go flags 源码
golang flags 代码
文件路径：/src/cmd/asm/internal/flags/flags.go
// Copyright 2015 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 flags implements top-level flags and the usage message for the assembler.
package flags
import (
"cmd/internal/obj"
"cmd/internal/objabi"
"flag"
"fmt"
"os"
"path/filepath"
"strings"
)
var (
Debug = flag.Bool("debug", false, "dump instructions as they are parsed")
OutputFile = flag.String("o", "", "output file; default foo.o for /a/b/c/foo.s as first argument")
TrimPath = flag.String("trimpath", "", "remove prefix from recorded source file paths")
Shared = flag.Bool("shared", false, "generate code that can be linked into a shared library")
Dynlink = flag.Bool("dynlink", false, "support references to Go symbols defined in other shared libraries")
Linkshared = flag.Bool("linkshared", false, "generate code that will be linked against Go shared libraries")
AllErrors = flag.Bool("e", false, "no limit on number of errors reported")
SymABIs = flag.Bool("gensymabis", false, "write symbol ABI information to output file, don't assemble")
Importpath = flag.String("p", obj.UnlinkablePkg, "set expected package import to path")
Spectre = flag.String("spectre", "", "enable spectre mitigations in `list` (all, ret)")
CompilingRuntime = flag.Bool("compiling-runtime", false, "source to be compiled is part of the Go runtime")
)
var DebugFlags struct {
MayMoreStack string `help:"call named function before all stack growth checks"`
PCTab string `help:"print named pc-value table\nOne of: pctospadj, pctofile, pctoline, pctoinline, pctopcdata"`
}
var (
D MultiFlag
I MultiFlag
PrintOut int
DebugV bool
)
func init() {
flag.Var(&D, "D", "predefined symbol with optional simple value -D=identifier=value; can be set multiple times")
flag.Var(&I, "I", "include directory; can be set multiple times")
flag.BoolVar(&DebugV, "v", false, "print debug output")
flag.Var(objabi.NewDebugFlag(&DebugFlags, nil), "d", "enable debugging settings; try -d help")
objabi.AddVersionFlag() // -V
objabi.Flagcount("S", "print assembly and machine code", &PrintOut)
}
// MultiFlag allows setting a value multiple times to collect a list, as in -I=dir1 -I=dir2.
type MultiFlag []string
func (m *MultiFlag) String() string {
if len(*m) == 0 {
return ""
}
return fmt.Sprint(*m)
}
func (m *MultiFlag) Set(val string) error {
(*m) = append(*m, val)
return nil
}
func Usage() {
fmt.Fprintf(os.Stderr, "usage: asm [options] file.s ...\n")
fmt.Fprintf(os.Stderr, "Flags:\n")
flag.PrintDefaults()
os.Exit(2)
}
func Parse() {
flag.Usage = Usage
flag.Parse()
if flag.NArg() == 0 {
flag.Usage()
}
// Flag refinement.
if *OutputFile == "" {
if flag.NArg() != 1 {
flag.Usage()
}
input := filepath.Base(flag.Arg(0))
if strings.HasSuffix(input, ".s") {
input = input[:len(input)-2]
}
*OutputFile = fmt.Sprintf("%s.o", input)
}
}
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