File: gc.go

package info (click to toggle)
golang-1.11 1.11.6-1
  • links: PTS, VCS
  • area: main
  • in suites: buster, experimental, sid
  • size: 107,332 kB
  • sloc: asm: 88,993; ansic: 8,174; perl: 2,007; sh: 1,804; xml: 623; python: 346; makefile: 123; cpp: 22; f90: 8; awk: 7
file content (508 lines) | stat: -rw-r--r-- 16,643 bytes parent folder | download | duplicates (6)
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
// 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 work

import (
	"bufio"
	"bytes"
	"fmt"
	"io"
	"io/ioutil"
	"log"
	"os"
	"path/filepath"
	"runtime"
	"strings"

	"cmd/go/internal/base"
	"cmd/go/internal/cfg"
	"cmd/go/internal/load"
	"cmd/go/internal/str"
	"cmd/internal/objabi"
	"crypto/sha1"
)

// The Go toolchain.

type gcToolchain struct{}

func (gcToolchain) compiler() string {
	return base.Tool("compile")
}

func (gcToolchain) linker() string {
	return base.Tool("link")
}

func (gcToolchain) gc(b *Builder, a *Action, archive string, importcfg []byte, asmhdr bool, gofiles []string) (ofile string, output []byte, err error) {
	p := a.Package
	objdir := a.Objdir
	if archive != "" {
		ofile = archive
	} else {
		out := "_go_.o"
		ofile = objdir + out
	}

	pkgpath := p.ImportPath
	if cfg.BuildBuildmode == "plugin" {
		pkgpath = pluginPath(a)
	} else if p.Name == "main" && !p.Internal.ForceLibrary {
		pkgpath = "main"
	}
	gcargs := []string{"-p", pkgpath}
	if p.Standard {
		gcargs = append(gcargs, "-std")
	}
	compilingRuntime := p.Standard && (p.ImportPath == "runtime" || strings.HasPrefix(p.ImportPath, "runtime/internal"))
	// The runtime package imports a couple of general internal packages.
	if p.Standard && (p.ImportPath == "internal/cpu" || p.ImportPath == "internal/bytealg") {
		compilingRuntime = true
	}
	if compilingRuntime {
		// runtime compiles with a special gc flag to check for
		// memory allocations that are invalid in the runtime package,
		// and to implement some special compiler pragmas.
		gcargs = append(gcargs, "-+")
	}

	// If we're giving the compiler the entire package (no C etc files), tell it that,
	// so that it can give good error messages about forward declarations.
	// Exceptions: a few standard packages have forward declarations for
	// pieces supplied behind-the-scenes by package runtime.
	extFiles := len(p.CgoFiles) + len(p.CFiles) + len(p.CXXFiles) + len(p.MFiles) + len(p.FFiles) + len(p.SFiles) + len(p.SysoFiles) + len(p.SwigFiles) + len(p.SwigCXXFiles)
	if p.Standard {
		switch p.ImportPath {
		case "bytes", "internal/poll", "net", "os", "runtime/pprof", "runtime/trace", "sync", "syscall", "time":
			extFiles++
		}
	}
	if extFiles == 0 {
		gcargs = append(gcargs, "-complete")
	}
	if cfg.BuildContext.InstallSuffix != "" {
		gcargs = append(gcargs, "-installsuffix", cfg.BuildContext.InstallSuffix)
	}
	if a.buildID != "" {
		gcargs = append(gcargs, "-buildid", a.buildID)
	}
	platform := cfg.Goos + "/" + cfg.Goarch
	if p.Internal.OmitDebug || platform == "nacl/amd64p32" || cfg.Goos == "plan9" || cfg.Goarch == "wasm" {
		gcargs = append(gcargs, "-dwarf=false")
	}
	if strings.HasPrefix(runtimeVersion, "go1") && !strings.Contains(os.Args[0], "go_bootstrap") {
		gcargs = append(gcargs, "-goversion", runtimeVersion)
	}

	gcflags := str.StringList(forcedGcflags, p.Internal.Gcflags)
	if compilingRuntime {
		// Remove -N, if present.
		// It is not possible to build the runtime with no optimizations,
		// because the compiler cannot eliminate enough write barriers.
		for i := 0; i < len(gcflags); i++ {
			if gcflags[i] == "-N" {
				copy(gcflags[i:], gcflags[i+1:])
				gcflags = gcflags[:len(gcflags)-1]
				i--
			}
		}
	}

	args := []interface{}{cfg.BuildToolexec, base.Tool("compile"), "-o", ofile, "-trimpath", trimDir(a.Objdir), gcflags, gcargs, "-D", p.Internal.LocalPrefix}
	if importcfg != nil {
		if err := b.writeFile(objdir+"importcfg", importcfg); err != nil {
			return "", nil, err
		}
		args = append(args, "-importcfg", objdir+"importcfg")
	}
	if ofile == archive {
		args = append(args, "-pack")
	}
	if asmhdr {
		args = append(args, "-asmhdr", objdir+"go_asm.h")
	}

	// Add -c=N to use concurrent backend compilation, if possible.
	if c := gcBackendConcurrency(gcflags); c > 1 {
		args = append(args, fmt.Sprintf("-c=%d", c))
	}

	for _, f := range gofiles {
		args = append(args, mkAbs(p.Dir, f))
	}

	output, err = b.runOut(p.Dir, nil, args...)
	return ofile, output, err
}

// gcBackendConcurrency returns the backend compiler concurrency level for a package compilation.
func gcBackendConcurrency(gcflags []string) int {
	// First, check whether we can use -c at all for this compilation.
	canDashC := concurrentGCBackendCompilationEnabledByDefault

	switch e := os.Getenv("GO19CONCURRENTCOMPILATION"); e {
	case "0":
		canDashC = false
	case "1":
		canDashC = true
	case "":
		// Not set. Use default.
	default:
		log.Fatalf("GO19CONCURRENTCOMPILATION must be 0, 1, or unset, got %q", e)
	}

CheckFlags:
	for _, flag := range gcflags {
		// Concurrent compilation is presumed incompatible with any gcflags,
		// except for a small whitelist of commonly used flags.
		// If the user knows better, they can manually add their own -c to the gcflags.
		switch flag {
		case "-N", "-l", "-S", "-B", "-C", "-I":
			// OK
		default:
			canDashC = false
			break CheckFlags
		}
	}

	// TODO: Test and delete these conditions.
	if objabi.Fieldtrack_enabled != 0 || objabi.Preemptibleloops_enabled != 0 || objabi.Clobberdead_enabled != 0 {
		canDashC = false
	}

	if !canDashC {
		return 1
	}

	// Decide how many concurrent backend compilations to allow.
	//
	// If we allow too many, in theory we might end up with p concurrent processes,
	// each with c concurrent backend compiles, all fighting over the same resources.
	// However, in practice, that seems not to happen too much.
	// Most build graphs are surprisingly serial, so p==1 for much of the build.
	// Furthermore, concurrent backend compilation is only enabled for a part
	// of the overall compiler execution, so c==1 for much of the build.
	// So don't worry too much about that interaction for now.
	//
	// However, in practice, setting c above 4 tends not to help very much.
	// See the analysis in CL 41192.
	//
	// TODO(josharian): attempt to detect whether this particular compilation
	// is likely to be a bottleneck, e.g. when:
	//   - it has no successor packages to compile (usually package main)
	//   - all paths through the build graph pass through it
	//   - critical path scheduling says it is high priority
	// and in such a case, set c to runtime.NumCPU.
	// We do this now when p==1.
	if cfg.BuildP == 1 {
		// No process parallelism. Max out c.
		return runtime.NumCPU()
	}
	// Some process parallelism. Set c to min(4, numcpu).
	c := 4
	if ncpu := runtime.NumCPU(); ncpu < c {
		c = ncpu
	}
	return c
}

func trimDir(dir string) string {
	if len(dir) > 1 && dir[len(dir)-1] == filepath.Separator {
		dir = dir[:len(dir)-1]
	}
	return dir
}

func (gcToolchain) asm(b *Builder, a *Action, sfiles []string) ([]string, error) {
	p := a.Package
	// Add -I pkg/GOOS_GOARCH so #include "textflag.h" works in .s files.
	inc := filepath.Join(cfg.GOROOT, "pkg", "include")
	args := []interface{}{cfg.BuildToolexec, base.Tool("asm"), "-trimpath", trimDir(a.Objdir), "-I", a.Objdir, "-I", inc, "-D", "GOOS_" + cfg.Goos, "-D", "GOARCH_" + cfg.Goarch, forcedAsmflags, p.Internal.Asmflags}
	if p.ImportPath == "runtime" && cfg.Goarch == "386" {
		for _, arg := range forcedAsmflags {
			if arg == "-dynlink" {
				args = append(args, "-D=GOBUILDMODE_shared=1")
			}
		}
	}

	if cfg.Goarch == "mips" || cfg.Goarch == "mipsle" {
		// Define GOMIPS_value from cfg.GOMIPS.
		args = append(args, "-D", "GOMIPS_"+cfg.GOMIPS)
	}

	if cfg.Goarch == "mips64" || cfg.Goarch == "mips64le" {
		// Define GOMIPS64_value from cfg.GOMIPS64.
		args = append(args, "-D", "GOMIPS64_"+cfg.GOMIPS64)
	}

	var ofiles []string
	for _, sfile := range sfiles {
		ofile := a.Objdir + sfile[:len(sfile)-len(".s")] + ".o"
		ofiles = append(ofiles, ofile)
		args1 := append(args, "-o", ofile, mkAbs(p.Dir, sfile))
		if err := b.run(a, p.Dir, p.ImportPath, nil, args1...); err != nil {
			return nil, err
		}
	}
	return ofiles, nil
}

// toolVerify checks that the command line args writes the same output file
// if run using newTool instead.
// Unused now but kept around for future use.
func toolVerify(a *Action, b *Builder, p *load.Package, newTool string, ofile string, args []interface{}) error {
	newArgs := make([]interface{}, len(args))
	copy(newArgs, args)
	newArgs[1] = base.Tool(newTool)
	newArgs[3] = ofile + ".new" // x.6 becomes x.6.new
	if err := b.run(a, p.Dir, p.ImportPath, nil, newArgs...); err != nil {
		return err
	}
	data1, err := ioutil.ReadFile(ofile)
	if err != nil {
		return err
	}
	data2, err := ioutil.ReadFile(ofile + ".new")
	if err != nil {
		return err
	}
	if !bytes.Equal(data1, data2) {
		return fmt.Errorf("%s and %s produced different output files:\n%s\n%s", filepath.Base(args[1].(string)), newTool, strings.Join(str.StringList(args...), " "), strings.Join(str.StringList(newArgs...), " "))
	}
	os.Remove(ofile + ".new")
	return nil
}

func (gcToolchain) pack(b *Builder, a *Action, afile string, ofiles []string) error {
	var absOfiles []string
	for _, f := range ofiles {
		absOfiles = append(absOfiles, mkAbs(a.Objdir, f))
	}
	absAfile := mkAbs(a.Objdir, afile)

	// The archive file should have been created by the compiler.
	// Since it used to not work that way, verify.
	if !cfg.BuildN {
		if _, err := os.Stat(absAfile); err != nil {
			base.Fatalf("os.Stat of archive file failed: %v", err)
		}
	}

	p := a.Package
	if cfg.BuildN || cfg.BuildX {
		cmdline := str.StringList(base.Tool("pack"), "r", absAfile, absOfiles)
		b.Showcmd(p.Dir, "%s # internal", joinUnambiguously(cmdline))
	}
	if cfg.BuildN {
		return nil
	}
	if err := packInternal(absAfile, absOfiles); err != nil {
		b.showOutput(a, p.Dir, p.Desc(), err.Error()+"\n")
		return errPrintedOutput
	}
	return nil
}

func packInternal(afile string, ofiles []string) error {
	dst, err := os.OpenFile(afile, os.O_WRONLY|os.O_APPEND, 0)
	if err != nil {
		return err
	}
	defer dst.Close() // only for error returns or panics
	w := bufio.NewWriter(dst)

	for _, ofile := range ofiles {
		src, err := os.Open(ofile)
		if err != nil {
			return err
		}
		fi, err := src.Stat()
		if err != nil {
			src.Close()
			return err
		}
		// Note: Not using %-16.16s format because we care
		// about bytes, not runes.
		name := fi.Name()
		if len(name) > 16 {
			name = name[:16]
		} else {
			name += strings.Repeat(" ", 16-len(name))
		}
		size := fi.Size()
		fmt.Fprintf(w, "%s%-12d%-6d%-6d%-8o%-10d`\n",
			name, 0, 0, 0, 0644, size)
		n, err := io.Copy(w, src)
		src.Close()
		if err == nil && n < size {
			err = io.ErrUnexpectedEOF
		} else if err == nil && n > size {
			err = fmt.Errorf("file larger than size reported by stat")
		}
		if err != nil {
			return fmt.Errorf("copying %s to %s: %v", ofile, afile, err)
		}
		if size&1 != 0 {
			w.WriteByte(0)
		}
	}

	if err := w.Flush(); err != nil {
		return err
	}
	return dst.Close()
}

// setextld sets the appropriate linker flags for the specified compiler.
func setextld(ldflags []string, compiler []string) []string {
	for _, f := range ldflags {
		if f == "-extld" || strings.HasPrefix(f, "-extld=") {
			// don't override -extld if supplied
			return ldflags
		}
	}
	ldflags = append(ldflags, "-extld="+compiler[0])
	if len(compiler) > 1 {
		extldflags := false
		add := strings.Join(compiler[1:], " ")
		for i, f := range ldflags {
			if f == "-extldflags" && i+1 < len(ldflags) {
				ldflags[i+1] = add + " " + ldflags[i+1]
				extldflags = true
				break
			} else if strings.HasPrefix(f, "-extldflags=") {
				ldflags[i] = "-extldflags=" + add + " " + ldflags[i][len("-extldflags="):]
				extldflags = true
				break
			}
		}
		if !extldflags {
			ldflags = append(ldflags, "-extldflags="+add)
		}
	}
	return ldflags
}

// pluginPath computes the package path for a plugin main package.
//
// This is typically the import path of the main package p, unless the
// plugin is being built directly from source files. In that case we
// combine the package build ID with the contents of the main package
// source files. This allows us to identify two different plugins
// built from two source files with the same name.
func pluginPath(a *Action) string {
	p := a.Package
	if p.ImportPath != "command-line-arguments" {
		return p.ImportPath
	}
	h := sha1.New()
	fmt.Fprintf(h, "build ID: %s\n", a.buildID)
	for _, file := range str.StringList(p.GoFiles, p.CgoFiles, p.SFiles) {
		data, err := ioutil.ReadFile(filepath.Join(p.Dir, file))
		if err != nil {
			base.Fatalf("go: %s", err)
		}
		h.Write(data)
	}
	return fmt.Sprintf("plugin/unnamed-%x", h.Sum(nil))
}

func (gcToolchain) ld(b *Builder, root *Action, out, importcfg, mainpkg string) error {
	cxx := len(root.Package.CXXFiles) > 0 || len(root.Package.SwigCXXFiles) > 0
	for _, a := range root.Deps {
		if a.Package != nil && (len(a.Package.CXXFiles) > 0 || len(a.Package.SwigCXXFiles) > 0) {
			cxx = true
		}
	}
	var ldflags []string
	if cfg.BuildContext.InstallSuffix != "" {
		ldflags = append(ldflags, "-installsuffix", cfg.BuildContext.InstallSuffix)
	}
	if root.Package.Internal.OmitDebug {
		ldflags = append(ldflags, "-s", "-w")
	}
	if cfg.BuildBuildmode == "plugin" {
		ldflags = append(ldflags, "-pluginpath", pluginPath(root))
	}

	// Store BuildID inside toolchain binaries as a unique identifier of the
	// tool being run, for use by content-based staleness determination.
	if root.Package.Goroot && strings.HasPrefix(root.Package.ImportPath, "cmd/") {
		ldflags = append(ldflags, "-X=cmd/internal/objabi.buildID="+root.buildID)
	}

	// If the user has not specified the -extld option, then specify the
	// appropriate linker. In case of C++ code, use the compiler named
	// by the CXX environment variable or defaultCXX if CXX is not set.
	// Else, use the CC environment variable and defaultCC as fallback.
	var compiler []string
	if cxx {
		compiler = envList("CXX", cfg.DefaultCXX(cfg.Goos, cfg.Goarch))
	} else {
		compiler = envList("CC", cfg.DefaultCC(cfg.Goos, cfg.Goarch))
	}
	ldflags = append(ldflags, "-buildmode="+ldBuildmode)
	if root.buildID != "" {
		ldflags = append(ldflags, "-buildid="+root.buildID)
	}
	ldflags = append(ldflags, forcedLdflags...)
	ldflags = append(ldflags, root.Package.Internal.Ldflags...)
	ldflags = setextld(ldflags, compiler)

	// On OS X when using external linking to build a shared library,
	// the argument passed here to -o ends up recorded in the final
	// shared library in the LC_ID_DYLIB load command.
	// To avoid putting the temporary output directory name there
	// (and making the resulting shared library useless),
	// run the link in the output directory so that -o can name
	// just the final path element.
	// On Windows, DLL file name is recorded in PE file
	// export section, so do like on OS X.
	dir := "."
	if (cfg.Goos == "darwin" || cfg.Goos == "windows") && cfg.BuildBuildmode == "c-shared" {
		dir, out = filepath.Split(out)
	}

	// Apply the rewrite of $WORK to /tmp/go-build also to DWARF file tables:
	env := []string{"BUILD_PATH_PREFIX_MAP=/tmp/go-build=" + b.WorkDir + ":" + os.Getenv("BUILD_PATH_PREFIX_MAP")}

	return b.run(root, dir, root.Package.ImportPath, env, cfg.BuildToolexec, base.Tool("link"), "-o", out, "-importcfg", importcfg, ldflags, mainpkg)
}

func (gcToolchain) ldShared(b *Builder, root *Action, toplevelactions []*Action, out, importcfg string, allactions []*Action) error {
	ldflags := []string{"-installsuffix", cfg.BuildContext.InstallSuffix}
	ldflags = append(ldflags, "-buildmode=shared")
	ldflags = append(ldflags, forcedLdflags...)
	ldflags = append(ldflags, root.Package.Internal.Ldflags...)
	cxx := false
	for _, a := range allactions {
		if a.Package != nil && (len(a.Package.CXXFiles) > 0 || len(a.Package.SwigCXXFiles) > 0) {
			cxx = true
		}
	}
	// If the user has not specified the -extld option, then specify the
	// appropriate linker. In case of C++ code, use the compiler named
	// by the CXX environment variable or defaultCXX if CXX is not set.
	// Else, use the CC environment variable and defaultCC as fallback.
	var compiler []string
	if cxx {
		compiler = envList("CXX", cfg.DefaultCXX(cfg.Goos, cfg.Goarch))
	} else {
		compiler = envList("CC", cfg.DefaultCC(cfg.Goos, cfg.Goarch))
	}
	ldflags = setextld(ldflags, compiler)
	for _, d := range toplevelactions {
		if !strings.HasSuffix(d.Target, ".a") { // omit unsafe etc and actions for other shared libraries
			continue
		}
		ldflags = append(ldflags, d.Package.ImportPath+"="+d.Target)
	}
	return b.run(root, ".", out, nil, cfg.BuildToolexec, base.Tool("link"), "-o", out, "-importcfg", importcfg, ldflags)
}

func (gcToolchain) cc(b *Builder, a *Action, ofile, cfile string) error {
	return fmt.Errorf("%s: C source files not supported without cgo", mkAbs(a.Package.Dir, cfile))
}