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  	"internal/godebug"
    17  	"internal/goroot"
    18  	"internal/goversion"
    19  	"internal/platform"
    20  	"internal/syslist"
    21  	"io"
    22  	"io/fs"
    23  	"os"
    24  	"os/exec"
    25  	pathpkg "path"
    26  	"path/filepath"
    27  	"runtime"
    28  	"slices"
    29  	"strconv"
    30  	"strings"
    31  	"unicode"
    32  	"unicode/utf8"
    33  	_ "unsafe" // for linkname
    34  )
    35  
    36  // A Context specifies the supporting context for a build.
    37  type Context struct {
    38  	GOARCH string // target architecture
    39  	GOOS   string // target operating system
    40  	GOROOT string // Go root
    41  	GOPATH string // Go paths
    42  
    43  	// Dir is the caller's working directory, or the empty string to use
    44  	// the current directory of the running process. In module mode, this is used
    45  	// to locate the main module.
    46  	//
    47  	// If Dir is non-empty, directories passed to Import and ImportDir must
    48  	// be absolute.
    49  	Dir string
    50  
    51  	CgoEnabled  bool   // whether cgo files are included
    52  	UseAllFiles bool   // use files regardless of go:build lines, file names
    53  	Compiler    string // compiler to assume when computing target paths
    54  
    55  	// The build, tool, and release tags specify build constraints
    56  	// that should be considered satisfied when processing go:build lines.
    57  	// Clients creating a new context may customize BuildTags, which
    58  	// defaults to empty, but it is usually an error to customize ToolTags or ReleaseTags.
    59  	// ToolTags defaults to build tags appropriate to the current Go toolchain configuration.
    60  	// ReleaseTags defaults to the list of Go releases the current release is compatible with.
    61  	// BuildTags is not set for the Default build Context.
    62  	// In addition to the BuildTags, ToolTags, and ReleaseTags, build constraints
    63  	// consider the values of GOARCH and GOOS as satisfied tags.
    64  	// The last element in ReleaseTags is assumed to be the current release.
    65  	BuildTags   []string
    66  	ToolTags    []string
    67  	ReleaseTags []string
    68  
    69  	// The install suffix specifies a suffix to use in the name of the installation
    70  	// directory. By default it is empty, but custom builds that need to keep
    71  	// their outputs separate can set InstallSuffix to do so. For example, when
    72  	// using the race detector, the go command uses InstallSuffix = "race", so
    73  	// that on a Linux/386 system, packages are written to a directory named
    74  	// "linux_386_race" instead of the usual "linux_386".
    75  	InstallSuffix string
    76  
    77  	// By default, Import uses the operating system's file system calls
    78  	// to read directories and files. To read from other sources,
    79  	// callers can set the following functions. They all have default
    80  	// behaviors that use the local file system, so clients need only set
    81  	// the functions whose behaviors they wish to change.
    82  
    83  	// JoinPath joins the sequence of path fragments into a single path.
    84  	// If JoinPath is nil, Import uses filepath.Join.
    85  	JoinPath func(elem ...string) string
    86  
    87  	// SplitPathList splits the path list into a slice of individual paths.
    88  	// If SplitPathList is nil, Import uses filepath.SplitList.
    89  	SplitPathList func(list string) []string
    90  
    91  	// IsAbsPath reports whether path is an absolute path.
    92  	// If IsAbsPath is nil, Import uses filepath.IsAbs.
    93  	IsAbsPath func(path string) bool
    94  
    95  	// IsDir reports whether the path names a directory.
    96  	// If IsDir is nil, Import calls os.Stat and uses the result's IsDir method.
    97  	IsDir func(path string) bool
    98  
    99  	// HasSubdir reports whether dir is lexically a subdirectory of
   100  	// root, perhaps multiple levels below. It does not try to check
   101  	// whether dir exists.
   102  	// If so, HasSubdir sets rel to a slash-separated path that
   103  	// can be joined to root to produce a path equivalent to dir.
   104  	// If HasSubdir is nil, Import uses an implementation built on
   105  	// filepath.EvalSymlinks.
   106  	HasSubdir func(root, dir string) (rel string, ok bool)
   107  
   108  	// ReadDir returns a slice of fs.FileInfo, sorted by Name,
   109  	// describing the content of the named directory.
   110  	// If ReadDir is nil, Import uses os.ReadDir.
   111  	ReadDir func(dir string) ([]fs.FileInfo, error)
   112  
   113  	// OpenFile opens a file (not a directory) for reading.
   114  	// If OpenFile is nil, Import uses os.Open.
   115  	OpenFile func(path string) (io.ReadCloser, error)
   116  }
   117  
   118  // joinPath calls ctxt.JoinPath (if not nil) or else filepath.Join.
   119  func (ctxt *Context) joinPath(elem ...string) string {
   120  	if f := ctxt.JoinPath; f != nil {
   121  		return f(elem...)
   122  	}
   123  	return filepath.Join(elem...)
   124  }
   125  
   126  // splitPathList calls ctxt.SplitPathList (if not nil) or else filepath.SplitList.
   127  func (ctxt *Context) splitPathList(s string) []string {
   128  	if f := ctxt.SplitPathList; f != nil {
   129  		return f(s)
   130  	}
   131  	return filepath.SplitList(s)
   132  }
   133  
   134  // isAbsPath calls ctxt.IsAbsPath (if not nil) or else filepath.IsAbs.
   135  func (ctxt *Context) isAbsPath(path string) bool {
   136  	if f := ctxt.IsAbsPath; f != nil {
   137  		return f(path)
   138  	}
   139  	return filepath.IsAbs(path)
   140  }
   141  
   142  // isDir calls ctxt.IsDir (if not nil) or else uses os.Stat.
   143  func (ctxt *Context) isDir(path string) bool {
   144  	if f := ctxt.IsDir; f != nil {
   145  		return f(path)
   146  	}
   147  	fi, err := os.Stat(path)
   148  	return err == nil && fi.IsDir()
   149  }
   150  
   151  // hasSubdir calls ctxt.HasSubdir (if not nil) or else uses
   152  // the local file system to answer the question.
   153  func (ctxt *Context) hasSubdir(root, dir string) (rel string, ok bool) {
   154  	if f := ctxt.HasSubdir; f != nil {
   155  		return f(root, dir)
   156  	}
   157  
   158  	// Try using paths we received.
   159  	if rel, ok = hasSubdir(root, dir); ok {
   160  		return
   161  	}
   162  
   163  	// Try expanding symlinks and comparing
   164  	// expanded against unexpanded and
   165  	// expanded against expanded.
   166  	rootSym, _ := filepath.EvalSymlinks(root)
   167  	dirSym, _ := filepath.EvalSymlinks(dir)
   168  
   169  	if rel, ok = hasSubdir(rootSym, dir); ok {
   170  		return
   171  	}
   172  	if rel, ok = hasSubdir(root, dirSym); ok {
   173  		return
   174  	}
   175  	return hasSubdir(rootSym, dirSym)
   176  }
   177  
   178  // hasSubdir reports if dir is within root by performing lexical analysis only.
   179  func hasSubdir(root, dir string) (rel string, ok bool) {
   180  	const sep = string(filepath.Separator)
   181  	root = filepath.Clean(root)
   182  	if !strings.HasSuffix(root, sep) {
   183  		root += sep
   184  	}
   185  	dir = filepath.Clean(dir)
   186  	after, found := strings.CutPrefix(dir, root)
   187  	if !found {
   188  		return "", false
   189  	}
   190  	return filepath.ToSlash(after), true
   191  }
   192  
   193  // readDir calls ctxt.ReadDir (if not nil) or else os.ReadDir.
   194  func (ctxt *Context) readDir(path string) ([]fs.DirEntry, error) {
   195  	// TODO: add a fs.DirEntry version of Context.ReadDir
   196  	if f := ctxt.ReadDir; f != nil {
   197  		fis, err := f(path)
   198  		if err != nil {
   199  			return nil, err
   200  		}
   201  		des := make([]fs.DirEntry, len(fis))
   202  		for i, fi := range fis {
   203  			des[i] = fs.FileInfoToDirEntry(fi)
   204  		}
   205  		return des, nil
   206  	}
   207  	return os.ReadDir(path)
   208  }
   209  
   210  // openFile calls ctxt.OpenFile (if not nil) or else os.Open.
   211  func (ctxt *Context) openFile(path string) (io.ReadCloser, error) {
   212  	if fn := ctxt.OpenFile; fn != nil {
   213  		return fn(path)
   214  	}
   215  
   216  	f, err := os.Open(path)
   217  	if err != nil {
   218  		return nil, err // nil interface
   219  	}
   220  	return f, nil
   221  }
   222  
   223  // isFile determines whether path is a file by trying to open it.
   224  // It reuses openFile instead of adding another function to the
   225  // list in Context.
   226  func (ctxt *Context) isFile(path string) bool {
   227  	f, err := ctxt.openFile(path)
   228  	if err != nil {
   229  		return false
   230  	}
   231  	f.Close()
   232  	return true
   233  }
   234  
   235  // gopath returns the list of Go path directories.
   236  func (ctxt *Context) gopath() []string {
   237  	var all []string
   238  	for _, p := range ctxt.splitPathList(ctxt.GOPATH) {
   239  		if p == "" || p == ctxt.GOROOT {
   240  			// Empty paths are uninteresting.
   241  			// If the path is the GOROOT, ignore it.
   242  			// People sometimes set GOPATH=$GOROOT.
   243  			// Do not get confused by this common mistake.
   244  			continue
   245  		}
   246  		if strings.HasPrefix(p, "~") {
   247  			// Path segments starting with ~ on Unix are almost always
   248  			// users who have incorrectly quoted ~ while setting GOPATH,
   249  			// preventing it from expanding to $HOME.
   250  			// The situation is made more confusing by the fact that
   251  			// bash allows quoted ~ in $PATH (most shells do not).
   252  			// Do not get confused by this, and do not try to use the path.
   253  			// It does not exist, and printing errors about it confuses
   254  			// those users even more, because they think "sure ~ exists!".
   255  			// The go command diagnoses this situation and prints a
   256  			// useful error.
   257  			// On Windows, ~ is used in short names, such as c:\progra~1
   258  			// for c:\program files.
   259  			continue
   260  		}
   261  		all = append(all, p)
   262  	}
   263  	return all
   264  }
   265  
   266  // SrcDirs returns a list of package source root directories.
   267  // It draws from the current Go root and Go path but omits directories
   268  // that do not exist.
   269  func (ctxt *Context) SrcDirs() []string {
   270  	var all []string
   271  	if ctxt.GOROOT != "" && ctxt.Compiler != "gccgo" {
   272  		dir := ctxt.joinPath(ctxt.GOROOT, "src")
   273  		if ctxt.isDir(dir) {
   274  			all = append(all, dir)
   275  		}
   276  	}
   277  	for _, p := range ctxt.gopath() {
   278  		dir := ctxt.joinPath(p, "src")
   279  		if ctxt.isDir(dir) {
   280  			all = append(all, dir)
   281  		}
   282  	}
   283  	return all
   284  }
   285  
   286  // Default is the default Context for builds.
   287  // It uses the GOARCH, GOOS, GOROOT, and GOPATH environment variables
   288  // if set, or else the compiled code's GOARCH, GOOS, and GOROOT.
   289  var Default Context = defaultContext()
   290  
   291  // Keep consistent with cmd/go/internal/cfg.defaultGOPATH.
   292  func defaultGOPATH() string {
   293  	env := "HOME"
   294  	if runtime.GOOS == "windows" {
   295  		env = "USERPROFILE"
   296  	} else if runtime.GOOS == "plan9" {
   297  		env = "home"
   298  	}
   299  	if home := os.Getenv(env); home != "" {
   300  		def := filepath.Join(home, "go")
   301  		if filepath.Clean(def) == filepath.Clean(runtime.GOROOT()) {
   302  			// Don't set the default GOPATH to GOROOT,
   303  			// as that will trigger warnings from the go tool.
   304  			return ""
   305  		}
   306  		return def
   307  	}
   308  	return ""
   309  }
   310  
   311  // defaultToolTags should be an internal detail,
   312  // but widely used packages access it using linkname.
   313  // Notable members of the hall of shame include:
   314  //   - github.com/gopherjs/gopherjs
   315  //
   316  // Do not remove or change the type signature.
   317  // See go.dev/issue/67401.
   318  //
   319  //go:linkname defaultToolTags
   320  var defaultToolTags []string
   321  
   322  // defaultReleaseTags should be an internal detail,
   323  // but widely used packages access it using linkname.
   324  // Notable members of the hall of shame include:
   325  //   - github.com/gopherjs/gopherjs
   326  //
   327  // Do not remove or change the type signature.
   328  // See go.dev/issue/67401.
   329  //
   330  //go:linkname defaultReleaseTags
   331  var defaultReleaseTags []string
   332  
   333  func defaultContext() Context {
   334  	var c Context
   335  
   336  	c.GOARCH = buildcfg.GOARCH
   337  	c.GOOS = buildcfg.GOOS
   338  	if goroot := runtime.GOROOT(); goroot != "" {
   339  		c.GOROOT = filepath.Clean(goroot)
   340  	}
   341  	c.GOPATH = envOr("GOPATH", defaultGOPATH())
   342  	c.Compiler = runtime.Compiler
   343  	c.ToolTags = append(c.ToolTags, buildcfg.ToolTags...)
   344  
   345  	defaultToolTags = append([]string{}, c.ToolTags...) // our own private copy
   346  
   347  	// Each major Go release in the Go 1.x series adds a new
   348  	// "go1.x" release tag. That is, the go1.x tag is present in
   349  	// all releases >= Go 1.x. Code that requires Go 1.x or later
   350  	// should say "go:build go1.x", and code that should only be
   351  	// built before Go 1.x (perhaps it is the stub to use in that
   352  	// case) should say "go:build !go1.x".
   353  	// The last element in ReleaseTags is the current release.
   354  	for i := 1; i <= goversion.Version; i++ {
   355  		c.ReleaseTags = append(c.ReleaseTags, "go1."+strconv.Itoa(i))
   356  	}
   357  
   358  	defaultReleaseTags = append([]string{}, c.ReleaseTags...) // our own private copy
   359  
   360  	env := os.Getenv("CGO_ENABLED")
   361  	if env == "" {
   362  		env = buildcfg.DefaultCGO_ENABLED
   363  	}
   364  	switch env {
   365  	case "1":
   366  		c.CgoEnabled = true
   367  	case "0":
   368  		c.CgoEnabled = false
   369  	default:
   370  		// cgo must be explicitly enabled for cross compilation builds
   371  		if runtime.GOARCH == c.GOARCH && runtime.GOOS == c.GOOS {
   372  			c.CgoEnabled = platform.CgoSupported(c.GOOS, c.GOARCH)
   373  			break
   374  		}
   375  		c.CgoEnabled = false
   376  	}
   377  
   378  	return c
   379  }
   380  
   381  func envOr(name, def string) string {
   382  	s := os.Getenv(name)
   383  	if s == "" {
   384  		return def
   385  	}
   386  	return s
   387  }
   388  
   389  // An ImportMode controls the behavior of the Import method.
   390  type ImportMode uint
   391  
   392  const (
   393  	// If FindOnly is set, Import stops after locating the directory
   394  	// that should contain the sources for a package. It does not
   395  	// read any files in the directory.
   396  	FindOnly ImportMode = 1 << iota
   397  
   398  	// If AllowBinary is set, Import can be satisfied by a compiled
   399  	// package object without corresponding sources.
   400  	//
   401  	// Deprecated:
   402  	// The supported way to create a compiled-only package is to
   403  	// write source code containing a //go:binary-only-package comment at
   404  	// the top of the file. Such a package will be recognized
   405  	// regardless of this flag setting (because it has source code)
   406  	// and will have BinaryOnly set to true in the returned Package.
   407  	AllowBinary
   408  
   409  	// If ImportComment is set, parse import comments on package statements.
   410  	// Import returns an error if it finds a comment it cannot understand
   411  	// or finds conflicting comments in multiple source files.
   412  	// See golang.org/s/go14customimport for more information.
   413  	ImportComment
   414  
   415  	// By default, Import searches vendor directories
   416  	// that apply in the given source directory before searching
   417  	// the GOROOT and GOPATH roots.
   418  	// If an Import finds and returns a package using a vendor
   419  	// directory, the resulting ImportPath is the complete path
   420  	// to the package, including the path elements leading up
   421  	// to and including "vendor".
   422  	// For example, if Import("y", "x/subdir", 0) finds
   423  	// "x/vendor/y", the returned package's ImportPath is "x/vendor/y",
   424  	// not plain "y".
   425  	// See golang.org/s/go15vendor for more information.
   426  	//
   427  	// Setting IgnoreVendor ignores vendor directories.
   428  	//
   429  	// In contrast to the package's ImportPath,
   430  	// the returned package's Imports, TestImports, and XTestImports
   431  	// are always the exact import paths from the source files:
   432  	// Import makes no attempt to resolve or check those paths.
   433  	IgnoreVendor
   434  )
   435  
   436  // A Package describes the Go package found in a directory.
   437  type Package struct {
   438  	Dir           string   // directory containing package sources
   439  	Name          string   // package name
   440  	ImportComment string   // path in import comment on package statement
   441  	Doc           string   // documentation synopsis
   442  	ImportPath    string   // import path of package ("" if unknown)
   443  	Root          string   // root of Go tree where this package lives
   444  	SrcRoot       string   // package source root directory ("" if unknown)
   445  	PkgRoot       string   // package install root directory ("" if unknown)
   446  	PkgTargetRoot string   // architecture dependent install root directory ("" if unknown)
   447  	BinDir        string   // command install directory ("" if unknown)
   448  	Goroot        bool     // package found in Go root
   449  	PkgObj        string   // installed .a file
   450  	AllTags       []string // tags that can influence file selection in this directory
   451  	ConflictDir   string   // this directory shadows Dir in $GOPATH
   452  	BinaryOnly    bool     // cannot be rebuilt from source (has //go:binary-only-package comment)
   453  
   454  	// Source files
   455  	GoFiles           []string // .go source files (excluding CgoFiles, TestGoFiles, XTestGoFiles)
   456  	CgoFiles          []string // .go source files that import "C"
   457  	IgnoredGoFiles    []string // .go source files ignored for this build (including ignored _test.go files)
   458  	InvalidGoFiles    []string // .go source files with detected problems (parse error, wrong package name, and so on)
   459  	IgnoredOtherFiles []string // non-.go source files ignored for this build
   460  	CFiles            []string // .c source files
   461  	CXXFiles          []string // .cc, .cpp and .cxx source files
   462  	MFiles            []string // .m (Objective-C) source files
   463  	HFiles            []string // .h, .hh, .hpp and .hxx source files
   464  	FFiles            []string // .f, .F, .for and .f90 Fortran source files
   465  	SFiles            []string // .s source files
   466  	SwigFiles         []string // .swig files
   467  	SwigCXXFiles      []string // .swigcxx files
   468  	SysoFiles         []string // .syso system object files to add to archive
   469  
   470  	// Cgo directives
   471  	CgoCFLAGS    []string // Cgo CFLAGS directives
   472  	CgoCPPFLAGS  []string // Cgo CPPFLAGS directives
   473  	CgoCXXFLAGS  []string // Cgo CXXFLAGS directives
   474  	CgoFFLAGS    []string // Cgo FFLAGS directives
   475  	CgoLDFLAGS   []string // Cgo LDFLAGS directives
   476  	CgoPkgConfig []string // Cgo pkg-config directives
   477  
   478  	// Test information
   479  	TestGoFiles  []string // _test.go files in package
   480  	XTestGoFiles []string // _test.go files outside package
   481  
   482  	// Go directive comments (//go:zzz...) found in source files.
   483  	Directives      []Directive
   484  	TestDirectives  []Directive
   485  	XTestDirectives []Directive
   486  
   487  	// Dependency information
   488  	Imports        []string                    // import paths from GoFiles, CgoFiles
   489  	ImportPos      map[string][]token.Position // line information for Imports
   490  	TestImports    []string                    // import paths from TestGoFiles
   491  	TestImportPos  map[string][]token.Position // line information for TestImports
   492  	XTestImports   []string                    // import paths from XTestGoFiles
   493  	XTestImportPos map[string][]token.Position // line information for XTestImports
   494  
   495  	// //go:embed patterns found in Go source files
   496  	// For example, if a source file says
   497  	//	//go:embed a* b.c
   498  	// then the list will contain those two strings as separate entries.
   499  	// (See package embed for more details about //go:embed.)
   500  	EmbedPatterns        []string                    // patterns from GoFiles, CgoFiles
   501  	EmbedPatternPos      map[string][]token.Position // line information for EmbedPatterns
   502  	TestEmbedPatterns    []string                    // patterns from TestGoFiles
   503  	TestEmbedPatternPos  map[string][]token.Position // line information for TestEmbedPatterns
   504  	XTestEmbedPatterns   []string                    // patterns from XTestGoFiles
   505  	XTestEmbedPatternPos map[string][]token.Position // line information for XTestEmbedPatternPos
   506  }
   507  
   508  // A Directive is a Go directive comment (//go:zzz...) found in a source file.
   509  type Directive struct {
   510  	Text string         // full line comment including leading slashes
   511  	Pos  token.Position // position of comment
   512  }
   513  
   514  // IsCommand reports whether the package is considered a
   515  // command to be installed (not just a library).
   516  // Packages named "main" are treated as commands.
   517  func (p *Package) IsCommand() bool {
   518  	return p.Name == "main"
   519  }
   520  
   521  // ImportDir is like [Import] but processes the Go package found in
   522  // the named directory.
   523  func (ctxt *Context) ImportDir(dir string, mode ImportMode) (*Package, error) {
   524  	return ctxt.Import(".", dir, mode)
   525  }
   526  
   527  // NoGoError is the error used by [Import] to describe a directory
   528  // containing no buildable Go source files. (It may still contain
   529  // test files, files hidden by build tags, and so on.)
   530  type NoGoError struct {
   531  	Dir string
   532  }
   533  
   534  func (e *NoGoError) Error() string {
   535  	return "no buildable Go source files in " + e.Dir
   536  }
   537  
   538  // MultiplePackageError describes a directory containing
   539  // multiple buildable Go source files for multiple packages.
   540  type MultiplePackageError struct {
   541  	Dir      string   // directory containing files
   542  	Packages []string // package names found
   543  	Files    []string // corresponding files: Files[i] declares package Packages[i]
   544  }
   545  
   546  func (e *MultiplePackageError) Error() string {
   547  	// Error string limited to two entries for compatibility.
   548  	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)
   549  }
   550  
   551  func nameExt(name string) string {
   552  	i := strings.LastIndex(name, ".")
   553  	if i < 0 {
   554  		return ""
   555  	}
   556  	return name[i:]
   557  }
   558  
   559  var installgoroot = godebug.New("installgoroot")
   560  
   561  // Import returns details about the Go package named by the import path,
   562  // interpreting local import paths relative to the srcDir directory.
   563  // If the path is a local import path naming a package that can be imported
   564  // using a standard import path, the returned package will set p.ImportPath
   565  // to that path.
   566  //
   567  // In the directory containing the package, .go, .c, .h, and .s files are
   568  // considered part of the package except for:
   569  //
   570  //   - .go files in package documentation
   571  //   - files starting with _ or . (likely editor temporary files)
   572  //   - files with build constraints not satisfied by the context
   573  //
   574  // If an error occurs, Import returns a non-nil error and a non-nil
   575  // *[Package] containing partial information.
   576  func (ctxt *Context) Import(path string, srcDir string, mode ImportMode) (*Package, error) {
   577  	p := &Package{
   578  		ImportPath: path,
   579  	}
   580  	if path == "" {
   581  		return p, fmt.Errorf("import %q: invalid import path", path)
   582  	}
   583  
   584  	var pkgtargetroot string
   585  	var pkga string
   586  	var pkgerr error
   587  	suffix := ""
   588  	if ctxt.InstallSuffix != "" {
   589  		suffix = "_" + ctxt.InstallSuffix
   590  	}
   591  	switch ctxt.Compiler {
   592  	case "gccgo":
   593  		pkgtargetroot = "pkg/gccgo_" + ctxt.GOOS + "_" + ctxt.GOARCH + suffix
   594  	case "gc":
   595  		pkgtargetroot = "pkg/" + ctxt.GOOS + "_" + ctxt.GOARCH + suffix
   596  	default:
   597  		// Save error for end of function.
   598  		pkgerr = fmt.Errorf("import %q: unknown compiler %q", path, ctxt.Compiler)
   599  	}
   600  	setPkga := func() {
   601  		switch ctxt.Compiler {
   602  		case "gccgo":
   603  			dir, elem := pathpkg.Split(p.ImportPath)
   604  			pkga = pkgtargetroot + "/" + dir + "lib" + elem + ".a"
   605  		case "gc":
   606  			pkga = pkgtargetroot + "/" + p.ImportPath + ".a"
   607  		}
   608  	}
   609  	setPkga()
   610  
   611  	binaryOnly := false
   612  	if IsLocalImport(path) {
   613  		pkga = "" // local imports have no installed path
   614  		if srcDir == "" {
   615  			return p, fmt.Errorf("import %q: import relative to unknown directory", path)
   616  		}
   617  		if !ctxt.isAbsPath(path) {
   618  			p.Dir = ctxt.joinPath(srcDir, path)
   619  		}
   620  		// p.Dir directory may or may not exist. Gather partial information first, check if it exists later.
   621  		// Determine canonical import path, if any.
   622  		// Exclude results where the import path would include /testdata/.
   623  		inTestdata := func(sub string) bool {
   624  			return strings.Contains(sub, "/testdata/") || strings.HasSuffix(sub, "/testdata") || strings.HasPrefix(sub, "testdata/") || sub == "testdata"
   625  		}
   626  		if ctxt.GOROOT != "" {
   627  			root := ctxt.joinPath(ctxt.GOROOT, "src")
   628  			if sub, ok := ctxt.hasSubdir(root, p.Dir); ok && !inTestdata(sub) {
   629  				p.Goroot = true
   630  				p.ImportPath = sub
   631  				p.Root = ctxt.GOROOT
   632  				setPkga() // p.ImportPath changed
   633  				goto Found
   634  			}
   635  		}
   636  		all := ctxt.gopath()
   637  		for i, root := range all {
   638  			rootsrc := ctxt.joinPath(root, "src")
   639  			if sub, ok := ctxt.hasSubdir(rootsrc, p.Dir); ok && !inTestdata(sub) {
   640  				// We found a potential import path for dir,
   641  				// but check that using it wouldn't find something
   642  				// else first.
   643  				if ctxt.GOROOT != "" && ctxt.Compiler != "gccgo" {
   644  					if dir := ctxt.joinPath(ctxt.GOROOT, "src", sub); ctxt.isDir(dir) {
   645  						p.ConflictDir = dir
   646  						goto Found
   647  					}
   648  				}
   649  				for _, earlyRoot := range all[:i] {
   650  					if dir := ctxt.joinPath(earlyRoot, "src", sub); ctxt.isDir(dir) {
   651  						p.ConflictDir = dir
   652  						goto Found
   653  					}
   654  				}
   655  
   656  				// sub would not name some other directory instead of this one.
   657  				// Record it.
   658  				p.ImportPath = sub
   659  				p.Root = root
   660  				setPkga() // p.ImportPath changed
   661  				goto Found
   662  			}
   663  		}
   664  		// It's okay that we didn't find a root containing dir.
   665  		// Keep going with the information we have.
   666  	} else {
   667  		if strings.HasPrefix(path, "/") {
   668  			return p, fmt.Errorf("import %q: cannot import absolute path", path)
   669  		}
   670  
   671  		if err := ctxt.importGo(p, path, srcDir, mode); err == nil {
   672  			goto Found
   673  		} else if err != errNoModules {
   674  			return p, err
   675  		}
   676  
   677  		gopath := ctxt.gopath() // needed twice below; avoid computing many times
   678  
   679  		// tried records the location of unsuccessful package lookups
   680  		var tried struct {
   681  			vendor []string
   682  			goroot string
   683  			gopath []string
   684  		}
   685  
   686  		// Vendor directories get first chance to satisfy import.
   687  		if mode&IgnoreVendor == 0 && srcDir != "" {
   688  			searchVendor := func(root string, isGoroot bool) bool {
   689  				sub, ok := ctxt.hasSubdir(root, srcDir)
   690  				if !ok || !strings.HasPrefix(sub, "src/") || strings.Contains(sub, "/testdata/") {
   691  					return false
   692  				}
   693  				for {
   694  					vendor := ctxt.joinPath(root, sub, "vendor")
   695  					if ctxt.isDir(vendor) {
   696  						dir := ctxt.joinPath(vendor, path)
   697  						if ctxt.isDir(dir) && hasGoFiles(ctxt, dir) {
   698  							p.Dir = dir
   699  							p.ImportPath = strings.TrimPrefix(pathpkg.Join(sub, "vendor", path), "src/")
   700  							p.Goroot = isGoroot
   701  							p.Root = root
   702  							setPkga() // p.ImportPath changed
   703  							return true
   704  						}
   705  						tried.vendor = append(tried.vendor, dir)
   706  					}
   707  					i := strings.LastIndex(sub, "/")
   708  					if i < 0 {
   709  						break
   710  					}
   711  					sub = sub[:i]
   712  				}
   713  				return false
   714  			}
   715  			if ctxt.Compiler != "gccgo" && ctxt.GOROOT != "" && searchVendor(ctxt.GOROOT, true) {
   716  				goto Found
   717  			}
   718  			for _, root := range gopath {
   719  				if searchVendor(root, false) {
   720  					goto Found
   721  				}
   722  			}
   723  		}
   724  
   725  		// Determine directory from import path.
   726  		if ctxt.GOROOT != "" {
   727  			// If the package path starts with "vendor/", only search GOROOT before
   728  			// GOPATH if the importer is also within GOROOT. That way, if the user has
   729  			// vendored in a package that is subsequently included in the standard
   730  			// distribution, they'll continue to pick up their own vendored copy.
   731  			gorootFirst := srcDir == "" || !strings.HasPrefix(path, "vendor/")
   732  			if !gorootFirst {
   733  				_, gorootFirst = ctxt.hasSubdir(ctxt.GOROOT, srcDir)
   734  			}
   735  			if gorootFirst {
   736  				dir := ctxt.joinPath(ctxt.GOROOT, "src", path)
   737  				if ctxt.Compiler != "gccgo" {
   738  					isDir := ctxt.isDir(dir)
   739  					binaryOnly = !isDir && mode&AllowBinary != 0 && pkga != "" && ctxt.isFile(ctxt.joinPath(ctxt.GOROOT, pkga))
   740  					if isDir || binaryOnly {
   741  						p.Dir = dir
   742  						p.Goroot = true
   743  						p.Root = ctxt.GOROOT
   744  						goto Found
   745  					}
   746  				}
   747  				tried.goroot = dir
   748  			}
   749  			if ctxt.Compiler == "gccgo" && goroot.IsStandardPackage(ctxt.GOROOT, ctxt.Compiler, path) {
   750  				// TODO(bcmills): Setting p.Dir here is misleading, because gccgo
   751  				// doesn't actually load its standard-library packages from this
   752  				// directory. See if we can leave it unset.
   753  				p.Dir = ctxt.joinPath(ctxt.GOROOT, "src", path)
   754  				p.Goroot = true
   755  				p.Root = ctxt.GOROOT
   756  				goto Found
   757  			}
   758  		}
   759  		for _, root := range gopath {
   760  			dir := ctxt.joinPath(root, "src", path)
   761  			isDir := ctxt.isDir(dir)
   762  			binaryOnly = !isDir && mode&AllowBinary != 0 && pkga != "" && ctxt.isFile(ctxt.joinPath(root, pkga))
   763  			if isDir || binaryOnly {
   764  				p.Dir = dir
   765  				p.Root = root
   766  				goto Found
   767  			}
   768  			tried.gopath = append(tried.gopath, dir)
   769  		}
   770  
   771  		// If we tried GOPATH first due to a "vendor/" prefix, fall back to GOPATH.
   772  		// That way, the user can still get useful results from 'go list' for
   773  		// standard-vendored paths passed on the command line.
   774  		if ctxt.GOROOT != "" && tried.goroot == "" {
   775  			dir := ctxt.joinPath(ctxt.GOROOT, "src", path)
   776  			if ctxt.Compiler != "gccgo" {
   777  				isDir := ctxt.isDir(dir)
   778  				binaryOnly = !isDir && mode&AllowBinary != 0 && pkga != "" && ctxt.isFile(ctxt.joinPath(ctxt.GOROOT, pkga))
   779  				if isDir || binaryOnly {
   780  					p.Dir = dir
   781  					p.Goroot = true
   782  					p.Root = ctxt.GOROOT
   783  					goto Found
   784  				}
   785  			}
   786  			tried.goroot = dir
   787  		}
   788  
   789  		// package was not found
   790  		var paths []string
   791  		format := "\t%s (vendor tree)"
   792  		for _, dir := range tried.vendor {
   793  			paths = append(paths, fmt.Sprintf(format, dir))
   794  			format = "\t%s"
   795  		}
   796  		if tried.goroot != "" {
   797  			paths = append(paths, fmt.Sprintf("\t%s (from $GOROOT)", tried.goroot))
   798  		} else {
   799  			paths = append(paths, "\t($GOROOT not set)")
   800  		}
   801  		format = "\t%s (from $GOPATH)"
   802  		for _, dir := range tried.gopath {
   803  			paths = append(paths, fmt.Sprintf(format, dir))
   804  			format = "\t%s"
   805  		}
   806  		if len(tried.gopath) == 0 {
   807  			paths = append(paths, "\t($GOPATH not set. For more details see: 'go help gopath')")
   808  		}
   809  		return p, fmt.Errorf("cannot find package %q in any of:\n%s", path, strings.Join(paths, "\n"))
   810  	}
   811  
   812  Found:
   813  	if p.Root != "" {
   814  		p.SrcRoot = ctxt.joinPath(p.Root, "src")
   815  		p.PkgRoot = ctxt.joinPath(p.Root, "pkg")
   816  		p.BinDir = ctxt.joinPath(p.Root, "bin")
   817  		if pkga != "" {
   818  			// Always set PkgTargetRoot. It might be used when building in shared
   819  			// mode.
   820  			p.PkgTargetRoot = ctxt.joinPath(p.Root, pkgtargetroot)
   821  
   822  			// Set the install target if applicable.
   823  			if !p.Goroot || (installgoroot.Value() == "all" && p.ImportPath != "unsafe" && p.ImportPath != "builtin") {
   824  				if p.Goroot {
   825  					installgoroot.IncNonDefault()
   826  				}
   827  				p.PkgObj = ctxt.joinPath(p.Root, pkga)
   828  			}
   829  		}
   830  	}
   831  
   832  	// If it's a local import path, by the time we get here, we still haven't checked
   833  	// that p.Dir directory exists. This is the right time to do that check.
   834  	// We can't do it earlier, because we want to gather partial information for the
   835  	// non-nil *Package returned when an error occurs.
   836  	// We need to do this before we return early on FindOnly flag.
   837  	if IsLocalImport(path) && !ctxt.isDir(p.Dir) {
   838  		if ctxt.Compiler == "gccgo" && p.Goroot {
   839  			// gccgo has no sources for GOROOT packages.
   840  			return p, nil
   841  		}
   842  
   843  		// package was not found
   844  		return p, fmt.Errorf("cannot find package %q in:\n\t%s", p.ImportPath, p.Dir)
   845  	}
   846  
   847  	if mode&FindOnly != 0 {
   848  		return p, pkgerr
   849  	}
   850  	if binaryOnly && (mode&AllowBinary) != 0 {
   851  		return p, pkgerr
   852  	}
   853  
   854  	if ctxt.Compiler == "gccgo" && p.Goroot {
   855  		// gccgo has no sources for GOROOT packages.
   856  		return p, nil
   857  	}
   858  
   859  	dirs, err := ctxt.readDir(p.Dir)
   860  	if err != nil {
   861  		return p, err
   862  	}
   863  
   864  	var badGoError error
   865  	badGoFiles := make(map[string]bool)
   866  	badGoFile := func(name string, err error) {
   867  		if badGoError == nil {
   868  			badGoError = err
   869  		}
   870  		if !badGoFiles[name] {
   871  			p.InvalidGoFiles = append(p.InvalidGoFiles, name)
   872  			badGoFiles[name] = true
   873  		}
   874  	}
   875  
   876  	var Sfiles []string // files with ".S"(capital S)/.sx(capital s equivalent for case insensitive filesystems)
   877  	var firstFile, firstCommentFile string
   878  	embedPos := make(map[string][]token.Position)
   879  	testEmbedPos := make(map[string][]token.Position)
   880  	xTestEmbedPos := make(map[string][]token.Position)
   881  	importPos := make(map[string][]token.Position)
   882  	testImportPos := make(map[string][]token.Position)
   883  	xTestImportPos := make(map[string][]token.Position)
   884  	allTags := make(map[string]bool)
   885  	fset := token.NewFileSet()
   886  	for _, d := range dirs {
   887  		if d.IsDir() {
   888  			continue
   889  		}
   890  		if d.Type() == fs.ModeSymlink {
   891  			if ctxt.isDir(ctxt.joinPath(p.Dir, d.Name())) {
   892  				// Symlinks to directories are not source files.
   893  				continue
   894  			}
   895  		}
   896  
   897  		name := d.Name()
   898  		ext := nameExt(name)
   899  
   900  		info, err := ctxt.matchFile(p.Dir, name, allTags, &p.BinaryOnly, fset)
   901  		if err != nil && strings.HasSuffix(name, ".go") {
   902  			badGoFile(name, err)
   903  			continue
   904  		}
   905  		if info == nil {
   906  			if strings.HasPrefix(name, "_") || strings.HasPrefix(name, ".") {
   907  				// not due to build constraints - don't report
   908  			} else if ext == ".go" {
   909  				p.IgnoredGoFiles = append(p.IgnoredGoFiles, name)
   910  			} else if fileListForExt(p, ext) != nil {
   911  				p.IgnoredOtherFiles = append(p.IgnoredOtherFiles, name)
   912  			}
   913  			continue
   914  		}
   915  
   916  		// Going to save the file. For non-Go files, can stop here.
   917  		switch ext {
   918  		case ".go":
   919  			// keep going
   920  		case ".S", ".sx":
   921  			// special case for cgo, handled at end
   922  			Sfiles = append(Sfiles, name)
   923  			continue
   924  		default:
   925  			if list := fileListForExt(p, ext); list != nil {
   926  				*list = append(*list, name)
   927  			}
   928  			continue
   929  		}
   930  
   931  		data, filename := info.header, info.name
   932  
   933  		if info.parseErr != nil {
   934  			badGoFile(name, info.parseErr)
   935  			// Fall through: we might still have a partial AST in info.parsed,
   936  			// and we want to list files with parse errors anyway.
   937  		}
   938  
   939  		var pkg string
   940  		if info.parsed != nil {
   941  			pkg = info.parsed.Name.Name
   942  			if pkg == "documentation" {
   943  				p.IgnoredGoFiles = append(p.IgnoredGoFiles, name)
   944  				continue
   945  			}
   946  		}
   947  
   948  		isTest := strings.HasSuffix(name, "_test.go")
   949  		isXTest := false
   950  		if isTest && strings.HasSuffix(pkg, "_test") && p.Name != pkg {
   951  			isXTest = true
   952  			pkg = pkg[:len(pkg)-len("_test")]
   953  		}
   954  
   955  		if p.Name == "" {
   956  			p.Name = pkg
   957  			firstFile = name
   958  		} else if pkg != p.Name {
   959  			// TODO(#45999): The choice of p.Name is arbitrary based on file iteration
   960  			// order. Instead of resolving p.Name arbitrarily, we should clear out the
   961  			// existing name and mark the existing files as also invalid.
   962  			badGoFile(name, &MultiplePackageError{
   963  				Dir:      p.Dir,
   964  				Packages: []string{p.Name, pkg},
   965  				Files:    []string{firstFile, name},
   966  			})
   967  		}
   968  		// Grab the first package comment as docs, provided it is not from a test file.
   969  		if info.parsed != nil && info.parsed.Doc != nil && p.Doc == "" && !isTest && !isXTest {
   970  			p.Doc = doc.Synopsis(info.parsed.Doc.Text())
   971  		}
   972  
   973  		if mode&ImportComment != 0 {
   974  			qcom, line := findImportComment(data)
   975  			if line != 0 {
   976  				com, err := strconv.Unquote(qcom)
   977  				if err != nil {
   978  					badGoFile(name, fmt.Errorf("%s:%d: cannot parse import comment", filename, line))
   979  				} else if p.ImportComment == "" {
   980  					p.ImportComment = com
   981  					firstCommentFile = name
   982  				} else if p.ImportComment != com {
   983  					badGoFile(name, fmt.Errorf("found import comments %q (%s) and %q (%s) in %s", p.ImportComment, firstCommentFile, com, name, p.Dir))
   984  				}
   985  			}
   986  		}
   987  
   988  		// Record imports and information about cgo.
   989  		isCgo := false
   990  		for _, imp := range info.imports {
   991  			if imp.path == "C" {
   992  				if isTest {
   993  					badGoFile(name, fmt.Errorf("use of cgo in test %s not supported", filename))
   994  					continue
   995  				}
   996  				isCgo = true
   997  				if imp.doc != nil {
   998  					if err := ctxt.saveCgo(filename, p, imp.doc); err != nil {
   999  						badGoFile(name, err)
  1000  					}
  1001  				}
  1002  			}
  1003  		}
  1004  
  1005  		var fileList *[]string
  1006  		var importMap, embedMap map[string][]token.Position
  1007  		var directives *[]Directive
  1008  		switch {
  1009  		case isCgo:
  1010  			allTags["cgo"] = true
  1011  			if ctxt.CgoEnabled {
  1012  				fileList = &p.CgoFiles
  1013  				importMap = importPos
  1014  				embedMap = embedPos
  1015  				directives = &p.Directives
  1016  			} else {
  1017  				// Ignore imports and embeds from cgo files if cgo is disabled.
  1018  				fileList = &p.IgnoredGoFiles
  1019  			}
  1020  		case isXTest:
  1021  			fileList = &p.XTestGoFiles
  1022  			importMap = xTestImportPos
  1023  			embedMap = xTestEmbedPos
  1024  			directives = &p.XTestDirectives
  1025  		case isTest:
  1026  			fileList = &p.TestGoFiles
  1027  			importMap = testImportPos
  1028  			embedMap = testEmbedPos
  1029  			directives = &p.TestDirectives
  1030  		default:
  1031  			fileList = &p.GoFiles
  1032  			importMap = importPos
  1033  			embedMap = embedPos
  1034  			directives = &p.Directives
  1035  		}
  1036  		*fileList = append(*fileList, name)
  1037  		if importMap != nil {
  1038  			for _, imp := range info.imports {
  1039  				importMap[imp.path] = append(importMap[imp.path], fset.Position(imp.pos))
  1040  			}
  1041  		}
  1042  		if embedMap != nil {
  1043  			for _, emb := range info.embeds {
  1044  				embedMap[emb.pattern] = append(embedMap[emb.pattern], emb.pos)
  1045  			}
  1046  		}
  1047  		if directives != nil {
  1048  			*directives = append(*directives, info.directives...)
  1049  		}
  1050  	}
  1051  
  1052  	for tag := range allTags {
  1053  		p.AllTags = append(p.AllTags, tag)
  1054  	}
  1055  	slices.Sort(p.AllTags)
  1056  
  1057  	p.EmbedPatterns, p.EmbedPatternPos = cleanDecls(embedPos)
  1058  	p.TestEmbedPatterns, p.TestEmbedPatternPos = cleanDecls(testEmbedPos)
  1059  	p.XTestEmbedPatterns, p.XTestEmbedPatternPos = cleanDecls(xTestEmbedPos)
  1060  
  1061  	p.Imports, p.ImportPos = cleanDecls(importPos)
  1062  	p.TestImports, p.TestImportPos = cleanDecls(testImportPos)
  1063  	p.XTestImports, p.XTestImportPos = cleanDecls(xTestImportPos)
  1064  
  1065  	// add the .S/.sx files only if we are using cgo
  1066  	// (which means gcc will compile them).
  1067  	// The standard assemblers expect .s files.
  1068  	if len(p.CgoFiles) > 0 {
  1069  		p.SFiles = append(p.SFiles, Sfiles...)
  1070  		slices.Sort(p.SFiles)
  1071  	} else {
  1072  		p.IgnoredOtherFiles = append(p.IgnoredOtherFiles, Sfiles...)
  1073  		slices.Sort(p.IgnoredOtherFiles)
  1074  	}
  1075  
  1076  	if badGoError != nil {
  1077  		return p, badGoError
  1078  	}
  1079  	if len(p.GoFiles)+len(p.CgoFiles)+len(p.TestGoFiles)+len(p.XTestGoFiles) == 0 {
  1080  		return p, &NoGoError{p.Dir}
  1081  	}
  1082  	return p, pkgerr
  1083  }
  1084  
  1085  func fileListForExt(p *Package, ext string) *[]string {
  1086  	switch ext {
  1087  	case ".c":
  1088  		return &p.CFiles
  1089  	case ".cc", ".cpp", ".cxx":
  1090  		return &p.CXXFiles
  1091  	case ".m":
  1092  		return &p.MFiles
  1093  	case ".h", ".hh", ".hpp", ".hxx":
  1094  		return &p.HFiles
  1095  	case ".f", ".F", ".for", ".f90":
  1096  		return &p.FFiles
  1097  	case ".s", ".S", ".sx":
  1098  		return &p.SFiles
  1099  	case ".swig":
  1100  		return &p.SwigFiles
  1101  	case ".swigcxx":
  1102  		return &p.SwigCXXFiles
  1103  	case ".syso":
  1104  		return &p.SysoFiles
  1105  	}
  1106  	return nil
  1107  }
  1108  
  1109  func uniq(list []string) []string {
  1110  	if list == nil {
  1111  		return nil
  1112  	}
  1113  	out := make([]string, len(list))
  1114  	copy(out, list)
  1115  	slices.Sort(out)
  1116  	uniq := out[:0]
  1117  	for _, x := range out {
  1118  		if len(uniq) == 0 || uniq[len(uniq)-1] != x {
  1119  			uniq = append(uniq, x)
  1120  		}
  1121  	}
  1122  	return uniq
  1123  }
  1124  
  1125  var errNoModules = errors.New("not using modules")
  1126  
  1127  // importGo checks whether it can use the go command to find the directory for path.
  1128  // If using the go command is not appropriate, importGo returns errNoModules.
  1129  // Otherwise, importGo tries using the go command and reports whether that succeeded.
  1130  // Using the go command lets build.Import and build.Context.Import find code
  1131  // in Go modules. In the long term we want tools to use go/packages (currently golang.org/x/tools/go/packages),
  1132  // which will also use the go command.
  1133  // Invoking the go command here is not very efficient in that it computes information
  1134  // about the requested package and all dependencies and then only reports about the requested package.
  1135  // Then we reinvoke it for every dependency. But this is still better than not working at all.
  1136  // See golang.org/issue/26504.
  1137  func (ctxt *Context) importGo(p *Package, path, srcDir string, mode ImportMode) error {
  1138  	// To invoke the go command,
  1139  	// we must not being doing special things like AllowBinary or IgnoreVendor,
  1140  	// and all the file system callbacks must be nil (we're meant to use the local file system).
  1141  	if mode&AllowBinary != 0 || mode&IgnoreVendor != 0 ||
  1142  		ctxt.JoinPath != nil || ctxt.SplitPathList != nil || ctxt.IsAbsPath != nil || ctxt.IsDir != nil || ctxt.HasSubdir != nil || ctxt.ReadDir != nil || ctxt.OpenFile != nil || !slices.Equal(ctxt.ToolTags, defaultToolTags) || !slices.Equal(ctxt.ReleaseTags, defaultReleaseTags) {
  1143  		return errNoModules
  1144  	}
  1145  
  1146  	// If ctxt.GOROOT is not set, we don't know which go command to invoke,
  1147  	// and even if we did we might return packages in GOROOT that we wouldn't otherwise find
  1148  	// (because we don't know to search in 'go env GOROOT' otherwise).
  1149  	if ctxt.GOROOT == "" {
  1150  		return errNoModules
  1151  	}
  1152  
  1153  	// Predict whether module aware mode is enabled by checking the value of
  1154  	// GO111MODULE and looking for a go.mod file in the source directory or
  1155  	// one of its parents. Running 'go env GOMOD' in the source directory would
  1156  	// give a canonical answer, but we'd prefer not to execute another command.
  1157  	go111Module := os.Getenv("GO111MODULE")
  1158  	switch go111Module {
  1159  	case "off":
  1160  		return errNoModules
  1161  	default: // "", "on", "auto", anything else
  1162  		// Maybe use modules.
  1163  	}
  1164  
  1165  	if srcDir != "" {
  1166  		var absSrcDir string
  1167  		if filepath.IsAbs(srcDir) {
  1168  			absSrcDir = srcDir
  1169  		} else if ctxt.Dir != "" {
  1170  			return fmt.Errorf("go/build: Dir is non-empty, so relative srcDir is not allowed: %v", srcDir)
  1171  		} else {
  1172  			// Find the absolute source directory. hasSubdir does not handle
  1173  			// relative paths (and can't because the callbacks don't support this).
  1174  			var err error
  1175  			absSrcDir, err = filepath.Abs(srcDir)
  1176  			if err != nil {
  1177  				return errNoModules
  1178  			}
  1179  		}
  1180  
  1181  		// If the source directory is in GOROOT, then the in-process code works fine
  1182  		// and we should keep using it. Moreover, the 'go list' approach below doesn't
  1183  		// take standard-library vendoring into account and will fail.
  1184  		if _, ok := ctxt.hasSubdir(filepath.Join(ctxt.GOROOT, "src"), absSrcDir); ok {
  1185  			return errNoModules
  1186  		}
  1187  	}
  1188  
  1189  	// For efficiency, if path is a standard library package, let the usual lookup code handle it.
  1190  	if dir := ctxt.joinPath(ctxt.GOROOT, "src", path); ctxt.isDir(dir) {
  1191  		return errNoModules
  1192  	}
  1193  
  1194  	// If GO111MODULE=auto, look to see if there is a go.mod.
  1195  	// Since go1.13, it doesn't matter if we're inside GOPATH.
  1196  	if go111Module == "auto" {
  1197  		var (
  1198  			parent string
  1199  			err    error
  1200  		)
  1201  		if ctxt.Dir == "" {
  1202  			parent, err = os.Getwd()
  1203  			if err != nil {
  1204  				// A nonexistent working directory can't be in a module.
  1205  				return errNoModules
  1206  			}
  1207  		} else {
  1208  			parent, err = filepath.Abs(ctxt.Dir)
  1209  			if err != nil {
  1210  				// If the caller passed a bogus Dir explicitly, that's materially
  1211  				// different from not having modules enabled.
  1212  				return err
  1213  			}
  1214  		}
  1215  		for {
  1216  			if f, err := ctxt.openFile(ctxt.joinPath(parent, "go.mod")); err == nil {
  1217  				buf := make([]byte, 100)
  1218  				_, err := f.Read(buf)
  1219  				f.Close()
  1220  				if err == nil || err == io.EOF {
  1221  					// go.mod exists and is readable (is a file, not a directory).
  1222  					break
  1223  				}
  1224  			}
  1225  			d := filepath.Dir(parent)
  1226  			if len(d) >= len(parent) {
  1227  				return errNoModules // reached top of file system, no go.mod
  1228  			}
  1229  			parent = d
  1230  		}
  1231  	}
  1232  
  1233  	goCmd := filepath.Join(ctxt.GOROOT, "bin", "go")
  1234  	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)
  1235  
  1236  	if ctxt.Dir != "" {
  1237  		cmd.Dir = ctxt.Dir
  1238  	}
  1239  
  1240  	var stdout, stderr strings.Builder
  1241  	cmd.Stdout = &stdout
  1242  	cmd.Stderr = &stderr
  1243  
  1244  	cgo := "0"
  1245  	if ctxt.CgoEnabled {
  1246  		cgo = "1"
  1247  	}
  1248  	cmd.Env = append(cmd.Environ(),
  1249  		"GOOS="+ctxt.GOOS,
  1250  		"GOARCH="+ctxt.GOARCH,
  1251  		"GOROOT="+ctxt.GOROOT,
  1252  		"GOPATH="+ctxt.GOPATH,
  1253  		"CGO_ENABLED="+cgo,
  1254  	)
  1255  
  1256  	if err := cmd.Run(); err != nil {
  1257  		return fmt.Errorf("go/build: go list %s: %v\n%s\n", path, err, stderr.String())
  1258  	}
  1259  
  1260  	f := strings.SplitN(stdout.String(), "\n", 5)
  1261  	if len(f) != 5 {
  1262  		return fmt.Errorf("go/build: importGo %s: unexpected output:\n%s\n", path, stdout.String())
  1263  	}
  1264  	dir := f[0]
  1265  	errStr := strings.TrimSpace(f[4])
  1266  	if errStr != "" && dir == "" {
  1267  		// If 'go list' could not locate the package (dir is empty),
  1268  		// return the same error that 'go list' reported.
  1269  		return errors.New(errStr)
  1270  	}
  1271  
  1272  	// If 'go list' did locate the package, ignore the error.
  1273  	// It was probably related to loading source files, and we'll
  1274  	// encounter it ourselves shortly if the FindOnly flag isn't set.
  1275  	p.Dir = dir
  1276  	p.ImportPath = f[1]
  1277  	p.Root = f[2]
  1278  	p.Goroot = f[3] == "true"
  1279  	return nil
  1280  }
  1281  
  1282  // hasGoFiles reports whether dir contains any files with names ending in .go.
  1283  // For a vendor check we must exclude directories that contain no .go files.
  1284  // Otherwise it is not possible to vendor just a/b/c and still import the
  1285  // non-vendored a/b. See golang.org/issue/13832.
  1286  func hasGoFiles(ctxt *Context, dir string) bool {
  1287  	ents, _ := ctxt.readDir(dir)
  1288  	for _, ent := range ents {
  1289  		if !ent.IsDir() && strings.HasSuffix(ent.Name(), ".go") {
  1290  			return true
  1291  		}
  1292  	}
  1293  	return false
  1294  }
  1295  
  1296  func findImportComment(data []byte) (s string, line int) {
  1297  	// expect keyword package
  1298  	word, data := parseWord(data)
  1299  	if string(word) != "package" {
  1300  		return "", 0
  1301  	}
  1302  
  1303  	// expect package name
  1304  	_, data = parseWord(data)
  1305  
  1306  	// now ready for import comment, a // or /* */ comment
  1307  	// beginning and ending on the current line.
  1308  	for len(data) > 0 && (data[0] == ' ' || data[0] == '\t' || data[0] == '\r') {
  1309  		data = data[1:]
  1310  	}
  1311  
  1312  	var comment []byte
  1313  	switch {
  1314  	case bytes.HasPrefix(data, slashSlash):
  1315  		comment, _, _ = bytes.Cut(data[2:], newline)
  1316  	case bytes.HasPrefix(data, slashStar):
  1317  		var ok bool
  1318  		comment, _, ok = bytes.Cut(data[2:], starSlash)
  1319  		if !ok {
  1320  			// malformed comment
  1321  			return "", 0
  1322  		}
  1323  		if bytes.Contains(comment, newline) {
  1324  			return "", 0
  1325  		}
  1326  	}
  1327  	comment = bytes.TrimSpace(comment)
  1328  
  1329  	// split comment into `import`, `"pkg"`
  1330  	word, arg := parseWord(comment)
  1331  	if string(word) != "import" {
  1332  		return "", 0
  1333  	}
  1334  
  1335  	line = 1 + bytes.Count(data[:cap(data)-cap(arg)], newline)
  1336  	return strings.TrimSpace(string(arg)), line
  1337  }
  1338  
  1339  var (
  1340  	slashSlash = []byte("//")
  1341  	slashStar  = []byte("/*")
  1342  	starSlash  = []byte("*/")
  1343  	newline    = []byte("\n")
  1344  )
  1345  
  1346  // skipSpaceOrComment returns data with any leading spaces or comments removed.
  1347  func skipSpaceOrComment(data []byte) []byte {
  1348  	for len(data) > 0 {
  1349  		switch data[0] {
  1350  		case ' ', '\t', '\r', '\n':
  1351  			data = data[1:]
  1352  			continue
  1353  		case '/':
  1354  			if bytes.HasPrefix(data, slashSlash) {
  1355  				i := bytes.Index(data, newline)
  1356  				if i < 0 {
  1357  					return nil
  1358  				}
  1359  				data = data[i+1:]
  1360  				continue
  1361  			}
  1362  			if bytes.HasPrefix(data, slashStar) {
  1363  				data = data[2:]
  1364  				i := bytes.Index(data, starSlash)
  1365  				if i < 0 {
  1366  					return nil
  1367  				}
  1368  				data = data[i+2:]
  1369  				continue
  1370  			}
  1371  		}
  1372  		break
  1373  	}
  1374  	return data
  1375  }
  1376  
  1377  // parseWord skips any leading spaces or comments in data
  1378  // and then parses the beginning of data as an identifier or keyword,
  1379  // returning that word and what remains after the word.
  1380  func parseWord(data []byte) (word, rest []byte) {
  1381  	data = skipSpaceOrComment(data)
  1382  
  1383  	// Parse past leading word characters.
  1384  	rest = data
  1385  	for {
  1386  		r, size := utf8.DecodeRune(rest)
  1387  		if unicode.IsLetter(r) || '0' <= r && r <= '9' || r == '_' {
  1388  			rest = rest[size:]
  1389  			continue
  1390  		}
  1391  		break
  1392  	}
  1393  
  1394  	word = data[:len(data)-len(rest)]
  1395  	if len(word) == 0 {
  1396  		return nil, nil
  1397  	}
  1398  
  1399  	return word, rest
  1400  }
  1401  
  1402  // MatchFile reports whether the file with the given name in the given directory
  1403  // matches the context and would be included in a [Package] created by [ImportDir]
  1404  // of that directory.
  1405  //
  1406  // MatchFile considers the name of the file and may use ctxt.OpenFile to
  1407  // read some or all of the file's content.
  1408  func (ctxt *Context) MatchFile(dir, name string) (match bool, err error) {
  1409  	info, err := ctxt.matchFile(dir, name, nil, nil, nil)
  1410  	return info != nil, err
  1411  }
  1412  
  1413  var dummyPkg Package
  1414  
  1415  // fileInfo records information learned about a file included in a build.
  1416  type fileInfo struct {
  1417  	name       string // full name including dir
  1418  	header     []byte
  1419  	fset       *token.FileSet
  1420  	parsed     *ast.File
  1421  	parseErr   error
  1422  	imports    []fileImport
  1423  	embeds     []fileEmbed
  1424  	directives []Directive
  1425  }
  1426  
  1427  type fileImport struct {
  1428  	path string
  1429  	pos  token.Pos
  1430  	doc  *ast.CommentGroup
  1431  }
  1432  
  1433  type fileEmbed struct {
  1434  	pattern string
  1435  	pos     token.Position
  1436  }
  1437  
  1438  // matchFile determines whether the file with the given name in the given directory
  1439  // should be included in the package being constructed.
  1440  // If the file should be included, matchFile returns a non-nil *fileInfo (and a nil error).
  1441  // Non-nil errors are reserved for unexpected problems.
  1442  //
  1443  // If name denotes a Go program, matchFile reads until the end of the
  1444  // imports and returns that section of the file in the fileInfo's header field,
  1445  // even though it only considers text until the first non-comment
  1446  // for go:build lines.
  1447  //
  1448  // If allTags is non-nil, matchFile records any encountered build tag
  1449  // by setting allTags[tag] = true.
  1450  func (ctxt *Context) matchFile(dir, name string, allTags map[string]bool, binaryOnly *bool, fset *token.FileSet) (*fileInfo, error) {
  1451  	if strings.HasPrefix(name, "_") ||
  1452  		strings.HasPrefix(name, ".") {
  1453  		return nil, nil
  1454  	}
  1455  
  1456  	i := strings.LastIndex(name, ".")
  1457  	if i < 0 {
  1458  		i = len(name)
  1459  	}
  1460  	ext := name[i:]
  1461  
  1462  	if ext != ".go" && fileListForExt(&dummyPkg, ext) == nil {
  1463  		// skip
  1464  		return nil, nil
  1465  	}
  1466  
  1467  	if !ctxt.goodOSArchFile(name, allTags) && !ctxt.UseAllFiles {
  1468  		return nil, nil
  1469  	}
  1470  
  1471  	info := &fileInfo{name: ctxt.joinPath(dir, name), fset: fset}
  1472  	if ext == ".syso" {
  1473  		// binary, no reading
  1474  		return info, nil
  1475  	}
  1476  
  1477  	f, err := ctxt.openFile(info.name)
  1478  	if err != nil {
  1479  		return nil, err
  1480  	}
  1481  
  1482  	if strings.HasSuffix(name, ".go") {
  1483  		err = readGoInfo(f, info)
  1484  		if strings.HasSuffix(name, "_test.go") {
  1485  			binaryOnly = nil // ignore //go:binary-only-package comments in _test.go files
  1486  		}
  1487  	} else {
  1488  		binaryOnly = nil // ignore //go:binary-only-package comments in non-Go sources
  1489  		info.header, err = readComments(f)
  1490  	}
  1491  	f.Close()
  1492  	if err != nil {
  1493  		return info, fmt.Errorf("read %s: %v", info.name, err)
  1494  	}
  1495  
  1496  	// Look for go:build comments to accept or reject the file.
  1497  	ok, sawBinaryOnly, err := ctxt.shouldBuild(info.header, allTags)
  1498  	if err != nil {
  1499  		return nil, fmt.Errorf("%s: %v", name, err)
  1500  	}
  1501  	if !ok && !ctxt.UseAllFiles {
  1502  		return nil, nil
  1503  	}
  1504  
  1505  	if binaryOnly != nil && sawBinaryOnly {
  1506  		*binaryOnly = true
  1507  	}
  1508  
  1509  	return info, nil
  1510  }
  1511  
  1512  func cleanDecls(m map[string][]token.Position) ([]string, map[string][]token.Position) {
  1513  	all := make([]string, 0, len(m))
  1514  	for path := range m {
  1515  		all = append(all, path)
  1516  	}
  1517  	slices.Sort(all)
  1518  	return all, m
  1519  }
  1520  
  1521  // Import is shorthand for Default.Import.
  1522  func Import(path, srcDir string, mode ImportMode) (*Package, error) {
  1523  	return Default.Import(path, srcDir, mode)
  1524  }
  1525  
  1526  // ImportDir is shorthand for Default.ImportDir.
  1527  func ImportDir(dir string, mode ImportMode) (*Package, error) {
  1528  	return Default.ImportDir(dir, mode)
  1529  }
  1530  
  1531  var (
  1532  	plusBuild = []byte("+build")
  1533  
  1534  	goBuildComment = []byte("//go:build")
  1535  
  1536  	errMultipleGoBuild = errors.New("multiple //go:build comments")
  1537  )
  1538  
  1539  func isGoBuildComment(line []byte) bool {
  1540  	if !bytes.HasPrefix(line, goBuildComment) {
  1541  		return false
  1542  	}
  1543  	line = bytes.TrimSpace(line)
  1544  	rest := line[len(goBuildComment):]
  1545  	return len(rest) == 0 || len(bytes.TrimSpace(rest)) < len(rest)
  1546  }
  1547  
  1548  // Special comment denoting a binary-only package.
  1549  // See https://golang.org/design/2775-binary-only-packages
  1550  // for more about the design of binary-only packages.
  1551  var binaryOnlyComment = []byte("//go:binary-only-package")
  1552  
  1553  // shouldBuild reports whether it is okay to use this file,
  1554  // The rule is that in the file's leading run of // comments
  1555  // and blank lines, which must be followed by a blank line
  1556  // (to avoid including a Go package clause doc comment),
  1557  // lines beginning with '//go:build' are taken as build directives.
  1558  //
  1559  // The file is accepted only if each such line lists something
  1560  // matching the file. For example:
  1561  //
  1562  //	//go:build windows linux
  1563  //
  1564  // marks the file as applicable only on Windows and Linux.
  1565  //
  1566  // For each build tag it consults, shouldBuild sets allTags[tag] = true.
  1567  //
  1568  // shouldBuild reports whether the file should be built
  1569  // and whether a //go:binary-only-package comment was found.
  1570  func (ctxt *Context) shouldBuild(content []byte, allTags map[string]bool) (shouldBuild, binaryOnly bool, err error) {
  1571  	// Identify leading run of // comments and blank lines,
  1572  	// which must be followed by a blank line.
  1573  	// Also identify any //go:build comments.
  1574  	content, goBuild, sawBinaryOnly, err := parseFileHeader(content)
  1575  	if err != nil {
  1576  		return false, false, err
  1577  	}
  1578  
  1579  	// If //go:build line is present, it controls.
  1580  	// Otherwise fall back to +build processing.
  1581  	switch {
  1582  	case goBuild != nil:
  1583  		x, err := constraint.Parse(string(goBuild))
  1584  		if err != nil {
  1585  			return false, false, fmt.Errorf("parsing //go:build line: %v", err)
  1586  		}
  1587  		shouldBuild = ctxt.eval(x, allTags)
  1588  
  1589  	default:
  1590  		shouldBuild = true
  1591  		p := content
  1592  		for len(p) > 0 {
  1593  			line := p
  1594  			if i := bytes.IndexByte(line, '\n'); i >= 0 {
  1595  				line, p = line[:i], p[i+1:]
  1596  			} else {
  1597  				p = p[len(p):]
  1598  			}
  1599  			line = bytes.TrimSpace(line)
  1600  			if !bytes.HasPrefix(line, slashSlash) || !bytes.Contains(line, plusBuild) {
  1601  				continue
  1602  			}
  1603  			text := string(line)
  1604  			if !constraint.IsPlusBuild(text) {
  1605  				continue
  1606  			}
  1607  			if x, err := constraint.Parse(text); err == nil {
  1608  				if !ctxt.eval(x, allTags) {
  1609  					shouldBuild = false
  1610  				}
  1611  			}
  1612  		}
  1613  	}
  1614  
  1615  	return shouldBuild, sawBinaryOnly, nil
  1616  }
  1617  
  1618  // parseFileHeader should be an internal detail,
  1619  // but widely used packages access it using linkname.
  1620  // Notable members of the hall of shame include:
  1621  //   - github.com/bazelbuild/bazel-gazelle
  1622  //
  1623  // Do not remove or change the type signature.
  1624  // See go.dev/issue/67401.
  1625  //
  1626  //go:linkname parseFileHeader
  1627  func parseFileHeader(content []byte) (trimmed, goBuild []byte, sawBinaryOnly bool, err error) {
  1628  	end := 0
  1629  	p := content
  1630  	ended := false       // found non-blank, non-// line, so stopped accepting //go:build lines
  1631  	inSlashStar := false // in /* */ comment
  1632  
  1633  Lines:
  1634  	for len(p) > 0 {
  1635  		line := p
  1636  		if i := bytes.IndexByte(line, '\n'); i >= 0 {
  1637  			line, p = line[:i], p[i+1:]
  1638  		} else {
  1639  			p = p[len(p):]
  1640  		}
  1641  		line = bytes.TrimSpace(line)
  1642  		if len(line) == 0 && !ended { // Blank line
  1643  			// Remember position of most recent blank line.
  1644  			// When we find the first non-blank, non-// line,
  1645  			// this "end" position marks the latest file position
  1646  			// where a //go:build line can appear.
  1647  			// (It must appear _before_ a blank line before the non-blank, non-// line.
  1648  			// Yes, that's confusing, which is part of why we moved to //go:build lines.)
  1649  			// Note that ended==false here means that inSlashStar==false,
  1650  			// since seeing a /* would have set ended==true.
  1651  			end = len(content) - len(p)
  1652  			continue Lines
  1653  		}
  1654  		if !bytes.HasPrefix(line, slashSlash) { // Not comment line
  1655  			ended = true
  1656  		}
  1657  
  1658  		if !inSlashStar && isGoBuildComment(line) {
  1659  			if goBuild != nil {
  1660  				return nil, nil, false, errMultipleGoBuild
  1661  			}
  1662  			goBuild = line
  1663  		}
  1664  		if !inSlashStar && bytes.Equal(line, binaryOnlyComment) {
  1665  			sawBinaryOnly = true
  1666  		}
  1667  
  1668  	Comments:
  1669  		for len(line) > 0 {
  1670  			if inSlashStar {
  1671  				if i := bytes.Index(line, starSlash); i >= 0 {
  1672  					inSlashStar = false
  1673  					line = bytes.TrimSpace(line[i+len(starSlash):])
  1674  					continue Comments
  1675  				}
  1676  				continue Lines
  1677  			}
  1678  			if bytes.HasPrefix(line, slashSlash) {
  1679  				continue Lines
  1680  			}
  1681  			if bytes.HasPrefix(line, slashStar) {
  1682  				inSlashStar = true
  1683  				line = bytes.TrimSpace(line[len(slashStar):])
  1684  				continue Comments
  1685  			}
  1686  			// Found non-comment text.
  1687  			break Lines
  1688  		}
  1689  	}
  1690  
  1691  	return content[:end], goBuild, sawBinaryOnly, nil
  1692  }
  1693  
  1694  // saveCgo saves the information from the #cgo lines in the import "C" comment.
  1695  // These lines set CFLAGS, CPPFLAGS, CXXFLAGS and LDFLAGS and pkg-config directives
  1696  // that affect the way cgo's C code is built.
  1697  func (ctxt *Context) saveCgo(filename string, di *Package, cg *ast.CommentGroup) error {
  1698  	text := cg.Text()
  1699  	for line := range strings.SplitSeq(text, "\n") {
  1700  		orig := line
  1701  
  1702  		// Line is
  1703  		//	#cgo [GOOS/GOARCH...] LDFLAGS: stuff
  1704  		//
  1705  		line = strings.TrimSpace(line)
  1706  		if len(line) < 5 || line[:4] != "#cgo" || (line[4] != ' ' && line[4] != '\t') {
  1707  			continue
  1708  		}
  1709  
  1710  		// #cgo (nocallback|noescape) <function name>
  1711  		if fields := strings.Fields(line); len(fields) == 3 && (fields[1] == "nocallback" || fields[1] == "noescape") {
  1712  			continue
  1713  		}
  1714  
  1715  		// Split at colon.
  1716  		line, argstr, ok := strings.Cut(strings.TrimSpace(line[4:]), ":")
  1717  		if !ok {
  1718  			return fmt.Errorf("%s: invalid #cgo line: %s", filename, orig)
  1719  		}
  1720  
  1721  		// Parse GOOS/GOARCH stuff.
  1722  		f := strings.Fields(line)
  1723  		if len(f) < 1 {
  1724  			return fmt.Errorf("%s: invalid #cgo line: %s", filename, orig)
  1725  		}
  1726  
  1727  		cond, verb := f[:len(f)-1], f[len(f)-1]
  1728  		if len(cond) > 0 {
  1729  			ok := false
  1730  			for _, c := range cond {
  1731  				if ctxt.matchAuto(c, nil) {
  1732  					ok = true
  1733  					break
  1734  				}
  1735  			}
  1736  			if !ok {
  1737  				continue
  1738  			}
  1739  		}
  1740  
  1741  		args, err := splitQuoted(argstr)
  1742  		if err != nil {
  1743  			return fmt.Errorf("%s: invalid #cgo line: %s", filename, orig)
  1744  		}
  1745  		for i, arg := range args {
  1746  			if arg, ok = expandSrcDir(arg, di.Dir); !ok {
  1747  				return fmt.Errorf("%s: malformed #cgo argument: %s", filename, arg)
  1748  			}
  1749  			args[i] = arg
  1750  		}
  1751  
  1752  		switch verb {
  1753  		case "CFLAGS", "CPPFLAGS", "CXXFLAGS", "FFLAGS", "LDFLAGS":
  1754  			// Change relative paths to absolute.
  1755  			ctxt.makePathsAbsolute(args, di.Dir)
  1756  		}
  1757  
  1758  		switch verb {
  1759  		case "CFLAGS":
  1760  			di.CgoCFLAGS = append(di.CgoCFLAGS, args...)
  1761  		case "CPPFLAGS":
  1762  			di.CgoCPPFLAGS = append(di.CgoCPPFLAGS, args...)
  1763  		case "CXXFLAGS":
  1764  			di.CgoCXXFLAGS = append(di.CgoCXXFLAGS, args...)
  1765  		case "FFLAGS":
  1766  			di.CgoFFLAGS = append(di.CgoFFLAGS, args...)
  1767  		case "LDFLAGS":
  1768  			di.CgoLDFLAGS = append(di.CgoLDFLAGS, args...)
  1769  		case "pkg-config":
  1770  			di.CgoPkgConfig = append(di.CgoPkgConfig, args...)
  1771  		default:
  1772  			return fmt.Errorf("%s: invalid #cgo verb: %s", filename, orig)
  1773  		}
  1774  	}
  1775  	return nil
  1776  }
  1777  
  1778  // expandSrcDir expands any occurrence of ${SRCDIR}, making sure
  1779  // the result is safe for the shell.
  1780  func expandSrcDir(str string, srcdir string) (string, bool) {
  1781  	// "\" delimited paths cause safeCgoName to fail
  1782  	// so convert native paths with a different delimiter
  1783  	// to "/" before starting (eg: on windows).
  1784  	srcdir = filepath.ToSlash(srcdir)
  1785  
  1786  	chunks := strings.Split(str, "${SRCDIR}")
  1787  	if len(chunks) < 2 {
  1788  		return str, safeCgoName(str)
  1789  	}
  1790  	ok := true
  1791  	for _, chunk := range chunks {
  1792  		ok = ok && (chunk == "" || safeCgoName(chunk))
  1793  	}
  1794  	ok = ok && (srcdir == "" || safeCgoName(srcdir))
  1795  	res := strings.Join(chunks, srcdir)
  1796  	return res, ok && res != ""
  1797  }
  1798  
  1799  // makePathsAbsolute looks for compiler options that take paths and
  1800  // makes them absolute. We do this because through the 1.8 release we
  1801  // ran the compiler in the package directory, so any relative -I or -L
  1802  // options would be relative to that directory. In 1.9 we changed to
  1803  // running the compiler in the build directory, to get consistent
  1804  // build results (issue #19964). To keep builds working, we change any
  1805  // relative -I or -L options to be absolute.
  1806  //
  1807  // Using filepath.IsAbs and filepath.Join here means the results will be
  1808  // different on different systems, but that's OK: -I and -L options are
  1809  // inherently system-dependent.
  1810  func (ctxt *Context) makePathsAbsolute(args []string, srcDir string) {
  1811  	nextPath := false
  1812  	for i, arg := range args {
  1813  		if nextPath {
  1814  			if !filepath.IsAbs(arg) {
  1815  				args[i] = filepath.Join(srcDir, arg)
  1816  			}
  1817  			nextPath = false
  1818  		} else if strings.HasPrefix(arg, "-I") || strings.HasPrefix(arg, "-L") {
  1819  			if len(arg) == 2 {
  1820  				nextPath = true
  1821  			} else {
  1822  				if !filepath.IsAbs(arg[2:]) {
  1823  					args[i] = arg[:2] + filepath.Join(srcDir, arg[2:])
  1824  				}
  1825  			}
  1826  		}
  1827  	}
  1828  }
  1829  
  1830  // NOTE: $ is not safe for the shell, but it is allowed here because of linker options like -Wl,$ORIGIN.
  1831  // We never pass these arguments to a shell (just to programs we construct argv for), so this should be okay.
  1832  // See golang.org/issue/6038.
  1833  // The @ is for OS X. See golang.org/issue/13720.
  1834  // The % is for Jenkins. See golang.org/issue/16959.
  1835  // The ! is because module paths may use them. See golang.org/issue/26716.
  1836  // The ~ and ^ are for sr.ht. See golang.org/issue/32260.
  1837  const safeString = "+-.,/0123456789=ABCDEFGHIJKLMNOPQRSTUVWXYZ_abcdefghijklmnopqrstuvwxyz:$@%! ~^"
  1838  
  1839  func safeCgoName(s string) bool {
  1840  	if s == "" {
  1841  		return false
  1842  	}
  1843  	for i := 0; i < len(s); i++ {
  1844  		if c := s[i]; c < utf8.RuneSelf && strings.IndexByte(safeString, c) < 0 {
  1845  			return false
  1846  		}
  1847  	}
  1848  	return true
  1849  }
  1850  
  1851  // splitQuoted splits the string s around each instance of one or more consecutive
  1852  // white space characters while taking into account quotes and escaping, and
  1853  // returns an array of substrings of s or an empty list if s contains only white space.
  1854  // Single quotes and double quotes are recognized to prevent splitting within the
  1855  // quoted region, and are removed from the resulting substrings. If a quote in s
  1856  // isn't closed err will be set and r will have the unclosed argument as the
  1857  // last element. The backslash is used for escaping.
  1858  //
  1859  // For example, the following string:
  1860  //
  1861  //	a b:"c d" 'e''f'  "g\""
  1862  //
  1863  // Would be parsed as:
  1864  //
  1865  //	[]string{"a", "b:c d", "ef", `g"`}
  1866  func splitQuoted(s string) (r []string, err error) {
  1867  	var args []string
  1868  	arg := make([]rune, len(s))
  1869  	escaped := false
  1870  	quoted := false
  1871  	quote := '\x00'
  1872  	i := 0
  1873  	for _, rune := range s {
  1874  		switch {
  1875  		case escaped:
  1876  			escaped = false
  1877  		case rune == '\\':
  1878  			escaped = true
  1879  			continue
  1880  		case quote != '\x00':
  1881  			if rune == quote {
  1882  				quote = '\x00'
  1883  				continue
  1884  			}
  1885  		case rune == '"' || rune == '\'':
  1886  			quoted = true
  1887  			quote = rune
  1888  			continue
  1889  		case unicode.IsSpace(rune):
  1890  			if quoted || i > 0 {
  1891  				quoted = false
  1892  				args = append(args, string(arg[:i]))
  1893  				i = 0
  1894  			}
  1895  			continue
  1896  		}
  1897  		arg[i] = rune
  1898  		i++
  1899  	}
  1900  	if quoted || i > 0 {
  1901  		args = append(args, string(arg[:i]))
  1902  	}
  1903  	if quote != 0 {
  1904  		err = errors.New("unclosed quote")
  1905  	} else if escaped {
  1906  		err = errors.New("unfinished escaping")
  1907  	}
  1908  	return args, err
  1909  }
  1910  
  1911  // matchAuto interprets text as either a +build or //go:build expression (whichever works),
  1912  // reporting whether the expression matches the build context.
  1913  //
  1914  // matchAuto is only used for testing of tag evaluation
  1915  // and in #cgo lines, which accept either syntax.
  1916  func (ctxt *Context) matchAuto(text string, allTags map[string]bool) bool {
  1917  	if strings.ContainsAny(text, "&|()") {
  1918  		text = "//go:build " + text
  1919  	} else {
  1920  		text = "// +build " + text
  1921  	}
  1922  	x, err := constraint.Parse(text)
  1923  	if err != nil {
  1924  		return false
  1925  	}
  1926  	return ctxt.eval(x, allTags)
  1927  }
  1928  
  1929  func (ctxt *Context) eval(x constraint.Expr, allTags map[string]bool) bool {
  1930  	return x.Eval(func(tag string) bool { return ctxt.matchTag(tag, allTags) })
  1931  }
  1932  
  1933  // matchTag reports whether the name is one of:
  1934  //
  1935  //	cgo (if cgo is enabled)
  1936  //	$GOOS
  1937  //	$GOARCH
  1938  //	ctxt.Compiler
  1939  //	linux (if GOOS = android)
  1940  //	solaris (if GOOS = illumos)
  1941  //	darwin (if GOOS = ios)
  1942  //	unix (if this is a Unix GOOS)
  1943  //	boringcrypto (if GOEXPERIMENT=boringcrypto is enabled)
  1944  //	tag (if tag is listed in ctxt.BuildTags, ctxt.ToolTags, or ctxt.ReleaseTags)
  1945  //
  1946  // It records all consulted tags in allTags.
  1947  func (ctxt *Context) matchTag(name string, allTags map[string]bool) bool {
  1948  	if allTags != nil {
  1949  		allTags[name] = true
  1950  	}
  1951  
  1952  	// special tags
  1953  	if ctxt.CgoEnabled && name == "cgo" {
  1954  		return true
  1955  	}
  1956  	if name == ctxt.GOOS || name == ctxt.GOARCH || name == ctxt.Compiler {
  1957  		return true
  1958  	}
  1959  	if ctxt.GOOS == "android" && name == "linux" {
  1960  		return true
  1961  	}
  1962  	if ctxt.GOOS == "illumos" && name == "solaris" {
  1963  		return true
  1964  	}
  1965  	if ctxt.GOOS == "ios" && name == "darwin" {
  1966  		return true
  1967  	}
  1968  	if name == "unix" && syslist.UnixOS[ctxt.GOOS] {
  1969  		return true
  1970  	}
  1971  	if name == "boringcrypto" {
  1972  		name = "goexperiment.boringcrypto" // boringcrypto is an old name for goexperiment.boringcrypto
  1973  	}
  1974  
  1975  	// other tags
  1976  	return slices.Contains(ctxt.BuildTags, name) || slices.Contains(ctxt.ToolTags, name) ||
  1977  		slices.Contains(ctxt.ReleaseTags, name)
  1978  }
  1979  
  1980  // goodOSArchFile returns false if the name contains a $GOOS or $GOARCH
  1981  // suffix which does not match the current system.
  1982  // The recognized name formats are:
  1983  //
  1984  //	name_$(GOOS).*
  1985  //	name_$(GOARCH).*
  1986  //	name_$(GOOS)_$(GOARCH).*
  1987  //	name_$(GOOS)_test.*
  1988  //	name_$(GOARCH)_test.*
  1989  //	name_$(GOOS)_$(GOARCH)_test.*
  1990  //
  1991  // Exceptions:
  1992  // if GOOS=android, then files with GOOS=linux are also matched.
  1993  // if GOOS=illumos, then files with GOOS=solaris are also matched.
  1994  // if GOOS=ios, then files with GOOS=darwin are also matched.
  1995  func (ctxt *Context) goodOSArchFile(name string, allTags map[string]bool) bool {
  1996  	name, _, _ = strings.Cut(name, ".")
  1997  
  1998  	// Before Go 1.4, a file called "linux.go" would be equivalent to having a
  1999  	// build tag "linux" in that file. For Go 1.4 and beyond, we require this
  2000  	// auto-tagging to apply only to files with a non-empty prefix, so
  2001  	// "foo_linux.go" is tagged but "linux.go" is not. This allows new operating
  2002  	// systems, such as android, to arrive without breaking existing code with
  2003  	// innocuous source code in "android.go". The easiest fix: cut everything
  2004  	// in the name before the initial _.
  2005  	i := strings.Index(name, "_")
  2006  	if i < 0 {
  2007  		return true
  2008  	}
  2009  	name = name[i:] // ignore everything before first _
  2010  
  2011  	l := strings.Split(name, "_")
  2012  	if n := len(l); n > 0 && l[n-1] == "test" {
  2013  		l = l[:n-1]
  2014  	}
  2015  	n := len(l)
  2016  	if n >= 2 && syslist.KnownOS[l[n-2]] && syslist.KnownArch[l[n-1]] {
  2017  		if allTags != nil {
  2018  			// In case we short-circuit on l[n-1].
  2019  			allTags[l[n-2]] = true
  2020  		}
  2021  		return ctxt.matchTag(l[n-1], allTags) && ctxt.matchTag(l[n-2], allTags)
  2022  	}
  2023  	if n >= 1 && (syslist.KnownOS[l[n-1]] || syslist.KnownArch[l[n-1]]) {
  2024  		return ctxt.matchTag(l[n-1], allTags)
  2025  	}
  2026  	return true
  2027  }
  2028  
  2029  // ToolDir is the directory containing build tools.
  2030  var ToolDir = getToolDir()
  2031  
  2032  // IsLocalImport reports whether the import path is
  2033  // a local import path, like ".", "..", "./foo", or "../foo".
  2034  func IsLocalImport(path string) bool {
  2035  	return path == "." || path == ".." ||
  2036  		strings.HasPrefix(path, "./") || strings.HasPrefix(path, "../")
  2037  }
  2038  
  2039  // ArchChar returns "?" and an error.
  2040  // In earlier versions of Go, the returned string was used to derive
  2041  // the compiler and linker tool names, the default object file suffix,
  2042  // and the default linker output name. As of Go 1.5, those strings
  2043  // no longer vary by architecture; they are compile, link, .o, and a.out, respectively.
  2044  func ArchChar(goarch string) (string, error) {
  2045  	return "?", errors.New("architecture letter no longer used")
  2046  }
  2047  

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