flag.go

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