flag.go

Documentation: cmd/compile/internal/base

     1  // Copyright 2009 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 base
     6  
     7  import (
     8  	"cmd/internal/cov/covcmd"
     9  	"cmd/internal/telemetry/counter"
    10  	"encoding/json"
    11  	"flag"
    12  	"fmt"
    13  	"internal/buildcfg"
    14  	"internal/platform"
    15  	"log"
    16  	"os"
    17  	"reflect"
    18  	"runtime"
    19  	"strings"
    20  
    21  	"cmd/internal/obj"
    22  	"cmd/internal/objabi"
    23  	"cmd/internal/sys"
    24  )
    25  
    26  func usage() {
    27  	fmt.Fprintf(os.Stderr, "usage: compile [options] file.go...\n")
    28  	objabi.Flagprint(os.Stderr)
    29  	Exit(2)
    30  }
    31  
    32  // Flag holds the parsed command-line flags.
    33  // See ParseFlag for non-zero defaults.
    34  var Flag CmdFlags
    35  
    36  // A CountFlag is a counting integer flag.
    37  // It accepts -name=value to set the value directly,
    38  // but it also accepts -name with no =value to increment the count.
    39  type CountFlag int
    40  
    41  // CmdFlags defines the command-line flags (see var Flag).
    42  // Each struct field is a different flag, by default named for the lower-case of the field name.
    43  // If the flag name is a single letter, the default flag name is left upper-case.
    44  // If the flag name is "Lower" followed by a single letter, the default flag name is the lower-case of the last letter.
    45  //
    46  // If this default flag name can't be made right, the `flag` struct tag can be used to replace it,
    47  // but this should be done only in exceptional circumstances: it helps everyone if the flag name
    48  // is obvious from the field name when the flag is used elsewhere in the compiler sources.
    49  // The `flag:"-"` struct tag makes a field invisible to the flag logic and should also be used sparingly.
    50  //
    51  // Each field must have a `help` struct tag giving the flag help message.
    52  //
    53  // The allowed field types are bool, int, string, pointers to those (for values stored elsewhere),
    54  // CountFlag (for a counting flag), and func(string) (for a flag that uses special code for parsing).
    55  type CmdFlags struct {
    56  	// Single letters
    57  	B CountFlag    "help:\"disable bounds checking\""
    58  	C CountFlag    "help:\"disable printing of columns in error messages\""
    59  	D string       "help:\"set relative `path` for local imports\""
    60  	E CountFlag    "help:\"debug symbol export\""
    61  	I func(string) "help:\"add `directory` to import search path\""
    62  	K CountFlag    "help:\"debug missing line numbers\""
    63  	L CountFlag    "help:\"also show actual source file names in error messages for positions affected by //line directives\""
    64  	N CountFlag    "help:\"disable optimizations\""
    65  	S CountFlag    "help:\"print assembly listing\""
    66  	// V is added by objabi.AddVersionFlag
    67  	W CountFlag "help:\"debug parse tree after type checking\""
    68  
    69  	LowerC int        "help:\"concurrency during compilation (1 means no concurrency)\""
    70  	LowerD flag.Value "help:\"enable debugging settings; try -d help\""
    71  	LowerE CountFlag  "help:\"no limit on number of errors reported\""
    72  	LowerH CountFlag  "help:\"halt on error\""
    73  	LowerJ CountFlag  "help:\"debug runtime-initialized variables\""
    74  	LowerL CountFlag  "help:\"disable inlining\""
    75  	LowerM CountFlag  "help:\"print optimization decisions\""
    76  	LowerO string     "help:\"write output to `file`\""
    77  	LowerP *string    "help:\"set expected package import `path`\"" // &Ctxt.Pkgpath, set below
    78  	LowerR CountFlag  "help:\"debug generated wrappers\""
    79  	LowerT bool       "help:\"enable tracing for debugging the compiler\""
    80  	LowerW CountFlag  "help:\"debug type checking\""
    81  	LowerV *bool      "help:\"increase debug verbosity\""
    82  
    83  	// Special characters
    84  	Percent          CountFlag "flag:\"%\" help:\"debug non-static initializers\""
    85  	CompilingRuntime bool      "flag:\"+\" help:\"compiling runtime\""
    86  
    87  	// Longer names
    88  	AsmHdr             string       "help:\"write assembly header to `file`\""
    89  	ASan               bool         "help:\"build code compatible with C/C++ address sanitizer\""
    90  	Bench              string       "help:\"append benchmark times to `file`\""
    91  	BlockProfile       string       "help:\"write block profile to `file`\""
    92  	BuildID            string       "help:\"record `id` as the build id in the export metadata\""
    93  	CPUProfile         string       "help:\"write cpu profile to `file`\""
    94  	Complete           bool         "help:\"compiling complete package (no C or assembly)\""
    95  	ClobberDead        bool         "help:\"clobber dead stack slots (for debugging)\""
    96  	ClobberDeadReg     bool         "help:\"clobber dead registers (for debugging)\""
    97  	Dwarf              bool         "help:\"generate DWARF symbols\""
    98  	DwarfBASEntries    *bool        "help:\"use base address selection entries in DWARF\""                        // &Ctxt.UseBASEntries, set below
    99  	DwarfLocationLists *bool        "help:\"add location lists to DWARF in optimized mode\""                      // &Ctxt.Flag_locationlists, set below
   100  	Dynlink            *bool        "help:\"support references to Go symbols defined in other shared libraries\"" // &Ctxt.Flag_dynlink, set below
   101  	EmbedCfg           func(string) "help:\"read go:embed configuration from `file`\""
   102  	Env                func(string) "help:\"add `definition` of the form key=value to environment\""
   103  	GenDwarfInl        int          "help:\"generate DWARF inline info records\"" // 0=disabled, 1=funcs, 2=funcs+formals/locals
   104  	GoVersion          string       "help:\"required version of the runtime\""
   105  	ImportCfg          func(string) "help:\"read import configuration from `file`\""
   106  	InstallSuffix      string       "help:\"set pkg directory `suffix`\""
   107  	JSON               string       "help:\"version,file for JSON compiler/optimizer detail output\""
   108  	Lang               string       "help:\"Go language version source code expects\""
   109  	LinkObj            string       "help:\"write linker-specific object to `file`\""
   110  	LinkShared         *bool        "help:\"generate code that will be linked against Go shared libraries\"" // &Ctxt.Flag_linkshared, set below
   111  	Live               CountFlag    "help:\"debug liveness analysis\""
   112  	MSan               bool         "help:\"build code compatible with C/C++ memory sanitizer\""
   113  	MemProfile         string       "help:\"write memory profile to `file`\""
   114  	MemProfileRate     int          "help:\"set runtime.MemProfileRate to `rate`\""
   115  	MutexProfile       string       "help:\"write mutex profile to `file`\""
   116  	NoLocalImports     bool         "help:\"reject local (relative) imports\""
   117  	CoverageCfg        func(string) "help:\"read coverage configuration from `file`\""
   118  	Pack               bool         "help:\"write to file.a instead of file.o\""
   119  	Race               bool         "help:\"enable race detector\""
   120  	Shared             *bool        "help:\"generate code that can be linked into a shared library\"" // &Ctxt.Flag_shared, set below
   121  	SmallFrames        bool         "help:\"reduce the size limit for stack allocated objects\""      // small stacks, to diagnose GC latency; see golang.org/issue/27732
   122  	Spectre            string       "help:\"enable spectre mitigations in `list` (all, index, ret)\""
   123  	Std                bool         "help:\"compiling standard library\""
   124  	SymABIs            string       "help:\"read symbol ABIs from `file`\""
   125  	TraceProfile       string       "help:\"write an execution trace to `file`\""
   126  	TrimPath           string       "help:\"remove `prefix` from recorded source file paths\""
   127  	WB                 bool         "help:\"enable write barrier\"" // TODO: remove
   128  	PgoProfile         string       "help:\"read profile or pre-process profile from `file`\""
   129  	ErrorURL           bool         "help:\"print explanatory URL with error message if applicable\""
   130  
   131  	// Configuration derived from flags; not a flag itself.
   132  	Cfg struct {
   133  		Embed struct { // set by -embedcfg
   134  			Patterns map[string][]string
   135  			Files    map[string]string
   136  		}
   137  		ImportDirs   []string                 // appended to by -I
   138  		ImportMap    map[string]string        // set by -importcfg
   139  		PackageFile  map[string]string        // set by -importcfg; nil means not in use
   140  		CoverageInfo *covcmd.CoverFixupConfig // set by -coveragecfg
   141  		SpectreIndex bool                     // set by -spectre=index or -spectre=all
   142  		// Whether we are adding any sort of code instrumentation, such as
   143  		// when the race detector is enabled.
   144  		Instrumenting bool
   145  	}
   146  }
   147  
   148  func addEnv(s string) {
   149  	i := strings.Index(s, "=")
   150  	if i < 0 {
   151  		log.Fatal("-env argument must be of the form key=value")
   152  	}
   153  	os.Setenv(s[:i], s[i+1:])
   154  }
   155  
   156  // ParseFlags parses the command-line flags into Flag.
   157  func ParseFlags() {
   158  	Flag.I = addImportDir
   159  
   160  	Flag.LowerC = runtime.GOMAXPROCS(0)
   161  	Flag.LowerD = objabi.NewDebugFlag(&Debug, DebugSSA)
   162  	Flag.LowerP = &Ctxt.Pkgpath
   163  	Flag.LowerV = &Ctxt.Debugvlog
   164  
   165  	Flag.Dwarf = buildcfg.GOARCH != "wasm"
   166  	Flag.DwarfBASEntries = &Ctxt.UseBASEntries
   167  	Flag.DwarfLocationLists = &Ctxt.Flag_locationlists
   168  	*Flag.DwarfLocationLists = true
   169  	Flag.Dynlink = &Ctxt.Flag_dynlink
   170  	Flag.EmbedCfg = readEmbedCfg
   171  	Flag.Env = addEnv
   172  	Flag.GenDwarfInl = 2
   173  	Flag.ImportCfg = readImportCfg
   174  	Flag.CoverageCfg = readCoverageCfg
   175  	Flag.LinkShared = &Ctxt.Flag_linkshared
   176  	Flag.Shared = &Ctxt.Flag_shared
   177  	Flag.WB = true
   178  
   179  	Debug.ConcurrentOk = true
   180  	Debug.MaxShapeLen = 500
   181  	Debug.AlignHot = 1
   182  	Debug.InlFuncsWithClosures = 1
   183  	Debug.InlStaticInit = 1
   184  	Debug.PGOInline = 1
   185  	Debug.PGODevirtualize = 2
   186  	Debug.SyncFrames = -1 // disable sync markers by default
   187  	Debug.ZeroCopy = 1
   188  	Debug.RangeFuncCheck = 1
   189  	Debug.MergeLocals = 1
   190  
   191  	Debug.Checkptr = -1 // so we can tell whether it is set explicitly
   192  
   193  	Flag.Cfg.ImportMap = make(map[string]string)
   194  
   195  	objabi.AddVersionFlag() // -V
   196  	registerFlags()
   197  	objabi.Flagparse(usage)
   198  	counter.CountFlags("compile/flag:", *flag.CommandLine)
   199  
   200  	if gcd := os.Getenv("GOCOMPILEDEBUG"); gcd != "" {
   201  		// This will only override the flags set in gcd;
   202  		// any others set on the command line remain set.
   203  		Flag.LowerD.Set(gcd)
   204  	}
   205  
   206  	if Debug.Gossahash != "" {
   207  		hashDebug = NewHashDebug("gossahash", Debug.Gossahash, nil)
   208  	}
   209  
   210  	// Compute whether we're compiling the runtime from the package path. Test
   211  	// code can also use the flag to set this explicitly.
   212  	if Flag.Std && objabi.LookupPkgSpecial(Ctxt.Pkgpath).Runtime {
   213  		Flag.CompilingRuntime = true
   214  	}
   215  
   216  	Ctxt.Std = Flag.Std
   217  
   218  	// Three inputs govern loop iteration variable rewriting, hash, experiment, flag.
   219  	// The loop variable rewriting is:
   220  	// IF non-empty hash, then hash determines behavior (function+line match) (*)
   221  	// ELSE IF experiment and flag==0, then experiment (set flag=1)
   222  	// ELSE flag (note that build sets flag per-package), with behaviors:
   223  	//  -1 => no change to behavior.
   224  	//   0 => no change to behavior (unless non-empty hash, see above)
   225  	//   1 => apply change to likely-iteration-variable-escaping loops
   226  	//   2 => apply change, log results
   227  	//   11 => apply change EVERYWHERE, do not log results (for debugging/benchmarking)
   228  	//   12 => apply change EVERYWHERE, log results (for debugging/benchmarking)
   229  	//
   230  	// The expected uses of the these inputs are, in believed most-likely to least likely:
   231  	//  GOEXPERIMENT=loopvar -- apply change to entire application
   232  	//  -gcflags=some_package=-d=loopvar=1 -- apply change to some_package (**)
   233  	//  -gcflags=some_package=-d=loopvar=2 -- apply change to some_package, log it
   234  	//  GOEXPERIMENT=loopvar -gcflags=some_package=-d=loopvar=-1 -- apply change to all but one package
   235  	//  GOCOMPILEDEBUG=loopvarhash=... -- search for failure cause
   236  	//
   237  	//  (*) For debugging purposes, providing loopvar flag >= 11 will expand the hash-eligible set of loops to all.
   238  	// (**) Loop semantics, changed or not, follow code from a package when it is inlined; that is, the behavior
   239  	//      of an application compiled with partially modified loop semantics does not depend on inlining.
   240  
   241  	if Debug.LoopVarHash != "" {
   242  		// This first little bit controls the inputs for debug-hash-matching.
   243  		mostInlineOnly := true
   244  		if strings.HasPrefix(Debug.LoopVarHash, "IL") {
   245  			// When hash-searching on a position that is an inline site, default is to use the
   246  			// most-inlined position only.  This makes the hash faster, plus there's no point
   247  			// reporting a problem with all the inlining; there's only one copy of the source.
   248  			// However, if for some reason you wanted it per-site, you can get this.  (The default
   249  			// hash-search behavior for compiler debugging is at an inline site.)
   250  			Debug.LoopVarHash = Debug.LoopVarHash[2:]
   251  			mostInlineOnly = false
   252  		}
   253  		// end of testing trickiness
   254  		LoopVarHash = NewHashDebug("loopvarhash", Debug.LoopVarHash, nil)
   255  		if Debug.LoopVar < 11 { // >= 11 means all loops are rewrite-eligible
   256  			Debug.LoopVar = 1 // 1 means those loops that syntactically escape their dcl vars are eligible.
   257  		}
   258  		LoopVarHash.SetInlineSuffixOnly(mostInlineOnly)
   259  	} else if buildcfg.Experiment.LoopVar && Debug.LoopVar == 0 {
   260  		Debug.LoopVar = 1
   261  	}
   262  
   263  	if Debug.Fmahash != "" {
   264  		FmaHash = NewHashDebug("fmahash", Debug.Fmahash, nil)
   265  	}
   266  	if Debug.PGOHash != "" {
   267  		PGOHash = NewHashDebug("pgohash", Debug.PGOHash, nil)
   268  	}
   269  	if Debug.MergeLocalsHash != "" {
   270  		MergeLocalsHash = NewHashDebug("mergelocals", Debug.MergeLocalsHash, nil)
   271  	}
   272  
   273  	if Flag.MSan && !platform.MSanSupported(buildcfg.GOOS, buildcfg.GOARCH) {
   274  		log.Fatalf("%s/%s does not support -msan", buildcfg.GOOS, buildcfg.GOARCH)
   275  	}
   276  	if Flag.ASan && !platform.ASanSupported(buildcfg.GOOS, buildcfg.GOARCH) {
   277  		log.Fatalf("%s/%s does not support -asan", buildcfg.GOOS, buildcfg.GOARCH)
   278  	}
   279  	if Flag.Race && !platform.RaceDetectorSupported(buildcfg.GOOS, buildcfg.GOARCH) {
   280  		log.Fatalf("%s/%s does not support -race", buildcfg.GOOS, buildcfg.GOARCH)
   281  	}
   282  	if (*Flag.Shared || *Flag.Dynlink || *Flag.LinkShared) && !Ctxt.Arch.InFamily(sys.AMD64, sys.ARM, sys.ARM64, sys.I386, sys.Loong64, sys.MIPS64, sys.PPC64, sys.RISCV64, sys.S390X) {
   283  		log.Fatalf("%s/%s does not support -shared", buildcfg.GOOS, buildcfg.GOARCH)
   284  	}
   285  	parseSpectre(Flag.Spectre) // left as string for RecordFlags
   286  
   287  	Ctxt.Flag_shared = Ctxt.Flag_dynlink || Ctxt.Flag_shared
   288  	Ctxt.Flag_optimize = Flag.N == 0
   289  	Ctxt.Debugasm = int(Flag.S)
   290  	Ctxt.Flag_maymorestack = Debug.MayMoreStack
   291  	Ctxt.Flag_noRefName = Debug.NoRefName != 0
   292  
   293  	if flag.NArg() < 1 {
   294  		usage()
   295  	}
   296  
   297  	if Flag.GoVersion != "" && Flag.GoVersion != runtime.Version() {
   298  		fmt.Printf("compile: version %q does not match go tool version %q\n", runtime.Version(), Flag.GoVersion)
   299  		Exit(2)
   300  	}
   301  
   302  	if *Flag.LowerP == "" {
   303  		*Flag.LowerP = obj.UnlinkablePkg
   304  	}
   305  
   306  	if Flag.LowerO == "" {
   307  		p := flag.Arg(0)
   308  		if i := strings.LastIndex(p, "/"); i >= 0 {
   309  			p = p[i+1:]
   310  		}
   311  		if runtime.GOOS == "windows" {
   312  			if i := strings.LastIndex(p, `\`); i >= 0 {
   313  				p = p[i+1:]
   314  			}
   315  		}
   316  		if i := strings.LastIndex(p, "."); i >= 0 {
   317  			p = p[:i]
   318  		}
   319  		suffix := ".o"
   320  		if Flag.Pack {
   321  			suffix = ".a"
   322  		}
   323  		Flag.LowerO = p + suffix
   324  	}
   325  	switch {
   326  	case Flag.Race && Flag.MSan:
   327  		log.Fatal("cannot use both -race and -msan")
   328  	case Flag.Race && Flag.ASan:
   329  		log.Fatal("cannot use both -race and -asan")
   330  	case Flag.MSan && Flag.ASan:
   331  		log.Fatal("cannot use both -msan and -asan")
   332  	}
   333  	if Flag.Race || Flag.MSan || Flag.ASan {
   334  		// -race, -msan and -asan imply -d=checkptr for now.
   335  		if Debug.Checkptr == -1 { // if not set explicitly
   336  			Debug.Checkptr = 1
   337  		}
   338  	}
   339  
   340  	if Flag.LowerC < 1 {
   341  		log.Fatalf("-c must be at least 1, got %d", Flag.LowerC)
   342  	}
   343  	if !concurrentBackendAllowed() {
   344  		Flag.LowerC = 1
   345  	}
   346  
   347  	if Flag.CompilingRuntime {
   348  		// It is not possible to build the runtime with no optimizations,
   349  		// because the compiler cannot eliminate enough write barriers.
   350  		Flag.N = 0
   351  		Ctxt.Flag_optimize = true
   352  
   353  		// Runtime can't use -d=checkptr, at least not yet.
   354  		Debug.Checkptr = 0
   355  
   356  		// Fuzzing the runtime isn't interesting either.
   357  		Debug.Libfuzzer = 0
   358  	}
   359  
   360  	if Debug.Checkptr == -1 { // if not set explicitly
   361  		Debug.Checkptr = 0
   362  	}
   363  
   364  	// set via a -d flag
   365  	Ctxt.Debugpcln = Debug.PCTab
   366  
   367  	// https://golang.org/issue/67502
   368  	if buildcfg.GOOS == "plan9" && buildcfg.GOARCH == "386" {
   369  		Debug.AlignHot = 0
   370  	}
   371  }
   372  
   373  // registerFlags adds flag registrations for all the fields in Flag.
   374  // See the comment on type CmdFlags for the rules.
   375  func registerFlags() {
   376  	var (
   377  		boolType      = reflect.TypeOf(bool(false))
   378  		intType       = reflect.TypeOf(int(0))
   379  		stringType    = reflect.TypeOf(string(""))
   380  		ptrBoolType   = reflect.TypeOf(new(bool))
   381  		ptrIntType    = reflect.TypeOf(new(int))
   382  		ptrStringType = reflect.TypeOf(new(string))
   383  		countType     = reflect.TypeOf(CountFlag(0))
   384  		funcType      = reflect.TypeOf((func(string))(nil))
   385  	)
   386  
   387  	v := reflect.ValueOf(&Flag).Elem()
   388  	t := v.Type()
   389  	for i := 0; i < t.NumField(); i++ {
   390  		f := t.Field(i)
   391  		if f.Name == "Cfg" {
   392  			continue
   393  		}
   394  
   395  		var name string
   396  		if len(f.Name) == 1 {
   397  			name = f.Name
   398  		} else if len(f.Name) == 6 && f.Name[:5] == "Lower" && 'A' <= f.Name[5] && f.Name[5] <= 'Z' {
   399  			name = string(rune(f.Name[5] + 'a' - 'A'))
   400  		} else {
   401  			name = strings.ToLower(f.Name)
   402  		}
   403  		if tag := f.Tag.Get("flag"); tag != "" {
   404  			name = tag
   405  		}
   406  
   407  		help := f.Tag.Get("help")
   408  		if help == "" {
   409  			panic(fmt.Sprintf("base.Flag.%s is missing help text", f.Name))
   410  		}
   411  
   412  		if k := f.Type.Kind(); (k == reflect.Ptr || k == reflect.Func) && v.Field(i).IsNil() {
   413  			panic(fmt.Sprintf("base.Flag.%s is uninitialized %v", f.Name, f.Type))
   414  		}
   415  
   416  		switch f.Type {
   417  		case boolType:
   418  			p := v.Field(i).Addr().Interface().(*bool)
   419  			flag.BoolVar(p, name, *p, help)
   420  		case intType:
   421  			p := v.Field(i).Addr().Interface().(*int)
   422  			flag.IntVar(p, name, *p, help)
   423  		case stringType:
   424  			p := v.Field(i).Addr().Interface().(*string)
   425  			flag.StringVar(p, name, *p, help)
   426  		case ptrBoolType:
   427  			p := v.Field(i).Interface().(*bool)
   428  			flag.BoolVar(p, name, *p, help)
   429  		case ptrIntType:
   430  			p := v.Field(i).Interface().(*int)
   431  			flag.IntVar(p, name, *p, help)
   432  		case ptrStringType:
   433  			p := v.Field(i).Interface().(*string)
   434  			flag.StringVar(p, name, *p, help)
   435  		case countType:
   436  			p := (*int)(v.Field(i).Addr().Interface().(*CountFlag))
   437  			objabi.Flagcount(name, help, p)
   438  		case funcType:
   439  			f := v.Field(i).Interface().(func(string))
   440  			objabi.Flagfn1(name, help, f)
   441  		default:
   442  			if val, ok := v.Field(i).Interface().(flag.Value); ok {
   443  				flag.Var(val, name, help)
   444  			} else {
   445  				panic(fmt.Sprintf("base.Flag.%s has unexpected type %s", f.Name, f.Type))
   446  			}
   447  		}
   448  	}
   449  }
   450  
   451  // concurrentFlagOk reports whether the current compiler flags
   452  // are compatible with concurrent compilation.
   453  func concurrentFlagOk() bool {
   454  	// TODO(rsc): Many of these are fine. Remove them.
   455  	return Flag.Percent == 0 &&
   456  		Flag.E == 0 &&
   457  		Flag.K == 0 &&
   458  		Flag.L == 0 &&
   459  		Flag.LowerH == 0 &&
   460  		Flag.LowerJ == 0 &&
   461  		Flag.LowerM == 0 &&
   462  		Flag.LowerR == 0
   463  }
   464  
   465  func concurrentBackendAllowed() bool {
   466  	if !concurrentFlagOk() {
   467  		return false
   468  	}
   469  
   470  	// Debug.S by itself is ok, because all printing occurs
   471  	// while writing the object file, and that is non-concurrent.
   472  	// Adding Debug_vlog, however, causes Debug.S to also print
   473  	// while flushing the plist, which happens concurrently.
   474  	if Ctxt.Debugvlog || !Debug.ConcurrentOk || Flag.Live > 0 {
   475  		return false
   476  	}
   477  	// TODO: Test and delete this condition.
   478  	if buildcfg.Experiment.FieldTrack {
   479  		return false
   480  	}
   481  	// TODO: fix races and enable the following flags
   482  	if Ctxt.Flag_dynlink || Flag.Race {
   483  		return false
   484  	}
   485  	return true
   486  }
   487  
   488  func addImportDir(dir string) {
   489  	if dir != "" {
   490  		Flag.Cfg.ImportDirs = append(Flag.Cfg.ImportDirs, dir)
   491  	}
   492  }
   493  
   494  func readImportCfg(file string) {
   495  	if Flag.Cfg.ImportMap == nil {
   496  		Flag.Cfg.ImportMap = make(map[string]string)
   497  	}
   498  	Flag.Cfg.PackageFile = map[string]string{}
   499  	data, err := os.ReadFile(file)
   500  	if err != nil {
   501  		log.Fatalf("-importcfg: %v", err)
   502  	}
   503  
   504  	for lineNum, line := range strings.Split(string(data), "\n") {
   505  		lineNum++ // 1-based
   506  		line = strings.TrimSpace(line)
   507  		if line == "" || strings.HasPrefix(line, "#") {
   508  			continue
   509  		}
   510  
   511  		verb, args, found := strings.Cut(line, " ")
   512  		if found {
   513  			args = strings.TrimSpace(args)
   514  		}
   515  		before, after, hasEq := strings.Cut(args, "=")
   516  
   517  		switch verb {
   518  		default:
   519  			log.Fatalf("%s:%d: unknown directive %q", file, lineNum, verb)
   520  		case "importmap":
   521  			if !hasEq || before == "" || after == "" {
   522  				log.Fatalf(`%s:%d: invalid importmap: syntax is "importmap old=new"`, file, lineNum)
   523  			}
   524  			Flag.Cfg.ImportMap[before] = after
   525  		case "packagefile":
   526  			if !hasEq || before == "" || after == "" {
   527  				log.Fatalf(`%s:%d: invalid packagefile: syntax is "packagefile path=filename"`, file, lineNum)
   528  			}
   529  			Flag.Cfg.PackageFile[before] = after
   530  		}
   531  	}
   532  }
   533  
   534  func readCoverageCfg(file string) {
   535  	var cfg covcmd.CoverFixupConfig
   536  	data, err := os.ReadFile(file)
   537  	if err != nil {
   538  		log.Fatalf("-coveragecfg: %v", err)
   539  	}
   540  	if err := json.Unmarshal(data, &cfg); err != nil {
   541  		log.Fatalf("error reading -coveragecfg file %q: %v", file, err)
   542  	}
   543  	Flag.Cfg.CoverageInfo = &cfg
   544  }
   545  
   546  func readEmbedCfg(file string) {
   547  	data, err := os.ReadFile(file)
   548  	if err != nil {
   549  		log.Fatalf("-embedcfg: %v", err)
   550  	}
   551  	if err := json.Unmarshal(data, &Flag.Cfg.Embed); err != nil {
   552  		log.Fatalf("%s: %v", file, err)
   553  	}
   554  	if Flag.Cfg.Embed.Patterns == nil {
   555  		log.Fatalf("%s: invalid embedcfg: missing Patterns", file)
   556  	}
   557  	if Flag.Cfg.Embed.Files == nil {
   558  		log.Fatalf("%s: invalid embedcfg: missing Files", file)
   559  	}
   560  }
   561  
   562  // parseSpectre parses the spectre configuration from the string s.
   563  func parseSpectre(s string) {
   564  	for _, f := range strings.Split(s, ",") {
   565  		f = strings.TrimSpace(f)
   566  		switch f {
   567  		default:
   568  			log.Fatalf("unknown setting -spectre=%s", f)
   569  		case "":
   570  			// nothing
   571  		case "all":
   572  			Flag.Cfg.SpectreIndex = true
   573  			Ctxt.Retpoline = true
   574  		case "index":
   575  			Flag.Cfg.SpectreIndex = true
   576  		case "ret":
   577  			Ctxt.Retpoline = true
   578  		}
   579  	}
   580  
   581  	if Flag.Cfg.SpectreIndex {
   582  		switch buildcfg.GOARCH {
   583  		case "amd64":
   584  			// ok
   585  		default:
   586  			log.Fatalf("GOARCH=%s does not support -spectre=index", buildcfg.GOARCH)
   587  		}
   588  	}
   589  }
   590
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