go flag 源码
golang flag 代码
文件路径：/src/cmd/compile/internal/base/flag.go
// Copyright 2009 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 base
import (
"encoding/json"
"flag"
"fmt"
"internal/buildcfg"
"io/ioutil"
"log"
"os"
"reflect"
"runtime"
"strings"
"cmd/internal/obj"
"cmd/internal/objabi"
"cmd/internal/sys"
)
func usage() {
fmt.Fprintf(os.Stderr, "usage: compile [options] file.go...\n")
objabi.Flagprint(os.Stderr)
Exit(2)
}
// Flag holds the parsed command-line flags.
// See ParseFlag for non-zero defaults.
var Flag CmdFlags
// A CountFlag is a counting integer flag.
// It accepts -name=value to set the value directly,
// but it also accepts -name with no =value to increment the count.
type CountFlag int
// CmdFlags defines the command-line flags (see var Flag).
// Each struct field is a different flag, by default named for the lower-case of the field name.
// If the flag name is a single letter, the default flag name is left upper-case.
// If the flag name is "Lower" followed by a single letter, the default flag name is the lower-case of the last letter.
//
// If this default flag name can't be made right, the `flag` struct tag can be used to replace it,
// but this should be done only in exceptional circumstances: it helps everyone if the flag name
// is obvious from the field name when the flag is used elsewhere in the compiler sources.
// The `flag:"-"` struct tag makes a field invisible to the flag logic and should also be used sparingly.
//
// Each field must have a `help` struct tag giving the flag help message.
//
// The allowed field types are bool, int, string, pointers to those (for values stored elsewhere),
// CountFlag (for a counting flag), and func(string) (for a flag that uses special code for parsing).
type CmdFlags struct {
// Single letters
B CountFlag "help:\"disable bounds checking\""
C CountFlag "help:\"disable printing of columns in error messages\""
D string "help:\"set relative `path` for local imports\""
E CountFlag "help:\"debug symbol export\""
I func(string) "help:\"add `directory` to import search path\""
K CountFlag "help:\"debug missing line numbers\""
L CountFlag "help:\"also show actual source file names in error messages for positions affected by //line directives\""
N CountFlag "help:\"disable optimizations\""
S CountFlag "help:\"print assembly listing\""
// V is added by objabi.AddVersionFlag
W CountFlag "help:\"debug parse tree after type checking\""
LowerC int "help:\"concurrency during compilation (1 means no concurrency)\""
LowerD flag.Value "help:\"enable debugging settings; try -d help\""
LowerE CountFlag "help:\"no limit on number of errors reported\""
LowerH CountFlag "help:\"halt on error\""
LowerJ CountFlag "help:\"debug runtime-initialized variables\""
LowerL CountFlag "help:\"disable inlining\""
LowerM CountFlag "help:\"print optimization decisions\""
LowerO string "help:\"write output to `file`\""
LowerP *string "help:\"set expected package import `path`\"" // &Ctxt.Pkgpath, set below
LowerR CountFlag "help:\"debug generated wrappers\""
LowerT bool "help:\"enable tracing for debugging the compiler\""
LowerW CountFlag "help:\"debug type checking\""
LowerV *bool "help:\"increase debug verbosity\""
// Special characters
Percent int "flag:\"%\" help:\"debug non-static initializers\""
CompilingRuntime bool "flag:\"+\" help:\"compiling runtime\""
// Longer names
AsmHdr string "help:\"write assembly header to `file`\""
ASan bool "help:\"build code compatible with C/C++ address sanitizer\""
Bench string "help:\"append benchmark times to `file`\""
BlockProfile string "help:\"write block profile to `file`\""
BuildID string "help:\"record `id` as the build id in the export metadata\""
CPUProfile string "help:\"write cpu profile to `file`\""
Complete bool "help:\"compiling complete package (no C or assembly)\""
ClobberDead bool "help:\"clobber dead stack slots (for debugging)\""
ClobberDeadReg bool "help:\"clobber dead registers (for debugging)\""
Dwarf bool "help:\"generate DWARF symbols\""
DwarfBASEntries *bool "help:\"use base address selection entries in DWARF\"" // &Ctxt.UseBASEntries, set below
DwarfLocationLists *bool "help:\"add location lists to DWARF in optimized mode\"" // &Ctxt.Flag_locationlists, set below
Dynlink *bool "help:\"support references to Go symbols defined in other shared libraries\"" // &Ctxt.Flag_dynlink, set below
EmbedCfg func(string) "help:\"read go:embed configuration from `file`\""
GenDwarfInl int "help:\"generate DWARF inline info records\"" // 0=disabled, 1=funcs, 2=funcs+formals/locals
GoVersion string "help:\"required version of the runtime\""
ImportCfg func(string) "help:\"read import configuration from `file`\""
InstallSuffix string "help:\"set pkg directory `suffix`\""
JSON string "help:\"version,file for JSON compiler/optimizer detail output\""
Lang string "help:\"Go language version source code expects\""
LinkObj string "help:\"write linker-specific object to `file`\""
LinkShared *bool "help:\"generate code that will be linked against Go shared libraries\"" // &Ctxt.Flag_linkshared, set below
Live CountFlag "help:\"debug liveness analysis\""
MSan bool "help:\"build code compatible with C/C++ memory sanitizer\""
MemProfile string "help:\"write memory profile to `file`\""
MemProfileRate int "help:\"set runtime.MemProfileRate to `rate`\""
MutexProfile string "help:\"write mutex profile to `file`\""
NoLocalImports bool "help:\"reject local (relative) imports\""
Pack bool "help:\"write to file.a instead of file.o\""
Race bool "help:\"enable race detector\""
Shared *bool "help:\"generate code that can be linked into a shared library\"" // &Ctxt.Flag_shared, set below
SmallFrames bool "help:\"reduce the size limit for stack allocated objects\"" // small stacks, to diagnose GC latency; see golang.org/issue/27732
Spectre string "help:\"enable spectre mitigations in `list` (all, index, ret)\""
Std bool "help:\"compiling standard library\""
SymABIs string "help:\"read symbol ABIs from `file`\""
TraceProfile string "help:\"write an execution trace to `file`\""
TrimPath string "help:\"remove `prefix` from recorded source file paths\""
WB bool "help:\"enable write barrier\"" // TODO: remove
// Configuration derived from flags; not a flag itself.
Cfg struct {
Embed struct { // set by -embedcfg
Patterns map[string][]string
Files map[string]string
}
ImportDirs []string // appended to by -I
ImportMap map[string]string // set by -importcfg
PackageFile map[string]string // set by -importcfg; nil means not in use
SpectreIndex bool // set by -spectre=index or -spectre=all
// Whether we are adding any sort of code instrumentation, such as
// when the race detector is enabled.
Instrumenting bool
}
}
// ParseFlags parses the command-line flags into Flag.
func ParseFlags() {
Flag.I = addImportDir
Flag.LowerC = 1
Flag.LowerD = objabi.NewDebugFlag(&Debug, DebugSSA)
Flag.LowerP = &Ctxt.Pkgpath
Flag.LowerV = &Ctxt.Debugvlog
Flag.Dwarf = buildcfg.GOARCH != "wasm"
Flag.DwarfBASEntries = &Ctxt.UseBASEntries
Flag.DwarfLocationLists = &Ctxt.Flag_locationlists
*Flag.DwarfLocationLists = true
Flag.Dynlink = &Ctxt.Flag_dynlink
Flag.EmbedCfg = readEmbedCfg
Flag.GenDwarfInl = 2
Flag.ImportCfg = readImportCfg
Flag.LinkShared = &Ctxt.Flag_linkshared
Flag.Shared = &Ctxt.Flag_shared
Flag.WB = true
Debug.InlFuncsWithClosures = 1
if buildcfg.Experiment.Unified {
Debug.Unified = 1
}
Debug.Checkptr = -1 // so we can tell whether it is set explicitly
Flag.Cfg.ImportMap = make(map[string]string)
objabi.AddVersionFlag() // -V
registerFlags()
objabi.Flagparse(usage)
if Flag.MSan && !sys.MSanSupported(buildcfg.GOOS, buildcfg.GOARCH) {
log.Fatalf("%s/%s does not support -msan", buildcfg.GOOS, buildcfg.GOARCH)
}
if Flag.ASan && !sys.ASanSupported(buildcfg.GOOS, buildcfg.GOARCH) {
log.Fatalf("%s/%s does not support -asan", buildcfg.GOOS, buildcfg.GOARCH)
}
if Flag.Race && !sys.RaceDetectorSupported(buildcfg.GOOS, buildcfg.GOARCH) {
log.Fatalf("%s/%s does not support -race", buildcfg.GOOS, buildcfg.GOARCH)
}
if (*Flag.Shared || *Flag.Dynlink || *Flag.LinkShared) && !Ctxt.Arch.InFamily(sys.AMD64, sys.ARM, sys.ARM64, sys.I386, sys.PPC64, sys.RISCV64, sys.S390X) {
log.Fatalf("%s/%s does not support -shared", buildcfg.GOOS, buildcfg.GOARCH)
}
parseSpectre(Flag.Spectre) // left as string for RecordFlags
Ctxt.Flag_shared = Ctxt.Flag_dynlink || Ctxt.Flag_shared
Ctxt.Flag_optimize = Flag.N == 0
Ctxt.Debugasm = int(Flag.S)
Ctxt.Flag_maymorestack = Debug.MayMoreStack
Ctxt.Flag_noRefName = Debug.NoRefName != 0
if flag.NArg() < 1 {
usage()
}
if Flag.GoVersion != "" && Flag.GoVersion != runtime.Version() {
fmt.Printf("compile: version %q does not match go tool version %q\n", runtime.Version(), Flag.GoVersion)
Exit(2)
}
if *Flag.LowerP == "" {
*Flag.LowerP = obj.UnlinkablePkg
}
if Flag.LowerO == "" {
p := flag.Arg(0)
if i := strings.LastIndex(p, "/"); i >= 0 {
p = p[i+1:]
}
if runtime.GOOS == "windows" {
if i := strings.LastIndex(p, `\`); i >= 0 {
p = p[i+1:]
}
}
if i := strings.LastIndex(p, "."); i >= 0 {
p = p[:i]
}
suffix := ".o"
if Flag.Pack {
suffix = ".a"
}
Flag.LowerO = p + suffix
}
switch {
case Flag.Race && Flag.MSan:
log.Fatal("cannot use both -race and -msan")
case Flag.Race && Flag.ASan:
log.Fatal("cannot use both -race and -asan")
case Flag.MSan && Flag.ASan:
log.Fatal("cannot use both -msan and -asan")
}
if Flag.Race || Flag.MSan || Flag.ASan {
// -race, -msan and -asan imply -d=checkptr for now.
if Debug.Checkptr == -1 { // if not set explicitly
Debug.Checkptr = 1
}
}
if Flag.CompilingRuntime && Flag.N != 0 {
log.Fatal("cannot disable optimizations while compiling runtime")
}
if Flag.LowerC < 1 {
log.Fatalf("-c must be at least 1, got %d", Flag.LowerC)
}
if Flag.LowerC > 1 && !concurrentBackendAllowed() {
log.Fatalf("cannot use concurrent backend compilation with provided flags; invoked as %v", os.Args)
}
if Flag.CompilingRuntime {
// Runtime can't use -d=checkptr, at least not yet.
Debug.Checkptr = 0
// Fuzzing the runtime isn't interesting either.
Debug.Libfuzzer = 0
}
if Debug.Checkptr == -1 { // if not set explicitly
Debug.Checkptr = 0
}
// set via a -d flag
Ctxt.Debugpcln = Debug.PCTab
}
// registerFlags adds flag registrations for all the fields in Flag.
// See the comment on type CmdFlags for the rules.
func registerFlags() {
var (
boolType = reflect.TypeOf(bool(false))
intType = reflect.TypeOf(int(0))
stringType = reflect.TypeOf(string(""))
ptrBoolType = reflect.TypeOf(new(bool))
ptrIntType = reflect.TypeOf(new(int))
ptrStringType = reflect.TypeOf(new(string))
countType = reflect.TypeOf(CountFlag(0))
funcType = reflect.TypeOf((func(string))(nil))
)
v := reflect.ValueOf(&Flag).Elem()
t := v.Type()
for i := 0; i < t.NumField(); i++ {
f := t.Field(i)
if f.Name == "Cfg" {
continue
}
var name string
if len(f.Name) == 1 {
name = f.Name
} else if len(f.Name) == 6 && f.Name[:5] == "Lower" && 'A' <= f.Name[5] && f.Name[5] <= 'Z' {
name = string(rune(f.Name[5] + 'a' - 'A'))
} else {
name = strings.ToLower(f.Name)
}
if tag := f.Tag.Get("flag"); tag != "" {
name = tag
}
help := f.Tag.Get("help")
if help == "" {
panic(fmt.Sprintf("base.Flag.%s is missing help text", f.Name))
}
if k := f.Type.Kind(); (k == reflect.Ptr || k == reflect.Func) && v.Field(i).IsNil() {
panic(fmt.Sprintf("base.Flag.%s is uninitialized %v", f.Name, f.Type))
}
switch f.Type {
case boolType:
p := v.Field(i).Addr().Interface().(*bool)
flag.BoolVar(p, name, *p, help)
case intType:
p := v.Field(i).Addr().Interface().(*int)
flag.IntVar(p, name, *p, help)
case stringType:
p := v.Field(i).Addr().Interface().(*string)
flag.StringVar(p, name, *p, help)
case ptrBoolType:
p := v.Field(i).Interface().(*bool)
flag.BoolVar(p, name, *p, help)
case ptrIntType:
p := v.Field(i).Interface().(*int)
flag.IntVar(p, name, *p, help)
case ptrStringType:
p := v.Field(i).Interface().(*string)
flag.StringVar(p, name, *p, help)
case countType:
p := (*int)(v.Field(i).Addr().Interface().(*CountFlag))
objabi.Flagcount(name, help, p)
case funcType:
f := v.Field(i).Interface().(func(string))
objabi.Flagfn1(name, help, f)
default:
if val, ok := v.Field(i).Interface().(flag.Value); ok {
flag.Var(val, name, help)
} else {
panic(fmt.Sprintf("base.Flag.%s has unexpected type %s", f.Name, f.Type))
}
}
}
}
// concurrentFlagOk reports whether the current compiler flags
// are compatible with concurrent compilation.
func concurrentFlagOk() bool {
// TODO(rsc): Many of these are fine. Remove them.
return Flag.Percent == 0 &&
Flag.E == 0 &&
Flag.K == 0 &&
Flag.L == 0 &&
Flag.LowerH == 0 &&
Flag.LowerJ == 0 &&
Flag.LowerM == 0 &&
Flag.LowerR == 0
}
func concurrentBackendAllowed() bool {
if !concurrentFlagOk() {
return false
}
// Debug.S by itself is ok, because all printing occurs
// while writing the object file, and that is non-concurrent.
// Adding Debug_vlog, however, causes Debug.S to also print
// while flushing the plist, which happens concurrently.
if Ctxt.Debugvlog || Debug.Any || Flag.Live > 0 {
return false
}
// TODO: Test and delete this condition.
if buildcfg.Experiment.FieldTrack {
return false
}
// TODO: fix races and enable the following flags
if Ctxt.Flag_dynlink || Flag.Race {
return false
}
return true
}
func addImportDir(dir string) {
if dir != "" {
Flag.Cfg.ImportDirs = append(Flag.Cfg.ImportDirs, dir)
}
}
func readImportCfg(file string) {
if Flag.Cfg.ImportMap == nil {
Flag.Cfg.ImportMap = make(map[string]string)
}
Flag.Cfg.PackageFile = map[string]string{}
data, err := ioutil.ReadFile(file)
if err != nil {
log.Fatalf("-importcfg: %v", err)
}
for lineNum, line := range strings.Split(string(data), "\n") {
lineNum++ // 1-based
line = strings.TrimSpace(line)
if line == "" || strings.HasPrefix(line, "#") {
continue
}
var verb, args string
if i := strings.Index(line, " "); i < 0 {
verb = line
} else {
verb, args = line[:i], strings.TrimSpace(line[i+1:])
}
var before, after string
if i := strings.Index(args, "="); i >= 0 {
before, after = args[:i], args[i+1:]
}
switch verb {
default:
log.Fatalf("%s:%d: unknown directive %q", file, lineNum, verb)
case "importmap":
if before == "" || after == "" {
log.Fatalf(`%s:%d: invalid importmap: syntax is "importmap old=new"`, file, lineNum)
}
Flag.Cfg.ImportMap[before] = after
case "packagefile":
if before == "" || after == "" {
log.Fatalf(`%s:%d: invalid packagefile: syntax is "packagefile path=filename"`, file, lineNum)
}
Flag.Cfg.PackageFile[before] = after
}
}
}
func readEmbedCfg(file string) {
data, err := ioutil.ReadFile(file)
if err != nil {
log.Fatalf("-embedcfg: %v", err)
}
if err := json.Unmarshal(data, &Flag.Cfg.Embed); err != nil {
log.Fatalf("%s: %v", file, err)
}
if Flag.Cfg.Embed.Patterns == nil {
log.Fatalf("%s: invalid embedcfg: missing Patterns", file)
}
if Flag.Cfg.Embed.Files == nil {
log.Fatalf("%s: invalid embedcfg: missing Files", file)
}
}
// parseSpectre parses the spectre configuration from the string s.
func parseSpectre(s string) {
for _, f := range strings.Split(s, ",") {
f = strings.TrimSpace(f)
switch f {
default:
log.Fatalf("unknown setting -spectre=%s", f)
case "":
// nothing
case "all":
Flag.Cfg.SpectreIndex = true
Ctxt.Retpoline = true
case "index":
Flag.Cfg.SpectreIndex = true
case "ret":
Ctxt.Retpoline = true
}
}
if Flag.Cfg.SpectreIndex {
switch buildcfg.GOARCH {
case "amd64":
// ok
default:
log.Fatalf("GOARCH=%s does not support -spectre=index", buildcfg.GOARCH)
}
}
}
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