Go 程序的生命周期要从执行 go 命令开始谈起。

5.1.1 Go Run 与 Go Build 命令

  • 设置具体的指令
  • go run —> run.CmdRun
  • go build —> work.CmdBuild

// src/cmd/go/main.go
func init() {
base.Go.Commands = []*base.Command{
work.CmdBuild,
run.CmdRun,
…
}
}
func main() {
flag.Usage = base.Usage
flag.Parse()
log.SetFlags(0)

args := flag.Args()
if len(args) < 1 {
base.Usage()
}

…

// 从左至右依次解析 go 指令
BigCmdLoop:
for bigCmd := base.Go; ; {
for _, cmd := range bigCmd.Commands {
// 匹配具体的指令，args[0] 是 go 指令后紧跟的第一个参数，如 run、build。
if cmd.Name() != args[0] {
continue
}
…
// 根据指令和参数执行编译或运行
cmd.Run(cmd, args)
base.Exit()
return
}
…
}
}
TODO:
// src/cmd/go/internal/work/build.go
var CmdBuild = &base.Command{
UsageLine: “go build [-o output] [-i] [build flags] [packages]”,
Short: “compile packages and dependencies”,
Long: ...,
}
func init() {
CmdBuild.Run = runBuild
// -o 参数解析
CmdBuild.Flag.StringVar(&cfg.BuildO, “o”, “”, “output file or directory”)
…

switch build.Default.Compiler {
case “gc”, “gccgo”:
buildCompiler{}.Set(build.Default.Compiler) // gc
}
}
type buildCompiler struct{}

func (c buildCompiler) Set(value string) error {
switch value {
case “gc”:
BuildToolchain = gcToolchain{}
…
}
…

return nil
}
func runBuild(cmd *base.Command, args []string) {
BuildInit()
var b Builder
b.Init()

pkgs := load.PackagesForBuild(args)
…

depMode := ModeBuild
if cfg.BuildI {
depMode = ModeInstall
}
…

a := &Action{Mode: “go build”}
for _, p := range pkgs {
a.Deps = append(a.Deps, b.AutoAction(ModeBuild, depMode, p))
}
…
b.Do(a)
}
type Builder struct {
WorkDir string // the temporary work directory (ends in filepath.Separator)
actionCache map[cacheKey]*Action // a cache of already-constructed actions
mkdirCache map[string]bool // a cache of created directories
flagCache map[[2]string]bool // a cache of supported compiler flags
Print func(args …interface{}) (int, error)

IsCmdList bool // running as part of go list; set p.Stale and additional fields below
NeedError bool // list needs p.Error
NeedExport bool // list needs p.Export
NeedCompiledGoFiles bool // list needs p.CompiledGoFIles

objdirSeq int // counter for NewObjdir
pkgSeq int

output sync.Mutex
scriptDir string // current directory in printed script

exec sync.Mutex
readySema chan bool
ready actionQueue

id sync.Mutex
toolIDCache map[string]string // tool name -> tool ID
buildIDCache map[string]string // file name -> build ID
}
// AutoAction returns the “right” action for go build or go install of p.
func (b Builder) AutoAction(mode, depMode BuildMode, p load.Package) *Action {
if p.Name == “main” {
return b.LinkAction(mode, depMode, p)
}
return b.CompileAction(mode, depMode, p)
}
TODO: 未完成，当前内容来源于 src/cmd/compile/README.md