Source file src/go/build/build.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  package build
     6  
     7  import (
     8  	"bytes"
     9  	"errors"
    10  	"fmt"
    11  	"go/ast"
    12  	"go/build/constraint"
    13  	"go/doc"
    14  	"go/token"
    15  	"internal/buildcfg"
    16  	exec "internal/execabs"
    17  	"internal/goroot"
    18  	"internal/goversion"
    19  	"io"
    20  	"io/fs"
    21  	"io/ioutil"
    22  	"os"
    23  	pathpkg "path"
    24  	"path/filepath"
    25  	"runtime"
    26  	"sort"
    27  	"strconv"
    28  	"strings"
    29  	"unicode"
    30  	"unicode/utf8"
    31  )
    32  
    33  // A Context specifies the supporting context for a build.
    34  type Context struct {
    35  	GOARCH string // target architecture
    36  	GOOS   string // target operating system
    37  	GOROOT string // Go root
    38  	GOPATH string // Go path
    39  
    40  	// Dir is the caller's working directory, or the empty string to use
    41  	// the current directory of the running process. In module mode, this is used
    42  	// to locate the main module.
    43  	//
    44  	// If Dir is non-empty, directories passed to Import and ImportDir must
    45  	// be absolute.
    46  	Dir string
    47  
    48  	CgoEnabled  bool   // whether cgo files are included
    49  	UseAllFiles bool   // use files regardless of +build lines, file names
    50  	Compiler    string // compiler to assume when computing target paths
    51  
    52  	// The build, tool, and release tags specify build constraints
    53  	// that should be considered satisfied when processing +build lines.
    54  	// Clients creating a new context may customize BuildTags, which
    55  	// defaults to empty, but it is usually an error to customize ToolTags or ReleaseTags.
    56  	// ToolTags defaults to build tags appropriate to the current Go toolchain configuration.
    57  	// ReleaseTags defaults to the list of Go releases the current release is compatible with.
    58  	// BuildTags is not set for the Default build Context.
    59  	// In addition to the BuildTags, ToolTags, and ReleaseTags, build constraints
    60  	// consider the values of GOARCH and GOOS as satisfied tags.
    61  	// The last element in ReleaseTags is assumed to be the current release.
    62  	BuildTags   []string
    63  	ToolTags    []string
    64  	ReleaseTags []string
    65  
    66  	// The install suffix specifies a suffix to use in the name of the installation
    67  	// directory. By default it is empty, but custom builds that need to keep
    68  	// their outputs separate can set InstallSuffix to do so. For example, when
    69  	// using the race detector, the go command uses InstallSuffix = "race", so
    70  	// that on a Linux/386 system, packages are written to a directory named
    71  	// "linux_386_race" instead of the usual "linux_386".
    72  	InstallSuffix string
    73  
    74  	// By default, Import uses the operating system's file system calls
    75  	// to read directories and files. To read from other sources,
    76  	// callers can set the following functions. They all have default
    77  	// behaviors that use the local file system, so clients need only set
    78  	// the functions whose behaviors they wish to change.
    79  
    80  	// JoinPath joins the sequence of path fragments into a single path.
    81  	// If JoinPath is nil, Import uses filepath.Join.
    82  	JoinPath func(elem ...string) string
    83  
    84  	// SplitPathList splits the path list into a slice of individual paths.
    85  	// If SplitPathList is nil, Import uses filepath.SplitList.
    86  	SplitPathList func(list string) []string
    87  
    88  	// IsAbsPath reports whether path is an absolute path.
    89  	// If IsAbsPath is nil, Import uses filepath.IsAbs.
    90  	IsAbsPath func(path string) bool
    91  
    92  	// IsDir reports whether the path names a directory.
    93  	// If IsDir is nil, Import calls os.Stat and uses the result's IsDir method.
    94  	IsDir func(path string) bool
    95  
    96  	// HasSubdir reports whether dir is lexically a subdirectory of
    97  	// root, perhaps multiple levels below. It does not try to check
    98  	// whether dir exists.
    99  	// If so, HasSubdir sets rel to a slash-separated path that
   100  	// can be joined to root to produce a path equivalent to dir.
   101  	// If HasSubdir is nil, Import uses an implementation built on
   102  	// filepath.EvalSymlinks.
   103  	HasSubdir func(root, dir string) (rel string, ok bool)
   104  
   105  	// ReadDir returns a slice of fs.FileInfo, sorted by Name,
   106  	// describing the content of the named directory.
   107  	// If ReadDir is nil, Import uses ioutil.ReadDir.
   108  	ReadDir func(dir string) ([]fs.FileInfo, error)
   109  
   110  	// OpenFile opens a file (not a directory) for reading.
   111  	// If OpenFile is nil, Import uses os.Open.
   112  	OpenFile func(path string) (io.ReadCloser, error)
   113  }
   114  
   115  // joinPath calls ctxt.JoinPath (if not nil) or else filepath.Join.
   116  func (ctxt *Context) joinPath(elem ...string) string {
   117  	if f := ctxt.JoinPath; f != nil {
   118  		return f(elem...)
   119  	}
   120  	return filepath.Join(elem...)
   121  }
   122  
   123  // splitPathList calls ctxt.SplitPathList (if not nil) or else filepath.SplitList.
   124  func (ctxt *Context) splitPathList(s string) []string {
   125  	if f := ctxt.SplitPathList; f != nil {
   126  		return f(s)
   127  	}
   128  	return filepath.SplitList(s)
   129  }
   130  
   131  // isAbsPath calls ctxt.IsAbsPath (if not nil) or else filepath.IsAbs.
   132  func (ctxt *Context) isAbsPath(path string) bool {
   133  	if f := ctxt.IsAbsPath; f != nil {
   134  		return f(path)
   135  	}
   136  	return filepath.IsAbs(path)
   137  }
   138  
   139  // isDir calls ctxt.IsDir (if not nil) or else uses os.Stat.
   140  func (ctxt *Context) isDir(path string) bool {
   141  	if f := ctxt.IsDir; f != nil {
   142  		return f(path)
   143  	}
   144  	fi, err := os.Stat(path)
   145  	return err == nil && fi.IsDir()
   146  }
   147  
   148  // hasSubdir calls ctxt.HasSubdir (if not nil) or else uses
   149  // the local file system to answer the question.
   150  func (ctxt *Context) hasSubdir(root, dir string) (rel string, ok bool) {
   151  	if f := ctxt.HasSubdir; f != nil {
   152  		return f(root, dir)
   153  	}
   154  
   155  	// Try using paths we received.
   156  	if rel, ok = hasSubdir(root, dir); ok {
   157  		return
   158  	}
   159  
   160  	// Try expanding symlinks and comparing
   161  	// expanded against unexpanded and
   162  	// expanded against expanded.
   163  	rootSym, _ := filepath.EvalSymlinks(root)
   164  	dirSym, _ := filepath.EvalSymlinks(dir)
   165  
   166  	if rel, ok = hasSubdir(rootSym, dir); ok {
   167  		return
   168  	}
   169  	if rel, ok = hasSubdir(root, dirSym); ok {
   170  		return
   171  	}
   172  	return hasSubdir(rootSym, dirSym)
   173  }
   174  
   175  // hasSubdir reports if dir is within root by performing lexical analysis only.
   176  func hasSubdir(root, dir string) (rel string, ok bool) {
   177  	const sep = string(filepath.Separator)
   178  	root = filepath.Clean(root)
   179  	if !strings.HasSuffix(root, sep) {
   180  		root += sep
   181  	}
   182  	dir = filepath.Clean(dir)
   183  	if !strings.HasPrefix(dir, root) {
   184  		return "", false
   185  	}
   186  	return filepath.ToSlash(dir[len(root):]), true
   187  }
   188  
   189  // readDir calls ctxt.ReadDir (if not nil) or else ioutil.ReadDir.
   190  func (ctxt *Context) readDir(path string) ([]fs.FileInfo, error) {
   191  	if f := ctxt.ReadDir; f != nil {
   192  		return f(path)
   193  	}
   194  	// TODO: use os.ReadDir
   195  	return ioutil.ReadDir(path)
   196  }
   197  
   198  // openFile calls ctxt.OpenFile (if not nil) or else os.Open.
   199  func (ctxt *Context) openFile(path string) (io.ReadCloser, error) {
   200  	if fn := ctxt.OpenFile; fn != nil {
   201  		return fn(path)
   202  	}
   203  
   204  	f, err := os.Open(path)
   205  	if err != nil {
   206  		return nil, err // nil interface
   207  	}
   208  	return f, nil
   209  }
   210  
   211  // isFile determines whether path is a file by trying to open it.
   212  // It reuses openFile instead of adding another function to the
   213  // list in Context.
   214  func (ctxt *Context) isFile(path string) bool {
   215  	f, err := ctxt.openFile(path)
   216  	if err != nil {
   217  		return false
   218  	}
   219  	f.Close()
   220  	return true
   221  }
   222  
   223  // gopath returns the list of Go path directories.
   224  func (ctxt *Context) gopath() []string {
   225  	var all []string
   226  	for _, p := range ctxt.splitPathList(ctxt.GOPATH) {
   227  		if p == "" || p == ctxt.GOROOT {
   228  			// Empty paths are uninteresting.
   229  			// If the path is the GOROOT, ignore it.
   230  			// People sometimes set GOPATH=$GOROOT.
   231  			// Do not get confused by this common mistake.
   232  			continue
   233  		}
   234  		if strings.HasPrefix(p, "~") {
   235  			// Path segments starting with ~ on Unix are almost always
   236  			// users who have incorrectly quoted ~ while setting GOPATH,
   237  			// preventing it from expanding to $HOME.
   238  			// The situation is made more confusing by the fact that
   239  			// bash allows quoted ~ in $PATH (most shells do not).
   240  			// Do not get confused by this, and do not try to use the path.
   241  			// It does not exist, and printing errors about it confuses
   242  			// those users even more, because they think "sure ~ exists!".
   243  			// The go command diagnoses this situation and prints a
   244  			// useful error.
   245  			// On Windows, ~ is used in short names, such as c:\progra~1
   246  			// for c:\program files.
   247  			continue
   248  		}
   249  		all = append(all, p)
   250  	}
   251  	return all
   252  }
   253  
   254  // SrcDirs returns a list of package source root directories.
   255  // It draws from the current Go root and Go path but omits directories
   256  // that do not exist.
   257  func (ctxt *Context) SrcDirs() []string {
   258  	var all []string
   259  	if ctxt.GOROOT != "" && ctxt.Compiler != "gccgo" {
   260  		dir := ctxt.joinPath(ctxt.GOROOT, "src")
   261  		if ctxt.isDir(dir) {
   262  			all = append(all, dir)
   263  		}
   264  	}
   265  	for _, p := range ctxt.gopath() {
   266  		dir := ctxt.joinPath(p, "src")
   267  		if ctxt.isDir(dir) {
   268  			all = append(all, dir)
   269  		}
   270  	}
   271  	return all
   272  }
   273  
   274  // Default is the default Context for builds.
   275  // It uses the GOARCH, GOOS, GOROOT, and GOPATH environment variables
   276  // if set, or else the compiled code's GOARCH, GOOS, and GOROOT.
   277  var Default Context = defaultContext()
   278  
   279  func defaultGOPATH() string {
   280  	env := "HOME"
   281  	if runtime.GOOS == "windows" {
   282  		env = "USERPROFILE"
   283  	} else if runtime.GOOS == "plan9" {
   284  		env = "home"
   285  	}
   286  	if home := os.Getenv(env); home != "" {
   287  		def := filepath.Join(home, "go")
   288  		if filepath.Clean(def) == filepath.Clean(runtime.GOROOT()) {
   289  			// Don't set the default GOPATH to GOROOT,
   290  			// as that will trigger warnings from the go tool.
   291  			return ""
   292  		}
   293  		return def
   294  	}
   295  	return ""
   296  }
   297  
   298  var defaultToolTags, defaultReleaseTags []string
   299  
   300  func defaultContext() Context {
   301  	var c Context
   302  
   303  	c.GOARCH = buildcfg.GOARCH
   304  	c.GOOS = buildcfg.GOOS
   305  	c.GOROOT = pathpkg.Clean(runtime.GOROOT())
   306  	c.GOPATH = envOr("GOPATH", defaultGOPATH())
   307  	c.Compiler = runtime.Compiler
   308  
   309  	// For each experiment that has been enabled in the toolchain, define a
   310  	// build tag with the same name but prefixed by "goexperiment." which can be
   311  	// used for compiling alternative files for the experiment. This allows
   312  	// changes for the experiment, like extra struct fields in the runtime,
   313  	// without affecting the base non-experiment code at all.
   314  	for _, exp := range buildcfg.EnabledExperiments() {
   315  		c.ToolTags = append(c.ToolTags, "goexperiment."+exp)
   316  	}
   317  	defaultToolTags = append([]string{}, c.ToolTags...) // our own private copy
   318  
   319  	// Each major Go release in the Go 1.x series adds a new
   320  	// "go1.x" release tag. That is, the go1.x tag is present in
   321  	// all releases >= Go 1.x. Code that requires Go 1.x or later
   322  	// should say "+build go1.x", and code that should only be
   323  	// built before Go 1.x (perhaps it is the stub to use in that
   324  	// case) should say "+build !go1.x".
   325  	// The last element in ReleaseTags is the current release.
   326  	for i := 1; i <= goversion.Version; i++ {
   327  		c.ReleaseTags = append(c.ReleaseTags, "go1."+strconv.Itoa(i))
   328  	}
   329  
   330  	defaultReleaseTags = append([]string{}, c.ReleaseTags...) // our own private copy
   331  
   332  	env := os.Getenv("CGO_ENABLED")
   333  	if env == "" {
   334  		env = defaultCGO_ENABLED
   335  	}
   336  	switch env {
   337  	case "1":
   338  		c.CgoEnabled = true
   339  	case "0":
   340  		c.CgoEnabled = false
   341  	default:
   342  		// cgo must be explicitly enabled for cross compilation builds
   343  		if runtime.GOARCH == c.GOARCH && runtime.GOOS == c.GOOS {
   344  			c.CgoEnabled = cgoEnabled[c.GOOS+"/"+c.GOARCH]
   345  			break
   346  		}
   347  		c.CgoEnabled = false
   348  	}
   349  
   350  	return c
   351  }
   352  
   353  func envOr(name, def string) string {
   354  	s := os.Getenv(name)
   355  	if s == "" {
   356  		return def
   357  	}
   358  	return s
   359  }
   360  
   361  // An ImportMode controls the behavior of the Import method.
   362  type ImportMode uint
   363  
   364  const (
   365  	// If FindOnly is set, Import stops after locating the directory
   366  	// that should contain the sources for a package. It does not
   367  	// read any files in the directory.
   368  	FindOnly ImportMode = 1 << iota
   369  
   370  	// If AllowBinary is set, Import can be satisfied by a compiled
   371  	// package object without corresponding sources.
   372  	//
   373  	// Deprecated:
   374  	// The supported way to create a compiled-only package is to
   375  	// write source code containing a //go:binary-only-package comment at
   376  	// the top of the file. Such a package will be recognized
   377  	// regardless of this flag setting (because it has source code)
   378  	// and will have BinaryOnly set to true in the returned Package.
   379  	AllowBinary
   380  
   381  	// If ImportComment is set, parse import comments on package statements.
   382  	// Import returns an error if it finds a comment it cannot understand
   383  	// or finds conflicting comments in multiple source files.
   384  	// See golang.org/s/go14customimport for more information.
   385  	ImportComment
   386  
   387  	// By default, Import searches vendor directories
   388  	// that apply in the given source directory before searching
   389  	// the GOROOT and GOPATH roots.
   390  	// If an Import finds and returns a package using a vendor
   391  	// directory, the resulting ImportPath is the complete path
   392  	// to the package, including the path elements leading up
   393  	// to and including "vendor".
   394  	// For example, if Import("y", "x/subdir", 0) finds
   395  	// "x/vendor/y", the returned package's ImportPath is "x/vendor/y",
   396  	// not plain "y".
   397  	// See golang.org/s/go15vendor for more information.
   398  	//
   399  	// Setting IgnoreVendor ignores vendor directories.
   400  	//
   401  	// In contrast to the package's ImportPath,
   402  	// the returned package's Imports, TestImports, and XTestImports
   403  	// are always the exact import paths from the source files:
   404  	// Import makes no attempt to resolve or check those paths.
   405  	IgnoreVendor
   406  )
   407  
   408  // A Package describes the Go package found in a directory.
   409  type Package struct {
   410  	Dir           string   // directory containing package sources
   411  	Name          string   // package name
   412  	ImportComment string   // path in import comment on package statement
   413  	Doc           string   // documentation synopsis
   414  	ImportPath    string   // import path of package ("" if unknown)
   415  	Root          string   // root of Go tree where this package lives
   416  	SrcRoot       string   // package source root directory ("" if unknown)
   417  	PkgRoot       string   // package install root directory ("" if unknown)
   418  	PkgTargetRoot string   // architecture dependent install root directory ("" if unknown)
   419  	BinDir        string   // command install directory ("" if unknown)
   420  	Goroot        bool     // package found in Go root
   421  	PkgObj        string   // installed .a file
   422  	AllTags       []string // tags that can influence file selection in this directory
   423  	ConflictDir   string   // this directory shadows Dir in $GOPATH
   424  	BinaryOnly    bool     // cannot be rebuilt from source (has //go:binary-only-package comment)
   425  
   426  	// Source files
   427  	GoFiles           []string // .go source files (excluding CgoFiles, TestGoFiles, XTestGoFiles)
   428  	CgoFiles          []string // .go source files that import "C"
   429  	IgnoredGoFiles    []string // .go source files ignored for this build (including ignored _test.go files)
   430  	InvalidGoFiles    []string // .go source files with detected problems (parse error, wrong package name, and so on)
   431  	IgnoredOtherFiles []string // non-.go source files ignored for this build
   432  	CFiles            []string // .c source files
   433  	CXXFiles          []string // .cc, .cpp and .cxx source files
   434  	MFiles            []string // .m (Objective-C) source files
   435  	HFiles            []string // .h, .hh, .hpp and .hxx source files
   436  	FFiles            []string // .f, .F, .for and .f90 Fortran source files
   437  	SFiles            []string // .s source files
   438  	SwigFiles         []string // .swig files
   439  	SwigCXXFiles      []string // .swigcxx files
   440  	SysoFiles         []string // .syso system object files to add to archive
   441  
   442  	// Cgo directives
   443  	CgoCFLAGS    []string // Cgo CFLAGS directives
   444  	CgoCPPFLAGS  []string // Cgo CPPFLAGS directives
   445  	CgoCXXFLAGS  []string // Cgo CXXFLAGS directives
   446  	CgoFFLAGS    []string // Cgo FFLAGS directives
   447  	CgoLDFLAGS   []string // Cgo LDFLAGS directives
   448  	CgoPkgConfig []string // Cgo pkg-config directives
   449  
   450  	// Test information
   451  	TestGoFiles  []string // _test.go files in package
   452  	XTestGoFiles []string // _test.go files outside package
   453  
   454  	// Dependency information
   455  	Imports        []string                    // import paths from GoFiles, CgoFiles
   456  	ImportPos      map[string][]token.Position // line information for Imports
   457  	TestImports    []string                    // import paths from TestGoFiles
   458  	TestImportPos  map[string][]token.Position // line information for TestImports
   459  	XTestImports   []string                    // import paths from XTestGoFiles
   460  	XTestImportPos map[string][]token.Position // line information for XTestImports
   461  
   462  	// //go:embed patterns found in Go source files
   463  	// For example, if a source file says
   464  	//	//go:embed a* b.c
   465  	// then the list will contain those two strings as separate entries.
   466  	// (See package embed for more details about //go:embed.)
   467  	EmbedPatterns        []string                    // patterns from GoFiles, CgoFiles
   468  	EmbedPatternPos      map[string][]token.Position // line information for EmbedPatterns
   469  	TestEmbedPatterns    []string                    // patterns from TestGoFiles
   470  	TestEmbedPatternPos  map[string][]token.Position // line information for TestEmbedPatterns
   471  	XTestEmbedPatterns   []string                    // patterns from XTestGoFiles
   472  	XTestEmbedPatternPos map[string][]token.Position // line information for XTestEmbedPatternPos
   473  }
   474  
   475  // IsCommand reports whether the package is considered a
   476  // command to be installed (not just a library).
   477  // Packages named "main" are treated as commands.
   478  func (p *Package) IsCommand() bool {
   479  	return p.Name == "main"
   480  }
   481  
   482  // ImportDir is like Import but processes the Go package found in
   483  // the named directory.
   484  func (ctxt *Context) ImportDir(dir string, mode ImportMode) (*Package, error) {
   485  	return ctxt.Import(".", dir, mode)
   486  }
   487  
   488  // NoGoError is the error used by Import to describe a directory
   489  // containing no buildable Go source files. (It may still contain
   490  // test files, files hidden by build tags, and so on.)
   491  type NoGoError struct {
   492  	Dir string
   493  }
   494  
   495  func (e *NoGoError) Error() string {
   496  	return "no buildable Go source files in " + e.Dir
   497  }
   498  
   499  // MultiplePackageError describes a directory containing
   500  // multiple buildable Go source files for multiple packages.
   501  type MultiplePackageError struct {
   502  	Dir      string   // directory containing files
   503  	Packages []string // package names found
   504  	Files    []string // corresponding files: Files[i] declares package Packages[i]
   505  }
   506  
   507  func (e *MultiplePackageError) Error() string {
   508  	// Error string limited to two entries for compatibility.
   509  	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)
   510  }
   511  
   512  func nameExt(name string) string {
   513  	i := strings.LastIndex(name, ".")
   514  	if i < 0 {
   515  		return ""
   516  	}
   517  	return name[i:]
   518  }
   519  
   520  // Import returns details about the Go package named by the import path,
   521  // interpreting local import paths relative to the srcDir directory.
   522  // If the path is a local import path naming a package that can be imported
   523  // using a standard import path, the returned package will set p.ImportPath
   524  // to that path.
   525  //
   526  // In the directory containing the package, .go, .c, .h, and .s files are
   527  // considered part of the package except for:
   528  //
   529  //	- .go files in package documentation
   530  //	- files starting with _ or . (likely editor temporary files)
   531  //	- files with build constraints not satisfied by the context
   532  //
   533  // If an error occurs, Import returns a non-nil error and a non-nil
   534  // *Package containing partial information.
   535  //
   536  func (ctxt *Context) Import(path string, srcDir string, mode ImportMode) (*Package, error) {
   537  	p := &Package{
   538  		ImportPath: path,
   539  	}
   540  	if path == "" {
   541  		return p, fmt.Errorf("import %q: invalid import path", path)
   542  	}
   543  
   544  	var pkgtargetroot string
   545  	var pkga string
   546  	var pkgerr error
   547  	suffix := ""
   548  	if ctxt.InstallSuffix != "" {
   549  		suffix = "_" + ctxt.InstallSuffix
   550  	}
   551  	switch ctxt.Compiler {
   552  	case "gccgo":
   553  		pkgtargetroot = "pkg/gccgo_" + ctxt.GOOS + "_" + ctxt.GOARCH + suffix
   554  	case "gc":
   555  		pkgtargetroot = "pkg/" + ctxt.GOOS + "_" + ctxt.GOARCH + suffix
   556  	default:
   557  		// Save error for end of function.
   558  		pkgerr = fmt.Errorf("import %q: unknown compiler %q", path, ctxt.Compiler)
   559  	}
   560  	setPkga := func() {
   561  		switch ctxt.Compiler {
   562  		case "gccgo":
   563  			dir, elem := pathpkg.Split(p.ImportPath)
   564  			pkga = pkgtargetroot + "/" + dir + "lib" + elem + ".a"
   565  		case "gc":
   566  			pkga = pkgtargetroot + "/" + p.ImportPath + ".a"
   567  		}
   568  	}
   569  	setPkga()
   570  
   571  	binaryOnly := false
   572  	if IsLocalImport(path) {
   573  		pkga = "" // local imports have no installed path
   574  		if srcDir == "" {
   575  			return p, fmt.Errorf("import %q: import relative to unknown directory", path)
   576  		}
   577  		if !ctxt.isAbsPath(path) {
   578  			p.Dir = ctxt.joinPath(srcDir, path)
   579  		}
   580  		// p.Dir directory may or may not exist. Gather partial information first, check if it exists later.
   581  		// Determine canonical import path, if any.
   582  		// Exclude results where the import path would include /testdata/.
   583  		inTestdata := func(sub string) bool {
   584  			return strings.Contains(sub, "/testdata/") || strings.HasSuffix(sub, "/testdata") || strings.HasPrefix(sub, "testdata/") || sub == "testdata"
   585  		}
   586  		if ctxt.GOROOT != "" {
   587  			root := ctxt.joinPath(ctxt.GOROOT, "src")
   588  			if sub, ok := ctxt.hasSubdir(root, p.Dir); ok && !inTestdata(sub) {
   589  				p.Goroot = true
   590  				p.ImportPath = sub
   591  				p.Root = ctxt.GOROOT
   592  				setPkga() // p.ImportPath changed
   593  				goto Found
   594  			}
   595  		}
   596  		all := ctxt.gopath()
   597  		for i, root := range all {
   598  			rootsrc := ctxt.joinPath(root, "src")
   599  			if sub, ok := ctxt.hasSubdir(rootsrc, p.Dir); ok && !inTestdata(sub) {
   600  				// We found a potential import path for dir,
   601  				// but check that using it wouldn't find something
   602  				// else first.
   603  				if ctxt.GOROOT != "" && ctxt.Compiler != "gccgo" {
   604  					if dir := ctxt.joinPath(ctxt.GOROOT, "src", sub); ctxt.isDir(dir) {
   605  						p.ConflictDir = dir
   606  						goto Found
   607  					}
   608  				}
   609  				for _, earlyRoot := range all[:i] {
   610  					if dir := ctxt.joinPath(earlyRoot, "src", sub); ctxt.isDir(dir) {
   611  						p.ConflictDir = dir
   612  						goto Found
   613  					}
   614  				}
   615  
   616  				// sub would not name some other directory instead of this one.
   617  				// Record it.
   618  				p.ImportPath = sub
   619  				p.Root = root
   620  				setPkga() // p.ImportPath changed
   621  				goto Found
   622  			}
   623  		}
   624  		// It's okay that we didn't find a root containing dir.
   625  		// Keep going with the information we have.
   626  	} else {
   627  		if strings.HasPrefix(path, "/") {
   628  			return p, fmt.Errorf("import %q: cannot import absolute path", path)
   629  		}
   630  
   631  		if err := ctxt.importGo(p, path, srcDir, mode); err == nil {
   632  			goto Found
   633  		} else if err != errNoModules {
   634  			return p, err
   635  		}
   636  
   637  		gopath := ctxt.gopath() // needed twice below; avoid computing many times
   638  
   639  		// tried records the location of unsuccessful package lookups
   640  		var tried struct {
   641  			vendor []string
   642  			goroot string
   643  			gopath []string
   644  		}
   645  
   646  		// Vendor directories get first chance to satisfy import.
   647  		if mode&IgnoreVendor == 0 && srcDir != "" {
   648  			searchVendor := func(root string, isGoroot bool) bool {
   649  				sub, ok := ctxt.hasSubdir(root, srcDir)
   650  				if !ok || !strings.HasPrefix(sub, "src/") || strings.Contains(sub, "/testdata/") {
   651  					return false
   652  				}
   653  				for {
   654  					vendor := ctxt.joinPath(root, sub, "vendor")
   655  					if ctxt.isDir(vendor) {
   656  						dir := ctxt.joinPath(vendor, path)
   657  						if ctxt.isDir(dir) && hasGoFiles(ctxt, dir) {
   658  							p.Dir = dir
   659  							p.ImportPath = strings.TrimPrefix(pathpkg.Join(sub, "vendor", path), "src/")
   660  							p.Goroot = isGoroot
   661  							p.Root = root
   662  							setPkga() // p.ImportPath changed
   663  							return true
   664  						}
   665  						tried.vendor = append(tried.vendor, dir)
   666  					}
   667  					i := strings.LastIndex(sub, "/")
   668  					if i < 0 {
   669  						break
   670  					}
   671  					sub = sub[:i]
   672  				}
   673  				return false
   674  			}
   675  			if ctxt.Compiler != "gccgo" && searchVendor(ctxt.GOROOT, true) {
   676  				goto Found
   677  			}
   678  			for _, root := range gopath {
   679  				if searchVendor(root, false) {
   680  					goto Found
   681  				}
   682  			}
   683  		}
   684  
   685  		// Determine directory from import path.
   686  		if ctxt.GOROOT != "" {
   687  			// If the package path starts with "vendor/", only search GOROOT before
   688  			// GOPATH if the importer is also within GOROOT. That way, if the user has
   689  			// vendored in a package that is subsequently included in the standard
   690  			// distribution, they'll continue to pick up their own vendored copy.
   691  			gorootFirst := srcDir == "" || !strings.HasPrefix(path, "vendor/")
   692  			if !gorootFirst {
   693  				_, gorootFirst = ctxt.hasSubdir(ctxt.GOROOT, srcDir)
   694  			}
   695  			if gorootFirst {
   696  				dir := ctxt.joinPath(ctxt.GOROOT, "src", path)
   697  				if ctxt.Compiler != "gccgo" {
   698  					isDir := ctxt.isDir(dir)
   699  					binaryOnly = !isDir && mode&AllowBinary != 0 && pkga != "" && ctxt.isFile(ctxt.joinPath(ctxt.GOROOT, pkga))
   700  					if isDir || binaryOnly {
   701  						p.Dir = dir
   702  						p.Goroot = true
   703  						p.Root = ctxt.GOROOT
   704  						goto Found
   705  					}
   706  				}
   707  				tried.goroot = dir
   708  			}
   709  		}
   710  		if ctxt.Compiler == "gccgo" && goroot.IsStandardPackage(ctxt.GOROOT, ctxt.Compiler, path) {
   711  			p.Dir = ctxt.joinPath(ctxt.GOROOT, "src", path)
   712  			p.Goroot = true
   713  			p.Root = ctxt.GOROOT
   714  			goto Found
   715  		}
   716  		for _, root := range gopath {
   717  			dir := ctxt.joinPath(root, "src", path)
   718  			isDir := ctxt.isDir(dir)
   719  			binaryOnly = !isDir && mode&AllowBinary != 0 && pkga != "" && ctxt.isFile(ctxt.joinPath(root, pkga))
   720  			if isDir || binaryOnly {
   721  				p.Dir = dir
   722  				p.Root = root
   723  				goto Found
   724  			}
   725  			tried.gopath = append(tried.gopath, dir)
   726  		}
   727  
   728  		// If we tried GOPATH first due to a "vendor/" prefix, fall back to GOPATH.
   729  		// That way, the user can still get useful results from 'go list' for
   730  		// standard-vendored paths passed on the command line.
   731  		if ctxt.GOROOT != "" && tried.goroot == "" {
   732  			dir := ctxt.joinPath(ctxt.GOROOT, "src", path)
   733  			if ctxt.Compiler != "gccgo" {
   734  				isDir := ctxt.isDir(dir)
   735  				binaryOnly = !isDir && mode&AllowBinary != 0 && pkga != "" && ctxt.isFile(ctxt.joinPath(ctxt.GOROOT, pkga))
   736  				if isDir || binaryOnly {
   737  					p.Dir = dir
   738  					p.Goroot = true
   739  					p.Root = ctxt.GOROOT
   740  					goto Found
   741  				}
   742  			}
   743  			tried.goroot = dir
   744  		}
   745  
   746  		// package was not found
   747  		var paths []string
   748  		format := "\t%s (vendor tree)"
   749  		for _, dir := range tried.vendor {
   750  			paths = append(paths, fmt.Sprintf(format, dir))
   751  			format = "\t%s"
   752  		}
   753  		if tried.goroot != "" {
   754  			paths = append(paths, fmt.Sprintf("\t%s (from $GOROOT)", tried.goroot))
   755  		} else {
   756  			paths = append(paths, "\t($GOROOT not set)")
   757  		}
   758  		format = "\t%s (from $GOPATH)"
   759  		for _, dir := range tried.gopath {
   760  			paths = append(paths, fmt.Sprintf(format, dir))
   761  			format = "\t%s"
   762  		}
   763  		if len(tried.gopath) == 0 {
   764  			paths = append(paths, "\t($GOPATH not set. For more details see: 'go help gopath')")
   765  		}
   766  		return p, fmt.Errorf("cannot find package %q in any of:\n%s", path, strings.Join(paths, "\n"))
   767  	}
   768  
   769  Found:
   770  	if p.Root != "" {
   771  		p.SrcRoot = ctxt.joinPath(p.Root, "src")
   772  		p.PkgRoot = ctxt.joinPath(p.Root, "pkg")
   773  		p.BinDir = ctxt.joinPath(p.Root, "bin")
   774  		if pkga != "" {
   775  			p.PkgTargetRoot = ctxt.joinPath(p.Root, pkgtargetroot)
   776  			p.PkgObj = ctxt.joinPath(p.Root, pkga)
   777  		}
   778  	}
   779  
   780  	// If it's a local import path, by the time we get here, we still haven't checked
   781  	// that p.Dir directory exists. This is the right time to do that check.
   782  	// We can't do it earlier, because we want to gather partial information for the
   783  	// non-nil *Package returned when an error occurs.
   784  	// We need to do this before we return early on FindOnly flag.
   785  	if IsLocalImport(path) && !ctxt.isDir(p.Dir) {
   786  		if ctxt.Compiler == "gccgo" && p.Goroot {
   787  			// gccgo has no sources for GOROOT packages.
   788  			return p, nil
   789  		}
   790  
   791  		// package was not found
   792  		return p, fmt.Errorf("cannot find package %q in:\n\t%s", path, p.Dir)
   793  	}
   794  
   795  	if mode&FindOnly != 0 {
   796  		return p, pkgerr
   797  	}
   798  	if binaryOnly && (mode&AllowBinary) != 0 {
   799  		return p, pkgerr
   800  	}
   801  
   802  	if ctxt.Compiler == "gccgo" && p.Goroot {
   803  		// gccgo has no sources for GOROOT packages.
   804  		return p, nil
   805  	}
   806  
   807  	dirs, err := ctxt.readDir(p.Dir)
   808  	if err != nil {
   809  		return p, err
   810  	}
   811  
   812  	var badGoError error
   813  	badFiles := make(map[string]bool)
   814  	badFile := func(name string, err error) {
   815  		if badGoError == nil {
   816  			badGoError = err
   817  		}
   818  		if !badFiles[name] {
   819  			p.InvalidGoFiles = append(p.InvalidGoFiles, name)
   820  			badFiles[name] = true
   821  		}
   822  	}
   823  
   824  	var Sfiles []string // files with ".S"(capital S)/.sx(capital s equivalent for case insensitive filesystems)
   825  	var firstFile, firstCommentFile string
   826  	embedPos := make(map[string][]token.Position)
   827  	testEmbedPos := make(map[string][]token.Position)
   828  	xTestEmbedPos := make(map[string][]token.Position)
   829  	importPos := make(map[string][]token.Position)
   830  	testImportPos := make(map[string][]token.Position)
   831  	xTestImportPos := make(map[string][]token.Position)
   832  	allTags := make(map[string]bool)
   833  	fset := token.NewFileSet()
   834  	for _, d := range dirs {
   835  		if d.IsDir() {
   836  			continue
   837  		}
   838  		if d.Mode()&fs.ModeSymlink != 0 {
   839  			if ctxt.isDir(ctxt.joinPath(p.Dir, d.Name())) {
   840  				// Symlinks to directories are not source files.
   841  				continue
   842  			}
   843  		}
   844  
   845  		name := d.Name()
   846  		ext := nameExt(name)
   847  
   848  		info, err := ctxt.matchFile(p.Dir, name, allTags, &p.BinaryOnly, fset)
   849  		if err != nil {
   850  			badFile(name, err)
   851  			continue
   852  		}
   853  		if info == nil {
   854  			if strings.HasPrefix(name, "_") || strings.HasPrefix(name, ".") {
   855  				// not due to build constraints - don't report
   856  			} else if ext == ".go" {
   857  				p.IgnoredGoFiles = append(p.IgnoredGoFiles, name)
   858  			} else if fileListForExt(p, ext) != nil {
   859  				p.IgnoredOtherFiles = append(p.IgnoredOtherFiles, name)
   860  			}
   861  			continue
   862  		}
   863  		data, filename := info.header, info.name
   864  
   865  		// Going to save the file. For non-Go files, can stop here.
   866  		switch ext {
   867  		case ".go":
   868  			// keep going
   869  		case ".S", ".sx":
   870  			// special case for cgo, handled at end
   871  			Sfiles = append(Sfiles, name)
   872  			continue
   873  		default:
   874  			if list := fileListForExt(p, ext); list != nil {
   875  				*list = append(*list, name)
   876  			}
   877  			continue
   878  		}
   879  
   880  		if info.parseErr != nil {
   881  			badFile(name, info.parseErr)
   882  			// Fall through: we might still have a partial AST in info.parsed,
   883  			// and we want to list files with parse errors anyway.
   884  		}
   885  
   886  		var pkg string
   887  		if info.parsed != nil {
   888  			pkg = info.parsed.Name.Name
   889  			if pkg == "documentation" {
   890  				p.IgnoredGoFiles = append(p.IgnoredGoFiles, name)
   891  				continue
   892  			}
   893  		}
   894  
   895  		isTest := strings.HasSuffix(name, "_test.go")
   896  		isXTest := false
   897  		if isTest && strings.HasSuffix(pkg, "_test") {
   898  			isXTest = true
   899  			pkg = pkg[:len(pkg)-len("_test")]
   900  		}
   901  
   902  		if p.Name == "" {
   903  			p.Name = pkg
   904  			firstFile = name
   905  		} else if pkg != p.Name {
   906  			// TODO(#45999): The choice of p.Name is arbitrary based on file iteration
   907  			// order. Instead of resolving p.Name arbitrarily, we should clear out the
   908  			// existing name and mark the existing files as also invalid.
   909  			badFile(name, &MultiplePackageError{
   910  				Dir:      p.Dir,
   911  				Packages: []string{p.Name, pkg},
   912  				Files:    []string{firstFile, name},
   913  			})
   914  		}
   915  		// Grab the first package comment as docs, provided it is not from a test file.
   916  		if info.parsed != nil && info.parsed.Doc != nil && p.Doc == "" && !isTest && !isXTest {
   917  			p.Doc = doc.Synopsis(info.parsed.Doc.Text())
   918  		}
   919  
   920  		if mode&ImportComment != 0 {
   921  			qcom, line := findImportComment(data)
   922  			if line != 0 {
   923  				com, err := strconv.Unquote(qcom)
   924  				if err != nil {
   925  					badFile(name, fmt.Errorf("%s:%d: cannot parse import comment", filename, line))
   926  				} else if p.ImportComment == "" {
   927  					p.ImportComment = com
   928  					firstCommentFile = name
   929  				} else if p.ImportComment != com {
   930  					badFile(name, fmt.Errorf("found import comments %q (%s) and %q (%s) in %s", p.ImportComment, firstCommentFile, com, name, p.Dir))
   931  				}
   932  			}
   933  		}
   934  
   935  		// Record imports and information about cgo.
   936  		isCgo := false
   937  		for _, imp := range info.imports {
   938  			if imp.path == "C" {
   939  				if isTest {
   940  					badFile(name, fmt.Errorf("use of cgo in test %s not supported", filename))
   941  					continue
   942  				}
   943  				isCgo = true
   944  				if imp.doc != nil {
   945  					if err := ctxt.saveCgo(filename, p, imp.doc); err != nil {
   946  						badFile(name, err)
   947  					}
   948  				}
   949  			}
   950  		}
   951  
   952  		var fileList *[]string
   953  		var importMap, embedMap map[string][]token.Position
   954  		switch {
   955  		case isCgo:
   956  			allTags["cgo"] = true
   957  			if ctxt.CgoEnabled {
   958  				fileList = &p.CgoFiles
   959  				importMap = importPos
   960  				embedMap = embedPos
   961  			} else {
   962  				// Ignore imports and embeds from cgo files if cgo is disabled.
   963  				fileList = &p.IgnoredGoFiles
   964  			}
   965  		case isXTest:
   966  			fileList = &p.XTestGoFiles
   967  			importMap = xTestImportPos
   968  			embedMap = xTestEmbedPos
   969  		case isTest:
   970  			fileList = &p.TestGoFiles
   971  			importMap = testImportPos
   972  			embedMap = testEmbedPos
   973  		default:
   974  			fileList = &p.GoFiles
   975  			importMap = importPos
   976  			embedMap = embedPos
   977  		}
   978  		*fileList = append(*fileList, name)
   979  		if importMap != nil {
   980  			for _, imp := range info.imports {
   981  				importMap[imp.path] = append(importMap[imp.path], fset.Position(imp.pos))
   982  			}
   983  		}
   984  		if embedMap != nil {
   985  			for _, emb := range info.embeds {
   986  				embedMap[emb.pattern] = append(embedMap[emb.pattern], emb.pos)
   987  			}
   988  		}
   989  	}
   990  
   991  	for tag := range allTags {
   992  		p.AllTags = append(p.AllTags, tag)
   993  	}
   994  	sort.Strings(p.AllTags)
   995  
   996  	p.EmbedPatterns, p.EmbedPatternPos = cleanDecls(embedPos)
   997  	p.TestEmbedPatterns, p.TestEmbedPatternPos = cleanDecls(testEmbedPos)
   998  	p.XTestEmbedPatterns, p.XTestEmbedPatternPos = cleanDecls(xTestEmbedPos)
   999  
  1000  	p.Imports, p.ImportPos = cleanDecls(importPos)
  1001  	p.TestImports, p.TestImportPos = cleanDecls(testImportPos)
  1002  	p.XTestImports, p.XTestImportPos = cleanDecls(xTestImportPos)
  1003  
  1004  	// add the .S/.sx files only if we are using cgo
  1005  	// (which means gcc will compile them).
  1006  	// The standard assemblers expect .s files.
  1007  	if len(p.CgoFiles) > 0 {
  1008  		p.SFiles = append(p.SFiles, Sfiles...)
  1009  		sort.Strings(p.SFiles)
  1010  	} else {
  1011  		p.IgnoredOtherFiles = append(p.IgnoredOtherFiles, Sfiles...)
  1012  		sort.Strings(p.IgnoredOtherFiles)
  1013  	}
  1014  
  1015  	if badGoError != nil {
  1016  		return p, badGoError
  1017  	}
  1018  	if len(p.GoFiles)+len(p.CgoFiles)+len(p.TestGoFiles)+len(p.XTestGoFiles) == 0 {
  1019  		return p, &NoGoError{p.Dir}
  1020  	}
  1021  	return p, pkgerr
  1022  }
  1023  
  1024  func fileListForExt(p *Package, ext string) *[]string {
  1025  	switch ext {
  1026  	case ".c":
  1027  		return &p.CFiles
  1028  	case ".cc", ".cpp", ".cxx":
  1029  		return &p.CXXFiles
  1030  	case ".m":
  1031  		return &p.MFiles
  1032  	case ".h", ".hh", ".hpp", ".hxx":
  1033  		return &p.HFiles
  1034  	case ".f", ".F", ".for", ".f90":
  1035  		return &p.FFiles
  1036  	case ".s", ".S", ".sx":
  1037  		return &p.SFiles
  1038  	case ".swig":
  1039  		return &p.SwigFiles
  1040  	case ".swigcxx":
  1041  		return &p.SwigCXXFiles
  1042  	case ".syso":
  1043  		return &p.SysoFiles
  1044  	}
  1045  	return nil
  1046  }
  1047  
  1048  func uniq(list []string) []string {
  1049  	if list == nil {
  1050  		return nil
  1051  	}
  1052  	out := make([]string, len(list))
  1053  	copy(out, list)
  1054  	sort.Strings(out)
  1055  	uniq := out[:0]
  1056  	for _, x := range out {
  1057  		if len(uniq) == 0 || uniq[len(uniq)-1] != x {
  1058  			uniq = append(uniq, x)
  1059  		}
  1060  	}
  1061  	return uniq
  1062  }
  1063  
  1064  var errNoModules = errors.New("not using modules")
  1065  
  1066  // importGo checks whether it can use the go command to find the directory for path.
  1067  // If using the go command is not appropriate, importGo returns errNoModules.
  1068  // Otherwise, importGo tries using the go command and reports whether that succeeded.
  1069  // Using the go command lets build.Import and build.Context.Import find code
  1070  // in Go modules. In the long term we want tools to use go/packages (currently golang.org/x/tools/go/packages),
  1071  // which will also use the go command.
  1072  // Invoking the go command here is not very efficient in that it computes information
  1073  // about the requested package and all dependencies and then only reports about the requested package.
  1074  // Then we reinvoke it for every dependency. But this is still better than not working at all.
  1075  // See golang.org/issue/26504.
  1076  func (ctxt *Context) importGo(p *Package, path, srcDir string, mode ImportMode) error {
  1077  	// To invoke the go command,
  1078  	// we must not being doing special things like AllowBinary or IgnoreVendor,
  1079  	// and all the file system callbacks must be nil (we're meant to use the local file system).
  1080  	if mode&AllowBinary != 0 || mode&IgnoreVendor != 0 ||
  1081  		ctxt.JoinPath != nil || ctxt.SplitPathList != nil || ctxt.IsAbsPath != nil || ctxt.IsDir != nil || ctxt.HasSubdir != nil || ctxt.ReadDir != nil || ctxt.OpenFile != nil || !equal(ctxt.ToolTags, defaultToolTags) || !equal(ctxt.ReleaseTags, defaultReleaseTags) {
  1082  		return errNoModules
  1083  	}
  1084  
  1085  	// Predict whether module aware mode is enabled by checking the value of
  1086  	// GO111MODULE and looking for a go.mod file in the source directory or
  1087  	// one of its parents. Running 'go env GOMOD' in the source directory would
  1088  	// give a canonical answer, but we'd prefer not to execute another command.
  1089  	go111Module := os.Getenv("GO111MODULE")
  1090  	switch go111Module {
  1091  	case "off":
  1092  		return errNoModules
  1093  	default: // "", "on", "auto", anything else
  1094  		// Maybe use modules.
  1095  	}
  1096  
  1097  	if srcDir != "" {
  1098  		var absSrcDir string
  1099  		if filepath.IsAbs(srcDir) {
  1100  			absSrcDir = srcDir
  1101  		} else if ctxt.Dir != "" {
  1102  			return fmt.Errorf("go/build: Dir is non-empty, so relative srcDir is not allowed: %v", srcDir)
  1103  		} else {
  1104  			// Find the absolute source directory. hasSubdir does not handle
  1105  			// relative paths (and can't because the callbacks don't support this).
  1106  			var err error
  1107  			absSrcDir, err = filepath.Abs(srcDir)
  1108  			if err != nil {
  1109  				return errNoModules
  1110  			}
  1111  		}
  1112  
  1113  		// If the source directory is in GOROOT, then the in-process code works fine
  1114  		// and we should keep using it. Moreover, the 'go list' approach below doesn't
  1115  		// take standard-library vendoring into account and will fail.
  1116  		if _, ok := ctxt.hasSubdir(filepath.Join(ctxt.GOROOT, "src"), absSrcDir); ok {
  1117  			return errNoModules
  1118  		}
  1119  	}
  1120  
  1121  	// For efficiency, if path is a standard library package, let the usual lookup code handle it.
  1122  	if ctxt.GOROOT != "" {
  1123  		dir := ctxt.joinPath(ctxt.GOROOT, "src", path)
  1124  		if ctxt.isDir(dir) {
  1125  			return errNoModules
  1126  		}
  1127  	}
  1128  
  1129  	// If GO111MODULE=auto, look to see if there is a go.mod.
  1130  	// Since go1.13, it doesn't matter if we're inside GOPATH.
  1131  	if go111Module == "auto" {
  1132  		var (
  1133  			parent string
  1134  			err    error
  1135  		)
  1136  		if ctxt.Dir == "" {
  1137  			parent, err = os.Getwd()
  1138  			if err != nil {
  1139  				// A nonexistent working directory can't be in a module.
  1140  				return errNoModules
  1141  			}
  1142  		} else {
  1143  			parent, err = filepath.Abs(ctxt.Dir)
  1144  			if err != nil {
  1145  				// If the caller passed a bogus Dir explicitly, that's materially
  1146  				// different from not having modules enabled.
  1147  				return err
  1148  			}
  1149  		}
  1150  		for {
  1151  			if f, err := ctxt.openFile(ctxt.joinPath(parent, "go.mod")); err == nil {
  1152  				buf := make([]byte, 100)
  1153  				_, err := f.Read(buf)
  1154  				f.Close()
  1155  				if err == nil || err == io.EOF {
  1156  					// go.mod exists and is readable (is a file, not a directory).
  1157  					break
  1158  				}
  1159  			}
  1160  			d := filepath.Dir(parent)
  1161  			if len(d) >= len(parent) {
  1162  				return errNoModules // reached top of file system, no go.mod
  1163  			}
  1164  			parent = d
  1165  		}
  1166  	}
  1167  
  1168  	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)
  1169  
  1170  	if ctxt.Dir != "" {
  1171  		cmd.Dir = ctxt.Dir
  1172  	}
  1173  
  1174  	var stdout, stderr strings.Builder
  1175  	cmd.Stdout = &stdout
  1176  	cmd.Stderr = &stderr
  1177  
  1178  	cgo := "0"
  1179  	if ctxt.CgoEnabled {
  1180  		cgo = "1"
  1181  	}
  1182  	cmd.Env = append(os.Environ(),
  1183  		"GOOS="+ctxt.GOOS,
  1184  		"GOARCH="+ctxt.GOARCH,
  1185  		"GOROOT="+ctxt.GOROOT,
  1186  		"GOPATH="+ctxt.GOPATH,
  1187  		"CGO_ENABLED="+cgo,
  1188  	)
  1189  
  1190  	if err := cmd.Run(); err != nil {
  1191  		return fmt.Errorf("go/build: go list %s: %v\n%s\n", path, err, stderr.String())
  1192  	}
  1193  
  1194  	f := strings.SplitN(stdout.String(), "\n", 5)
  1195  	if len(f) != 5 {
  1196  		return fmt.Errorf("go/build: importGo %s: unexpected output:\n%s\n", path, stdout.String())
  1197  	}
  1198  	dir := f[0]
  1199  	errStr := strings.TrimSpace(f[4])
  1200  	if errStr != "" && dir == "" {
  1201  		// If 'go list' could not locate the package (dir is empty),
  1202  		// return the same error that 'go list' reported.
  1203  		return errors.New(errStr)
  1204  	}
  1205  
  1206  	// If 'go list' did locate the package, ignore the error.
  1207  	// It was probably related to loading source files, and we'll
  1208  	// encounter it ourselves shortly if the FindOnly flag isn't set.
  1209  	p.Dir = dir
  1210  	p.ImportPath = f[1]
  1211  	p.Root = f[2]
  1212  	p.Goroot = f[3] == "true"
  1213  	return nil
  1214  }
  1215  
  1216  func equal(x, y []string) bool {
  1217  	if len(x) != len(y) {
  1218  		return false
  1219  	}
  1220  	for i, xi := range x {
  1221  		if xi != y[i] {
  1222  			return false
  1223  		}
  1224  	}
  1225  	return true
  1226  }
  1227  
  1228  // hasGoFiles reports whether dir contains any files with names ending in .go.
  1229  // For a vendor check we must exclude directories that contain no .go files.
  1230  // Otherwise it is not possible to vendor just a/b/c and still import the
  1231  // non-vendored a/b. See golang.org/issue/13832.
  1232  func hasGoFiles(ctxt *Context, dir string) bool {
  1233  	ents, _ := ctxt.readDir(dir)
  1234  	for _, ent := range ents {
  1235  		if !ent.IsDir() && strings.HasSuffix(ent.Name(), ".go") {
  1236  			return true
  1237  		}
  1238  	}
  1239  	return false
  1240  }
  1241  
  1242  func findImportComment(data []byte) (s string, line int) {
  1243  	// expect keyword package
  1244  	word, data := parseWord(data)
  1245  	if string(word) != "package" {
  1246  		return "", 0
  1247  	}
  1248  
  1249  	// expect package name
  1250  	_, data = parseWord(data)
  1251  
  1252  	// now ready for import comment, a // or /* */ comment
  1253  	// beginning and ending on the current line.
  1254  	for len(data) > 0 && (data[0] == ' ' || data[0] == '\t' || data[0] == '\r') {
  1255  		data = data[1:]
  1256  	}
  1257  
  1258  	var comment []byte
  1259  	switch {
  1260  	case bytes.HasPrefix(data, slashSlash):
  1261  		i := bytes.Index(data, newline)
  1262  		if i < 0 {
  1263  			i = len(data)
  1264  		}
  1265  		comment = data[2:i]
  1266  	case bytes.HasPrefix(data, slashStar):
  1267  		data = data[2:]
  1268  		i := bytes.Index(data, starSlash)
  1269  		if i < 0 {
  1270  			// malformed comment
  1271  			return "", 0
  1272  		}
  1273  		comment = data[:i]
  1274  		if bytes.Contains(comment, newline) {
  1275  			return "", 0
  1276  		}
  1277  	}
  1278  	comment = bytes.TrimSpace(comment)
  1279  
  1280  	// split comment into `import`, `"pkg"`
  1281  	word, arg := parseWord(comment)
  1282  	if string(word) != "import" {
  1283  		return "", 0
  1284  	}
  1285  
  1286  	line = 1 + bytes.Count(data[:cap(data)-cap(arg)], newline)
  1287  	return strings.TrimSpace(string(arg)), line
  1288  }
  1289  
  1290  var (
  1291  	slashSlash = []byte("//")
  1292  	slashStar  = []byte("/*")
  1293  	starSlash  = []byte("*/")
  1294  	newline    = []byte("\n")
  1295  )
  1296  
  1297  // skipSpaceOrComment returns data with any leading spaces or comments removed.
  1298  func skipSpaceOrComment(data []byte) []byte {
  1299  	for len(data) > 0 {
  1300  		switch data[0] {
  1301  		case ' ', '\t', '\r', '\n':
  1302  			data = data[1:]
  1303  			continue
  1304  		case '/':
  1305  			if bytes.HasPrefix(data, slashSlash) {
  1306  				i := bytes.Index(data, newline)
  1307  				if i < 0 {
  1308  					return nil
  1309  				}
  1310  				data = data[i+1:]
  1311  				continue
  1312  			}
  1313  			if bytes.HasPrefix(data, slashStar) {
  1314  				data = data[2:]
  1315  				i := bytes.Index(data, starSlash)
  1316  				if i < 0 {
  1317  					return nil
  1318  				}
  1319  				data = data[i+2:]
  1320  				continue
  1321  			}
  1322  		}
  1323  		break
  1324  	}
  1325  	return data
  1326  }
  1327  
  1328  // parseWord skips any leading spaces or comments in data
  1329  // and then parses the beginning of data as an identifier or keyword,
  1330  // returning that word and what remains after the word.
  1331  func parseWord(data []byte) (word, rest []byte) {
  1332  	data = skipSpaceOrComment(data)
  1333  
  1334  	// Parse past leading word characters.
  1335  	rest = data
  1336  	for {
  1337  		r, size := utf8.DecodeRune(rest)
  1338  		if unicode.IsLetter(r) || '0' <= r && r <= '9' || r == '_' {
  1339  			rest = rest[size:]
  1340  			continue
  1341  		}
  1342  		break
  1343  	}
  1344  
  1345  	word = data[:len(data)-len(rest)]
  1346  	if len(word) == 0 {
  1347  		return nil, nil
  1348  	}
  1349  
  1350  	return word, rest
  1351  }
  1352  
  1353  // MatchFile reports whether the file with the given name in the given directory
  1354  // matches the context and would be included in a Package created by ImportDir
  1355  // of that directory.
  1356  //
  1357  // MatchFile considers the name of the file and may use ctxt.OpenFile to
  1358  // read some or all of the file's content.
  1359  func (ctxt *Context) MatchFile(dir, name string) (match bool, err error) {
  1360  	info, err := ctxt.matchFile(dir, name, nil, nil, nil)
  1361  	return info != nil, err
  1362  }
  1363  
  1364  var dummyPkg Package
  1365  
  1366  // fileInfo records information learned about a file included in a build.
  1367  type fileInfo struct {
  1368  	name     string // full name including dir
  1369  	header   []byte
  1370  	fset     *token.FileSet
  1371  	parsed   *ast.File
  1372  	parseErr error
  1373  	imports  []fileImport
  1374  	embeds   []fileEmbed
  1375  	embedErr error
  1376  }
  1377  
  1378  type fileImport struct {
  1379  	path string
  1380  	pos  token.Pos
  1381  	doc  *ast.CommentGroup
  1382  }
  1383  
  1384  type fileEmbed struct {
  1385  	pattern string
  1386  	pos     token.Position
  1387  }
  1388  
  1389  // matchFile determines whether the file with the given name in the given directory
  1390  // should be included in the package being constructed.
  1391  // If the file should be included, matchFile returns a non-nil *fileInfo (and a nil error).
  1392  // Non-nil errors are reserved for unexpected problems.
  1393  //
  1394  // If name denotes a Go program, matchFile reads until the end of the
  1395  // imports and returns that section of the file in the fileInfo's header field,
  1396  // even though it only considers text until the first non-comment
  1397  // for +build lines.
  1398  //
  1399  // If allTags is non-nil, matchFile records any encountered build tag
  1400  // by setting allTags[tag] = true.
  1401  func (ctxt *Context) matchFile(dir, name string, allTags map[string]bool, binaryOnly *bool, fset *token.FileSet) (*fileInfo, error) {
  1402  	if strings.HasPrefix(name, "_") ||
  1403  		strings.HasPrefix(name, ".") {
  1404  		return nil, nil
  1405  	}
  1406  
  1407  	i := strings.LastIndex(name, ".")
  1408  	if i < 0 {
  1409  		i = len(name)
  1410  	}
  1411  	ext := name[i:]
  1412  
  1413  	if !ctxt.goodOSArchFile(name, allTags) && !ctxt.UseAllFiles {
  1414  		return nil, nil
  1415  	}
  1416  
  1417  	if ext != ".go" && fileListForExt(&dummyPkg, ext) == nil {
  1418  		// skip
  1419  		return nil, nil
  1420  	}
  1421  
  1422  	info := &fileInfo{name: ctxt.joinPath(dir, name), fset: fset}
  1423  	if ext == ".syso" {
  1424  		// binary, no reading
  1425  		return info, nil
  1426  	}
  1427  
  1428  	f, err := ctxt.openFile(info.name)
  1429  	if err != nil {
  1430  		return nil, err
  1431  	}
  1432  
  1433  	if strings.HasSuffix(name, ".go") {
  1434  		err = readGoInfo(f, info)
  1435  		if strings.HasSuffix(name, "_test.go") {
  1436  			binaryOnly = nil // ignore //go:binary-only-package comments in _test.go files
  1437  		}
  1438  	} else {
  1439  		binaryOnly = nil // ignore //go:binary-only-package comments in non-Go sources
  1440  		info.header, err = readComments(f)
  1441  	}
  1442  	f.Close()
  1443  	if err != nil {
  1444  		return nil, fmt.Errorf("read %s: %v", info.name, err)
  1445  	}
  1446  
  1447  	// Look for +build comments to accept or reject the file.
  1448  	ok, sawBinaryOnly, err := ctxt.shouldBuild(info.header, allTags)
  1449  	if err != nil {
  1450  		return nil, fmt.Errorf("%s: %v", name, err)
  1451  	}
  1452  	if !ok && !ctxt.UseAllFiles {
  1453  		return nil, nil
  1454  	}
  1455  
  1456  	if binaryOnly != nil && sawBinaryOnly {
  1457  		*binaryOnly = true
  1458  	}
  1459  
  1460  	return info, nil
  1461  }
  1462  
  1463  func cleanDecls(m map[string][]token.Position) ([]string, map[string][]token.Position) {
  1464  	all := make([]string, 0, len(m))
  1465  	for path := range m {
  1466  		all = append(all, path)
  1467  	}
  1468  	sort.Strings(all)
  1469  	return all, m
  1470  }
  1471  
  1472  // Import is shorthand for Default.Import.
  1473  func Import(path, srcDir string, mode ImportMode) (*Package, error) {
  1474  	return Default.Import(path, srcDir, mode)
  1475  }
  1476  
  1477  // ImportDir is shorthand for Default.ImportDir.
  1478  func ImportDir(dir string, mode ImportMode) (*Package, error) {
  1479  	return Default.ImportDir(dir, mode)
  1480  }
  1481  
  1482  var (
  1483  	bSlashSlash = []byte(slashSlash)
  1484  	bStarSlash  = []byte(starSlash)
  1485  	bSlashStar  = []byte(slashStar)
  1486  	bPlusBuild  = []byte("+build")
  1487  
  1488  	goBuildComment = []byte("//go:build")
  1489  
  1490  	errGoBuildWithoutBuild = errors.New("//go:build comment without // +build comment")
  1491  	errMultipleGoBuild     = errors.New("multiple //go:build comments")
  1492  )
  1493  
  1494  func isGoBuildComment(line []byte) bool {
  1495  	if !bytes.HasPrefix(line, goBuildComment) {
  1496  		return false
  1497  	}
  1498  	line = bytes.TrimSpace(line)
  1499  	rest := line[len(goBuildComment):]
  1500  	return len(rest) == 0 || len(bytes.TrimSpace(rest)) < len(rest)
  1501  }
  1502  
  1503  // Special comment denoting a binary-only package.
  1504  // See https://golang.org/design/2775-binary-only-packages
  1505  // for more about the design of binary-only packages.
  1506  var binaryOnlyComment = []byte("//go:binary-only-package")
  1507  
  1508  // shouldBuild reports whether it is okay to use this file,
  1509  // The rule is that in the file's leading run of // comments
  1510  // and blank lines, which must be followed by a blank line
  1511  // (to avoid including a Go package clause doc comment),
  1512  // lines beginning with '// +build' are taken as build directives.
  1513  //
  1514  // The file is accepted only if each such line lists something
  1515  // matching the file. For example:
  1516  //
  1517  //	// +build windows linux
  1518  //
  1519  // marks the file as applicable only on Windows and Linux.
  1520  //
  1521  // For each build tag it consults, shouldBuild sets allTags[tag] = true.
  1522  //
  1523  // shouldBuild reports whether the file should be built
  1524  // and whether a //go:binary-only-package comment was found.
  1525  func (ctxt *Context) shouldBuild(content []byte, allTags map[string]bool) (shouldBuild, binaryOnly bool, err error) {
  1526  	// Identify leading run of // comments and blank lines,
  1527  	// which must be followed by a blank line.
  1528  	// Also identify any //go:build comments.
  1529  	content, goBuild, sawBinaryOnly, err := parseFileHeader(content)
  1530  	if err != nil {
  1531  		return false, false, err
  1532  	}
  1533  
  1534  	// If //go:build line is present, it controls.
  1535  	// Otherwise fall back to +build processing.
  1536  	switch {
  1537  	case goBuild != nil:
  1538  		x, err := constraint.Parse(string(goBuild))
  1539  		if err != nil {
  1540  			return false, false, fmt.Errorf("parsing //go:build line: %v", err)
  1541  		}
  1542  		shouldBuild = ctxt.eval(x, allTags)
  1543  
  1544  	default:
  1545  		shouldBuild = true
  1546  		p := content
  1547  		for len(p) > 0 {
  1548  			line := p
  1549  			if i := bytes.IndexByte(line, '\n'); i >= 0 {
  1550  				line, p = line[:i], p[i+1:]
  1551  			} else {
  1552  				p = p[len(p):]
  1553  			}
  1554  			line = bytes.TrimSpace(line)
  1555  			if !bytes.HasPrefix(line, bSlashSlash) || !bytes.Contains(line, bPlusBuild) {
  1556  				continue
  1557  			}
  1558  			text := string(line)
  1559  			if !constraint.IsPlusBuild(text) {
  1560  				continue
  1561  			}
  1562  			if x, err := constraint.Parse(text); err == nil {
  1563  				if !ctxt.eval(x, allTags) {
  1564  					shouldBuild = false
  1565  				}
  1566  			}
  1567  		}
  1568  	}
  1569  
  1570  	return shouldBuild, sawBinaryOnly, nil
  1571  }
  1572  
  1573  func parseFileHeader(content []byte) (trimmed, goBuild []byte, sawBinaryOnly bool, err error) {
  1574  	end := 0
  1575  	p := content
  1576  	ended := false       // found non-blank, non-// line, so stopped accepting // +build lines
  1577  	inSlashStar := false // in /* */ comment
  1578  
  1579  Lines:
  1580  	for len(p) > 0 {
  1581  		line := p
  1582  		if i := bytes.IndexByte(line, '\n'); i >= 0 {
  1583  			line, p = line[:i], p[i+1:]
  1584  		} else {
  1585  			p = p[len(p):]
  1586  		}
  1587  		line = bytes.TrimSpace(line)
  1588  		if len(line) == 0 && !ended { // Blank line
  1589  			// Remember position of most recent blank line.
  1590  			// When we find the first non-blank, non-// line,
  1591  			// this "end" position marks the latest file position
  1592  			// where a // +build line can appear.
  1593  			// (It must appear _before_ a blank line before the non-blank, non-// line.
  1594  			// Yes, that's confusing, which is part of why we moved to //go:build lines.)
  1595  			// Note that ended==false here means that inSlashStar==false,
  1596  			// since seeing a /* would have set ended==true.
  1597  			end = len(content) - len(p)
  1598  			continue Lines
  1599  		}
  1600  		if !bytes.HasPrefix(line, slashSlash) { // Not comment line
  1601  			ended = true
  1602  		}
  1603  
  1604  		if !inSlashStar && isGoBuildComment(line) {
  1605  			if goBuild != nil {
  1606  				return nil, nil, false, errMultipleGoBuild
  1607  			}
  1608  			goBuild = line
  1609  		}
  1610  		if !inSlashStar && bytes.Equal(line, binaryOnlyComment) {
  1611  			sawBinaryOnly = true
  1612  		}
  1613  
  1614  	Comments:
  1615  		for len(line) > 0 {
  1616  			if inSlashStar {
  1617  				if i := bytes.Index(line, starSlash); i >= 0 {
  1618  					inSlashStar = false
  1619  					line = bytes.TrimSpace(line[i+len(starSlash):])
  1620  					continue Comments
  1621  				}
  1622  				continue Lines
  1623  			}
  1624  			if bytes.HasPrefix(line, bSlashSlash) {
  1625  				continue Lines
  1626  			}
  1627  			if bytes.HasPrefix(line, bSlashStar) {
  1628  				inSlashStar = true
  1629  				line = bytes.TrimSpace(line[len(bSlashStar):])
  1630  				continue Comments
  1631  			}
  1632  			// Found non-comment text.
  1633  			break Lines
  1634  		}
  1635  	}
  1636  
  1637  	return content[:end], goBuild, sawBinaryOnly, nil
  1638  }
  1639  
  1640  // saveCgo saves the information from the #cgo lines in the import "C" comment.
  1641  // These lines set CFLAGS, CPPFLAGS, CXXFLAGS and LDFLAGS and pkg-config directives
  1642  // that affect the way cgo's C code is built.
  1643  func (ctxt *Context) saveCgo(filename string, di *Package, cg *ast.CommentGroup) error {
  1644  	text := cg.Text()
  1645  	for _, line := range strings.Split(text, "\n") {
  1646  		orig := line
  1647  
  1648  		// Line is
  1649  		//	#cgo [GOOS/GOARCH...] LDFLAGS: stuff
  1650  		//
  1651  		line = strings.TrimSpace(line)
  1652  		if len(line) < 5 || line[:4] != "#cgo" || (line[4] != ' ' && line[4] != '\t') {
  1653  			continue
  1654  		}
  1655  
  1656  		// Split at colon.
  1657  		line = strings.TrimSpace(line[4:])
  1658  		i := strings.Index(line, ":")
  1659  		if i < 0 {
  1660  			return fmt.Errorf("%s: invalid #cgo line: %s", filename, orig)
  1661  		}
  1662  		line, argstr := line[:i], line[i+1:]
  1663  
  1664  		// Parse GOOS/GOARCH stuff.
  1665  		f := strings.Fields(line)
  1666  		if len(f) < 1 {
  1667  			return fmt.Errorf("%s: invalid #cgo line: %s", filename, orig)
  1668  		}
  1669  
  1670  		cond, verb := f[:len(f)-1], f[len(f)-1]
  1671  		if len(cond) > 0 {
  1672  			ok := false
  1673  			for _, c := range cond {
  1674  				if ctxt.matchAuto(c, nil) {
  1675  					ok = true
  1676  					break
  1677  				}
  1678  			}
  1679  			if !ok {
  1680  				continue
  1681  			}
  1682  		}
  1683  
  1684  		args, err := splitQuoted(argstr)
  1685  		if err != nil {
  1686  			return fmt.Errorf("%s: invalid #cgo line: %s", filename, orig)
  1687  		}
  1688  		var ok bool
  1689  		for i, arg := range args {
  1690  			if arg, ok = expandSrcDir(arg, di.Dir); !ok {
  1691  				return fmt.Errorf("%s: malformed #cgo argument: %s", filename, arg)
  1692  			}
  1693  			args[i] = arg
  1694  		}
  1695  
  1696  		switch verb {
  1697  		case "CFLAGS", "CPPFLAGS", "CXXFLAGS", "FFLAGS", "LDFLAGS":
  1698  			// Change relative paths to absolute.
  1699  			ctxt.makePathsAbsolute(args, di.Dir)
  1700  		}
  1701  
  1702  		switch verb {
  1703  		case "CFLAGS":
  1704  			di.CgoCFLAGS = append(di.CgoCFLAGS, args...)
  1705  		case "CPPFLAGS":
  1706  			di.CgoCPPFLAGS = append(di.CgoCPPFLAGS, args...)
  1707  		case "CXXFLAGS":
  1708  			di.CgoCXXFLAGS = append(di.CgoCXXFLAGS, args...)
  1709  		case "FFLAGS":
  1710  			di.CgoFFLAGS = append(di.CgoFFLAGS, args...)
  1711  		case "LDFLAGS":
  1712  			di.CgoLDFLAGS = append(di.CgoLDFLAGS, args...)
  1713  		case "pkg-config":
  1714  			di.CgoPkgConfig = append(di.CgoPkgConfig, args...)
  1715  		default:
  1716  			return fmt.Errorf("%s: invalid #cgo verb: %s", filename, orig)
  1717  		}
  1718  	}
  1719  	return nil
  1720  }
  1721  
  1722  // expandSrcDir expands any occurrence of ${SRCDIR}, making sure
  1723  // the result is safe for the shell.
  1724  func expandSrcDir(str string, srcdir string) (string, bool) {
  1725  	// "\" delimited paths cause safeCgoName to fail
  1726  	// so convert native paths with a different delimiter
  1727  	// to "/" before starting (eg: on windows).
  1728  	srcdir = filepath.ToSlash(srcdir)
  1729  
  1730  	chunks := strings.Split(str, "${SRCDIR}")
  1731  	if len(chunks) < 2 {
  1732  		return str, safeCgoName(str)
  1733  	}
  1734  	ok := true
  1735  	for _, chunk := range chunks {
  1736  		ok = ok && (chunk == "" || safeCgoName(chunk))
  1737  	}
  1738  	ok = ok && (srcdir == "" || safeCgoName(srcdir))
  1739  	res := strings.Join(chunks, srcdir)
  1740  	return res, ok && res != ""
  1741  }
  1742  
  1743  // makePathsAbsolute looks for compiler options that take paths and
  1744  // makes them absolute. We do this because through the 1.8 release we
  1745  // ran the compiler in the package directory, so any relative -I or -L
  1746  // options would be relative to that directory. In 1.9 we changed to
  1747  // running the compiler in the build directory, to get consistent
  1748  // build results (issue #19964). To keep builds working, we change any
  1749  // relative -I or -L options to be absolute.
  1750  //
  1751  // Using filepath.IsAbs and filepath.Join here means the results will be
  1752  // different on different systems, but that's OK: -I and -L options are
  1753  // inherently system-dependent.
  1754  func (ctxt *Context) makePathsAbsolute(args []string, srcDir string) {
  1755  	nextPath := false
  1756  	for i, arg := range args {
  1757  		if nextPath {
  1758  			if !filepath.IsAbs(arg) {
  1759  				args[i] = filepath.Join(srcDir, arg)
  1760  			}
  1761  			nextPath = false
  1762  		} else if strings.HasPrefix(arg, "-I") || strings.HasPrefix(arg, "-L") {
  1763  			if len(arg) == 2 {
  1764  				nextPath = true
  1765  			} else {
  1766  				if !filepath.IsAbs(arg[2:]) {
  1767  					args[i] = arg[:2] + filepath.Join(srcDir, arg[2:])
  1768  				}
  1769  			}
  1770  		}
  1771  	}
  1772  }
  1773  
  1774  // NOTE: $ is not safe for the shell, but it is allowed here because of linker options like -Wl,$ORIGIN.
  1775  // We never pass these arguments to a shell (just to programs we construct argv for), so this should be okay.
  1776  // See golang.org/issue/6038.
  1777  // The @ is for OS X. See golang.org/issue/13720.
  1778  // The % is for Jenkins. See golang.org/issue/16959.
  1779  // The ! is because module paths may use them. See golang.org/issue/26716.
  1780  // The ~ and ^ are for sr.ht. See golang.org/issue/32260.
  1781  const safeString = "+-.,/0123456789=ABCDEFGHIJKLMNOPQRSTUVWXYZ_abcdefghijklmnopqrstuvwxyz:$@%! ~^"
  1782  
  1783  func safeCgoName(s string) bool {
  1784  	if s == "" {
  1785  		return false
  1786  	}
  1787  	for i := 0; i < len(s); i++ {
  1788  		if c := s[i]; c < utf8.RuneSelf && strings.IndexByte(safeString, c) < 0 {
  1789  			return false
  1790  		}
  1791  	}
  1792  	return true
  1793  }
  1794  
  1795  // splitQuoted splits the string s around each instance of one or more consecutive
  1796  // white space characters while taking into account quotes and escaping, and
  1797  // returns an array of substrings of s or an empty list if s contains only white space.
  1798  // Single quotes and double quotes are recognized to prevent splitting within the
  1799  // quoted region, and are removed from the resulting substrings. If a quote in s
  1800  // isn't closed err will be set and r will have the unclosed argument as the
  1801  // last element. The backslash is used for escaping.
  1802  //
  1803  // For example, the following string:
  1804  //
  1805  //     a b:"c d" 'e''f'  "g\""
  1806  //
  1807  // Would be parsed as:
  1808  //
  1809  //     []string{"a", "b:c d", "ef", `g"`}
  1810  //
  1811  func splitQuoted(s string) (r []string, err error) {
  1812  	var args []string
  1813  	arg := make([]rune, len(s))
  1814  	escaped := false
  1815  	quoted := false
  1816  	quote := '\x00'
  1817  	i := 0
  1818  	for _, rune := range s {
  1819  		switch {
  1820  		case escaped:
  1821  			escaped = false
  1822  		case rune == '\\':
  1823  			escaped = true
  1824  			continue
  1825  		case quote != '\x00':
  1826  			if rune == quote {
  1827  				quote = '\x00'
  1828  				continue
  1829  			}
  1830  		case rune == '"' || rune == '\'':
  1831  			quoted = true
  1832  			quote = rune
  1833  			continue
  1834  		case unicode.IsSpace(rune):
  1835  			if quoted || i > 0 {
  1836  				quoted = false
  1837  				args = append(args, string(arg[:i]))
  1838  				i = 0
  1839  			}
  1840  			continue
  1841  		}
  1842  		arg[i] = rune
  1843  		i++
  1844  	}
  1845  	if quoted || i > 0 {
  1846  		args = append(args, string(arg[:i]))
  1847  	}
  1848  	if quote != 0 {
  1849  		err = errors.New("unclosed quote")
  1850  	} else if escaped {
  1851  		err = errors.New("unfinished escaping")
  1852  	}
  1853  	return args, err
  1854  }
  1855  
  1856  // matchAuto interprets text as either a +build or //go:build expression (whichever works),
  1857  // reporting whether the expression matches the build context.
  1858  //
  1859  // matchAuto is only used for testing of tag evaluation
  1860  // and in #cgo lines, which accept either syntax.
  1861  func (ctxt *Context) matchAuto(text string, allTags map[string]bool) bool {
  1862  	if strings.ContainsAny(text, "&|()") {
  1863  		text = "//go:build " + text
  1864  	} else {
  1865  		text = "// +build " + text
  1866  	}
  1867  	x, err := constraint.Parse(text)
  1868  	if err != nil {
  1869  		return false
  1870  	}
  1871  	return ctxt.eval(x, allTags)
  1872  }
  1873  
  1874  func (ctxt *Context) eval(x constraint.Expr, allTags map[string]bool) bool {
  1875  	return x.Eval(func(tag string) bool { return ctxt.matchTag(tag, allTags) })
  1876  }
  1877  
  1878  // matchTag reports whether the name is one of:
  1879  //
  1880  //	cgo (if cgo is enabled)
  1881  //	$GOOS
  1882  //	$GOARCH
  1883  //	ctxt.Compiler
  1884  //	linux (if GOOS = android)
  1885  //	solaris (if GOOS = illumos)
  1886  //	tag (if tag is listed in ctxt.BuildTags or ctxt.ReleaseTags)
  1887  //
  1888  // It records all consulted tags in allTags.
  1889  func (ctxt *Context) matchTag(name string, allTags map[string]bool) bool {
  1890  	if allTags != nil {
  1891  		allTags[name] = true
  1892  	}
  1893  
  1894  	// special tags
  1895  	if ctxt.CgoEnabled && name == "cgo" {
  1896  		return true
  1897  	}
  1898  	if name == ctxt.GOOS || name == ctxt.GOARCH || name == ctxt.Compiler {
  1899  		return true
  1900  	}
  1901  	if ctxt.GOOS == "android" && name == "linux" {
  1902  		return true
  1903  	}
  1904  	if ctxt.GOOS == "illumos" && name == "solaris" {
  1905  		return true
  1906  	}
  1907  	if ctxt.GOOS == "ios" && name == "darwin" {
  1908  		return true
  1909  	}
  1910  
  1911  	// other tags
  1912  	for _, tag := range ctxt.BuildTags {
  1913  		if tag == name {
  1914  			return true
  1915  		}
  1916  	}
  1917  	for _, tag := range ctxt.ToolTags {
  1918  		if tag == name {
  1919  			return true
  1920  		}
  1921  	}
  1922  	for _, tag := range ctxt.ReleaseTags {
  1923  		if tag == name {
  1924  			return true
  1925  		}
  1926  	}
  1927  
  1928  	return false
  1929  }
  1930  
  1931  // goodOSArchFile returns false if the name contains a $GOOS or $GOARCH
  1932  // suffix which does not match the current system.
  1933  // The recognized name formats are:
  1934  //
  1935  //     name_$(GOOS).*
  1936  //     name_$(GOARCH).*
  1937  //     name_$(GOOS)_$(GOARCH).*
  1938  //     name_$(GOOS)_test.*
  1939  //     name_$(GOARCH)_test.*
  1940  //     name_$(GOOS)_$(GOARCH)_test.*
  1941  //
  1942  // Exceptions:
  1943  // if GOOS=android, then files with GOOS=linux are also matched.
  1944  // if GOOS=illumos, then files with GOOS=solaris are also matched.
  1945  // if GOOS=ios, then files with GOOS=darwin are also matched.
  1946  func (ctxt *Context) goodOSArchFile(name string, allTags map[string]bool) bool {
  1947  	if dot := strings.Index(name, "."); dot != -1 {
  1948  		name = name[:dot]
  1949  	}
  1950  
  1951  	// Before Go 1.4, a file called "linux.go" would be equivalent to having a
  1952  	// build tag "linux" in that file. For Go 1.4 and beyond, we require this
  1953  	// auto-tagging to apply only to files with a non-empty prefix, so
  1954  	// "foo_linux.go" is tagged but "linux.go" is not. This allows new operating
  1955  	// systems, such as android, to arrive without breaking existing code with
  1956  	// innocuous source code in "android.go". The easiest fix: cut everything
  1957  	// in the name before the initial _.
  1958  	i := strings.Index(name, "_")
  1959  	if i < 0 {
  1960  		return true
  1961  	}
  1962  	name = name[i:] // ignore everything before first _
  1963  
  1964  	l := strings.Split(name, "_")
  1965  	if n := len(l); n > 0 && l[n-1] == "test" {
  1966  		l = l[:n-1]
  1967  	}
  1968  	n := len(l)
  1969  	if n >= 2 && knownOS[l[n-2]] && knownArch[l[n-1]] {
  1970  		return ctxt.matchTag(l[n-1], allTags) && ctxt.matchTag(l[n-2], allTags)
  1971  	}
  1972  	if n >= 1 && (knownOS[l[n-1]] || knownArch[l[n-1]]) {
  1973  		return ctxt.matchTag(l[n-1], allTags)
  1974  	}
  1975  	return true
  1976  }
  1977  
  1978  var knownOS = make(map[string]bool)
  1979  var knownArch = make(map[string]bool)
  1980  
  1981  func init() {
  1982  	for _, v := range strings.Fields(goosList) {
  1983  		knownOS[v] = true
  1984  	}
  1985  	for _, v := range strings.Fields(goarchList) {
  1986  		knownArch[v] = true
  1987  	}
  1988  }
  1989  
  1990  // ToolDir is the directory containing build tools.
  1991  var ToolDir = getToolDir()
  1992  
  1993  // IsLocalImport reports whether the import path is
  1994  // a local import path, like ".", "..", "./foo", or "../foo".
  1995  func IsLocalImport(path string) bool {
  1996  	return path == "." || path == ".." ||
  1997  		strings.HasPrefix(path, "./") || strings.HasPrefix(path, "../")
  1998  }
  1999  
  2000  // ArchChar returns "?" and an error.
  2001  // In earlier versions of Go, the returned string was used to derive
  2002  // the compiler and linker tool names, the default object file suffix,
  2003  // and the default linker output name. As of Go 1.5, those strings
  2004  // no longer vary by architecture; they are compile, link, .o, and a.out, respectively.
  2005  func ArchChar(goarch string) (string, error) {
  2006  	return "?", errors.New("architecture letter no longer used")
  2007  }
  2008  

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