summaryrefslogtreecommitdiff
path: root/src/cmd/go/pkg.go
blob: b71feb7a67faa7c9f8021e297cc0463f5504a02d (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
// Copyright 2011 The Go Authors.  All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

package main

import (
	"bytes"
	"errors"
	"fmt"
	"go/build"
	"go/scanner"
	"go/token"
	"os"
	pathpkg "path"
	"path/filepath"
	"runtime"
	"sort"
	"strings"
	"time"
	"unicode"
)

// A Package describes a single package found in a directory.
type Package struct {
	// Note: These fields are part of the go command's public API.
	// See list.go.  It is okay to add fields, but not to change or
	// remove existing ones.  Keep in sync with list.go
	Dir           string `json:",omitempty"` // directory containing package sources
	ImportPath    string `json:",omitempty"` // import path of package in dir
	ImportComment string `json:",omitempty"` // path in import comment on package statement
	Name          string `json:",omitempty"` // package name
	Doc           string `json:",omitempty"` // package documentation string
	Target        string `json:",omitempty"` // install path
	Goroot        bool   `json:",omitempty"` // is this package found in the Go root?
	Standard      bool   `json:",omitempty"` // is this package part of the standard Go library?
	Stale         bool   `json:",omitempty"` // would 'go install' do anything for this package?
	Root          string `json:",omitempty"` // Go root or Go path dir containing this package
	ConflictDir   string `json:",omitempty"` // Dir is hidden by this other directory

	// Source files
	GoFiles        []string `json:",omitempty"` // .go source files (excluding CgoFiles, TestGoFiles, XTestGoFiles)
	CgoFiles       []string `json:",omitempty"` // .go sources files that import "C"
	IgnoredGoFiles []string `json:",omitempty"` // .go sources ignored due to build constraints
	CFiles         []string `json:",omitempty"` // .c source files
	CXXFiles       []string `json:",omitempty"` // .cc, .cpp and .cxx source files
	MFiles         []string `json:",omitempty"` // .m source files
	HFiles         []string `json:",omitempty"` // .h, .hh, .hpp and .hxx source files
	SFiles         []string `json:",omitempty"` // .s source files
	SwigFiles      []string `json:",omitempty"` // .swig files
	SwigCXXFiles   []string `json:",omitempty"` // .swigcxx files
	SysoFiles      []string `json:",omitempty"` // .syso system object files added to package

	// Cgo directives
	CgoCFLAGS    []string `json:",omitempty"` // cgo: flags for C compiler
	CgoCPPFLAGS  []string `json:",omitempty"` // cgo: flags for C preprocessor
	CgoCXXFLAGS  []string `json:",omitempty"` // cgo: flags for C++ compiler
	CgoLDFLAGS   []string `json:",omitempty"` // cgo: flags for linker
	CgoPkgConfig []string `json:",omitempty"` // cgo: pkg-config names

	// Dependency information
	Imports []string `json:",omitempty"` // import paths used by this package
	Deps    []string `json:",omitempty"` // all (recursively) imported dependencies

	// Error information
	Incomplete bool            `json:",omitempty"` // was there an error loading this package or dependencies?
	Error      *PackageError   `json:",omitempty"` // error loading this package (not dependencies)
	DepsErrors []*PackageError `json:",omitempty"` // errors loading dependencies

	// Test information
	TestGoFiles  []string `json:",omitempty"` // _test.go files in package
	TestImports  []string `json:",omitempty"` // imports from TestGoFiles
	XTestGoFiles []string `json:",omitempty"` // _test.go files outside package
	XTestImports []string `json:",omitempty"` // imports from XTestGoFiles

	// Unexported fields are not part of the public API.
	build        *build.Package
	pkgdir       string // overrides build.PkgDir
	imports      []*Package
	deps         []*Package
	gofiles      []string // GoFiles+CgoFiles+TestGoFiles+XTestGoFiles files, absolute paths
	sfiles       []string
	allgofiles   []string             // gofiles + IgnoredGoFiles, absolute paths
	target       string               // installed file for this package (may be executable)
	fake         bool                 // synthesized package
	forceBuild   bool                 // this package must be rebuilt
	forceLibrary bool                 // this package is a library (even if named "main")
	cmdline      bool                 // defined by files listed on command line
	local        bool                 // imported via local path (./ or ../)
	localPrefix  string               // interpret ./ and ../ imports relative to this prefix
	exeName      string               // desired name for temporary executable
	coverMode    string               // preprocess Go source files with the coverage tool in this mode
	coverVars    map[string]*CoverVar // variables created by coverage analysis
	omitDWARF    bool                 // tell linker not to write DWARF information
}

// CoverVar holds the name of the generated coverage variables targeting the named file.
type CoverVar struct {
	File string // local file name
	Var  string // name of count struct
}

func (p *Package) copyBuild(pp *build.Package) {
	p.build = pp

	p.Dir = pp.Dir
	p.ImportPath = pp.ImportPath
	p.ImportComment = pp.ImportComment
	p.Name = pp.Name
	p.Doc = pp.Doc
	p.Root = pp.Root
	p.ConflictDir = pp.ConflictDir
	// TODO? Target
	p.Goroot = pp.Goroot
	p.Standard = p.Goroot && p.ImportPath != "" && !strings.Contains(p.ImportPath, ".")
	p.GoFiles = pp.GoFiles
	p.CgoFiles = pp.CgoFiles
	p.IgnoredGoFiles = pp.IgnoredGoFiles
	p.CFiles = pp.CFiles
	p.CXXFiles = pp.CXXFiles
	p.MFiles = pp.MFiles
	p.HFiles = pp.HFiles
	p.SFiles = pp.SFiles
	p.SwigFiles = pp.SwigFiles
	p.SwigCXXFiles = pp.SwigCXXFiles
	p.SysoFiles = pp.SysoFiles
	p.CgoCFLAGS = pp.CgoCFLAGS
	p.CgoCPPFLAGS = pp.CgoCPPFLAGS
	p.CgoCXXFLAGS = pp.CgoCXXFLAGS
	p.CgoLDFLAGS = pp.CgoLDFLAGS
	p.CgoPkgConfig = pp.CgoPkgConfig
	p.Imports = pp.Imports
	p.TestGoFiles = pp.TestGoFiles
	p.TestImports = pp.TestImports
	p.XTestGoFiles = pp.XTestGoFiles
	p.XTestImports = pp.XTestImports
}

// A PackageError describes an error loading information about a package.
type PackageError struct {
	ImportStack   []string // shortest path from package named on command line to this one
	Pos           string   // position of error
	Err           string   // the error itself
	isImportCycle bool     // the error is an import cycle
	hard          bool     // whether the error is soft or hard; soft errors are ignored in some places
}

func (p *PackageError) Error() string {
	// Import cycles deserve special treatment.
	if p.isImportCycle {
		return fmt.Sprintf("%s\npackage %s\n", p.Err, strings.Join(p.ImportStack, "\n\timports "))
	}
	if p.Pos != "" {
		// Omit import stack.  The full path to the file where the error
		// is the most important thing.
		return p.Pos + ": " + p.Err
	}
	if len(p.ImportStack) == 0 {
		return p.Err
	}
	return "package " + strings.Join(p.ImportStack, "\n\timports ") + ": " + p.Err
}

// An importStack is a stack of import paths.
type importStack []string

func (s *importStack) push(p string) {
	*s = append(*s, p)
}

func (s *importStack) pop() {
	*s = (*s)[0 : len(*s)-1]
}

func (s *importStack) copy() []string {
	return append([]string{}, *s...)
}

// shorterThan returns true if sp is shorter than t.
// We use this to record the shortest import sequence
// that leads to a particular package.
func (sp *importStack) shorterThan(t []string) bool {
	s := *sp
	if len(s) != len(t) {
		return len(s) < len(t)
	}
	// If they are the same length, settle ties using string ordering.
	for i := range s {
		if s[i] != t[i] {
			return s[i] < t[i]
		}
	}
	return false // they are equal
}

// packageCache is a lookup cache for loadPackage,
// so that if we look up a package multiple times
// we return the same pointer each time.
var packageCache = map[string]*Package{}

// reloadPackage is like loadPackage but makes sure
// not to use the package cache.
func reloadPackage(arg string, stk *importStack) *Package {
	p := packageCache[arg]
	if p != nil {
		delete(packageCache, p.Dir)
		delete(packageCache, p.ImportPath)
	}
	return loadPackage(arg, stk)
}

// dirToImportPath returns the pseudo-import path we use for a package
// outside the Go path.  It begins with _/ and then contains the full path
// to the directory.  If the package lives in c:\home\gopher\my\pkg then
// the pseudo-import path is _/c_/home/gopher/my/pkg.
// Using a pseudo-import path like this makes the ./ imports no longer
// a special case, so that all the code to deal with ordinary imports works
// automatically.
func dirToImportPath(dir string) string {
	return pathpkg.Join("_", strings.Map(makeImportValid, filepath.ToSlash(dir)))
}

func makeImportValid(r rune) rune {
	// Should match Go spec, compilers, and ../../go/parser/parser.go:/isValidImport.
	const illegalChars = `!"#$%&'()*,:;<=>?[\]^{|}` + "`\uFFFD"
	if !unicode.IsGraphic(r) || unicode.IsSpace(r) || strings.ContainsRune(illegalChars, r) {
		return '_'
	}
	return r
}

// loadImport scans the directory named by path, which must be an import path,
// but possibly a local import path (an absolute file system path or one beginning
// with ./ or ../).  A local relative path is interpreted relative to srcDir.
// It returns a *Package describing the package found in that directory.
func loadImport(path string, srcDir string, stk *importStack, importPos []token.Position) *Package {
	stk.push(path)
	defer stk.pop()

	// Determine canonical identifier for this package.
	// For a local import the identifier is the pseudo-import path
	// we create from the full directory to the package.
	// Otherwise it is the usual import path.
	importPath := path
	isLocal := build.IsLocalImport(path)
	if isLocal {
		importPath = dirToImportPath(filepath.Join(srcDir, path))
	}
	if p := packageCache[importPath]; p != nil {
		if perr := disallowInternal(srcDir, p, stk); perr != p {
			return perr
		}
		return reusePackage(p, stk)
	}

	p := new(Package)
	p.local = isLocal
	p.ImportPath = importPath
	packageCache[importPath] = p

	// Load package.
	// Import always returns bp != nil, even if an error occurs,
	// in order to return partial information.
	//
	// TODO: After Go 1, decide when to pass build.AllowBinary here.
	// See issue 3268 for mistakes to avoid.
	bp, err := buildContext.Import(path, srcDir, build.ImportComment)
	bp.ImportPath = importPath
	if gobin != "" {
		bp.BinDir = gobin
	}
	if err == nil && !isLocal && bp.ImportComment != "" && bp.ImportComment != path {
		err = fmt.Errorf("code in directory %s expects import %q", bp.Dir, bp.ImportComment)
	}
	p.load(stk, bp, err)
	if p.Error != nil && len(importPos) > 0 {
		pos := importPos[0]
		pos.Filename = shortPath(pos.Filename)
		p.Error.Pos = pos.String()
	}

	if perr := disallowInternal(srcDir, p, stk); perr != p {
		return perr
	}

	return p
}

// reusePackage reuses package p to satisfy the import at the top
// of the import stack stk.  If this use causes an import loop,
// reusePackage updates p's error information to record the loop.
func reusePackage(p *Package, stk *importStack) *Package {
	// We use p.imports==nil to detect a package that
	// is in the midst of its own loadPackage call
	// (all the recursion below happens before p.imports gets set).
	if p.imports == nil {
		if p.Error == nil {
			p.Error = &PackageError{
				ImportStack:   stk.copy(),
				Err:           "import cycle not allowed",
				isImportCycle: true,
			}
		}
		p.Incomplete = true
	}
	// Don't rewrite the import stack in the error if we have an import cycle.
	// If we do, we'll lose the path that describes the cycle.
	if p.Error != nil && !p.Error.isImportCycle && stk.shorterThan(p.Error.ImportStack) {
		p.Error.ImportStack = stk.copy()
	}
	return p
}

// disallowInternal checks that srcDir is allowed to import p.
// If the import is allowed, disallowInternal returns the original package p.
// If not, it returns a new package containing just an appropriate error.
func disallowInternal(srcDir string, p *Package, stk *importStack) *Package {
	// golang.org/s/go14internal:
	// An import of a path containing the element “internal”
	// is disallowed if the importing code is outside the tree
	// rooted at the parent of the “internal” directory.
	//
	// ... For Go 1.4, we will implement the rule first for $GOROOT, but not $GOPATH.

	// Only applies to $GOROOT.
	if !p.Standard {
		return p
	}

	// The stack includes p.ImportPath.
	// If that's the only thing on the stack, we started
	// with a name given on the command line, not an
	// import. Anything listed on the command line is fine.
	if len(*stk) == 1 {
		return p
	}

	// Check for "internal" element: four cases depending on begin of string and/or end of string.
	i, ok := findInternal(p.ImportPath)
	if !ok {
		return p
	}

	// Internal is present.
	// Map import path back to directory corresponding to parent of internal.
	if i > 0 {
		i-- // rewind over slash in ".../internal"
	}
	parent := p.Dir[:i+len(p.Dir)-len(p.ImportPath)]
	if hasPathPrefix(filepath.ToSlash(srcDir), filepath.ToSlash(parent)) {
		return p
	}

	// Internal is present, and srcDir is outside parent's tree. Not allowed.
	perr := *p
	perr.Error = &PackageError{
		ImportStack: stk.copy(),
		Err:         "use of internal package not allowed",
	}
	perr.Incomplete = true
	return &perr
}

// findInternal looks for the final "internal" path element in the given import path.
// If there isn't one, findInternal returns ok=false.
// Otherwise, findInternal returns ok=true and the index of the "internal".
func findInternal(path string) (index int, ok bool) {
	// Four cases, depending on internal at start/end of string or not.
	// The order matters: we must return the index of the final element,
	// because the final one produces the most restrictive requirement
	// on the importer.
	switch {
	case strings.HasSuffix(path, "/internal"):
		return len(path) - len("internal"), true
	case strings.Contains(path, "/internal/"):
		return strings.LastIndex(path, "/internal/") + 1, true
	case path == "internal", strings.HasPrefix(path, "internal/"):
		return 0, true
	}
	return 0, false
}

type targetDir int

const (
	toRoot    targetDir = iota // to bin dir inside package root (default)
	toTool                     // GOROOT/pkg/tool
	toBin                      // GOROOT/bin
	stalePath                  // the old import path; fail to build
)

// goTools is a map of Go program import path to install target directory.
var goTools = map[string]targetDir{
	"cmd/addr2line":                        toTool,
	"cmd/api":                              toTool,
	"cmd/cgo":                              toTool,
	"cmd/fix":                              toTool,
	"cmd/link":                             toTool,
	"cmd/nm":                               toTool,
	"cmd/objdump":                          toTool,
	"cmd/pack":                             toTool,
	"cmd/pprof":                            toTool,
	"cmd/yacc":                             toTool,
	"golang.org/x/tools/cmd/cover":         toTool,
	"golang.org/x/tools/cmd/godoc":         toBin,
	"golang.org/x/tools/cmd/vet":           toTool,
	"code.google.com/p/go.tools/cmd/cover": stalePath,
	"code.google.com/p/go.tools/cmd/godoc": stalePath,
	"code.google.com/p/go.tools/cmd/vet":   stalePath,
}

// expandScanner expands a scanner.List error into all the errors in the list.
// The default Error method only shows the first error.
func expandScanner(err error) error {
	// Look for parser errors.
	if err, ok := err.(scanner.ErrorList); ok {
		// Prepare error with \n before each message.
		// When printed in something like context: %v
		// this will put the leading file positions each on
		// its own line.  It will also show all the errors
		// instead of just the first, as err.Error does.
		var buf bytes.Buffer
		for _, e := range err {
			e.Pos.Filename = shortPath(e.Pos.Filename)
			buf.WriteString("\n")
			buf.WriteString(e.Error())
		}
		return errors.New(buf.String())
	}
	return err
}

var raceExclude = map[string]bool{
	"runtime/race": true,
	"runtime/cgo":  true,
	"cmd/cgo":      true,
	"syscall":      true,
	"errors":       true,
}

var cgoExclude = map[string]bool{
	"runtime/cgo": true,
}

var cgoSyscallExclude = map[string]bool{
	"runtime/cgo":  true,
	"runtime/race": true,
}

// load populates p using information from bp, err, which should
// be the result of calling build.Context.Import.
func (p *Package) load(stk *importStack, bp *build.Package, err error) *Package {
	p.copyBuild(bp)

	// The localPrefix is the path we interpret ./ imports relative to.
	// Synthesized main packages sometimes override this.
	p.localPrefix = dirToImportPath(p.Dir)

	if err != nil {
		p.Incomplete = true
		err = expandScanner(err)
		p.Error = &PackageError{
			ImportStack: stk.copy(),
			Err:         err.Error(),
		}
		return p
	}

	if p.Name == "main" {
		// Report an error when the old code.google.com/p/go.tools paths are used.
		if goTools[p.ImportPath] == stalePath {
			newPath := strings.Replace(p.ImportPath, "code.google.com/p/go.", "golang.org/x/", 1)
			e := fmt.Sprintf("the %v command has moved; use %v instead.", p.ImportPath, newPath)
			p.Error = &PackageError{Err: e}
			return p
		}
		_, elem := filepath.Split(p.Dir)
		full := buildContext.GOOS + "_" + buildContext.GOARCH + "/" + elem
		if buildContext.GOOS != toolGOOS || buildContext.GOARCH != toolGOARCH {
			// Install cross-compiled binaries to subdirectories of bin.
			elem = full
		}
		if p.build.BinDir != gobin && goTools[p.ImportPath] == toBin {
			// Override BinDir.
			// This is from a subrepo but installs to $GOROOT/bin
			// by default anyway (like godoc).
			p.target = filepath.Join(gorootBin, elem)
		} else if p.build.BinDir != "" {
			// Install to GOBIN or bin of GOPATH entry.
			p.target = filepath.Join(p.build.BinDir, elem)
		}
		if goTools[p.ImportPath] == toTool {
			// This is for 'go tool'.
			// Override all the usual logic and force it into the tool directory.
			p.target = filepath.Join(gorootPkg, "tool", full)
		}
		if p.target != "" && buildContext.GOOS == "windows" {
			p.target += ".exe"
		}
	} else if p.local {
		// Local import turned into absolute path.
		// No permanent install target.
		p.target = ""
	} else {
		p.target = p.build.PkgObj
	}

	importPaths := p.Imports
	// Packages that use cgo import runtime/cgo implicitly.
	// Packages that use cgo also import syscall implicitly,
	// to wrap errno.
	// Exclude certain packages to avoid circular dependencies.
	if len(p.CgoFiles) > 0 && (!p.Standard || !cgoExclude[p.ImportPath]) {
		importPaths = append(importPaths, "runtime/cgo")
	}
	if len(p.CgoFiles) > 0 && (!p.Standard || !cgoSyscallExclude[p.ImportPath]) {
		importPaths = append(importPaths, "syscall")
	}
	// Everything depends on runtime, except runtime and unsafe.
	if !p.Standard || (p.ImportPath != "runtime" && p.ImportPath != "unsafe") {
		importPaths = append(importPaths, "runtime")
		// When race detection enabled everything depends on runtime/race.
		// Exclude certain packages to avoid circular dependencies.
		if buildRace && (!p.Standard || !raceExclude[p.ImportPath]) {
			importPaths = append(importPaths, "runtime/race")
		}
	}

	// Build list of full paths to all Go files in the package,
	// for use by commands like go fmt.
	p.gofiles = stringList(p.GoFiles, p.CgoFiles, p.TestGoFiles, p.XTestGoFiles)
	for i := range p.gofiles {
		p.gofiles[i] = filepath.Join(p.Dir, p.gofiles[i])
	}
	sort.Strings(p.gofiles)

	p.sfiles = stringList(p.SFiles)
	for i := range p.sfiles {
		p.sfiles[i] = filepath.Join(p.Dir, p.sfiles[i])
	}
	sort.Strings(p.sfiles)

	p.allgofiles = stringList(p.IgnoredGoFiles)
	for i := range p.allgofiles {
		p.allgofiles[i] = filepath.Join(p.Dir, p.allgofiles[i])
	}
	p.allgofiles = append(p.allgofiles, p.gofiles...)
	sort.Strings(p.allgofiles)

	// Check for case-insensitive collision of input files.
	// To avoid problems on case-insensitive files, we reject any package
	// where two different input files have equal names under a case-insensitive
	// comparison.
	f1, f2 := foldDup(stringList(
		p.GoFiles,
		p.CgoFiles,
		p.IgnoredGoFiles,
		p.CFiles,
		p.CXXFiles,
		p.MFiles,
		p.HFiles,
		p.SFiles,
		p.SysoFiles,
		p.SwigFiles,
		p.SwigCXXFiles,
		p.TestGoFiles,
		p.XTestGoFiles,
	))
	if f1 != "" {
		p.Error = &PackageError{
			ImportStack: stk.copy(),
			Err:         fmt.Sprintf("case-insensitive file name collision: %q and %q", f1, f2),
		}
		return p
	}

	// Build list of imported packages and full dependency list.
	imports := make([]*Package, 0, len(p.Imports))
	deps := make(map[string]*Package)
	for i, path := range importPaths {
		if path == "C" {
			continue
		}
		p1 := loadImport(path, p.Dir, stk, p.build.ImportPos[path])
		if p1.local {
			if !p.local && p.Error == nil {
				p.Error = &PackageError{
					ImportStack: stk.copy(),
					Err:         fmt.Sprintf("local import %q in non-local package", path),
				}
				pos := p.build.ImportPos[path]
				if len(pos) > 0 {
					p.Error.Pos = pos[0].String()
				}
			}
			path = p1.ImportPath
			importPaths[i] = path
		}
		deps[path] = p1
		imports = append(imports, p1)
		for _, dep := range p1.deps {
			deps[dep.ImportPath] = dep
		}
		if p1.Incomplete {
			p.Incomplete = true
		}
	}
	p.imports = imports

	p.Deps = make([]string, 0, len(deps))
	for dep := range deps {
		p.Deps = append(p.Deps, dep)
	}
	sort.Strings(p.Deps)
	for _, dep := range p.Deps {
		p1 := deps[dep]
		if p1 == nil {
			panic("impossible: missing entry in package cache for " + dep + " imported by " + p.ImportPath)
		}
		p.deps = append(p.deps, p1)
		if p1.Error != nil {
			p.DepsErrors = append(p.DepsErrors, p1.Error)
		}
	}

	// unsafe is a fake package.
	if p.Standard && (p.ImportPath == "unsafe" || buildContext.Compiler == "gccgo") {
		p.target = ""
	}
	p.Target = p.target

	// Check for C code compiled with Plan 9 C compiler.
	// No longer allowed except in runtime and runtime/cgo, for now.
	if len(p.CFiles) > 0 && !p.usesCgo() && (!p.Standard || p.ImportPath != "runtime") {
		p.Error = &PackageError{
			ImportStack: stk.copy(),
			Err:         fmt.Sprintf("C source files not allowed when not using cgo: %s", strings.Join(p.CFiles, " ")),
		}
		return p
	}

	// In the absence of errors lower in the dependency tree,
	// check for case-insensitive collisions of import paths.
	if len(p.DepsErrors) == 0 {
		dep1, dep2 := foldDup(p.Deps)
		if dep1 != "" {
			p.Error = &PackageError{
				ImportStack: stk.copy(),
				Err:         fmt.Sprintf("case-insensitive import collision: %q and %q", dep1, dep2),
			}
			return p
		}
	}

	return p
}

// usesSwig reports whether the package needs to run SWIG.
func (p *Package) usesSwig() bool {
	return len(p.SwigFiles) > 0 || len(p.SwigCXXFiles) > 0
}

// usesCgo reports whether the package needs to run cgo
func (p *Package) usesCgo() bool {
	return len(p.CgoFiles) > 0
}

// packageList returns the list of packages in the dag rooted at roots
// as visited in a depth-first post-order traversal.
func packageList(roots []*Package) []*Package {
	seen := map[*Package]bool{}
	all := []*Package{}
	var walk func(*Package)
	walk = func(p *Package) {
		if seen[p] {
			return
		}
		seen[p] = true
		for _, p1 := range p.imports {
			walk(p1)
		}
		all = append(all, p)
	}
	for _, root := range roots {
		walk(root)
	}
	return all
}

// computeStale computes the Stale flag in the package dag that starts
// at the named pkgs (command-line arguments).
func computeStale(pkgs ...*Package) {
	topRoot := map[string]bool{}
	for _, p := range pkgs {
		topRoot[p.Root] = true
	}

	for _, p := range packageList(pkgs) {
		p.Stale = isStale(p, topRoot)
	}
}

// The runtime version string takes one of two forms:
// "go1.X[.Y]" for Go releases, and "devel +hash" at tip.
// Determine whether we are in a released copy by
// inspecting the version.
var isGoRelease = strings.HasPrefix(runtime.Version(), "go1")

// isStale reports whether package p needs to be rebuilt.
func isStale(p *Package, topRoot map[string]bool) bool {
	if p.Standard && (p.ImportPath == "unsafe" || buildContext.Compiler == "gccgo") {
		// fake, builtin package
		return false
	}
	if p.Error != nil {
		return true
	}

	// A package without Go sources means we only found
	// the installed .a file.  Since we don't know how to rebuild
	// it, it can't be stale, even if -a is set.  This enables binary-only
	// distributions of Go packages, although such binaries are
	// only useful with the specific version of the toolchain that
	// created them.
	if len(p.gofiles) == 0 && !p.usesSwig() {
		return false
	}

	// If we are running a release copy of Go, do not rebuild the standard packages.
	// They may not be writable anyway, but they are certainly not changing.
	// This makes 'go build -a' skip the standard packages when using an official release.
	// See issue 4106 and issue 8290.
	pkgBuildA := buildA
	if p.Standard && isGoRelease {
		pkgBuildA = false
	}

	if pkgBuildA || p.target == "" || p.Stale {
		return true
	}

	// Package is stale if completely unbuilt.
	var built time.Time
	if fi, err := os.Stat(p.target); err == nil {
		built = fi.ModTime()
	}
	if built.IsZero() {
		return true
	}

	olderThan := func(file string) bool {
		fi, err := os.Stat(file)
		return err != nil || fi.ModTime().After(built)
	}

	// Package is stale if a dependency is, or if a dependency is newer.
	for _, p1 := range p.deps {
		if p1.Stale || p1.target != "" && olderThan(p1.target) {
			return true
		}
	}

	// As a courtesy to developers installing new versions of the compiler
	// frequently, define that packages are stale if they are
	// older than the compiler, and commands if they are older than
	// the linker.  This heuristic will not work if the binaries are
	// back-dated, as some binary distributions may do, but it does handle
	// a very common case.
	// See issue 3036.
	// Assume code in $GOROOT is up to date, since it may not be writeable.
	// See issue 4106.
	if p.Root != goroot {
		if olderThan(buildToolchain.compiler()) {
			return true
		}
		if p.build.IsCommand() && olderThan(buildToolchain.linker()) {
			return true
		}
	}

	// Have installed copy, probably built using current compilers,
	// and built after its imported packages.  The only reason now
	// that we'd have to rebuild it is if the sources were newer than
	// the package.   If a package p is not in the same tree as any
	// package named on the command-line, assume it is up-to-date
	// no matter what the modification times on the source files indicate.
	// This avoids rebuilding $GOROOT packages when people are
	// working outside the Go root, and it effectively makes each tree
	// listed in $GOPATH a separate compilation world.
	// See issue 3149.
	if p.Root != "" && !topRoot[p.Root] {
		return false
	}

	srcs := stringList(p.GoFiles, p.CFiles, p.CXXFiles, p.MFiles, p.HFiles, p.SFiles, p.CgoFiles, p.SysoFiles, p.SwigFiles, p.SwigCXXFiles)
	for _, src := range srcs {
		if olderThan(filepath.Join(p.Dir, src)) {
			return true
		}
	}

	return false
}

var cwd, _ = os.Getwd()

var cmdCache = map[string]*Package{}

// loadPackage is like loadImport but is used for command-line arguments,
// not for paths found in import statements.  In addition to ordinary import paths,
// loadPackage accepts pseudo-paths beginning with cmd/ to denote commands
// in the Go command directory, as well as paths to those directories.
func loadPackage(arg string, stk *importStack) *Package {
	if build.IsLocalImport(arg) {
		dir := arg
		if !filepath.IsAbs(dir) {
			if abs, err := filepath.Abs(dir); err == nil {
				// interpret relative to current directory
				dir = abs
			}
		}
		if sub, ok := hasSubdir(gorootSrc, dir); ok && strings.HasPrefix(sub, "cmd/") && !strings.Contains(sub[4:], "/") {
			arg = sub
		}
	}
	if strings.HasPrefix(arg, "cmd/") && !strings.Contains(arg[4:], "/") {
		if p := cmdCache[arg]; p != nil {
			return p
		}
		stk.push(arg)
		defer stk.pop()

		bp, err := buildContext.ImportDir(filepath.Join(gorootSrc, arg), 0)
		bp.ImportPath = arg
		bp.Goroot = true
		bp.BinDir = gorootBin
		if gobin != "" {
			bp.BinDir = gobin
		}
		bp.Root = goroot
		bp.SrcRoot = gorootSrc
		p := new(Package)
		cmdCache[arg] = p
		p.load(stk, bp, err)
		if p.Error == nil && p.Name != "main" {
			p.Error = &PackageError{
				ImportStack: stk.copy(),
				Err:         fmt.Sprintf("expected package main but found package %s in %s", p.Name, p.Dir),
			}
		}
		return p
	}

	// Wasn't a command; must be a package.
	// If it is a local import path but names a standard package,
	// we treat it as if the user specified the standard package.
	// This lets you run go test ./ioutil in package io and be
	// referring to io/ioutil rather than a hypothetical import of
	// "./ioutil".
	if build.IsLocalImport(arg) {
		bp, _ := buildContext.ImportDir(filepath.Join(cwd, arg), build.FindOnly)
		if bp.ImportPath != "" && bp.ImportPath != "." {
			arg = bp.ImportPath
		}
	}

	return loadImport(arg, cwd, stk, nil)
}

// packages returns the packages named by the
// command line arguments 'args'.  If a named package
// cannot be loaded at all (for example, if the directory does not exist),
// then packages prints an error and does not include that
// package in the results.  However, if errors occur trying
// to load dependencies of a named package, the named
// package is still returned, with p.Incomplete = true
// and details in p.DepsErrors.
func packages(args []string) []*Package {
	var pkgs []*Package
	for _, pkg := range packagesAndErrors(args) {
		if pkg.Error != nil {
			errorf("can't load package: %s", pkg.Error)
			continue
		}
		pkgs = append(pkgs, pkg)
	}
	return pkgs
}

// packagesAndErrors is like 'packages' but returns a
// *Package for every argument, even the ones that
// cannot be loaded at all.
// The packages that fail to load will have p.Error != nil.
func packagesAndErrors(args []string) []*Package {
	if len(args) > 0 && strings.HasSuffix(args[0], ".go") {
		return []*Package{goFilesPackage(args)}
	}

	args = importPaths(args)
	var pkgs []*Package
	var stk importStack
	var set = make(map[string]bool)

	for _, arg := range args {
		if !set[arg] {
			pkgs = append(pkgs, loadPackage(arg, &stk))
			set[arg] = true
		}
	}
	computeStale(pkgs...)

	return pkgs
}

// packagesForBuild is like 'packages' but fails if any of
// the packages or their dependencies have errors
// (cannot be built).
func packagesForBuild(args []string) []*Package {
	pkgs := packagesAndErrors(args)
	printed := map[*PackageError]bool{}
	for _, pkg := range pkgs {
		if pkg.Error != nil {
			errorf("can't load package: %s", pkg.Error)
		}
		for _, err := range pkg.DepsErrors {
			// Since these are errors in dependencies,
			// the same error might show up multiple times,
			// once in each package that depends on it.
			// Only print each once.
			if !printed[err] {
				printed[err] = true
				errorf("%s", err)
			}
		}
	}
	exitIfErrors()
	return pkgs
}

// hasSubdir reports whether dir is a subdirectory of
// (possibly multiple levels below) root.
// If so, it sets rel to the path fragment that must be
// appended to root to reach dir.
func hasSubdir(root, dir string) (rel string, ok bool) {
	if p, err := filepath.EvalSymlinks(root); err == nil {
		root = p
	}
	if p, err := filepath.EvalSymlinks(dir); err == nil {
		dir = p
	}
	const sep = string(filepath.Separator)
	root = filepath.Clean(root)
	if !strings.HasSuffix(root, sep) {
		root += sep
	}
	dir = filepath.Clean(dir)
	if !strings.HasPrefix(dir, root) {
		return "", false
	}
	return filepath.ToSlash(dir[len(root):]), true
}