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/build/constraint"
    13  	"go/doc"
    14  	"go/token"
    15  	"internal/buildcfg"
    16  	"internal/godebug"
    17  	"internal/goroot"
    18  	"internal/goversion"
    19  	"internal/platform"
    20  	"io"
    21  	"io/fs"
    22  	"os"
    23  	"os/exec"
    24  	pathpkg "path"
    25  	"path/filepath"
    26  	"runtime"
    27  	"sort"
    28  	"strconv"
    29  	"strings"
    30  	"unicode"
    31  	"unicode/utf8"
    32  )
    33  
    34  // A Context specifies the supporting context for a build.
    35  type Context struct {
    36  	GOARCH string // target architecture
    37  	GOOS   string // target operating system
    38  	GOROOT string // Go root
    39  	GOPATH string // Go paths
    40  
    41  	// Dir is the caller's working directory, or the empty string to use
    42  	// the current directory of the running process. In module mode, this is used
    43  	// to locate the main module.
    44  	//
    45  	// If Dir is non-empty, directories passed to Import and ImportDir must
    46  	// be absolute.
    47  	Dir string
    48  
    49  	CgoEnabled  bool   // whether cgo files are included
    50  	UseAllFiles bool   // use files regardless of go:build lines, file names
    51  	Compiler    string // compiler to assume when computing target paths
    52  
    53  	// The build, tool, and release tags specify build constraints
    54  	// that should be considered satisfied when processing go:build lines.
    55  	// Clients creating a new context may customize BuildTags, which
    56  	// defaults to empty, but it is usually an error to customize ToolTags or ReleaseTags.
    57  	// ToolTags defaults to build tags appropriate to the current Go toolchain configuration.
    58  	// ReleaseTags defaults to the list of Go releases the current release is compatible with.
    59  	// BuildTags is not set for the Default build Context.
    60  	// In addition to the BuildTags, ToolTags, and ReleaseTags, build constraints
    61  	// consider the values of GOARCH and GOOS as satisfied tags.
    62  	// The last element in ReleaseTags is assumed to be the current release.
    63  	BuildTags   []string
    64  	ToolTags    []string
    65  	ReleaseTags []string
    66  
    67  	// The install suffix specifies a suffix to use in the name of the installation
    68  	// directory. By default it is empty, but custom builds that need to keep
    69  	// their outputs separate can set InstallSuffix to do so. For example, when
    70  	// using the race detector, the go command uses InstallSuffix = "race", so
    71  	// that on a Linux/386 system, packages are written to a directory named
    72  	// "linux_386_race" instead of the usual "linux_386".
    73  	InstallSuffix string
    74  
    75  	// By default, Import uses the operating system's file system calls
    76  	// to read directories and files. To read from other sources,
    77  	// callers can set the following functions. They all have default
    78  	// behaviors that use the local file system, so clients need only set
    79  	// the functions whose behaviors they wish to change.
    80  
    81  	// JoinPath joins the sequence of path fragments into a single path.
    82  	// If JoinPath is nil, Import uses filepath.Join.
    83  	JoinPath func(elem ...string) string
    84  
    85  	// SplitPathList splits the path list into a slice of individual paths.
    86  	// If SplitPathList is nil, Import uses filepath.SplitList.
    87  	SplitPathList func(list string) []string
    88  
    89  	// IsAbsPath reports whether path is an absolute path.
    90  	// If IsAbsPath is nil, Import uses filepath.IsAbs.
    91  	IsAbsPath func(path string) bool
    92  
    93  	// IsDir reports whether the path names a directory.
    94  	// If IsDir is nil, Import calls os.Stat and uses the result's IsDir method.
    95  	IsDir func(path string) bool
    96  
    97  	// HasSubdir reports whether dir is lexically a subdirectory of
    98  	// root, perhaps multiple levels below. It does not try to check
    99  	// whether dir exists.
   100  	// If so, HasSubdir sets rel to a slash-separated path that
   101  	// can be joined to root to produce a path equivalent to dir.
   102  	// If HasSubdir is nil, Import uses an implementation built on
   103  	// filepath.EvalSymlinks.
   104  	HasSubdir func(root, dir string) (rel string, ok bool)
   105  
   106  	// ReadDir returns a slice of fs.FileInfo, sorted by Name,
   107  	// describing the content of the named directory.
   108  	// If ReadDir is nil, Import uses os.ReadDir.
   109  	ReadDir func(dir string) ([]fs.FileInfo, error)
   110  
   111  	// OpenFile opens a file (not a directory) for reading.
   112  	// If OpenFile is nil, Import uses os.Open.
   113  	OpenFile func(path string) (io.ReadCloser, error)
   114  }
   115  
   116  // joinPath calls ctxt.JoinPath (if not nil) or else filepath.Join.
   117  func (ctxt *Context) joinPath(elem ...string) string {
   118  	if f := ctxt.JoinPath; f != nil {
   119  		return f(elem...)
   120  	}
   121  	return filepath.Join(elem...)
   122  }
   123  
   124  // splitPathList calls ctxt.SplitPathList (if not nil) or else filepath.SplitList.
   125  func (ctxt *Context) splitPathList(s string) []string {
   126  	if f := ctxt.SplitPathList; f != nil {
   127  		return f(s)
   128  	}
   129  	return filepath.SplitList(s)
   130  }
   131  
   132  // isAbsPath calls ctxt.IsAbsPath (if not nil) or else filepath.IsAbs.
   133  func (ctxt *Context) isAbsPath(path string) bool {
   134  	if f := ctxt.IsAbsPath; f != nil {
   135  		return f(path)
   136  	}
   137  	return filepath.IsAbs(path)
   138  }
   139  
   140  // isDir calls ctxt.IsDir (if not nil) or else uses os.Stat.
   141  func (ctxt *Context) isDir(path string) bool {
   142  	if f := ctxt.IsDir; f != nil {
   143  		return f(path)
   144  	}
   145  	fi, err := os.Stat(path)
   146  	return err == nil && fi.IsDir()
   147  }
   148  
   149  // hasSubdir calls ctxt.HasSubdir (if not nil) or else uses
   150  // the local file system to answer the question.
   151  func (ctxt *Context) hasSubdir(root, dir string) (rel string, ok bool) {
   152  	if f := ctxt.HasSubdir; f != nil {
   153  		return f(root, dir)
   154  	}
   155  
   156  	// Try using paths we received.
   157  	if rel, ok = hasSubdir(root, dir); ok {
   158  		return
   159  	}
   160  
   161  	// Try expanding symlinks and comparing
   162  	// expanded against unexpanded and
   163  	// expanded against expanded.
   164  	rootSym, _ := filepath.EvalSymlinks(root)
   165  	dirSym, _ := filepath.EvalSymlinks(dir)
   166  
   167  	if rel, ok = hasSubdir(rootSym, dir); ok {
   168  		return
   169  	}
   170  	if rel, ok = hasSubdir(root, dirSym); ok {
   171  		return
   172  	}
   173  	return hasSubdir(rootSym, dirSym)
   174  }
   175  
   176  // hasSubdir reports if dir is within root by performing lexical analysis only.
   177  func hasSubdir(root, dir string) (rel string, ok bool) {
   178  	const sep = string(filepath.Separator)
   179  	root = filepath.Clean(root)
   180  	if !strings.HasSuffix(root, sep) {
   181  		root += sep
   182  	}
   183  	dir = filepath.Clean(dir)
   184  	after, found := strings.CutPrefix(dir, root)
   185  	if !found {
   186  		return "", false
   187  	}
   188  	return filepath.ToSlash(after), true
   189  }
   190  
   191  // readDir calls ctxt.ReadDir (if not nil) or else os.ReadDir.
   192  func (ctxt *Context) readDir(path string) ([]fs.DirEntry, error) {
   193  	// TODO: add a fs.DirEntry version of Context.ReadDir
   194  	if f := ctxt.ReadDir; f != nil {
   195  		fis, err := f(path)
   196  		if err != nil {
   197  			return nil, err
   198  		}
   199  		des := make([]fs.DirEntry, len(fis))
   200  		for i, fi := range fis {
   201  			des[i] = fs.FileInfoToDirEntry(fi)
   202  		}
   203  		return des, nil
   204  	}
   205  	return os.ReadDir(path)
   206  }
   207  
   208  // openFile calls ctxt.OpenFile (if not nil) or else os.Open.
   209  func (ctxt *Context) openFile(path string) (io.ReadCloser, error) {
   210  	if fn := ctxt.OpenFile; fn != nil {
   211  		return fn(path)
   212  	}
   213  
   214  	f, err := os.Open(path)
   215  	if err != nil {
   216  		return nil, err // nil interface
   217  	}
   218  	return f, nil
   219  }
   220  
   221  // isFile determines whether path is a file by trying to open it.
   222  // It reuses openFile instead of adding another function to the
   223  // list in Context.
   224  func (ctxt *Context) isFile(path string) bool {
   225  	f, err := ctxt.openFile(path)
   226  	if err != nil {
   227  		return false
   228  	}
   229  	f.Close()
   230  	return true
   231  }
   232  
   233  // gopath returns the list of Go path directories.
   234  func (ctxt *Context) gopath() []string {
   235  	var all []string
   236  	for _, p := range ctxt.splitPathList(ctxt.GOPATH) {
   237  		if p == "" || p == ctxt.GOROOT {
   238  			// Empty paths are uninteresting.
   239  			// If the path is the GOROOT, ignore it.
   240  			// People sometimes set GOPATH=$GOROOT.
   241  			// Do not get confused by this common mistake.
   242  			continue
   243  		}
   244  		if strings.HasPrefix(p, "~") {
   245  			// Path segments starting with ~ on Unix are almost always
   246  			// users who have incorrectly quoted ~ while setting GOPATH,
   247  			// preventing it from expanding to $HOME.
   248  			// The situation is made more confusing by the fact that
   249  			// bash allows quoted ~ in $PATH (most shells do not).
   250  			// Do not get confused by this, and do not try to use the path.
   251  			// It does not exist, and printing errors about it confuses
   252  			// those users even more, because they think "sure ~ exists!".
   253  			// The go command diagnoses this situation and prints a
   254  			// useful error.
   255  			// On Windows, ~ is used in short names, such as c:\progra~1
   256  			// for c:\program files.
   257  			continue
   258  		}
   259  		all = append(all, p)
   260  	}
   261  	return all
   262  }
   263  
   264  // SrcDirs returns a list of package source root directories.
   265  // It draws from the current Go root and Go path but omits directories
   266  // that do not exist.
   267  func (ctxt *Context) SrcDirs() []string {
   268  	var all []string
   269  	if ctxt.GOROOT != "" && ctxt.Compiler != "gccgo" {
   270  		dir := ctxt.joinPath(ctxt.GOROOT, "src")
   271  		if ctxt.isDir(dir) {
   272  			all = append(all, dir)
   273  		}
   274  	}
   275  	for _, p := range ctxt.gopath() {
   276  		dir := ctxt.joinPath(p, "src")
   277  		if ctxt.isDir(dir) {
   278  			all = append(all, dir)
   279  		}
   280  	}
   281  	return all
   282  }
   283  
   284  // Default is the default Context for builds.
   285  // It uses the GOARCH, GOOS, GOROOT, and GOPATH environment variables
   286  // if set, or else the compiled code's GOARCH, GOOS, and GOROOT.
   287  var Default Context = defaultContext()
   288  
   289  func defaultGOPATH() string {
   290  	env := "HOME"
   291  	if runtime.GOOS == "windows" {
   292  		env = "USERPROFILE"
   293  	} else if runtime.GOOS == "plan9" {
   294  		env = "home"
   295  	}
   296  	if home := os.Getenv(env); home != "" {
   297  		def := filepath.Join(home, "go")
   298  		if filepath.Clean(def) == filepath.Clean(runtime.GOROOT()) {
   299  			// Don't set the default GOPATH to GOROOT,
   300  			// as that will trigger warnings from the go tool.
   301  			return ""
   302  		}
   303  		return def
   304  	}
   305  	return ""
   306  }
   307  
   308  var defaultToolTags, defaultReleaseTags []string
   309  
   310  func defaultContext() Context {
   311  	var c Context
   312  
   313  	c.GOARCH = buildcfg.GOARCH
   314  	c.GOOS = buildcfg.GOOS
   315  	if goroot := runtime.GOROOT(); goroot != "" {
   316  		c.GOROOT = filepath.Clean(goroot)
   317  	}
   318  	c.GOPATH = envOr("GOPATH", defaultGOPATH())
   319  	c.Compiler = runtime.Compiler
   320  	c.ToolTags = append(c.ToolTags, buildcfg.ToolTags...)
   321  
   322  	defaultToolTags = append([]string{}, c.ToolTags...) // our own private copy
   323  
   324  	// Each major Go release in the Go 1.x series adds a new
   325  	// "go1.x" release tag. That is, the go1.x tag is present in
   326  	// all releases >= Go 1.x. Code that requires Go 1.x or later
   327  	// should say "go:build go1.x", and code that should only be
   328  	// built before Go 1.x (perhaps it is the stub to use in that
   329  	// case) should say "go:build !go1.x".
   330  	// The last element in ReleaseTags is the current release.
   331  	for i := 1; i <= goversion.Version; i++ {
   332  		c.ReleaseTags = append(c.ReleaseTags, "go1."+strconv.Itoa(i))
   333  	}
   334  
   335  	defaultReleaseTags = append([]string{}, c.ReleaseTags...) // our own private copy
   336  
   337  	env := os.Getenv("CGO_ENABLED")
   338  	if env == "" {
   339  		env = defaultCGO_ENABLED
   340  	}
   341  	switch env {
   342  	case "1":
   343  		c.CgoEnabled = true
   344  	case "0":
   345  		c.CgoEnabled = false
   346  	default:
   347  		// cgo must be explicitly enabled for cross compilation builds
   348  		if runtime.GOARCH == c.GOARCH && runtime.GOOS == c.GOOS {
   349  			c.CgoEnabled = platform.CgoSupported(c.GOOS, c.GOARCH)
   350  			break
   351  		}
   352  		c.CgoEnabled = false
   353  	}
   354  
   355  	return c
   356  }
   357  
   358  func envOr(name, def string) string {
   359  	s := os.Getenv(name)
   360  	if s == "" {
   361  		return def
   362  	}
   363  	return s
   364  }
   365  
   366  // An ImportMode controls the behavior of the Import method.
   367  type ImportMode uint
   368  
   369  const (
   370  	// If FindOnly is set, Import stops after locating the directory
   371  	// that should contain the sources for a package. It does not
   372  	// read any files in the directory.
   373  	FindOnly ImportMode = 1 << iota
   374  
   375  	// If AllowBinary is set, Import can be satisfied by a compiled
   376  	// package object without corresponding sources.
   377  	//
   378  	// Deprecated:
   379  	// The supported way to create a compiled-only package is to
   380  	// write source code containing a //go:binary-only-package comment at
   381  	// the top of the file. Such a package will be recognized
   382  	// regardless of this flag setting (because it has source code)
   383  	// and will have BinaryOnly set to true in the returned Package.
   384  	AllowBinary
   385  
   386  	// If ImportComment is set, parse import comments on package statements.
   387  	// Import returns an error if it finds a comment it cannot understand
   388  	// or finds conflicting comments in multiple source files.
   389  	// See golang.org/s/go14customimport for more information.
   390  	ImportComment
   391  
   392  	// By default, Import searches vendor directories
   393  	// that apply in the given source directory before searching
   394  	// the GOROOT and GOPATH roots.
   395  	// If an Import finds and returns a package using a vendor
   396  	// directory, the resulting ImportPath is the complete path
   397  	// to the package, including the path elements leading up
   398  	// to and including "vendor".
   399  	// For example, if Import("y", "x/subdir", 0) finds
   400  	// "x/vendor/y", the returned package's ImportPath is "x/vendor/y",
   401  	// not plain "y".
   402  	// See golang.org/s/go15vendor for more information.
   403  	//
   404  	// Setting IgnoreVendor ignores vendor directories.
   405  	//
   406  	// In contrast to the package's ImportPath,
   407  	// the returned package's Imports, TestImports, and XTestImports
   408  	// are always the exact import paths from the source files:
   409  	// Import makes no attempt to resolve or check those paths.
   410  	IgnoreVendor
   411  )
   412  
   413  // A Package describes the Go package found in a directory.
   414  type Package struct {
   415  	Dir           string   // directory containing package sources
   416  	Name          string   // package name
   417  	ImportComment string   // path in import comment on package statement
   418  	Doc           string   // documentation synopsis
   419  	ImportPath    string   // import path of package ("" if unknown)
   420  	Root          string   // root of Go tree where this package lives
   421  	SrcRoot       string   // package source root directory ("" if unknown)
   422  	PkgRoot       string   // package install root directory ("" if unknown)
   423  	PkgTargetRoot string   // architecture dependent install root directory ("" if unknown)
   424  	BinDir        string   // command install directory ("" if unknown)
   425  	Goroot        bool     // package found in Go root
   426  	PkgObj        string   // installed .a file
   427  	AllTags       []string // tags that can influence file selection in this directory
   428  	ConflictDir   string   // this directory shadows Dir in $GOPATH
   429  	BinaryOnly    bool     // cannot be rebuilt from source (has //go:binary-only-package comment)
   430  
   431  	// Source files
   432  	GoFiles           []string // .go source files (excluding CgoFiles, TestGoFiles, XTestGoFiles)
   433  	CgoFiles          []string // .go source files that import "C"
   434  	IgnoredGoFiles    []string // .go source files ignored for this build (including ignored _test.go files)
   435  	InvalidGoFiles    []string // .go source files with detected problems (parse error, wrong package name, and so on)
   436  	IgnoredOtherFiles []string // non-.go source files ignored for this build
   437  	CFiles            []string // .c source files
   438  	CXXFiles          []string // .cc, .cpp and .cxx source files
   439  	MFiles            []string // .m (Objective-C) source files
   440  	HFiles            []string // .h, .hh, .hpp and .hxx source files
   441  	FFiles            []string // .f, .F, .for and .f90 Fortran source files
   442  	SFiles            []string // .s source files
   443  	SwigFiles         []string // .swig files
   444  	SwigCXXFiles      []string // .swigcxx files
   445  	SysoFiles         []string // .syso system object files to add to archive
   446  
   447  	// Cgo directives
   448  	CgoCFLAGS    []string // Cgo CFLAGS directives
   449  	CgoCPPFLAGS  []string // Cgo CPPFLAGS directives
   450  	CgoCXXFLAGS  []string // Cgo CXXFLAGS directives
   451  	CgoFFLAGS    []string // Cgo FFLAGS directives
   452  	CgoLDFLAGS   []string // Cgo LDFLAGS directives
   453  	CgoPkgConfig []string // Cgo pkg-config directives
   454  
   455  	// Test information
   456  	TestGoFiles  []string // _test.go files in package
   457  	XTestGoFiles []string // _test.go files outside package
   458  
   459  	// Go directive comments (//go:zzz...) found in source files.
   460  	Directives      []Directive
   461  	TestDirectives  []Directive
   462  	XTestDirectives []Directive
   463  
   464  	// Dependency information
   465  	Imports        []string                    // import paths from GoFiles, CgoFiles
   466  	ImportPos      map[string][]token.Position // line information for Imports
   467  	TestImports    []string                    // import paths from TestGoFiles
   468  	TestImportPos  map[string][]token.Position // line information for TestImports
   469  	XTestImports   []string                    // import paths from XTestGoFiles
   470  	XTestImportPos map[string][]token.Position // line information for XTestImports
   471  
   472  	// //go:embed patterns found in Go source files
   473  	// For example, if a source file says
   474  	//	//go:embed a* b.c
   475  	// then the list will contain those two strings as separate entries.
   476  	// (See package embed for more details about //go:embed.)
   477  	EmbedPatterns        []string                    // patterns from GoFiles, CgoFiles
   478  	EmbedPatternPos      map[string][]token.Position // line information for EmbedPatterns
   479  	TestEmbedPatterns    []string                    // patterns from TestGoFiles
   480  	TestEmbedPatternPos  map[string][]token.Position // line information for TestEmbedPatterns
   481  	XTestEmbedPatterns   []string                    // patterns from XTestGoFiles
   482  	XTestEmbedPatternPos map[string][]token.Position // line information for XTestEmbedPatternPos
   483  }
   484  
   485  // A Directive is a Go directive comment (//go:zzz...) found in a source file.
   486  type Directive struct {
   487  	Text string         // full line comment including leading slashes
   488  	Pos  token.Position // position of comment
   489  }
   490  
   491  // IsCommand reports whether the package is considered a
   492  // command to be installed (not just a library).
   493  // Packages named "main" are treated as commands.
   494  func (p *Package) IsCommand() bool {
   495  	return p.Name == "main"
   496  }
   497  
   498  // ImportDir is like [Import] but processes the Go package found in
   499  // the named directory.
   500  func (ctxt *Context) ImportDir(dir string, mode ImportMode) (*Package, error) {
   501  	return ctxt.Import(".", dir, mode)
   502  }
   503  
   504  // NoGoError is the error used by [Import] to describe a directory
   505  // containing no buildable Go source files. (It may still contain
   506  // test files, files hidden by build tags, and so on.)
   507  type NoGoError struct {
   508  	Dir string
   509  }
   510  
   511  func (e *NoGoError) Error() string {
   512  	return "no buildable Go source files in " + e.Dir
   513  }
   514  
   515  // MultiplePackageError describes a directory containing
   516  // multiple buildable Go source files for multiple packages.
   517  type MultiplePackageError struct {
   518  	Dir      string   // directory containing files
   519  	Packages []string // package names found
   520  	Files    []string // corresponding files: Files[i] declares package Packages[i]
   521  }
   522  
   523  func (e *MultiplePackageError) Error() string {
   524  	// Error string limited to two entries for compatibility.
   525  	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)
   526  }
   527  
   528  func nameExt(name string) string {
   529  	i := strings.LastIndex(name, ".")
   530  	if i < 0 {
   531  		return ""
   532  	}
   533  	return name[i:]
   534  }
   535  
   536  var installgoroot = godebug.New("installgoroot")
   537  
   538  // Import returns details about the Go package named by the import path,
   539  // interpreting local import paths relative to the srcDir directory.
   540  // If the path is a local import path naming a package that can be imported
   541  // using a standard import path, the returned package will set p.ImportPath
   542  // to that path.
   543  //
   544  // In the directory containing the package, .go, .c, .h, and .s files are
   545  // considered part of the package except for:
   546  //
   547  //   - .go files in package documentation
   548  //   - files starting with _ or . (likely editor temporary files)
   549  //   - files with build constraints not satisfied by the context
   550  //
   551  // If an error occurs, Import returns a non-nil error and a non-nil
   552  // *[Package] containing partial information.
   553  func (ctxt *Context) Import(path string, srcDir string, mode ImportMode) (*Package, error) {
   554  	p := &Package{
   555  		ImportPath: path,
   556  	}
   557  	if path == "" {
   558  		return p, fmt.Errorf("import %q: invalid import path", path)
   559  	}
   560  
   561  	var pkgtargetroot string
   562  	var pkga string
   563  	var pkgerr error
   564  	suffix := ""
   565  	if ctxt.InstallSuffix != "" {
   566  		suffix = "_" + ctxt.InstallSuffix
   567  	}
   568  	switch ctxt.Compiler {
   569  	case "gccgo":
   570  		pkgtargetroot = "pkg/gccgo_" + ctxt.GOOS + "_" + ctxt.GOARCH + suffix
   571  	case "gc":
   572  		pkgtargetroot = "pkg/" + ctxt.GOOS + "_" + ctxt.GOARCH + suffix
   573  	default:
   574  		// Save error for end of function.
   575  		pkgerr = fmt.Errorf("import %q: unknown compiler %q", path, ctxt.Compiler)
   576  	}
   577  	setPkga := func() {
   578  		switch ctxt.Compiler {
   579  		case "gccgo":
   580  			dir, elem := pathpkg.Split(p.ImportPath)
   581  			pkga = pkgtargetroot + "/" + dir + "lib" + elem + ".a"
   582  		case "gc":
   583  			pkga = pkgtargetroot + "/" + p.ImportPath + ".a"
   584  		}
   585  	}
   586  	setPkga()
   587  
   588  	binaryOnly := false
   589  	if IsLocalImport(path) {
   590  		pkga = "" // local imports have no installed path
   591  		if srcDir == "" {
   592  			return p, fmt.Errorf("import %q: import relative to unknown directory", path)
   593  		}
   594  		if !ctxt.isAbsPath(path) {
   595  			p.Dir = ctxt.joinPath(srcDir, path)
   596  		}
   597  		// p.Dir directory may or may not exist. Gather partial information first, check if it exists later.
   598  		// Determine canonical import path, if any.
   599  		// Exclude results where the import path would include /testdata/.
   600  		inTestdata := func(sub string) bool {
   601  			return strings.Contains(sub, "/testdata/") || strings.HasSuffix(sub, "/testdata") || strings.HasPrefix(sub, "testdata/") || sub == "testdata"
   602  		}
   603  		if ctxt.GOROOT != "" {
   604  			root := ctxt.joinPath(ctxt.GOROOT, "src")
   605  			if sub, ok := ctxt.hasSubdir(root, p.Dir); ok && !inTestdata(sub) {
   606  				p.Goroot = true
   607  				p.ImportPath = sub
   608  				p.Root = ctxt.GOROOT
   609  				setPkga() // p.ImportPath changed
   610  				goto Found
   611  			}
   612  		}
   613  		all := ctxt.gopath()
   614  		for i, root := range all {
   615  			rootsrc := ctxt.joinPath(root, "src")
   616  			if sub, ok := ctxt.hasSubdir(rootsrc, p.Dir); ok && !inTestdata(sub) {
   617  				// We found a potential import path for dir,
   618  				// but check that using it wouldn't find something
   619  				// else first.
   620  				if ctxt.GOROOT != "" && ctxt.Compiler != "gccgo" {
   621  					if dir := ctxt.joinPath(ctxt.GOROOT, "src", sub); ctxt.isDir(dir) {
   622  						p.ConflictDir = dir
   623  						goto Found
   624  					}
   625  				}
   626  				for _, earlyRoot := range all[:i] {
   627  					if dir := ctxt.joinPath(earlyRoot, "src", sub); ctxt.isDir(dir) {
   628  						p.ConflictDir = dir
   629  						goto Found
   630  					}
   631  				}
   632  
   633  				// sub would not name some other directory instead of this one.
   634  				// Record it.
   635  				p.ImportPath = sub
   636  				p.Root = root
   637  				setPkga() // p.ImportPath changed
   638  				goto Found
   639  			}
   640  		}
   641  		// It's okay that we didn't find a root containing dir.
   642  		// Keep going with the information we have.
   643  	} else {
   644  		if strings.HasPrefix(path, "/") {
   645  			return p, fmt.Errorf("import %q: cannot import absolute path", path)
   646  		}
   647  
   648  		if err := ctxt.importGo(p, path, srcDir, mode); err == nil {
   649  			goto Found
   650  		} else if err != errNoModules {
   651  			return p, err
   652  		}
   653  
   654  		gopath := ctxt.gopath() // needed twice below; avoid computing many times
   655  
   656  		// tried records the location of unsuccessful package lookups
   657  		var tried struct {
   658  			vendor []string
   659  			goroot string
   660  			gopath []string
   661  		}
   662  
   663  		// Vendor directories get first chance to satisfy import.
   664  		if mode&IgnoreVendor == 0 && srcDir != "" {
   665  			searchVendor := func(root string, isGoroot bool) bool {
   666  				sub, ok := ctxt.hasSubdir(root, srcDir)
   667  				if !ok || !strings.HasPrefix(sub, "src/") || strings.Contains(sub, "/testdata/") {
   668  					return false
   669  				}
   670  				for {
   671  					vendor := ctxt.joinPath(root, sub, "vendor")
   672  					if ctxt.isDir(vendor) {
   673  						dir := ctxt.joinPath(vendor, path)
   674  						if ctxt.isDir(dir) && hasGoFiles(ctxt, dir) {
   675  							p.Dir = dir
   676  							p.ImportPath = strings.TrimPrefix(pathpkg.Join(sub, "vendor", path), "src/")
   677  							p.Goroot = isGoroot
   678  							p.Root = root
   679  							setPkga() // p.ImportPath changed
   680  							return true
   681  						}
   682  						tried.vendor = append(tried.vendor, dir)
   683  					}
   684  					i := strings.LastIndex(sub, "/")
   685  					if i < 0 {
   686  						break
   687  					}
   688  					sub = sub[:i]
   689  				}
   690  				return false
   691  			}
   692  			if ctxt.Compiler != "gccgo" && ctxt.GOROOT != "" && searchVendor(ctxt.GOROOT, true) {
   693  				goto Found
   694  			}
   695  			for _, root := range gopath {
   696  				if searchVendor(root, false) {
   697  					goto Found
   698  				}
   699  			}
   700  		}
   701  
   702  		// Determine directory from import path.
   703  		if ctxt.GOROOT != "" {
   704  			// If the package path starts with "vendor/", only search GOROOT before
   705  			// GOPATH if the importer is also within GOROOT. That way, if the user has
   706  			// vendored in a package that is subsequently included in the standard
   707  			// distribution, they'll continue to pick up their own vendored copy.
   708  			gorootFirst := srcDir == "" || !strings.HasPrefix(path, "vendor/")
   709  			if !gorootFirst {
   710  				_, gorootFirst = ctxt.hasSubdir(ctxt.GOROOT, srcDir)
   711  			}
   712  			if gorootFirst {
   713  				dir := ctxt.joinPath(ctxt.GOROOT, "src", path)
   714  				if ctxt.Compiler != "gccgo" {
   715  					isDir := ctxt.isDir(dir)
   716  					binaryOnly = !isDir && mode&AllowBinary != 0 && pkga != "" && ctxt.isFile(ctxt.joinPath(ctxt.GOROOT, pkga))
   717  					if isDir || binaryOnly {
   718  						p.Dir = dir
   719  						p.Goroot = true
   720  						p.Root = ctxt.GOROOT
   721  						goto Found
   722  					}
   723  				}
   724  				tried.goroot = dir
   725  			}
   726  			if ctxt.Compiler == "gccgo" && goroot.IsStandardPackage(ctxt.GOROOT, ctxt.Compiler, path) {
   727  				// TODO(bcmills): Setting p.Dir here is misleading, because gccgo
   728  				// doesn't actually load its standard-library packages from this
   729  				// directory. See if we can leave it unset.
   730  				p.Dir = ctxt.joinPath(ctxt.GOROOT, "src", path)
   731  				p.Goroot = true
   732  				p.Root = ctxt.GOROOT
   733  				goto Found
   734  			}
   735  		}
   736  		for _, root := range gopath {
   737  			dir := ctxt.joinPath(root, "src", path)
   738  			isDir := ctxt.isDir(dir)
   739  			binaryOnly = !isDir && mode&AllowBinary != 0 && pkga != "" && ctxt.isFile(ctxt.joinPath(root, pkga))
   740  			if isDir || binaryOnly {
   741  				p.Dir = dir
   742  				p.Root = root
   743  				goto Found
   744  			}
   745  			tried.gopath = append(tried.gopath, dir)
   746  		}
   747  
   748  		// If we tried GOPATH first due to a "vendor/" prefix, fall back to GOPATH.
   749  		// That way, the user can still get useful results from 'go list' for
   750  		// standard-vendored paths passed on the command line.
   751  		if ctxt.GOROOT != "" && tried.goroot == "" {
   752  			dir := ctxt.joinPath(ctxt.GOROOT, "src", path)
   753  			if ctxt.Compiler != "gccgo" {
   754  				isDir := ctxt.isDir(dir)
   755  				binaryOnly = !isDir && mode&AllowBinary != 0 && pkga != "" && ctxt.isFile(ctxt.joinPath(ctxt.GOROOT, pkga))
   756  				if isDir || binaryOnly {
   757  					p.Dir = dir
   758  					p.Goroot = true
   759  					p.Root = ctxt.GOROOT
   760  					goto Found
   761  				}
   762  			}
   763  			tried.goroot = dir
   764  		}
   765  
   766  		// package was not found
   767  		var paths []string
   768  		format := "\t%s (vendor tree)"
   769  		for _, dir := range tried.vendor {
   770  			paths = append(paths, fmt.Sprintf(format, dir))
   771  			format = "\t%s"
   772  		}
   773  		if tried.goroot != "" {
   774  			paths = append(paths, fmt.Sprintf("\t%s (from $GOROOT)", tried.goroot))
   775  		} else {
   776  			paths = append(paths, "\t($GOROOT not set)")
   777  		}
   778  		format = "\t%s (from $GOPATH)"
   779  		for _, dir := range tried.gopath {
   780  			paths = append(paths, fmt.Sprintf(format, dir))
   781  			format = "\t%s"
   782  		}
   783  		if len(tried.gopath) == 0 {
   784  			paths = append(paths, "\t($GOPATH not set. For more details see: 'go help gopath')")
   785  		}
   786  		return p, fmt.Errorf("cannot find package %q in any of:\n%s", path, strings.Join(paths, "\n"))
   787  	}
   788  
   789  Found:
   790  	if p.Root != "" {
   791  		p.SrcRoot = ctxt.joinPath(p.Root, "src")
   792  		p.PkgRoot = ctxt.joinPath(p.Root, "pkg")
   793  		p.BinDir = ctxt.joinPath(p.Root, "bin")
   794  		if pkga != "" {
   795  			// Always set PkgTargetRoot. It might be used when building in shared
   796  			// mode.
   797  			p.PkgTargetRoot = ctxt.joinPath(p.Root, pkgtargetroot)
   798  
   799  			// Set the install target if applicable.
   800  			if !p.Goroot || (installgoroot.Value() == "all" && p.ImportPath != "unsafe" && p.ImportPath != "builtin") {
   801  				if p.Goroot {
   802  					installgoroot.IncNonDefault()
   803  				}
   804  				p.PkgObj = ctxt.joinPath(p.Root, pkga)
   805  			}
   806  		}
   807  	}
   808  
   809  	// If it's a local import path, by the time we get here, we still haven't checked
   810  	// that p.Dir directory exists. This is the right time to do that check.
   811  	// We can't do it earlier, because we want to gather partial information for the
   812  	// non-nil *Package returned when an error occurs.
   813  	// We need to do this before we return early on FindOnly flag.
   814  	if IsLocalImport(path) && !ctxt.isDir(p.Dir) {
   815  		if ctxt.Compiler == "gccgo" && p.Goroot {
   816  			// gccgo has no sources for GOROOT packages.
   817  			return p, nil
   818  		}
   819  
   820  		// package was not found
   821  		return p, fmt.Errorf("cannot find package %q in:\n\t%s", p.ImportPath, p.Dir)
   822  	}
   823  
   824  	if mode&FindOnly != 0 {
   825  		return p, pkgerr
   826  	}
   827  	if binaryOnly && (mode&AllowBinary) != 0 {
   828  		return p, pkgerr
   829  	}
   830  
   831  	if ctxt.Compiler == "gccgo" && p.Goroot {
   832  		// gccgo has no sources for GOROOT packages.
   833  		return p, nil
   834  	}
   835  
   836  	dirs, err := ctxt.readDir(p.Dir)
   837  	if err != nil {
   838  		return p, err
   839  	}
   840  
   841  	var badGoError error
   842  	badGoFiles := make(map[string]bool)
   843  	badGoFile := func(name string, err error) {
   844  		if badGoError == nil {
   845  			badGoError = err
   846  		}
   847  		if !badGoFiles[name] {
   848  			p.InvalidGoFiles = append(p.InvalidGoFiles, name)
   849  			badGoFiles[name] = true
   850  		}
   851  	}
   852  
   853  	var Sfiles []string // files with ".S"(capital S)/.sx(capital s equivalent for case insensitive filesystems)
   854  	var firstFile, firstCommentFile string
   855  	embedPos := make(map[string][]token.Position)
   856  	testEmbedPos := make(map[string][]token.Position)
   857  	xTestEmbedPos := make(map[string][]token.Position)
   858  	importPos := make(map[string][]token.Position)
   859  	testImportPos := make(map[string][]token.Position)
   860  	xTestImportPos := make(map[string][]token.Position)
   861  	allTags := make(map[string]bool)
   862  	fset := token.NewFileSet()
   863  	for _, d := range dirs {
   864  		if d.IsDir() {
   865  			continue
   866  		}
   867  		if d.Type() == fs.ModeSymlink {
   868  			if ctxt.isDir(ctxt.joinPath(p.Dir, d.Name())) {
   869  				// Symlinks to directories are not source files.
   870  				continue
   871  			}
   872  		}
   873  
   874  		name := d.Name()
   875  		ext := nameExt(name)
   876  
   877  		info, err := ctxt.matchFile(p.Dir, name, allTags, &p.BinaryOnly, fset)
   878  		if err != nil && strings.HasSuffix(name, ".go") {
   879  			badGoFile(name, err)
   880  			continue
   881  		}
   882  		if info == nil {
   883  			if strings.HasPrefix(name, "_") || strings.HasPrefix(name, ".") {
   884  				// not due to build constraints - don't report
   885  			} else if ext == ".go" {
   886  				p.IgnoredGoFiles = append(p.IgnoredGoFiles, name)
   887  			} else if fileListForExt(p, ext) != nil {
   888  				p.IgnoredOtherFiles = append(p.IgnoredOtherFiles, name)
   889  			}
   890  			continue
   891  		}
   892  
   893  		// Going to save the file. For non-Go files, can stop here.
   894  		switch ext {
   895  		case ".go":
   896  			// keep going
   897  		case ".S", ".sx":
   898  			// special case for cgo, handled at end
   899  			Sfiles = append(Sfiles, name)
   900  			continue
   901  		default:
   902  			if list := fileListForExt(p, ext); list != nil {
   903  				*list = append(*list, name)
   904  			}
   905  			continue
   906  		}
   907  
   908  		data, filename := info.header, info.name
   909  
   910  		if info.parseErr != nil {
   911  			badGoFile(name, info.parseErr)
   912  			// Fall through: we might still have a partial AST in info.parsed,
   913  			// and we want to list files with parse errors anyway.
   914  		}
   915  
   916  		var pkg string
   917  		if info.parsed != nil {
   918  			pkg = info.parsed.Name.Name
   919  			if pkg == "documentation" {
   920  				p.IgnoredGoFiles = append(p.IgnoredGoFiles, name)
   921  				continue
   922  			}
   923  		}
   924  
   925  		isTest := strings.HasSuffix(name, "_test.go")
   926  		isXTest := false
   927  		if isTest && strings.HasSuffix(pkg, "_test") && p.Name != pkg {
   928  			isXTest = true
   929  			pkg = pkg[:len(pkg)-len("_test")]
   930  		}
   931  
   932  		if p.Name == "" {
   933  			p.Name = pkg
   934  			firstFile = name
   935  		} else if pkg != p.Name {
   936  			// TODO(#45999): The choice of p.Name is arbitrary based on file iteration
   937  			// order. Instead of resolving p.Name arbitrarily, we should clear out the
   938  			// existing name and mark the existing files as also invalid.
   939  			badGoFile(name, &MultiplePackageError{
   940  				Dir:      p.Dir,
   941  				Packages: []string{p.Name, pkg},
   942  				Files:    []string{firstFile, name},
   943  			})
   944  		}
   945  		// Grab the first package comment as docs, provided it is not from a test file.
   946  		if info.parsed != nil && info.parsed.Doc != nil && p.Doc == "" && !isTest && !isXTest {
   947  			p.Doc = doc.Synopsis(info.parsed.Doc.Text())
   948  		}
   949  
   950  		if mode&ImportComment != 0 {
   951  			qcom, line := findImportComment(data)
   952  			if line != 0 {
   953  				com, err := strconv.Unquote(qcom)
   954  				if err != nil {
   955  					badGoFile(name, fmt.Errorf("%s:%d: cannot parse import comment", filename, line))
   956  				} else if p.ImportComment == "" {
   957  					p.ImportComment = com
   958  					firstCommentFile = name
   959  				} else if p.ImportComment != com {
   960  					badGoFile(name, fmt.Errorf("found import comments %q (%s) and %q (%s) in %s", p.ImportComment, firstCommentFile, com, name, p.Dir))
   961  				}
   962  			}
   963  		}
   964  
   965  		// Record imports and information about cgo.
   966  		isCgo := false
   967  		for _, imp := range info.imports {
   968  			if imp.path == "C" {
   969  				if isTest {
   970  					badGoFile(name, fmt.Errorf("use of cgo in test %s not supported", filename))
   971  					continue
   972  				}
   973  				isCgo = true
   974  				if imp.doc != nil {
   975  					if err := ctxt.saveCgo(filename, p, imp.doc); err != nil {
   976  						badGoFile(name, err)
   977  					}
   978  				}
   979  			}
   980  		}
   981  
   982  		var fileList *[]string
   983  		var importMap, embedMap map[string][]token.Position
   984  		var directives *[]Directive
   985  		switch {
   986  		case isCgo:
   987  			allTags["cgo"] = true
   988  			if ctxt.CgoEnabled {
   989  				fileList = &p.CgoFiles
   990  				importMap = importPos
   991  				embedMap = embedPos
   992  				directives = &p.Directives
   993  			} else {
   994  				// Ignore imports and embeds from cgo files if cgo is disabled.
   995  				fileList = &p.IgnoredGoFiles
   996  			}
   997  		case isXTest:
   998  			fileList = &p.XTestGoFiles
   999  			importMap = xTestImportPos
  1000  			embedMap = xTestEmbedPos
  1001  			directives = &p.XTestDirectives
  1002  		case isTest:
  1003  			fileList = &p.TestGoFiles
  1004  			importMap = testImportPos
  1005  			embedMap = testEmbedPos
  1006  			directives = &p.TestDirectives
  1007  		default:
  1008  			fileList = &p.GoFiles
  1009  			importMap = importPos
  1010  			embedMap = embedPos
  1011  			directives = &p.Directives
  1012  		}
  1013  		*fileList = append(*fileList, name)
  1014  		if importMap != nil {
  1015  			for _, imp := range info.imports {
  1016  				importMap[imp.path] = append(importMap[imp.path], fset.Position(imp.pos))
  1017  			}
  1018  		}
  1019  		if embedMap != nil {
  1020  			for _, emb := range info.embeds {
  1021  				embedMap[emb.pattern] = append(embedMap[emb.pattern], emb.pos)
  1022  			}
  1023  		}
  1024  		if directives != nil {
  1025  			*directives = append(*directives, info.directives...)
  1026  		}
  1027  	}
  1028  
  1029  	for tag := range allTags {
  1030  		p.AllTags = append(p.AllTags, tag)
  1031  	}
  1032  	sort.Strings(p.AllTags)
  1033  
  1034  	p.EmbedPatterns, p.EmbedPatternPos = cleanDecls(embedPos)
  1035  	p.TestEmbedPatterns, p.TestEmbedPatternPos = cleanDecls(testEmbedPos)
  1036  	p.XTestEmbedPatterns, p.XTestEmbedPatternPos = cleanDecls(xTestEmbedPos)
  1037  
  1038  	p.Imports, p.ImportPos = cleanDecls(importPos)
  1039  	p.TestImports, p.TestImportPos = cleanDecls(testImportPos)
  1040  	p.XTestImports, p.XTestImportPos = cleanDecls(xTestImportPos)
  1041  
  1042  	// add the .S/.sx files only if we are using cgo
  1043  	// (which means gcc will compile them).
  1044  	// The standard assemblers expect .s files.
  1045  	if len(p.CgoFiles) > 0 {
  1046  		p.SFiles = append(p.SFiles, Sfiles...)
  1047  		sort.Strings(p.SFiles)
  1048  	} else {
  1049  		p.IgnoredOtherFiles = append(p.IgnoredOtherFiles, Sfiles...)
  1050  		sort.Strings(p.IgnoredOtherFiles)
  1051  	}
  1052  
  1053  	if badGoError != nil {
  1054  		return p, badGoError
  1055  	}
  1056  	if len(p.GoFiles)+len(p.CgoFiles)+len(p.TestGoFiles)+len(p.XTestGoFiles) == 0 {
  1057  		return p, &NoGoError{p.Dir}
  1058  	}
  1059  	return p, pkgerr
  1060  }
  1061  
  1062  func fileListForExt(p *Package, ext string) *[]string {
  1063  	switch ext {
  1064  	case ".c":
  1065  		return &p.CFiles
  1066  	case ".cc", ".cpp", ".cxx":
  1067  		return &p.CXXFiles
  1068  	case ".m":
  1069  		return &p.MFiles
  1070  	case ".h", ".hh", ".hpp", ".hxx":
  1071  		return &p.HFiles
  1072  	case ".f", ".F", ".for", ".f90":
  1073  		return &p.FFiles
  1074  	case ".s", ".S", ".sx":
  1075  		return &p.SFiles
  1076  	case ".swig":
  1077  		return &p.SwigFiles
  1078  	case ".swigcxx":
  1079  		return &p.SwigCXXFiles
  1080  	case ".syso":
  1081  		return &p.SysoFiles
  1082  	}
  1083  	return nil
  1084  }
  1085  
  1086  func uniq(list []string) []string {
  1087  	if list == nil {
  1088  		return nil
  1089  	}
  1090  	out := make([]string, len(list))
  1091  	copy(out, list)
  1092  	sort.Strings(out)
  1093  	uniq := out[:0]
  1094  	for _, x := range out {
  1095  		if len(uniq) == 0 || uniq[len(uniq)-1] != x {
  1096  			uniq = append(uniq, x)
  1097  		}
  1098  	}
  1099  	return uniq
  1100  }
  1101  
  1102  var errNoModules = errors.New("not using modules")
  1103  
  1104  // importGo checks whether it can use the go command to find the directory for path.
  1105  // If using the go command is not appropriate, importGo returns errNoModules.
  1106  // Otherwise, importGo tries using the go command and reports whether that succeeded.
  1107  // Using the go command lets build.Import and build.Context.Import find code
  1108  // in Go modules. In the long term we want tools to use go/packages (currently golang.org/x/tools/go/packages),
  1109  // which will also use the go command.
  1110  // Invoking the go command here is not very efficient in that it computes information
  1111  // about the requested package and all dependencies and then only reports about the requested package.
  1112  // Then we reinvoke it for every dependency. But this is still better than not working at all.
  1113  // See golang.org/issue/26504.
  1114  func (ctxt *Context) importGo(p *Package, path, srcDir string, mode ImportMode) error {
  1115  	// To invoke the go command,
  1116  	// we must not being doing special things like AllowBinary or IgnoreVendor,
  1117  	// and all the file system callbacks must be nil (we're meant to use the local file system).
  1118  	if mode&AllowBinary != 0 || mode&IgnoreVendor != 0 ||
  1119  		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) {
  1120  		return errNoModules
  1121  	}
  1122  
  1123  	// If ctxt.GOROOT is not set, we don't know which go command to invoke,
  1124  	// and even if we did we might return packages in GOROOT that we wouldn't otherwise find
  1125  	// (because we don't know to search in 'go env GOROOT' otherwise).
  1126  	if ctxt.GOROOT == "" {
  1127  		return errNoModules
  1128  	}
  1129  
  1130  	// Predict whether module aware mode is enabled by checking the value of
  1131  	// GO111MODULE and looking for a go.mod file in the source directory or
  1132  	// one of its parents. Running 'go env GOMOD' in the source directory would
  1133  	// give a canonical answer, but we'd prefer not to execute another command.
  1134  	go111Module := os.Getenv("GO111MODULE")
  1135  	switch go111Module {
  1136  	case "off":
  1137  		return errNoModules
  1138  	default: // "", "on", "auto", anything else
  1139  		// Maybe use modules.
  1140  	}
  1141  
  1142  	if srcDir != "" {
  1143  		var absSrcDir string
  1144  		if filepath.IsAbs(srcDir) {
  1145  			absSrcDir = srcDir
  1146  		} else if ctxt.Dir != "" {
  1147  			return fmt.Errorf("go/build: Dir is non-empty, so relative srcDir is not allowed: %v", srcDir)
  1148  		} else {
  1149  			// Find the absolute source directory. hasSubdir does not handle
  1150  			// relative paths (and can't because the callbacks don't support this).
  1151  			var err error
  1152  			absSrcDir, err = filepath.Abs(srcDir)
  1153  			if err != nil {
  1154  				return errNoModules
  1155  			}
  1156  		}
  1157  
  1158  		// If the source directory is in GOROOT, then the in-process code works fine
  1159  		// and we should keep using it. Moreover, the 'go list' approach below doesn't
  1160  		// take standard-library vendoring into account and will fail.
  1161  		if _, ok := ctxt.hasSubdir(filepath.Join(ctxt.GOROOT, "src"), absSrcDir); ok {
  1162  			return errNoModules
  1163  		}
  1164  	}
  1165  
  1166  	// For efficiency, if path is a standard library package, let the usual lookup code handle it.
  1167  	if dir := ctxt.joinPath(ctxt.GOROOT, "src", path); ctxt.isDir(dir) {
  1168  		return errNoModules
  1169  	}
  1170  
  1171  	// If GO111MODULE=auto, look to see if there is a go.mod.
  1172  	// Since go1.13, it doesn't matter if we're inside GOPATH.
  1173  	if go111Module == "auto" {
  1174  		var (
  1175  			parent string
  1176  			err    error
  1177  		)
  1178  		if ctxt.Dir == "" {
  1179  			parent, err = os.Getwd()
  1180  			if err != nil {
  1181  				// A nonexistent working directory can't be in a module.
  1182  				return errNoModules
  1183  			}
  1184  		} else {
  1185  			parent, err = filepath.Abs(ctxt.Dir)
  1186  			if err != nil {
  1187  				// If the caller passed a bogus Dir explicitly, that's materially
  1188  				// different from not having modules enabled.
  1189  				return err
  1190  			}
  1191  		}
  1192  		for {
  1193  			if f, err := ctxt.openFile(ctxt.joinPath(parent, "go.mod")); err == nil {
  1194  				buf := make([]byte, 100)
  1195  				_, err := f.Read(buf)
  1196  				f.Close()
  1197  				if err == nil || err == io.EOF {
  1198  					// go.mod exists and is readable (is a file, not a directory).
  1199  					break
  1200  				}
  1201  			}
  1202  			d := filepath.Dir(parent)
  1203  			if len(d) >= len(parent) {
  1204  				return errNoModules // reached top of file system, no go.mod
  1205  			}
  1206  			parent = d
  1207  		}
  1208  	}
  1209  
  1210  	goCmd := filepath.Join(ctxt.GOROOT, "bin", "go")
  1211  	cmd := exec.Command(goCmd, "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)
  1212  
  1213  	if ctxt.Dir != "" {
  1214  		cmd.Dir = ctxt.Dir
  1215  	}
  1216  
  1217  	var stdout, stderr strings.Builder
  1218  	cmd.Stdout = &stdout
  1219  	cmd.Stderr = &stderr
  1220  
  1221  	cgo := "0"
  1222  	if ctxt.CgoEnabled {
  1223  		cgo = "1"
  1224  	}
  1225  	cmd.Env = append(cmd.Environ(),
  1226  		"GOOS="+ctxt.GOOS,
  1227  		"GOARCH="+ctxt.GOARCH,
  1228  		"GOROOT="+ctxt.GOROOT,
  1229  		"GOPATH="+ctxt.GOPATH,
  1230  		"CGO_ENABLED="+cgo,
  1231  	)
  1232  
  1233  	if err := cmd.Run(); err != nil {
  1234  		return fmt.Errorf("go/build: go list %s: %v\n%s\n", path, err, stderr.String())
  1235  	}
  1236  
  1237  	f := strings.SplitN(stdout.String(), "\n", 5)
  1238  	if len(f) != 5 {
  1239  		return fmt.Errorf("go/build: importGo %s: unexpected output:\n%s\n", path, stdout.String())
  1240  	}
  1241  	dir := f[0]
  1242  	errStr := strings.TrimSpace(f[4])
  1243  	if errStr != "" && dir == "" {
  1244  		// If 'go list' could not locate the package (dir is empty),
  1245  		// return the same error that 'go list' reported.
  1246  		return errors.New(errStr)
  1247  	}
  1248  
  1249  	// If 'go list' did locate the package, ignore the error.
  1250  	// It was probably related to loading source files, and we'll
  1251  	// encounter it ourselves shortly if the FindOnly flag isn't set.
  1252  	p.Dir = dir
  1253  	p.ImportPath = f[1]
  1254  	p.Root = f[2]
  1255  	p.Goroot = f[3] == "true"
  1256  	return nil
  1257  }
  1258  
  1259  func equal(x, y []string) bool {
  1260  	if len(x) != len(y) {
  1261  		return false
  1262  	}
  1263  	for i, xi := range x {
  1264  		if xi != y[i] {
  1265  			return false
  1266  		}
  1267  	}
  1268  	return true
  1269  }
  1270  
  1271  // hasGoFiles reports whether dir contains any files with names ending in .go.
  1272  // For a vendor check we must exclude directories that contain no .go files.
  1273  // Otherwise it is not possible to vendor just a/b/c and still import the
  1274  // non-vendored a/b. See golang.org/issue/13832.
  1275  func hasGoFiles(ctxt *Context, dir string) bool {
  1276  	ents, _ := ctxt.readDir(dir)
  1277  	for _, ent := range ents {
  1278  		if !ent.IsDir() && strings.HasSuffix(ent.Name(), ".go") {
  1279  			return true
  1280  		}
  1281  	}
  1282  	return false
  1283  }
  1284  
  1285  func findImportComment(data []byte) (s string, line int) {
  1286  	// expect keyword package
  1287  	word, data := parseWord(data)
  1288  	if string(word) != "package" {
  1289  		return "", 0
  1290  	}
  1291  
  1292  	// expect package name
  1293  	_, data = parseWord(data)
  1294  
  1295  	// now ready for import comment, a // or /* */ comment
  1296  	// beginning and ending on the current line.
  1297  	for len(data) > 0 && (data[0] == ' ' || data[0] == '\t' || data[0] == '\r') {
  1298  		data = data[1:]
  1299  	}
  1300  
  1301  	var comment []byte
  1302  	switch {
  1303  	case bytes.HasPrefix(data, slashSlash):
  1304  		comment, _, _ = bytes.Cut(data[2:], newline)
  1305  	case bytes.HasPrefix(data, slashStar):
  1306  		var ok bool
  1307  		comment, _, ok = bytes.Cut(data[2:], starSlash)
  1308  		if !ok {
  1309  			// malformed comment
  1310  			return "", 0
  1311  		}
  1312  		if bytes.Contains(comment, newline) {
  1313  			return "", 0
  1314  		}
  1315  	}
  1316  	comment = bytes.TrimSpace(comment)
  1317  
  1318  	// split comment into `import`, `"pkg"`
  1319  	word, arg := parseWord(comment)
  1320  	if string(word) != "import" {
  1321  		return "", 0
  1322  	}
  1323  
  1324  	line = 1 + bytes.Count(data[:cap(data)-cap(arg)], newline)
  1325  	return strings.TrimSpace(string(arg)), line
  1326  }
  1327  
  1328  var (
  1329  	slashSlash = []byte("//")
  1330  	slashStar  = []byte("/*")
  1331  	starSlash  = []byte("*/")
  1332  	newline    = []byte("\n")
  1333  )
  1334  
  1335  // skipSpaceOrComment returns data with any leading spaces or comments removed.
  1336  func skipSpaceOrComment(data []byte) []byte {
  1337  	for len(data) > 0 {
  1338  		switch data[0] {
  1339  		case ' ', '\t', '\r', '\n':
  1340  			data = data[1:]
  1341  			continue
  1342  		case '/':
  1343  			if bytes.HasPrefix(data, slashSlash) {
  1344  				i := bytes.Index(data, newline)
  1345  				if i < 0 {
  1346  					return nil
  1347  				}
  1348  				data = data[i+1:]
  1349  				continue
  1350  			}
  1351  			if bytes.HasPrefix(data, slashStar) {
  1352  				data = data[2:]
  1353  				i := bytes.Index(data, starSlash)
  1354  				if i < 0 {
  1355  					return nil
  1356  				}
  1357  				data = data[i+2:]
  1358  				continue
  1359  			}
  1360  		}
  1361  		break
  1362  	}
  1363  	return data
  1364  }
  1365  
  1366  // parseWord skips any leading spaces or comments in data
  1367  // and then parses the beginning of data as an identifier or keyword,
  1368  // returning that word and what remains after the word.
  1369  func parseWord(data []byte) (word, rest []byte) {
  1370  	data = skipSpaceOrComment(data)
  1371  
  1372  	// Parse past leading word characters.
  1373  	rest = data
  1374  	for {
  1375  		r, size := utf8.DecodeRune(rest)
  1376  		if unicode.IsLetter(r) || '0' <= r && r <= '9' || r == '_' {
  1377  			rest = rest[size:]
  1378  			continue
  1379  		}
  1380  		break
  1381  	}
  1382  
  1383  	word = data[:len(data)-len(rest)]
  1384  	if len(word) == 0 {
  1385  		return nil, nil
  1386  	}
  1387  
  1388  	return word, rest
  1389  }
  1390  
  1391  // MatchFile reports whether the file with the given name in the given directory
  1392  // matches the context and would be included in a [Package] created by [ImportDir]
  1393  // of that directory.
  1394  //
  1395  // MatchFile considers the name of the file and may use ctxt.OpenFile to
  1396  // read some or all of the file's content.
  1397  func (ctxt *Context) MatchFile(dir, name string) (match bool, err error) {
  1398  	info, err := ctxt.matchFile(dir, name, nil, nil, nil)
  1399  	return info != nil, err
  1400  }
  1401  
  1402  var dummyPkg Package
  1403  
  1404  // fileInfo records information learned about a file included in a build.
  1405  type fileInfo struct {
  1406  	name       string // full name including dir
  1407  	header     []byte
  1408  	fset       *token.FileSet
  1409  	parsed     *ast.File
  1410  	parseErr   error
  1411  	imports    []fileImport
  1412  	embeds     []fileEmbed
  1413  	directives []Directive
  1414  }
  1415  
  1416  type fileImport struct {
  1417  	path string
  1418  	pos  token.Pos
  1419  	doc  *ast.CommentGroup
  1420  }
  1421  
  1422  type fileEmbed struct {
  1423  	pattern string
  1424  	pos     token.Position
  1425  }
  1426  
  1427  // matchFile determines whether the file with the given name in the given directory
  1428  // should be included in the package being constructed.
  1429  // If the file should be included, matchFile returns a non-nil *fileInfo (and a nil error).
  1430  // Non-nil errors are reserved for unexpected problems.
  1431  //
  1432  // If name denotes a Go program, matchFile reads until the end of the
  1433  // imports and returns that section of the file in the fileInfo's header field,
  1434  // even though it only considers text until the first non-comment
  1435  // for go:build lines.
  1436  //
  1437  // If allTags is non-nil, matchFile records any encountered build tag
  1438  // by setting allTags[tag] = true.
  1439  func (ctxt *Context) matchFile(dir, name string, allTags map[string]bool, binaryOnly *bool, fset *token.FileSet) (*fileInfo, error) {
  1440  	if strings.HasPrefix(name, "_") ||
  1441  		strings.HasPrefix(name, ".") {
  1442  		return nil, nil
  1443  	}
  1444  
  1445  	i := strings.LastIndex(name, ".")
  1446  	if i < 0 {
  1447  		i = len(name)
  1448  	}
  1449  	ext := name[i:]
  1450  
  1451  	if ext != ".go" && fileListForExt(&dummyPkg, ext) == nil {
  1452  		// skip
  1453  		return nil, nil
  1454  	}
  1455  
  1456  	if !ctxt.goodOSArchFile(name, allTags) && !ctxt.UseAllFiles {
  1457  		return nil, nil
  1458  	}
  1459  
  1460  	info := &fileInfo{name: ctxt.joinPath(dir, name), fset: fset}
  1461  	if ext == ".syso" {
  1462  		// binary, no reading
  1463  		return info, nil
  1464  	}
  1465  
  1466  	f, err := ctxt.openFile(info.name)
  1467  	if err != nil {
  1468  		return nil, err
  1469  	}
  1470  
  1471  	if strings.HasSuffix(name, ".go") {
  1472  		err = readGoInfo(f, info)
  1473  		if strings.HasSuffix(name, "_test.go") {
  1474  			binaryOnly = nil // ignore //go:binary-only-package comments in _test.go files
  1475  		}
  1476  	} else {
  1477  		binaryOnly = nil // ignore //go:binary-only-package comments in non-Go sources
  1478  		info.header, err = readComments(f)
  1479  	}
  1480  	f.Close()
  1481  	if err != nil {
  1482  		return info, fmt.Errorf("read %s: %v", info.name, err)
  1483  	}
  1484  
  1485  	// Look for go:build comments to accept or reject the file.
  1486  	ok, sawBinaryOnly, err := ctxt.shouldBuild(info.header, allTags)
  1487  	if err != nil {
  1488  		return nil, fmt.Errorf("%s: %v", name, err)
  1489  	}
  1490  	if !ok && !ctxt.UseAllFiles {
  1491  		return nil, nil
  1492  	}
  1493  
  1494  	if binaryOnly != nil && sawBinaryOnly {
  1495  		*binaryOnly = true
  1496  	}
  1497  
  1498  	return info, nil
  1499  }
  1500  
  1501  func cleanDecls(m map[string][]token.Position) ([]string, map[string][]token.Position) {
  1502  	all := make([]string, 0, len(m))
  1503  	for path := range m {
  1504  		all = append(all, path)
  1505  	}
  1506  	sort.Strings(all)
  1507  	return all, m
  1508  }
  1509  
  1510  // Import is shorthand for Default.Import.
  1511  func Import(path, srcDir string, mode ImportMode) (*Package, error) {
  1512  	return Default.Import(path, srcDir, mode)
  1513  }
  1514  
  1515  // ImportDir is shorthand for Default.ImportDir.
  1516  func ImportDir(dir string, mode ImportMode) (*Package, error) {
  1517  	return Default.ImportDir(dir, mode)
  1518  }
  1519  
  1520  var (
  1521  	plusBuild = []byte("+build")
  1522  
  1523  	goBuildComment = []byte("//go:build")
  1524  
  1525  	errMultipleGoBuild = errors.New("multiple //go:build comments")
  1526  )
  1527  
  1528  func isGoBuildComment(line []byte) bool {
  1529  	if !bytes.HasPrefix(line, goBuildComment) {
  1530  		return false
  1531  	}
  1532  	line = bytes.TrimSpace(line)
  1533  	rest := line[len(goBuildComment):]
  1534  	return len(rest) == 0 || len(bytes.TrimSpace(rest)) < len(rest)
  1535  }
  1536  
  1537  // Special comment denoting a binary-only package.
  1538  // See https://golang.org/design/2775-binary-only-packages
  1539  // for more about the design of binary-only packages.
  1540  var binaryOnlyComment = []byte("//go:binary-only-package")
  1541  
  1542  // shouldBuild reports whether it is okay to use this file,
  1543  // The rule is that in the file's leading run of // comments
  1544  // and blank lines, which must be followed by a blank line
  1545  // (to avoid including a Go package clause doc comment),
  1546  // lines beginning with '//go:build' are taken as build directives.
  1547  //
  1548  // The file is accepted only if each such line lists something
  1549  // matching the file. For example:
  1550  //
  1551  //	//go:build windows linux
  1552  //
  1553  // marks the file as applicable only on Windows and Linux.
  1554  //
  1555  // For each build tag it consults, shouldBuild sets allTags[tag] = true.
  1556  //
  1557  // shouldBuild reports whether the file should be built
  1558  // and whether a //go:binary-only-package comment was found.
  1559  func (ctxt *Context) shouldBuild(content []byte, allTags map[string]bool) (shouldBuild, binaryOnly bool, err error) {
  1560  	// Identify leading run of // comments and blank lines,
  1561  	// which must be followed by a blank line.
  1562  	// Also identify any //go:build comments.
  1563  	content, goBuild, sawBinaryOnly, err := parseFileHeader(content)
  1564  	if err != nil {
  1565  		return false, false, err
  1566  	}
  1567  
  1568  	// If //go:build line is present, it controls.
  1569  	// Otherwise fall back to +build processing.
  1570  	switch {
  1571  	case goBuild != nil:
  1572  		x, err := constraint.Parse(string(goBuild))
  1573  		if err != nil {
  1574  			return false, false, fmt.Errorf("parsing //go:build line: %v", err)
  1575  		}
  1576  		shouldBuild = ctxt.eval(x, allTags)
  1577  
  1578  	default:
  1579  		shouldBuild = true
  1580  		p := content
  1581  		for len(p) > 0 {
  1582  			line := p
  1583  			if i := bytes.IndexByte(line, '\n'); i >= 0 {
  1584  				line, p = line[:i], p[i+1:]
  1585  			} else {
  1586  				p = p[len(p):]
  1587  			}
  1588  			line = bytes.TrimSpace(line)
  1589  			if !bytes.HasPrefix(line, slashSlash) || !bytes.Contains(line, plusBuild) {
  1590  				continue
  1591  			}
  1592  			text := string(line)
  1593  			if !constraint.IsPlusBuild(text) {
  1594  				continue
  1595  			}
  1596  			if x, err := constraint.Parse(text); err == nil {
  1597  				if !ctxt.eval(x, allTags) {
  1598  					shouldBuild = false
  1599  				}
  1600  			}
  1601  		}
  1602  	}
  1603  
  1604  	return shouldBuild, sawBinaryOnly, nil
  1605  }
  1606  
  1607  func parseFileHeader(content []byte) (trimmed, goBuild []byte, sawBinaryOnly bool, err error) {
  1608  	end := 0
  1609  	p := content
  1610  	ended := false       // found non-blank, non-// line, so stopped accepting //go:build lines
  1611  	inSlashStar := false // in /* */ comment
  1612  
  1613  Lines:
  1614  	for len(p) > 0 {
  1615  		line := p
  1616  		if i := bytes.IndexByte(line, '\n'); i >= 0 {
  1617  			line, p = line[:i], p[i+1:]
  1618  		} else {
  1619  			p = p[len(p):]
  1620  		}
  1621  		line = bytes.TrimSpace(line)
  1622  		if len(line) == 0 && !ended { // Blank line
  1623  			// Remember position of most recent blank line.
  1624  			// When we find the first non-blank, non-// line,
  1625  			// this "end" position marks the latest file position
  1626  			// where a //go:build line can appear.
  1627  			// (It must appear _before_ a blank line before the non-blank, non-// line.
  1628  			// Yes, that's confusing, which is part of why we moved to //go:build lines.)
  1629  			// Note that ended==false here means that inSlashStar==false,
  1630  			// since seeing a /* would have set ended==true.
  1631  			end = len(content) - len(p)
  1632  			continue Lines
  1633  		}
  1634  		if !bytes.HasPrefix(line, slashSlash) { // Not comment line
  1635  			ended = true
  1636  		}
  1637  
  1638  		if !inSlashStar && isGoBuildComment(line) {
  1639  			if goBuild != nil {
  1640  				return nil, nil, false, errMultipleGoBuild
  1641  			}
  1642  			goBuild = line
  1643  		}
  1644  		if !inSlashStar && bytes.Equal(line, binaryOnlyComment) {
  1645  			sawBinaryOnly = true
  1646  		}
  1647  
  1648  	Comments:
  1649  		for len(line) > 0 {
  1650  			if inSlashStar {
  1651  				if i := bytes.Index(line, starSlash); i >= 0 {
  1652  					inSlashStar = false
  1653  					line = bytes.TrimSpace(line[i+len(starSlash):])
  1654  					continue Comments
  1655  				}
  1656  				continue Lines
  1657  			}
  1658  			if bytes.HasPrefix(line, slashSlash) {
  1659  				continue Lines
  1660  			}
  1661  			if bytes.HasPrefix(line, slashStar) {
  1662  				inSlashStar = true
  1663  				line = bytes.TrimSpace(line[len(slashStar):])
  1664  				continue Comments
  1665  			}
  1666  			// Found non-comment text.
  1667  			break Lines
  1668  		}
  1669  	}
  1670  
  1671  	return content[:end], goBuild, sawBinaryOnly, nil
  1672  }
  1673  
  1674  // saveCgo saves the information from the #cgo lines in the import "C" comment.
  1675  // These lines set CFLAGS, CPPFLAGS, CXXFLAGS and LDFLAGS and pkg-config directives
  1676  // that affect the way cgo's C code is built.
  1677  func (ctxt *Context) saveCgo(filename string, di *Package, cg *ast.CommentGroup) error {
  1678  	text := cg.Text()
  1679  	for _, line := range strings.Split(text, "\n") {
  1680  		orig := line
  1681  
  1682  		// Line is
  1683  		//	#cgo [GOOS/GOARCH...] LDFLAGS: stuff
  1684  		//
  1685  		line = strings.TrimSpace(line)
  1686  		if len(line) < 5 || line[:4] != "#cgo" || (line[4] != ' ' && line[4] != '\t') {
  1687  			continue
  1688  		}
  1689  
  1690  		// #cgo (nocallback|noescape) <function name>
  1691  		if fields := strings.Fields(line); len(fields) == 3 && (fields[1] == "nocallback" || fields[1] == "noescape") {
  1692  			continue
  1693  		}
  1694  
  1695  		// Split at colon.
  1696  		line, argstr, ok := strings.Cut(strings.TrimSpace(line[4:]), ":")
  1697  		if !ok {
  1698  			return fmt.Errorf("%s: invalid #cgo line: %s", filename, orig)
  1699  		}
  1700  
  1701  		// Parse GOOS/GOARCH stuff.
  1702  		f := strings.Fields(line)
  1703  		if len(f) < 1 {
  1704  			return fmt.Errorf("%s: invalid #cgo line: %s", filename, orig)
  1705  		}
  1706  
  1707  		cond, verb := f[:len(f)-1], f[len(f)-1]
  1708  		if len(cond) > 0 {
  1709  			ok := false
  1710  			for _, c := range cond {
  1711  				if ctxt.matchAuto(c, nil) {
  1712  					ok = true
  1713  					break
  1714  				}
  1715  			}
  1716  			if !ok {
  1717  				continue
  1718  			}
  1719  		}
  1720  
  1721  		args, err := splitQuoted(argstr)
  1722  		if err != nil {
  1723  			return fmt.Errorf("%s: invalid #cgo line: %s", filename, orig)
  1724  		}
  1725  		for i, arg := range args {
  1726  			if arg, ok = expandSrcDir(arg, di.Dir); !ok {
  1727  				return fmt.Errorf("%s: malformed #cgo argument: %s", filename, arg)
  1728  			}
  1729  			args[i] = arg
  1730  		}
  1731  
  1732  		switch verb {
  1733  		case "CFLAGS", "CPPFLAGS", "CXXFLAGS", "FFLAGS", "LDFLAGS":
  1734  			// Change relative paths to absolute.
  1735  			ctxt.makePathsAbsolute(args, di.Dir)
  1736  		}
  1737  
  1738  		switch verb {
  1739  		case "CFLAGS":
  1740  			di.CgoCFLAGS = append(di.CgoCFLAGS, args...)
  1741  		case "CPPFLAGS":
  1742  			di.CgoCPPFLAGS = append(di.CgoCPPFLAGS, args...)
  1743  		case "CXXFLAGS":
  1744  			di.CgoCXXFLAGS = append(di.CgoCXXFLAGS, args...)
  1745  		case "FFLAGS":
  1746  			di.CgoFFLAGS = append(di.CgoFFLAGS, args...)
  1747  		case "LDFLAGS":
  1748  			di.CgoLDFLAGS = append(di.CgoLDFLAGS, args...)
  1749  		case "pkg-config":
  1750  			di.CgoPkgConfig = append(di.CgoPkgConfig, args...)
  1751  		default:
  1752  			return fmt.Errorf("%s: invalid #cgo verb: %s", filename, orig)
  1753  		}
  1754  	}
  1755  	return nil
  1756  }
  1757  
  1758  // expandSrcDir expands any occurrence of ${SRCDIR}, making sure
  1759  // the result is safe for the shell.
  1760  func expandSrcDir(str string, srcdir string) (string, bool) {
  1761  	// "\" delimited paths cause safeCgoName to fail
  1762  	// so convert native paths with a different delimiter
  1763  	// to "/" before starting (eg: on windows).
  1764  	srcdir = filepath.ToSlash(srcdir)
  1765  
  1766  	chunks := strings.Split(str, "${SRCDIR}")
  1767  	if len(chunks) < 2 {
  1768  		return str, safeCgoName(str)
  1769  	}
  1770  	ok := true
  1771  	for _, chunk := range chunks {
  1772  		ok = ok && (chunk == "" || safeCgoName(chunk))
  1773  	}
  1774  	ok = ok && (srcdir == "" || safeCgoName(srcdir))
  1775  	res := strings.Join(chunks, srcdir)
  1776  	return res, ok && res != ""
  1777  }
  1778  
  1779  // makePathsAbsolute looks for compiler options that take paths and
  1780  // makes them absolute. We do this because through the 1.8 release we
  1781  // ran the compiler in the package directory, so any relative -I or -L
  1782  // options would be relative to that directory. In 1.9 we changed to
  1783  // running the compiler in the build directory, to get consistent
  1784  // build results (issue #19964). To keep builds working, we change any
  1785  // relative -I or -L options to be absolute.
  1786  //
  1787  // Using filepath.IsAbs and filepath.Join here means the results will be
  1788  // different on different systems, but that's OK: -I and -L options are
  1789  // inherently system-dependent.
  1790  func (ctxt *Context) makePathsAbsolute(args []string, srcDir string) {
  1791  	nextPath := false
  1792  	for i, arg := range args {
  1793  		if nextPath {
  1794  			if !filepath.IsAbs(arg) {
  1795  				args[i] = filepath.Join(srcDir, arg)
  1796  			}
  1797  			nextPath = false
  1798  		} else if strings.HasPrefix(arg, "-I") || strings.HasPrefix(arg, "-L") {
  1799  			if len(arg) == 2 {
  1800  				nextPath = true
  1801  			} else {
  1802  				if !filepath.IsAbs(arg[2:]) {
  1803  					args[i] = arg[:2] + filepath.Join(srcDir, arg[2:])
  1804  				}
  1805  			}
  1806  		}
  1807  	}
  1808  }
  1809  
  1810  // NOTE: $ is not safe for the shell, but it is allowed here because of linker options like -Wl,$ORIGIN.
  1811  // We never pass these arguments to a shell (just to programs we construct argv for), so this should be okay.
  1812  // See golang.org/issue/6038.
  1813  // The @ is for OS X. See golang.org/issue/13720.
  1814  // The % is for Jenkins. See golang.org/issue/16959.
  1815  // The ! is because module paths may use them. See golang.org/issue/26716.
  1816  // The ~ and ^ are for sr.ht. See golang.org/issue/32260.
  1817  const safeString = "+-.,/0123456789=ABCDEFGHIJKLMNOPQRSTUVWXYZ_abcdefghijklmnopqrstuvwxyz:$@%! ~^"
  1818  
  1819  func safeCgoName(s string) bool {
  1820  	if s == "" {
  1821  		return false
  1822  	}
  1823  	for i := 0; i < len(s); i++ {
  1824  		if c := s[i]; c < utf8.RuneSelf && strings.IndexByte(safeString, c) < 0 {
  1825  			return false
  1826  		}
  1827  	}
  1828  	return true
  1829  }
  1830  
  1831  // splitQuoted splits the string s around each instance of one or more consecutive
  1832  // white space characters while taking into account quotes and escaping, and
  1833  // returns an array of substrings of s or an empty list if s contains only white space.
  1834  // Single quotes and double quotes are recognized to prevent splitting within the
  1835  // quoted region, and are removed from the resulting substrings. If a quote in s
  1836  // isn't closed err will be set and r will have the unclosed argument as the
  1837  // last element. The backslash is used for escaping.
  1838  //
  1839  // For example, the following string:
  1840  //
  1841  //	a b:"c d" 'e''f'  "g\""
  1842  //
  1843  // Would be parsed as:
  1844  //
  1845  //	[]string{"a", "b:c d", "ef", `g"`}
  1846  func splitQuoted(s string) (r []string, err error) {
  1847  	var args []string
  1848  	arg := make([]rune, len(s))
  1849  	escaped := false
  1850  	quoted := false
  1851  	quote := '\x00'
  1852  	i := 0
  1853  	for _, rune := range s {
  1854  		switch {
  1855  		case escaped:
  1856  			escaped = false
  1857  		case rune == '\\':
  1858  			escaped = true
  1859  			continue
  1860  		case quote != '\x00':
  1861  			if rune == quote {
  1862  				quote = '\x00'
  1863  				continue
  1864  			}
  1865  		case rune == '"' || rune == '\'':
  1866  			quoted = true
  1867  			quote = rune
  1868  			continue
  1869  		case unicode.IsSpace(rune):
  1870  			if quoted || i > 0 {
  1871  				quoted = false
  1872  				args = append(args, string(arg[:i]))
  1873  				i = 0
  1874  			}
  1875  			continue
  1876  		}
  1877  		arg[i] = rune
  1878  		i++
  1879  	}
  1880  	if quoted || i > 0 {
  1881  		args = append(args, string(arg[:i]))
  1882  	}
  1883  	if quote != 0 {
  1884  		err = errors.New("unclosed quote")
  1885  	} else if escaped {
  1886  		err = errors.New("unfinished escaping")
  1887  	}
  1888  	return args, err
  1889  }
  1890  
  1891  // matchAuto interprets text as either a +build or //go:build expression (whichever works),
  1892  // reporting whether the expression matches the build context.
  1893  //
  1894  // matchAuto is only used for testing of tag evaluation
  1895  // and in #cgo lines, which accept either syntax.
  1896  func (ctxt *Context) matchAuto(text string, allTags map[string]bool) bool {
  1897  	if strings.ContainsAny(text, "&|()") {
  1898  		text = "//go:build " + text
  1899  	} else {
  1900  		text = "// +build " + text
  1901  	}
  1902  	x, err := constraint.Parse(text)
  1903  	if err != nil {
  1904  		return false
  1905  	}
  1906  	return ctxt.eval(x, allTags)
  1907  }
  1908  
  1909  func (ctxt *Context) eval(x constraint.Expr, allTags map[string]bool) bool {
  1910  	return x.Eval(func(tag string) bool { return ctxt.matchTag(tag, allTags) })
  1911  }
  1912  
  1913  // matchTag reports whether the name is one of:
  1914  //
  1915  //	cgo (if cgo is enabled)
  1916  //	$GOOS
  1917  //	$GOARCH
  1918  //	ctxt.Compiler
  1919  //	linux (if GOOS = android)
  1920  //	solaris (if GOOS = illumos)
  1921  //	darwin (if GOOS = ios)
  1922  //	unix (if this is a Unix GOOS)
  1923  //	boringcrypto (if GOEXPERIMENT=boringcrypto is enabled)
  1924  //	tag (if tag is listed in ctxt.BuildTags, ctxt.ToolTags, or ctxt.ReleaseTags)
  1925  //
  1926  // It records all consulted tags in allTags.
  1927  func (ctxt *Context) matchTag(name string, allTags map[string]bool) bool {
  1928  	if allTags != nil {
  1929  		allTags[name] = true
  1930  	}
  1931  
  1932  	// special tags
  1933  	if ctxt.CgoEnabled && name == "cgo" {
  1934  		return true
  1935  	}
  1936  	if name == ctxt.GOOS || name == ctxt.GOARCH || name == ctxt.Compiler {
  1937  		return true
  1938  	}
  1939  	if ctxt.GOOS == "android" && name == "linux" {
  1940  		return true
  1941  	}
  1942  	if ctxt.GOOS == "illumos" && name == "solaris" {
  1943  		return true
  1944  	}
  1945  	if ctxt.GOOS == "ios" && name == "darwin" {
  1946  		return true
  1947  	}
  1948  	if name == "unix" && unixOS[ctxt.GOOS] {
  1949  		return true
  1950  	}
  1951  	if name == "boringcrypto" {
  1952  		name = "goexperiment.boringcrypto" // boringcrypto is an old name for goexperiment.boringcrypto
  1953  	}
  1954  
  1955  	// other tags
  1956  	for _, tag := range ctxt.BuildTags {
  1957  		if tag == name {
  1958  			return true
  1959  		}
  1960  	}
  1961  	for _, tag := range ctxt.ToolTags {
  1962  		if tag == name {
  1963  			return true
  1964  		}
  1965  	}
  1966  	for _, tag := range ctxt.ReleaseTags {
  1967  		if tag == name {
  1968  			return true
  1969  		}
  1970  	}
  1971  
  1972  	return false
  1973  }
  1974  
  1975  // goodOSArchFile returns false if the name contains a $GOOS or $GOARCH
  1976  // suffix which does not match the current system.
  1977  // The recognized name formats are:
  1978  //
  1979  //	name_$(GOOS).*
  1980  //	name_$(GOARCH).*
  1981  //	name_$(GOOS)_$(GOARCH).*
  1982  //	name_$(GOOS)_test.*
  1983  //	name_$(GOARCH)_test.*
  1984  //	name_$(GOOS)_$(GOARCH)_test.*
  1985  //
  1986  // Exceptions:
  1987  // if GOOS=android, then files with GOOS=linux are also matched.
  1988  // if GOOS=illumos, then files with GOOS=solaris are also matched.
  1989  // if GOOS=ios, then files with GOOS=darwin are also matched.
  1990  func (ctxt *Context) goodOSArchFile(name string, allTags map[string]bool) bool {
  1991  	name, _, _ = strings.Cut(name, ".")
  1992  
  1993  	// Before Go 1.4, a file called "linux.go" would be equivalent to having a
  1994  	// build tag "linux" in that file. For Go 1.4 and beyond, we require this
  1995  	// auto-tagging to apply only to files with a non-empty prefix, so
  1996  	// "foo_linux.go" is tagged but "linux.go" is not. This allows new operating
  1997  	// systems, such as android, to arrive without breaking existing code with
  1998  	// innocuous source code in "android.go". The easiest fix: cut everything
  1999  	// in the name before the initial _.
  2000  	i := strings.Index(name, "_")
  2001  	if i < 0 {
  2002  		return true
  2003  	}
  2004  	name = name[i:] // ignore everything before first _
  2005  
  2006  	l := strings.Split(name, "_")
  2007  	if n := len(l); n > 0 && l[n-1] == "test" {
  2008  		l = l[:n-1]
  2009  	}
  2010  	n := len(l)
  2011  	if n >= 2 && knownOS[l[n-2]] && knownArch[l[n-1]] {
  2012  		if allTags != nil {
  2013  			// In case we short-circuit on l[n-1].
  2014  			allTags[l[n-2]] = true
  2015  		}
  2016  		return ctxt.matchTag(l[n-1], allTags) && ctxt.matchTag(l[n-2], allTags)
  2017  	}
  2018  	if n >= 1 && (knownOS[l[n-1]] || knownArch[l[n-1]]) {
  2019  		return ctxt.matchTag(l[n-1], allTags)
  2020  	}
  2021  	return true
  2022  }
  2023  
  2024  // ToolDir is the directory containing build tools.
  2025  var ToolDir = getToolDir()
  2026  
  2027  // IsLocalImport reports whether the import path is
  2028  // a local import path, like ".", "..", "./foo", or "../foo".
  2029  func IsLocalImport(path string) bool {
  2030  	return path == "." || path == ".." ||
  2031  		strings.HasPrefix(path, "./") || strings.HasPrefix(path, "../")
  2032  }
  2033  
  2034  // ArchChar returns "?" and an error.
  2035  // In earlier versions of Go, the returned string was used to derive
  2036  // the compiler and linker tool names, the default object file suffix,
  2037  // and the default linker output name. As of Go 1.5, those strings
  2038  // no longer vary by architecture; they are compile, link, .o, and a.out, respectively.
  2039  func ArchChar(goarch string) (string, error) {
  2040  	return "?", errors.New("architecture letter no longer used")
  2041  }
  2042  

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