text: // Copyright 2016 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.
  
  // +build ignore
  
  // mkpost processes the output of cgo -godefs to
  // modify the generated types. It is used to clean up
  // the sys API in an architecture specific manner.
  //
  // mkpost is run after cgo -godefs; see README.md.
  package main
  
  import (
  	"bytes"
  	"fmt"
  	"go/format"
  	"io/ioutil"
  	"log"
  	"os"
  	"regexp"
  )
  
  func main() {
  	// Get the OS and architecture (using GOARCH_TARGET if it exists)
  	goos := os.Getenv("GOOS")
  	goarch := os.Getenv("GOARCH_TARGET")
  	if goarch == "" {
  		goarch = os.Getenv("GOARCH")
  	}
  	// Check that we are using the new build system if we should be.
  	if goos == "linux" && goarch != "sparc64" {
  		if os.Getenv("GOLANG_SYS_BUILD") != "docker" {
  			os.Stderr.WriteString("In the new build system, mkpost should not be called directly.\n")
  			os.Stderr.WriteString("See README.md\n")
  			os.Exit(1)
  		}
  	}
  
  	b, err := ioutil.ReadAll(os.Stdin)
  	if err != nil {
  		log.Fatal(err)
  	}
  
  	// Intentionally export __val fields in Fsid and Sigset_t
  	valRegex := regexp.MustCompile(`type (Fsid|Sigset_t) struct {(\s+)X__val(\s+\S+\s+)}`)
  	b = valRegex.ReplaceAll(b, []byte("type $1 struct {${2}Val$3}"))
  
  	// If we have empty Ptrace structs, we should delete them. Only s390x emits
  	// nonempty Ptrace structs.
  	ptraceRexexp := regexp.MustCompile(`type Ptrace((Psw|Fpregs|Per) struct {\s*})`)
  	b = ptraceRexexp.ReplaceAll(b, nil)
  
  	// Replace the control_regs union with a blank identifier for now.
  	controlRegsRegex := regexp.MustCompile(`(Control_regs)\s+\[0\]uint64`)
  	b = controlRegsRegex.ReplaceAll(b, []byte("_ [0]uint64"))
  
  	// Remove fields that are added by glibc
  	// Note that this is unstable as the identifers are private.
  	removeFieldsRegex := regexp.MustCompile(`X__glibc\S*`)
  	b = removeFieldsRegex.ReplaceAll(b, []byte("_"))
  
  	// Convert [65]int8 to [65]byte in Utsname members to simplify
  	// conversion to string; see golang.org/issue/20753
  	convertUtsnameRegex := regexp.MustCompile(`((Sys|Node|Domain)name|Release|Version|Machine)(\s+)\[(\d+)\]u?int8`)
  	b = convertUtsnameRegex.ReplaceAll(b, []byte("$1$3[$4]byte"))
  
  	// Remove spare fields (e.g. in Statx_t)
  	spareFieldsRegex := regexp.MustCompile(`X__spare\S*`)
  	b = spareFieldsRegex.ReplaceAll(b, []byte("_"))
  
  	// Remove cgo padding fields
  	removePaddingFieldsRegex := regexp.MustCompile(`Pad_cgo_\d+`)
  	b = removePaddingFieldsRegex.ReplaceAll(b, []byte("_"))
  
  	// Remove padding, hidden, or unused fields
  	removeFieldsRegex = regexp.MustCompile(`\b(X_\S+|Padding)`)
  	b = removeFieldsRegex.ReplaceAll(b, []byte("_"))
  
  	// Remove the first line of warning from cgo
  	b = b[bytes.IndexByte(b, '\n')+1:]
  	// Modify the command in the header to include:
  	//  mkpost, our own warning, and a build tag.
  	replacement := fmt.Sprintf(`$1 | go run mkpost.go
  // Code generated by the command above; see README.md. DO NOT EDIT.
  
  // +build %s,%s`, goarch, goos)
  	cgoCommandRegex := regexp.MustCompile(`(cgo -godefs .*)`)
  	b = cgoCommandRegex.ReplaceAll(b, []byte(replacement))
  
  	// gofmt
  	b, err = format.Source(b)
  	if err != nil {
  		log.Fatal(err)
  	}
  
  	os.Stdout.Write(b)
  }
  