// intends to use the same 'go' as 'go generate' itself.
		// Prefer to resolve the binary from GOROOT/bin, and for consistency
		// prefer to resolve any other commands there too.
		gorootBinPath, err := cfg.LookPath(filepath.Join(cfg.GOROOTbin, path))
		if err == nil {
			path = gorootBinPath
		}
	}
	cmd := exec.Command(path, words[1:]...)
	cmd.Args[0] = words[0] // Overwrite with the original in case it was rewritten above.

		// This makes go builds work automatically on systems
		// without a C compiler installed.
		if ctxt.CgoEnabled {
			if os.Getenv("CC") == "" {
				cc := DefaultCC(ctxt.GOOS, ctxt.GOARCH)
				if _, err := LookPath(cc); err != nil {
					defaultCgoEnabled = false
				}
			}
		}
	}
	ctxt.CgoEnabled = defaultCgoEnabled
	if v := Getenv("CGO_ENABLED"); v == "0" || v == "1" {
		ctxt.CgoEnabled = v[0] == '1'
	}

type gccgoToolchain struct{}

var GccgoName, GccgoBin string
var gccgoErr error

func init() {
	GccgoName = cfg.Getenv("GCCGO")
	if GccgoName == "" {
		GccgoName = "gccgo"
	}
	GccgoBin, gccgoErr = cfg.LookPath(GccgoName)
}

func (gccgoToolchain) compiler() string {
	checkGccgoBin()
	return GccgoBin
}

func (gccgoToolchain) linker() string {
	checkGccgoBin()
	return GccgoBin
}

			}
		}
		envcmdline += joinUnambiguously(cmdline)
		sh.ShowCmd(dir, "%s", envcmdline)
		if cfg.BuildN {
			return nil, nil
		}
	}

	var buf bytes.Buffer
	path, err := cfg.LookPath(cmdline[0])
	if err != nil {
		return nil, err
	}
	cmd := exec.Command(path, cmdline[1:]...)
	if cmd.Path != "" {
		cmd.Args[0] = cmd.Path
	}
	cmd.Stdout = &buf
	cmd.Stderr = &buf

		if filepath.Ext(dlltoolpath) == "" {
			// Some compilers report slash-separated paths without extensions
			// instead of ordinary Windows paths.
			// Try to find the canonical name for the path.
			if lp, err := exec.LookPath(dlltoolpath); err == nil {
				dlltoolpath = lp
			}
		}

		args := []string{dlltoolpath, "-D", args[6], "-l", libgoname, "-d", "libgo.def"}

		if filepath.Ext(dlltoolpath) == "" {

// If it cannot find it, returns cmd.
func findExe(cmd string, paths []string) (string, bool) {
	for _, p := range paths {
		cp := filepath.Join(p, cmd)
		if c, err := exec.LookPath(cp); err == nil {
			return c, true
		}
	}
	return cmd, false
}

// Disasm returns the assembly instructions for the specified address range
// of a binary.

		if len(fields) == 0 {
			return "", "", fmt.Errorf("%s: compilation command confusion %q", name, out)
		}
		exe = fields[0]
		if !strings.ContainsAny(exe, `/\`) {
			if lp, err := cfg.LookPath(exe); err == nil {
				exe = lp
			}
		}
		id, err = buildid.ReadFile(exe)
		if err != nil {
			return "", "", err
		}

		// If we can't find a build ID, use a hash.
		if id == "" {

	}

	// Look in PATH for the toolchain before we download one.
	// This allows custom toolchains as well as reuse of toolchains
	// already installed using go install golang.org/dl/go1.2.3@latest.
	if exe, err := cfg.LookPath(gotoolchain); err == nil {
		execGoToolchain(gotoolchain, "", exe)
	}

	// GOTOOLCHAIN=auto looks in PATH and then falls back to download.
	// GOTOOLCHAIN=path only looks in PATH.
	if pathOnly {

			fmt.Printf("range is not valid: %v\n", r)
			return nil
		}
		for p := first; p <= last; p++ {
			ph[passes[p].name] = true
		}
	}

	path, err := exec.LookPath("dot")
	if err != nil {
		fmt.Println(err)
		return nil
	}
	return &dotWriter{path: path, phases: ph}
}

func passIdxByName(name string) int {
	for i, p := range passes {

	}
	return strings.TrimSpace(string(out))
}

func cmdToRun(name string) []string {
	execScript := "go_" + goEnv("GOOS") + "_" + goEnv("GOARCH") + "_exec"
	executor, err := exec.LookPath(execScript)
	if err != nil {
		return []string{name}
	}
	return []string{executor, name}
}

// genHeader writes a C header file for the C-exported declarations found in .go
// source files in dir.
//