Source file src/cmd/go/internal/work/buildid.go
1 // Copyright 2017 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 work 6 7 import ( 8 "bytes" 9 "fmt" 10 "os" 11 "os/exec" 12 "strings" 13 "sync" 14 15 "cmd/go/internal/base" 16 "cmd/go/internal/cache" 17 "cmd/go/internal/cfg" 18 "cmd/go/internal/fsys" 19 "cmd/go/internal/str" 20 "cmd/internal/buildid" 21 "cmd/internal/pathcache" 22 "cmd/internal/quoted" 23 "cmd/internal/telemetry/counter" 24 ) 25 26 // Build IDs 27 // 28 // Go packages and binaries are stamped with build IDs that record both 29 // the action ID, which is a hash of the inputs to the action that produced 30 // the packages or binary, and the content ID, which is a hash of the action 31 // output, namely the archive or binary itself. The hash is the same one 32 // used by the build artifact cache (see cmd/go/internal/cache), but 33 // truncated when stored in packages and binaries, as the full length is not 34 // needed and is a bit unwieldy. The precise form is 35 // 36 // actionID/[.../]contentID 37 // 38 // where the actionID and contentID are prepared by buildid.HashToString below. 39 // and are found by looking for the first or last slash. 40 // Usually the buildID is simply actionID/contentID, but see below for an 41 // exception. 42 // 43 // The build ID serves two primary purposes. 44 // 45 // 1. The action ID half allows installed packages and binaries to serve as 46 // one-element cache entries. If we intend to build math.a with a given 47 // set of inputs summarized in the action ID, and the installed math.a already 48 // has that action ID, we can reuse the installed math.a instead of rebuilding it. 49 // 50 // 2. The content ID half allows the easy preparation of action IDs for steps 51 // that consume a particular package or binary. The content hash of every 52 // input file for a given action must be included in the action ID hash. 53 // Storing the content ID in the build ID lets us read it from the file with 54 // minimal I/O, instead of reading and hashing the entire file. 55 // This is especially effective since packages and binaries are typically 56 // the largest inputs to an action. 57 // 58 // Separating action ID from content ID is important for reproducible builds. 59 // The compiler is compiled with itself. If an output were represented by its 60 // own action ID (instead of content ID) when computing the action ID of 61 // the next step in the build process, then the compiler could never have its 62 // own input action ID as its output action ID (short of a miraculous hash collision). 63 // Instead we use the content IDs to compute the next action ID, and because 64 // the content IDs converge, so too do the action IDs and therefore the 65 // build IDs and the overall compiler binary. See cmd/dist's cmdbootstrap 66 // for the actual convergence sequence. 67 // 68 // The “one-element cache” purpose is a bit more complex for installed 69 // binaries. For a binary, like cmd/gofmt, there are two steps: compile 70 // cmd/gofmt/*.go into main.a, and then link main.a into the gofmt binary. 71 // We do not install gofmt's main.a, only the gofmt binary. Being able to 72 // decide that the gofmt binary is up-to-date means computing the action ID 73 // for the final link of the gofmt binary and comparing it against the 74 // already-installed gofmt binary. But computing the action ID for the link 75 // means knowing the content ID of main.a, which we did not keep. 76 // To sidestep this problem, each binary actually stores an expanded build ID: 77 // 78 // actionID(binary)/actionID(main.a)/contentID(main.a)/contentID(binary) 79 // 80 // (Note that this can be viewed equivalently as: 81 // 82 // actionID(binary)/buildID(main.a)/contentID(binary) 83 // 84 // Storing the buildID(main.a) in the middle lets the computations that care 85 // about the prefix or suffix halves ignore the middle and preserves the 86 // original build ID as a contiguous string.) 87 // 88 // During the build, when it's time to build main.a, the gofmt binary has the 89 // information needed to decide whether the eventual link would produce 90 // the same binary: if the action ID for main.a's inputs matches and then 91 // the action ID for the link step matches when assuming the given main.a 92 // content ID, then the binary as a whole is up-to-date and need not be rebuilt. 93 // 94 // This is all a bit complex and may be simplified once we can rely on the 95 // main cache, but at least at the start we will be using the content-based 96 // staleness determination without a cache beyond the usual installed 97 // package and binary locations. 98 99 const buildIDSeparator = "/" 100 101 // actionID returns the action ID half of a build ID. 102 func actionID(buildID string) string { 103 i := strings.Index(buildID, buildIDSeparator) 104 if i < 0 { 105 return buildID 106 } 107 return buildID[:i] 108 } 109 110 // contentID returns the content ID half of a build ID. 111 func contentID(buildID string) string { 112 return buildID[strings.LastIndex(buildID, buildIDSeparator)+1:] 113 } 114 115 // toolID returns the unique ID to use for the current copy of the 116 // named tool (asm, compile, cover, link). 117 // 118 // It is important that if the tool changes (for example a compiler bug is fixed 119 // and the compiler reinstalled), toolID returns a different string, so that old 120 // package archives look stale and are rebuilt (with the fixed compiler). 121 // This suggests using a content hash of the tool binary, as stored in the build ID. 122 // 123 // Unfortunately, we can't just open the tool binary, because the tool might be 124 // invoked via a wrapper program specified by -toolexec and we don't know 125 // what the wrapper program does. In particular, we want "-toolexec toolstash" 126 // to continue working: it does no good if "-toolexec toolstash" is executing a 127 // stashed copy of the compiler but the go command is acting as if it will run 128 // the standard copy of the compiler. The solution is to ask the tool binary to tell 129 // us its own build ID using the "-V=full" flag now supported by all tools. 130 // Then we know we're getting the build ID of the compiler that will actually run 131 // during the build. (How does the compiler binary know its own content hash? 132 // We store it there using updateBuildID after the standard link step.) 133 // 134 // A final twist is that we'd prefer to have reproducible builds for release toolchains. 135 // It should be possible to cross-compile for Windows from either Linux or Mac 136 // or Windows itself and produce the same binaries, bit for bit. If the tool ID, 137 // which influences the action ID half of the build ID, is based on the content ID, 138 // then the Linux compiler binary and Mac compiler binary will have different tool IDs 139 // and therefore produce executables with different action IDs. 140 // To avoid this problem, for releases we use the release version string instead 141 // of the compiler binary's content hash. This assumes that all compilers built 142 // on all different systems are semantically equivalent, which is of course only true 143 // modulo bugs. (Producing the exact same executables also requires that the different 144 // build setups agree on details like $GOROOT and file name paths, but at least the 145 // tool IDs do not make it impossible.) 146 func (b *Builder) toolID(name string) string { 147 b.id.Lock() 148 id := b.toolIDCache[name] 149 b.id.Unlock() 150 151 if id != "" { 152 return id 153 } 154 155 path := base.Tool(name) 156 desc := "go tool " + name 157 158 // Special case: undocumented -vettool overrides usual vet, 159 // for testing vet or supplying an alternative analysis tool. 160 if name == "vet" && VetTool != "" { 161 path = VetTool 162 desc = VetTool 163 } 164 165 cmdline := str.StringList(cfg.BuildToolexec, path, "-V=full") 166 cmd := exec.Command(cmdline[0], cmdline[1:]...) 167 var stdout, stderr strings.Builder 168 cmd.Stdout = &stdout 169 cmd.Stderr = &stderr 170 if err := cmd.Run(); err != nil { 171 if stderr.Len() > 0 { 172 os.Stderr.WriteString(stderr.String()) 173 } 174 base.Fatalf("go: error obtaining buildID for %s: %v", desc, err) 175 } 176 177 line := stdout.String() 178 f := strings.Fields(line) 179 if len(f) < 3 || f[0] != name && path != VetTool || f[1] != "version" || f[2] == "devel" && !strings.HasPrefix(f[len(f)-1], "buildID=") { 180 base.Fatalf("go: parsing buildID from %s -V=full: unexpected output:\n\t%s", desc, line) 181 } 182 if f[2] == "devel" { 183 // On the development branch, use the content ID part of the build ID. 184 id = contentID(f[len(f)-1]) 185 } else { 186 // For a release, the output is like: "compile version go1.9.1 X:framepointer". 187 // Use the whole line. 188 id = strings.TrimSpace(line) 189 } 190 191 b.id.Lock() 192 b.toolIDCache[name] = id 193 b.id.Unlock() 194 195 return id 196 } 197 198 // gccToolID returns the unique ID to use for a tool that is invoked 199 // by the GCC driver. This is used particularly for gccgo, but this can also 200 // be used for gcc, g++, gfortran, etc.; those tools all use the GCC 201 // driver under different names. The approach used here should also 202 // work for sufficiently new versions of clang. Unlike toolID, the 203 // name argument is the program to run. The language argument is the 204 // type of input file as passed to the GCC driver's -x option. 205 // 206 // For these tools we have no -V=full option to dump the build ID, 207 // but we can run the tool with -v -### to reliably get the compiler proper 208 // and hash that. That will work in the presence of -toolexec. 209 // 210 // In order to get reproducible builds for released compilers, we 211 // detect a released compiler by the absence of "experimental" in the 212 // --version output, and in that case we just use the version string. 213 // 214 // gccToolID also returns the underlying executable for the compiler. 215 // The caller assumes that stat of the exe can be used, combined with the id, 216 // to detect changes in the underlying compiler. The returned exe can be empty, 217 // which means to rely only on the id. 218 func (b *Builder) gccToolID(name, language string) (id, exe string, err error) { 219 key := name + "." + language 220 b.id.Lock() 221 id = b.toolIDCache[key] 222 exe = b.toolIDCache[key+".exe"] 223 b.id.Unlock() 224 225 if id != "" { 226 return id, exe, nil 227 } 228 229 // Invoke the driver with -### to see the subcommands and the 230 // version strings. Use -x to set the language. Pretend to 231 // compile an empty file on standard input. 232 cmdline := str.StringList(cfg.BuildToolexec, name, "-###", "-x", language, "-c", "-") 233 cmd := exec.Command(cmdline[0], cmdline[1:]...) 234 // Force untranslated output so that we see the string "version". 235 cmd.Env = append(os.Environ(), "LC_ALL=C") 236 out, err := cmd.CombinedOutput() 237 if err != nil { 238 return "", "", fmt.Errorf("%s: %v; output: %q", name, err, out) 239 } 240 241 version := "" 242 lines := strings.Split(string(out), "\n") 243 for _, line := range lines { 244 fields := strings.Fields(line) 245 for i, field := range fields { 246 if strings.HasSuffix(field, ":") { 247 // Avoid parsing fields of lines like "Configured with: …", which may 248 // contain arbitrary substrings. 249 break 250 } 251 if field == "version" && i < len(fields)-1 { 252 // Check that the next field is plausibly a version number. 253 // We require only that it begins with an ASCII digit, 254 // since we don't know what version numbering schemes a given 255 // C compiler may use. (Clang and GCC mostly seem to follow the scheme X.Y.Z, 256 // but in https://go.dev/issue/64619 we saw "8.3 [DragonFly]", and who knows 257 // what other C compilers like "zig cc" might report?) 258 next := fields[i+1] 259 if len(next) > 0 && next[0] >= '0' && next[0] <= '9' { 260 version = line 261 break 262 } 263 } 264 } 265 if version != "" { 266 break 267 } 268 } 269 if version == "" { 270 return "", "", fmt.Errorf("%s: can not find version number in %q", name, out) 271 } 272 273 if !strings.Contains(version, "experimental") { 274 // This is a release. Use this line as the tool ID. 275 id = version 276 } else { 277 // This is a development version. The first line with 278 // a leading space is the compiler proper. 279 compiler := "" 280 for _, line := range lines { 281 if strings.HasPrefix(line, " ") && !strings.HasPrefix(line, " (in-process)") { 282 compiler = line 283 break 284 } 285 } 286 if compiler == "" { 287 return "", "", fmt.Errorf("%s: can not find compilation command in %q", name, out) 288 } 289 290 fields, _ := quoted.Split(compiler) 291 if len(fields) == 0 { 292 return "", "", fmt.Errorf("%s: compilation command confusion %q", name, out) 293 } 294 exe = fields[0] 295 if !strings.ContainsAny(exe, `/\`) { 296 if lp, err := pathcache.LookPath(exe); err == nil { 297 exe = lp 298 } 299 } 300 id, err = buildid.ReadFile(exe) 301 if err != nil { 302 return "", "", err 303 } 304 305 // If we can't find a build ID, use a hash. 306 if id == "" { 307 id = b.fileHash(exe) 308 } 309 } 310 311 b.id.Lock() 312 b.toolIDCache[key] = id 313 b.toolIDCache[key+".exe"] = exe 314 b.id.Unlock() 315 316 return id, exe, nil 317 } 318 319 // Check if assembler used by gccgo is GNU as. 320 func assemblerIsGas() bool { 321 cmd := exec.Command(BuildToolchain.compiler(), "-print-prog-name=as") 322 assembler, err := cmd.Output() 323 if err == nil { 324 cmd := exec.Command(strings.TrimSpace(string(assembler)), "--version") 325 out, err := cmd.Output() 326 return err == nil && strings.Contains(string(out), "GNU") 327 } else { 328 return false 329 } 330 } 331 332 // gccgoBuildIDFile creates an assembler file that records the 333 // action's build ID in an SHF_EXCLUDE section for ELF files or 334 // in a CSECT in XCOFF files. 335 func (b *Builder) gccgoBuildIDFile(a *Action) (string, error) { 336 sfile := a.Objdir + "_buildid.s" 337 338 var buf bytes.Buffer 339 if cfg.Goos == "aix" { 340 fmt.Fprintf(&buf, "\t.csect .go.buildid[XO]\n") 341 } else if (cfg.Goos != "solaris" && cfg.Goos != "illumos") || assemblerIsGas() { 342 fmt.Fprintf(&buf, "\t"+`.section .go.buildid,"e"`+"\n") 343 } else if cfg.Goarch == "sparc" || cfg.Goarch == "sparc64" { 344 fmt.Fprintf(&buf, "\t"+`.section ".go.buildid",#exclude`+"\n") 345 } else { // cfg.Goarch == "386" || cfg.Goarch == "amd64" 346 fmt.Fprintf(&buf, "\t"+`.section .go.buildid,#exclude`+"\n") 347 } 348 fmt.Fprintf(&buf, "\t.byte ") 349 for i := 0; i < len(a.buildID); i++ { 350 if i > 0 { 351 if i%8 == 0 { 352 fmt.Fprintf(&buf, "\n\t.byte ") 353 } else { 354 fmt.Fprintf(&buf, ",") 355 } 356 } 357 fmt.Fprintf(&buf, "%#02x", a.buildID[i]) 358 } 359 fmt.Fprintf(&buf, "\n") 360 if cfg.Goos != "solaris" && cfg.Goos != "illumos" && cfg.Goos != "aix" { 361 secType := "@progbits" 362 if cfg.Goarch == "arm" { 363 secType = "%progbits" 364 } 365 fmt.Fprintf(&buf, "\t"+`.section .note.GNU-stack,"",%s`+"\n", secType) 366 fmt.Fprintf(&buf, "\t"+`.section .note.GNU-split-stack,"",%s`+"\n", secType) 367 } 368 369 if err := b.Shell(a).writeFile(sfile, buf.Bytes()); err != nil { 370 return "", err 371 } 372 373 return sfile, nil 374 } 375 376 // buildID returns the build ID found in the given file. 377 // If no build ID is found, buildID returns the content hash of the file. 378 func (b *Builder) buildID(file string) string { 379 b.id.Lock() 380 id := b.buildIDCache[file] 381 b.id.Unlock() 382 383 if id != "" { 384 return id 385 } 386 387 id, err := buildid.ReadFile(file) 388 if err != nil { 389 id = b.fileHash(file) 390 } 391 392 b.id.Lock() 393 b.buildIDCache[file] = id 394 b.id.Unlock() 395 396 return id 397 } 398 399 // fileHash returns the content hash of the named file. 400 func (b *Builder) fileHash(file string) string { 401 sum, err := cache.FileHash(fsys.Actual(file)) 402 if err != nil { 403 return "" 404 } 405 return buildid.HashToString(sum) 406 } 407 408 var ( 409 counterCacheHit = counter.New("go/buildcache/hit") 410 counterCacheMiss = counter.New("go/buildcache/miss") 411 412 stdlibRecompiled = counter.New("go/buildcache/stdlib-recompiled") 413 stdlibRecompiledIncOnce = sync.OnceFunc(stdlibRecompiled.Inc) 414 ) 415 416 // useCache tries to satisfy the action a, which has action ID actionHash, 417 // by using a cached result from an earlier build. 418 // If useCache decides that the cache can be used, it sets a.buildID 419 // and a.built for use by parent actions and then returns true. 420 // Otherwise it sets a.buildID to a temporary build ID for use in the build 421 // and returns false. When useCache returns false the expectation is that 422 // the caller will build the target and then call updateBuildID to finish the 423 // build ID computation. 424 // When useCache returns false, it may have initiated buffering of output 425 // during a's work. The caller should defer b.flushOutput(a), to make sure 426 // that flushOutput is eventually called regardless of whether the action 427 // succeeds. The flushOutput call must happen after updateBuildID. 428 func (b *Builder) useCache(a *Action, actionHash cache.ActionID, target string, printOutput bool) (ok bool) { 429 // The second half of the build ID here is a placeholder for the content hash. 430 // It's important that the overall buildID be unlikely verging on impossible 431 // to appear in the output by chance, but that should be taken care of by 432 // the actionID half; if it also appeared in the input that would be like an 433 // engineered 120-bit partial SHA256 collision. 434 a.actionID = actionHash 435 actionID := buildid.HashToString(actionHash) 436 if a.json != nil { 437 a.json.ActionID = actionID 438 } 439 contentID := actionID // temporary placeholder, likely unique 440 a.buildID = actionID + buildIDSeparator + contentID 441 442 // Executable binaries also record the main build ID in the middle. 443 // See "Build IDs" comment above. 444 if a.Mode == "link" { 445 mainpkg := a.Deps[0] 446 a.buildID = actionID + buildIDSeparator + mainpkg.buildID + buildIDSeparator + contentID 447 } 448 449 // If user requested -a, we force a rebuild, so don't use the cache. 450 if cfg.BuildA { 451 if p := a.Package; p != nil && !p.Stale { 452 p.Stale = true 453 p.StaleReason = "build -a flag in use" 454 } 455 // Begin saving output for later writing to cache. 456 a.output = []byte{} 457 return false 458 } 459 460 defer func() { 461 // Increment counters for cache hits and misses based on the return value 462 // of this function. Don't increment counters if we return early because of 463 // cfg.BuildA above because we don't even look at the cache in that case. 464 if ok { 465 counterCacheHit.Inc() 466 } else { 467 if a.Package != nil && a.Package.Standard { 468 stdlibRecompiledIncOnce() 469 } 470 counterCacheMiss.Inc() 471 } 472 }() 473 474 c := cache.Default() 475 476 if target != "" { 477 buildID, _ := buildid.ReadFile(target) 478 if strings.HasPrefix(buildID, actionID+buildIDSeparator) { 479 a.buildID = buildID 480 if a.json != nil { 481 a.json.BuildID = a.buildID 482 } 483 a.built = target 484 // Poison a.Target to catch uses later in the build. 485 a.Target = "DO NOT USE - " + a.Mode 486 return true 487 } 488 // Special case for building a main package: if the only thing we 489 // want the package for is to link a binary, and the binary is 490 // already up-to-date, then to avoid a rebuild, report the package 491 // as up-to-date as well. See "Build IDs" comment above. 492 // TODO(rsc): Rewrite this code to use a TryCache func on the link action. 493 if !b.NeedExport && a.Mode == "build" && len(a.triggers) == 1 && a.triggers[0].Mode == "link" { 494 if id := strings.Split(buildID, buildIDSeparator); len(id) == 4 && id[1] == actionID { 495 // Temporarily assume a.buildID is the package build ID 496 // stored in the installed binary, and see if that makes 497 // the upcoming link action ID a match. If so, report that 498 // we built the package, safe in the knowledge that the 499 // link step will not ask us for the actual package file. 500 // Note that (*Builder).LinkAction arranged that all of 501 // a.triggers[0]'s dependencies other than a are also 502 // dependencies of a, so that we can be sure that, 503 // other than a.buildID, b.linkActionID is only accessing 504 // build IDs of completed actions. 505 oldBuildID := a.buildID 506 a.buildID = id[1] + buildIDSeparator + id[2] 507 linkID := buildid.HashToString(b.linkActionID(a.triggers[0])) 508 if id[0] == linkID { 509 // Best effort attempt to display output from the compile and link steps. 510 // If it doesn't work, it doesn't work: reusing the cached binary is more 511 // important than reprinting diagnostic information. 512 if printOutput { 513 showStdout(b, c, a, "stdout") // compile output 514 showStdout(b, c, a, "link-stdout") // link output 515 } 516 517 // Poison a.Target to catch uses later in the build. 518 a.Target = "DO NOT USE - main build pseudo-cache Target" 519 a.built = "DO NOT USE - main build pseudo-cache built" 520 if a.json != nil { 521 a.json.BuildID = a.buildID 522 } 523 return true 524 } 525 // Otherwise restore old build ID for main build. 526 a.buildID = oldBuildID 527 } 528 } 529 } 530 531 // TODO(matloob): If we end up caching all executables, the test executable will 532 // already be cached so building it won't do any work. But for now we won't 533 // cache all executables and instead only want to cache some: 534 // we only cache executables produced for 'go run' (and soon, for 'go tool'). 535 // 536 // Special case for linking a test binary: if the only thing we 537 // want the binary for is to run the test, and the test result is cached, 538 // then to avoid the link step, report the link as up-to-date. 539 // We avoid the nested build ID problem in the previous special case 540 // by recording the test results in the cache under the action ID half. 541 if len(a.triggers) == 1 && a.triggers[0].TryCache != nil && a.triggers[0].TryCache(b, a.triggers[0]) { 542 // Best effort attempt to display output from the compile and link steps. 543 // If it doesn't work, it doesn't work: reusing the test result is more 544 // important than reprinting diagnostic information. 545 if printOutput { 546 showStdout(b, c, a.Deps[0], "stdout") // compile output 547 showStdout(b, c, a.Deps[0], "link-stdout") // link output 548 } 549 550 // Poison a.Target to catch uses later in the build. 551 a.Target = "DO NOT USE - pseudo-cache Target" 552 a.built = "DO NOT USE - pseudo-cache built" 553 return true 554 } 555 556 // Check to see if the action output is cached. 557 if file, _, err := cache.GetFile(c, actionHash); err == nil { 558 if a.Mode == "preprocess PGO profile" { 559 // Preprocessed PGO profiles don't embed a build ID, so 560 // skip the build ID lookup. 561 // TODO(prattmic): better would be to add a build ID to the format. 562 a.built = file 563 a.Target = "DO NOT USE - using cache" 564 return true 565 } 566 if buildID, err := buildid.ReadFile(file); err == nil { 567 if printOutput { 568 switch a.Mode { 569 case "link": 570 // The link output is stored using the build action's action ID. 571 // See corresponding code storing the link output in updateBuildID. 572 for _, a1 := range a.Deps { 573 showStdout(b, c, a1, "link-stdout") // link output 574 } 575 default: 576 showStdout(b, c, a, "stdout") // compile output 577 } 578 } 579 a.built = file 580 a.Target = "DO NOT USE - using cache" 581 a.buildID = buildID 582 if a.json != nil { 583 a.json.BuildID = a.buildID 584 } 585 if p := a.Package; p != nil && target != "" { 586 p.Stale = true 587 // Clearer than explaining that something else is stale. 588 p.StaleReason = "not installed but available in build cache" 589 } 590 return true 591 } 592 } 593 594 // If we've reached this point, we can't use the cache for the action. 595 if p := a.Package; p != nil && !p.Stale { 596 p.Stale = true 597 p.StaleReason = "build ID mismatch" 598 if b.IsCmdList { 599 // Since we may end up printing StaleReason, include more detail. 600 for _, p1 := range p.Internal.Imports { 601 if p1.Stale && p1.StaleReason != "" { 602 if strings.HasPrefix(p1.StaleReason, "stale dependency: ") { 603 p.StaleReason = p1.StaleReason 604 break 605 } 606 if strings.HasPrefix(p.StaleReason, "build ID mismatch") { 607 p.StaleReason = "stale dependency: " + p1.ImportPath 608 } 609 } 610 } 611 } 612 } 613 614 // Begin saving output for later writing to cache. 615 a.output = []byte{} 616 return false 617 } 618 619 func showStdout(b *Builder, c cache.Cache, a *Action, key string) error { 620 actionID := a.actionID 621 622 stdout, stdoutEntry, err := cache.GetBytes(c, cache.Subkey(actionID, key)) 623 if err != nil { 624 return err 625 } 626 627 if len(stdout) > 0 { 628 sh := b.Shell(a) 629 if cfg.BuildX || cfg.BuildN { 630 sh.ShowCmd("", "%s # internal", joinUnambiguously(str.StringList("cat", c.OutputFile(stdoutEntry.OutputID)))) 631 } 632 if !cfg.BuildN { 633 sh.Printf("%s", stdout) 634 } 635 } 636 return nil 637 } 638 639 // flushOutput flushes the output being queued in a. 640 func (b *Builder) flushOutput(a *Action) { 641 b.Shell(a).Printf("%s", a.output) 642 a.output = nil 643 } 644 645 // updateBuildID updates the build ID in the target written by action a. 646 // It requires that useCache was called for action a and returned false, 647 // and that the build was then carried out and given the temporary 648 // a.buildID to record as the build ID in the resulting package or binary. 649 // updateBuildID computes the final content ID and updates the build IDs 650 // in the binary. 651 // 652 // Keep in sync with src/cmd/buildid/buildid.go 653 func (b *Builder) updateBuildID(a *Action, target string) error { 654 sh := b.Shell(a) 655 656 if cfg.BuildX || cfg.BuildN { 657 sh.ShowCmd("", "%s # internal", joinUnambiguously(str.StringList(base.Tool("buildid"), "-w", target))) 658 if cfg.BuildN { 659 return nil 660 } 661 } 662 663 c := cache.Default() 664 665 // Cache output from compile/link, even if we don't do the rest. 666 switch a.Mode { 667 case "build": 668 cache.PutBytes(c, cache.Subkey(a.actionID, "stdout"), a.output) 669 case "link": 670 // Even though we don't cache the binary, cache the linker text output. 671 // We might notice that an installed binary is up-to-date but still 672 // want to pretend to have run the linker. 673 // Store it under the main package's action ID 674 // to make it easier to find when that's all we have. 675 for _, a1 := range a.Deps { 676 if p1 := a1.Package; p1 != nil && p1.Name == "main" { 677 cache.PutBytes(c, cache.Subkey(a1.actionID, "link-stdout"), a.output) 678 break 679 } 680 } 681 } 682 683 // Find occurrences of old ID and compute new content-based ID. 684 r, err := os.Open(target) 685 if err != nil { 686 return err 687 } 688 matches, hash, err := buildid.FindAndHash(r, a.buildID, 0) 689 r.Close() 690 if err != nil { 691 return err 692 } 693 newID := a.buildID[:strings.LastIndex(a.buildID, buildIDSeparator)] + buildIDSeparator + buildid.HashToString(hash) 694 if len(newID) != len(a.buildID) { 695 return fmt.Errorf("internal error: build ID length mismatch %q vs %q", a.buildID, newID) 696 } 697 698 // Replace with new content-based ID. 699 a.buildID = newID 700 if a.json != nil { 701 a.json.BuildID = a.buildID 702 } 703 if len(matches) == 0 { 704 // Assume the user specified -buildid= to override what we were going to choose. 705 return nil 706 } 707 708 // Replace the build id in the file with the content-based ID. 709 w, err := os.OpenFile(target, os.O_RDWR, 0) 710 if err != nil { 711 return err 712 } 713 err = buildid.Rewrite(w, matches, newID) 714 if err != nil { 715 w.Close() 716 return err 717 } 718 if err := w.Close(); err != nil { 719 return err 720 } 721 722 // Cache package builds, and cache executable builds if 723 // executable caching was requested. Executables are not 724 // cached by default because they are not reused 725 // nearly as often as individual packages, and they're 726 // much larger, so the cache-footprint-to-utility ratio 727 // of executables is much lower for executables. 728 if a.Mode == "build" { 729 r, err := os.Open(target) 730 if err == nil { 731 if a.output == nil { 732 panic("internal error: a.output not set") 733 } 734 outputID, _, err := c.Put(a.actionID, r) 735 r.Close() 736 if err == nil && cfg.BuildX { 737 sh.ShowCmd("", "%s # internal", joinUnambiguously(str.StringList("cp", target, c.OutputFile(outputID)))) 738 } 739 if b.NeedExport { 740 if err != nil { 741 return err 742 } 743 a.Package.Export = c.OutputFile(outputID) 744 a.Package.BuildID = a.buildID 745 } 746 } 747 } 748 if c, ok := c.(*cache.DiskCache); a.Mode == "link" && a.CacheExecutable && ok { 749 r, err := os.Open(target) 750 if err == nil { 751 if a.output == nil { 752 panic("internal error: a.output not set") 753 } 754 name := a.Package.Internal.ExeName 755 if name == "" { 756 name = a.Package.DefaultExecName() 757 } 758 outputID, _, err := c.PutExecutable(a.actionID, name+cfg.ExeSuffix, r) 759 r.Close() 760 if err == nil && cfg.BuildX { 761 sh.ShowCmd("", "%s # internal", joinUnambiguously(str.StringList("cp", target, c.OutputFile(outputID)))) 762 } 763 } 764 } 765 766 return nil 767 } 768