TrimSpace(line)
  1474  	rest := line[len(goBuildComment):]
  1475  	return len(rest) == 0 || len(bytes.TrimSpace(rest)) < len(rest)
  1476  }
  1477  
  1478  // Special comment denoting a binary-only package.
  1479  // See https://golang.org/design/2775-binary-only-packages
  1480  // for more about the design of binary-only packages.
  1481  var binaryOnlyComment = []byte("//go:binary-only-package")
  1482  
  1483  // shouldBuild reports whether it is okay to use this file,
  1484  // The rule is that in the file's leading run of // comments
  1485  // and blank lines, which must be followed by a blank line
  1486  // (to avoid including a Go package clause doc comment),
  1487  // lines beginning with '// +build' are taken as build directives.
  1488  //
  1489  // The file is accepted only if each such line lists something
  1490  // matching the file. For example:
  1491  //
  1492  //	// +build windows linux
  1493  //
  1494  // marks the file as applicable only on Windows and Linux.
  1495  //
  1496  // For each build tag it consults, shouldBuild sets allTags[tag] = true.
  1497  //
  1498  // shouldBuild reports whether the file should be built
  1499  // and whether a //go:binary-only-package comment was found.
  1500  func (ctxt *Context) shouldBuild(content []byte, allTags map[string]bool) (shouldBuild, binaryOnly bool, err error) {
  1501  
  1502  	// Pass 1. Identify leading run of // comments and blank lines,
  1503  	// which must be followed by a blank line.
  1504  	// Also identify any //go:build comments.
  1505  	content, goBuild, sawBinaryOnly, err := parseFileHeader(content)
  1506  	if err != nil {
  1507  		return false, false, err
  1508  	}
  1509  
  1510  	// Pass 2.  Process each +build line in the run.
  1511  	p := content
  1512  	shouldBuild = true
  1513  	sawBuild := false
  1514  	for len(p) > 0 {
  1515  		line := p
  1516  		if i := bytes.IndexByte(line, '\n'); i >= 0 {
  1517  			line, p = line[:i], p[i+1:]
  1518  		} else {
  1519  			p = p[len(p):]
  1520  		}
  1521  		line = bytes.TrimSpace(line)
  1522  		if !bytes.HasPrefix(line, bSlashSlash) {
  1523  			continue
  1524  		}
  1525  		line = bytes.TrimSpace(line[len(bSlashSlash):])
  1526  		if len(line) > 0 && line[0] == '+' {
  1527  			// Looks like a comment +line.
  1528  			f := strings.Fields(string(line))
  1529  			if f[0] == "+build" {
  1530  				sawBuild = true
  1531  				ok := false
  1532  				for _, tok := range f[1:] {
  1533  					if ctxt.match(tok, allTags) {
  1534  						ok = true
  1535  					}
  1536  				}
  1537  				if !ok {
  1538  					shouldBuild = false
  1539  				}
  1540  			}
  1541  		}
  1542  	}
  1543  
  1544  	if goBuild != nil && !sawBuild {
  1545  		return false, false, errGoBuildWithoutBuild
  1546  	}
  1547  
  1548  	return shouldBuild, sawBinaryOnly, nil
  1549  }
  1550  
  1551  func parseFileHeader(content []byte) (trimmed, goBuild []byte, sawBinaryOnly bool, err error) {
  1552  	end := 0
  1553  	p := content
  1554  	ended := false       // found non-blank, non-// line, so stopped accepting // +build lines
  1555  	inSlashStar := false // in /* */ comment
  1556  
  1557  Lines:
  1558  	for len(p) > 0 {
  1559  		line := p
  1560  		if i := bytes.IndexByte(line, '\n'); i >= 0 {
  1561  			line, p = line[:i], p[i+1:]
  1562  		} else {
  1563  			p = p[len(p):]
  1564  		}
  1565  		line = bytes.TrimSpace(line)
  1566  		if len(line) == 0 && !ended { // Blank line
  1567  			// Remember position of most recent blank line.
  1568  			// When we find the first non-blank, non-// line,
  1569  			// this "end" position marks the latest file position
  1570  			// where a // +build line can appear.
  1571  			// (It must appear _before_ a blank line before the non-blank, non-// line.
  1572  			// Yes, that's confusing, which is part of why we moved to //go:build lines.)
  1573  			// Note that ended==false here means that inSlashStar==false,
  1574  			// since seeing a /* would have set ended==true.
  1575  			end = len(content) - len(p)
  1576  			continue Lines
  1577  		}
  1578  		if !bytes.HasPrefix(line, slashSlash) { // Not comment line
  1579  			ended = true
  1580  		}
  1581  
  1582  		if !inSlashStar && isGoBuildComment(line) {
  1583  			if false && goBuild != nil { // enabled in Go 1.N
  1584  				return nil, nil, false, errMultipleGoBuild
  1585  			}
  1586  			goBuild = line
  1587  		}
  1588  		if !inSlashStar && bytes.Equal(line, binaryOnlyComment) {
  1589  			sawBinaryOnly = true
  1590  		}
  1591  
  1592  	Comments:
  1593  		for len(line) > 0 {
  1594  			if inSlashStar {
  1595  				if i := bytes.Index(line, starSlash); i >= 0 {
  1596  					inSlashStar = false
  1597  					line = bytes.TrimSpace(line[i+len(starSlash):])
  1598  					continue Comments
  1599  				}
  1600  				continue Lines
  1601  			}
  1602  			if bytes.HasPrefix(line, bSlashSlash) {
  1603  				continue Lines
  1604  			}
  1605  			if bytes.HasPrefix(line, bSlashStar) {
  1606  				inSlashStar = true
  1607  				line = bytes.TrimSpace(line[len(bSlashStar):])
  1608  				continue Comments
  1609  			}
  1610  			// Found non-comment text.
  1611  			break Lines
  1612  		}
  1613  	}
  1614  
  1615  	return content[:end], goBuild, sawBinaryOnly, nil
  1616  }
  1617  
  1618  // saveCgo saves the information from the #cgo lines in the import "C" comment.
  1619  // These lines set CFLAGS, CPPFLAGS, CXXFLAGS and LDFLAGS and pkg-config directives
  1620  // that affect the way cgo's C code is built.
  1621  func (ctxt *Context) saveCgo(filename string, di *Package, cg *ast.CommentGroup) error {
  1622  	text := cg.Text()
  1623  	for _, line := range strings.Split(text, "\n") {
  1624  		orig := line
  1625  
  1626  		// Line is
  1627  		//	#cgo [GOOS/GOARCH...] LDFLAGS: stuff
  1628  		//
  1629  		line = strings.TrimSpace(line)
  1630  		if len(line) < 5 || line[:4] != "#cgo" || (line[4] != ' ' && line[4] != '\t') {
  1631  			continue
  1632  		}
  1633  
  1634  		// Split at colon.
  1635  		line = strings.TrimSpace(line[4:])
  1636  		i := strings.Index(line, ":")
  1637  		if i < 0 {
  1638  			return fmt.Errorf("%s: invalid #cgo line: %s", filename, orig)
  1639  		}
  1640  		line, argstr := line[:i], line[i+1:]
  1641  
  1642  		// Parse GOOS/GOARCH stuff.
  1643  		f := strings.Fields(line)
  1644  		if len(f) < 1 {
  1645  			return fmt.Errorf("%s: invalid #cgo line: %s", filename, orig)
  1646  		}
  1647  
  1648  		cond, verb := f[:len(f)-1], f[len(f)-1]
  1649  		if len(cond) > 0 {
  1650  			ok := false
  1651  			for _, c := range cond {
  1652  				if ctxt.match(c, nil) {
  1653  					ok = true
  1654  					break
  1655  				}
  1656  			}
  1657  			if !ok {
  1658  				continue
  1659  			}
  1660  		}
  1661  
  1662  		args, err := splitQuoted(argstr)
  1663  		if err != nil {
  1664  			return fmt.Errorf("%s: invalid #cgo line: %s", filename, orig)
  1665  		}
  1666  		var ok bool
  1667  		for i, arg := range args {
  1668  			if arg, ok = expandSrcDir(arg, di.Dir); !ok {
  1669  				return fmt.Errorf("%s: malformed #cgo argument: %s", filename, arg)
  1670  			}
  1671  			args[i] = arg
  1672  		}
  1673  
  1674  		switch verb {
  1675  		case "CFLAGS", "CPPFLAGS", "CXXFLAGS", "FFLAGS", "LDFLAGS":
  1676  			// Change relative paths to absolute.
  1677  			ctxt.makePathsAbsolute(args, di.Dir)
  1678  		}
  1679  
  1680  		switch verb {
  1681  		case "CFLAGS":
  1682  			di.CgoCFLAGS = append(di.CgoCFLAGS, args...)
  1683  		case "CPPFLAGS":
  1684  			di.CgoCPPFLAGS = append(di.CgoCPPFLAGS, args...)
  1685  		case "CXXFLAGS":
  1686  			di.CgoCXXFLAGS = append(di.CgoCXXFLAGS, args...)
  1687  		case "FFLAGS":
  1688  			di.CgoFFLAGS = append(di.CgoFFLAGS, args...)
  1689  		case "LDFLAGS":
  1690  			di.CgoLDFLAGS = append(di.CgoLDFLAGS, args...)
  1691  		case "pkg-config":
  1692  			di.CgoPkgConfig = append(di.CgoPkgConfig, args...)
  1693  		default:
  1694  			return fmt.Errorf("%s: invalid #cgo verb: %s", filename, orig)
  1695  		}
  1696  	}
  1697  	return nil
  1698  }
  1699  
  1700  // expandSrcDir expands any occurrence of ${SRCDIR}, making sure
  1701  // the result is safe for the shell.
  1702  func expandSrcDir(str string, srcdir string) (string, bool) {
  1703  	// "\" delimited paths cause safeCgoName to fail
  1704  	// so convert native paths with a different delimiter
  1705  	// to "/" before starting (eg: on windows).
  1706  	srcdir = filepath.ToSlash(srcdir)
  1707  
  1708  	chunks := strings.Split(str, "${SRCDIR}")
  1709  	if len(chunks) < 2 {
  1710  		return str, safeCgoName(str)
  1711  	}
  1712  	ok := true
  1713  	for _, chunk := range chunks {
  1714  		ok = ok && (chunk == "" || safeCgoName(chunk))
  1715  	}
  1716  	ok = ok && (srcdir == "" || safeCgoName(srcdir))
  1717  	res := strings.Join(chunks, srcdir)
  1718  	return res, ok && res != ""
  1719  }
  1720  
  1721  // makePathsAbsolute looks for compiler options that take paths and
  1722  // makes them absolute. We do this because through the 1.8 release we
  1723  // ran the compiler in the package directory, so any relative -I or -L
  1724  // options would be relative to that directory. In 1.9 we changed to
  1725  // running the compiler in the build directory, to get consistent
  1726  // build results (issue #19964). To keep builds working, we change any
  1727  // relative -I or -L options to be absolute.
  1728  //
  1729  // Using filepath.IsAbs and filepath.Join here means the results will be
  1730  // different on different systems, but that's OK: -I and -L options are
  1731  // inherently system-dependent.
  1732  func (ctxt *Context) makePathsAbsolute(args []string, srcDir string) {
  1733  	nextPath := false
  1734  	for i, arg := range args {
  1735  		if nextPath {
  1736  			if !filepath.IsAbs(arg) {
  1737  				args[i] = filepath.Join(srcDir, arg)
  1738  			}
  1739  			nextPath = false
  1740  		} else if strings.HasPrefix(arg, "-I") || strings.HasPrefix(arg, "-L") {
  1741  			if len(arg) == 2 {
  1742  				nextPath = true
  1743  			} else {
  1744  				if !filepath.IsAbs(arg[2:]) {
  1745  					args[i] = arg[:2] + filepath.Join(srcDir, arg[2:])
  1746  				}
  1747  			}
  1748  		}
  1749  	}
  1750  }
  1751  
  1752  // NOTE: $ is not safe for the shell, but it is allowed here because of linker options like -Wl,$ORIGIN.
  1753  // We never pass these arguments to a shell (just to programs we construct argv for), so this should be okay.
  1754  // See golang.org/issue/6038.
  1755  // The @ is for OS X. See golang.org/issue/13720.
  1756  // The % is for Jenkins. See golang.org/issue/16959.
  1757  // The ! is because module paths may use them. See golang.org/issue/26716.
  1758  // The ~ and ^ are for sr.ht. See golang.org/issue/32260.
  1759  const safeString = "+-.,/0123456789=ABCDEFGHIJKLMNOPQRSTUVWXYZ_abcdefghijklmnopqrstuvwxyz:$@%! ~^"
  1760  
  1761  func safeCgoName(s string) bool {
  1762  	if s == "" {
  1763  		return false
  1764  	}
  1765  	for i := 0; i < len(s); i++ {
  1766  		if c := s[i]; c < utf8.RuneSelf && strings.IndexByte(safeString, c) < 0 {
  1767  			return false
  1768  		}
  1769  	}
  1770  	return true
  1771  }
  1772  
  1773  // splitQuoted splits the string s around each instance of one or more consecutive
  1774  // white space characters while taking into account quotes and escaping, and
  1775  // returns an array of substrings of s or an empty list if s contains only white space.
  1776  // Single quotes and double quotes are recognized to prevent splitting within the
  1777  // quoted region, and are removed from the resulting substrings. If a quote in s
  1778  // isn't closed err will be set and r will have the unclosed argument as the
  1779  // last element. The backslash is used for escaping.
  1780  //
  1781  // For example, the following string:
  1782  //
  1783  //     a b:"c d" 'e''f'  "g\""
  1784  //
  1785  // Would be parsed as:
  1786  //
  1787  //     []string{"a", "b:c d", "ef", `g"`}
  1788  //
  1789  func splitQuoted(s string) (r []string, err error) {
  1790  	var args []string
  1791  	arg := make([]rune, len(s))
  1792  	escaped := false
  1793  	quoted := false
  1794  	quote := '\x00'
  1795  	i := 0
  1796  	for _, rune := range s {
  1797  		switch {
  1798  		case escaped:
  1799  			escaped = false
  1800  		case rune == '\\':
  1801  			escaped = true
  1802  			continue
  1803  		case quote != '\x00':
  1804  			if rune == quote {
  1805  				quote = '\x00'
  1806  				continue
  1807  			}
  1808  		case rune == '"' || rune == '\'':
  1809  			quoted = true
  1810  			quote = rune
  1811  			continue
  1812  		case unicode.IsSpace(rune):
  1813  			if quoted || i > 0 {
  1814  				quoted = false
  1815  				args = append(args, string(arg[:i]))
  1816  				i = 0
  1817  			}
  1818  			continue
  1819  		}
  1820  		arg[i] = rune
  1821  		i++
  1822  	}
  1823  	if quoted || i > 0 {
  1824  		args = append(args, string(arg[:i]))
  1825  	}
  1826  	if quote != 0 {
  1827  		err = errors.New("unclosed quote")
  1828  	} else if escaped {
  1829  		err = errors.New("unfinished escaping")
  1830  	}
  1831  	return args, err
  1832  }
  1833  
  1834  // match reports whether the name is one of:
  1835  //
  1836  //	$GOOS
  1837  //	$GOARCH
  1838  //	cgo (if cgo is enabled)
  1839  //	!cgo (if cgo is disabled)
  1840  //	ctxt.Compiler
  1841  //	!ctxt.Compiler
  1842  //	tag (if tag is listed in ctxt.BuildTags or ctxt.ReleaseTags)
  1843  //	!tag (if tag is not listed in ctxt.BuildTags or ctxt.ReleaseTags)
  1844  //	a comma-separated list of any of these
  1845  //
  1846  func (ctxt *Context) match(name string, allTags map[string]bool) bool {
  1847  	if name == "" {
  1848  		if allTags != nil {
  1849  			allTags[name] = true
  1850  		}
  1851  		return false
  1852  	}
  1853  	if i := strings.Index(name, ","); i >= 0 {
  1854  		// comma-separated list
  1855  		ok1 := ctxt.match(name[:i], allTags)
  1856  		ok2 := ctxt.match(name[i+1:], allTags)
  1857  		return ok1 && ok2
  1858  	}
  1859  	if strings.HasPrefix(name, "!!") { // bad syntax, reject always
  1860  		return false
  1861  	}
  1862  	if strings.HasPrefix(name, "!") { // negation
  1863  		return len(name) > 1 && !ctxt.match(name[1:], allTags)
  1864  	}
  1865  
  1866  	if allTags != nil {
  1867  		allTags[name] = true
  1868  	}
  1869  
  1870  	// Tags must be letters, digits, underscores or dots.
  1871  	// Unlike in Go identifiers, all digits are fine (e.g., "386").
  1872  	for _, c := range name {
  1873  		if !unicode.IsLetter(c) && !unicode.IsDigit(c) && c != '_' && c != '.' {
  1874  			return false
  1875  		}
  1876  	}
  1877  
  1878  	// special tags
  1879  	if ctxt.CgoEnabled && name == "cgo" {
  1880  		return true
  1881  	}
  1882  	if name == ctxt.GOOS || name == ctxt.GOARCH || name == ctxt.Compiler {
  1883  		return true
  1884  	}
  1885  	if ctxt.GOOS == "android" && name == "linux" {
  1886  		return true
  1887  	}
  1888  	if ctxt.GOOS == "illumos" && name == "solaris" {
  1889  		return true
  1890  	}
  1891  	if ctxt.GOOS == "ios" && name == "darwin" {
  1892  		return true
  1893  	}
  1894  
  1895  	// other tags
  1896  	for _, tag := range ctxt.BuildTags {
  1897  		if tag == name {
  1898  			return true
  1899  		}
  1900  	}
  1901  	for _, tag := range ctxt.ReleaseTags {
  1902  		if tag == name {
  1903  			return true
  1904  		}
  1905  	}
  1906  
  1907  	return false
  1908  }
  1909  
  1910  // goodOSArchFile returns false if the name contains a $GOOS or $GOARCH
  1911  // suffix which does not match the current system.
  1912  // The recognized name formats are:
  1913  //
  1914  //     name_$(GOOS).*
  1915  //     name_$(GOARCH).*
  1916  //     name_$(GOOS)_$(GOARCH).*
  1917  //     name_$(GOOS)_test.*
  1918  //     name_$(GOARCH)_test.*
  1919  //     name_$(GOOS)_$(GOARCH)_test.*
  1920  //
  1921  // Exceptions:
  1922  // if GOOS=android, then files with GOOS=linux are also matched.
  1923  // if GOOS=illumos, then files with GOOS=solaris are also matched.
  1924  // if GOOS=ios, then files with GOOS=darwin are also matched.
  1925  func (ctxt *Context) goodOSArchFile(name string, allTags map[string]bool) bool {
  1926  	if dot := strings.Index(name, "."); dot != -1 {
  1927  		name = name[:dot]
  1928  	}
  1929  
  1930  	// Before Go 1.4, a file called "linux.go" would be equivalent to having a
  1931  	// build tag "linux" in that file. For Go 1.4 and beyond, we require this
  1932  	// auto-tagging to apply only to files with a non-empty prefix, so
  1933  	// "foo_linux.go" is tagged but "linux.go" is not. This allows new operating
  1934  	// systems, such as android, to arrive without breaking existing code with
  1935  	// innocuous source code in "android.go". The easiest fix: cut everything
  1936  	// in the name before the initial _.
  1937  	i := strings.Index(name, "_")
  1938  	if i < 0 {
  1939  		return true
  1940  	}
  1941  	name = name[i:] // ignore everything before first _
  1942  
  1943  	l := strings.Split(name, "_")
  1944  	if n := len(l); n > 0 && l[n-1] == "test" {
  1945  		l = l[:n-1]
  1946  	}
  1947  	n := len(l)
  1948  	if n >= 2 && knownOS[l[n-2]] && knownArch[l[n-1]] {
  1949  		return ctxt.match(l[n-1], allTags) && ctxt.match(l[n-2], allTags)
  1950  	}
  1951  	if n >= 1 && (knownOS[l[n-1]] || knownArch[l[n-1]]) {
  1952  		return ctxt.match(l[n-1], allTags)
  1953  	}
  1954  	return true
  1955  }
  1956  
  1957  var knownOS = make(map[string]bool)
  1958  var knownArch = make(map[string]bool)
  1959  
  1960  func init() {
  1961  	for _, v := range strings.Fields(goosList) {
  1962  		knownOS[v] = true
  1963  	}
  1964  	for _, v := range strings.Fields(goarchList) {
  1965  		knownArch[v] = true
  1966  	}
  1967  }
  1968  
  1969  // ToolDir is the directory containing build tools.
  1970  var ToolDir = getToolDir()
  1971  
  1972  // IsLocalImport reports whether the import path is
  1973  // a local import path, like ".", "..", "./foo", or "../foo".
  1974  func IsLocalImport(path string) bool {
  1975  	return path == "." || path == ".." ||
  1976  		strings.HasPrefix(path, "./") || strings.HasPrefix(path, "../")
  1977  }
  1978  
  1979  // ArchChar returns "?" and an error.
  1980  // In earlier versions of Go, the returned string was used to derive
  1981  // the compiler and linker tool names, the default object file suffix,
  1982  // and the default linker output name. As of Go 1.5, those strings
  1983  // no longer vary by architecture; they are compile, link, .o, and a.out, respectively.
  1984  func ArchChar(goarch string) (string, error) {
  1985  	return "?", errors.New("architecture letter no longer used")
  1986  }
  1987  

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