Go 1.8rc3 源代码学习：cmd go

概述前言 命令行工具 go 相关的代码在 <go-src>/src/cmd/go，目录结构 <go-src>/src/cmd/go internal testdata alldocs.go go11.go go_test.go go_unix_test.go go_windows_test.go main.go mkalldocs 前言

命令行工具 go 相关的代码在 <go-src>/src/cmd/go，目录结构

<go-src>/src/cmd/go    internal    testdata    alldocs.go    go11.go    go_test.go    go_unix_test.go    go_windows_test.go    main.go    mkalldocs.sh    note_test.sh    note_test.go    vendor_test.go

main.go，入口函数

*_test.go，单元测试代码

internal，go 内部实现相关代码

internal 目录下基本上按照 go "子命令" 进行组织，可以看到常用的子命令比如 help,List,run .etc

<go-src>/src/cmd/go    internal        base        BUG        get        help        List        run        ...

main.go

main.go 是 go 命令的入口，为了优雅的支持各种 "子命令"，main.go 将各个子命令对象保存在数组里，通过遍历数组找到具体的子命令，然后调用各个子命令的 run 方法

for _,cmd := range base.Commands {    if cmd.name() == args[0] && cmd.Runnable() {        cmd.Flag.Usage = func() { cmd.Usage() }        if cmd.CustomFlags {            args = args[1:]        } else {            cmd.Flag.Parse(args[1:])            args = cmd.Flag.Args()        }        cmd.Run(cmd,args)        base.Exit()        return    }}

Command struct

A command is an implementation of a go command

type Command struct {    // Run runs the command.    // The args are the arguments after the command name.    Run func(cmd *Command,args []string)    // Usageline is the one-line usage message.    // The first word in the line is taken to be the command name.    Usageline string    // Short is the short description shown in the 'go help' output.    Short string    // Long is the long message shown in the 'go help <this-command>' output.    Long string    // Flag is a set of flags specific to this command.    Flag flag.FlagSet    // CustomFlags indicates that the command will do its own    // flag parsing.    CustomFlags bool}

go 支持的所有 Command 存放在 base package 的 Command 数组 Command，并在 main.go 的 init 函数中初始化

func init() {        base.Commands = []*base.Command{        work.CmdBuild,clean.CmdClean,doc.CmdDoc,envcmd.CmdEnv,BUG.CmdBUG,fix.CmdFix,fmtcmd.CmdFmt,generate.CmdGenerate,get.CmdGet,work.CmdInstall,List.CmdList,run.CmdRun,test.CmdTest,tool.CmdTool,version.CmdVersion,vet.CmdVet,.etc    }}

go build

build command 的相关代码在 <go-src>/src/cmd/go/internal/work/build.go，在讨论具体的流程之前，我们先来看一些和 build 相关的数据结构

toolchain interface

toolchain 接口定义了在编译过程中一些通用的方法

type toolchain interface {    // gc runs the compiler in a specific directory on a set of files    // and returns the name of the generated output file.    gc(b *Builder,p *load.Package,archive,obj string,asmhdr bool,importArgs []string,gofiles []string)   (ofile string,out []byte,err error)    // cc runs the toolchain's C compiler in a directory on a C file    // to produce an output file.    cc(b *Builder,objdir,ofile,cfile string) error    // asm runs the assembler in a specific directory on specific files    // and returns a List of named output files.    asm(b *Builder,sfiles []string) ([]string,error)    // pkgpath builds an appropriate path for a temporary package file.    Pkgpath(basedir string,p *load.Package) string    // pack runs the archive packer in a specific directory to create    // an archive from a set of object files.    // typically it is run in the object directory.    pack(b *Builder,objdir,afile string,ofiles []string) error    // ld runs the linker to create an executable starting at mainpkg.    ld(b *Builder,root *Action,out string,allactions []*Action,mainpkg string,ofiles []string) error    // ldShared runs the linker to create a shared library containing the pkgs built by toplevelactions    ldShared(b *Builder,toplevelactions []*Action,allactions []*Action) error    compiler() string    linker() string}

noToolchain goToolchain gccgoToolchain Action

An action represents a single action in the action graph
Action 结构封装了 build 过程中的一个阶段性的"动作"，Deps 字段描述它依赖哪些 Action，triggers 字段描述哪些 Action 依赖它，通过这两个字段，所有的 Action 组成一个 action graphic

type Action struct {    ...    Deps []*Action    triggers []*Action    ...}

Builder

A Builder holds global state about a build. It does not hold per-package state,because we build packages in parallel,and the builder is shared.

type Builder struct {    ...    ready     actionQueue}

总结 总结

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