go env
stdout GOFLAGS

# Flags listed in GOFLAGS should be safe to duplicate on the command line.
env GOFLAGS=-tags=magic
go list -tags=magic
go test -tags=magic -c -o $devnull
go vet -tags=magic

# GOFLAGS uses the same quoting rules (quoted.Split) as the rest of
# the go command env variables
env GOFLAGS='"-tags=magic wizardry"'
go list

-- foo_test.go --

const (
	magic         = "adl\x01"
	marshaledSize = len(magic) + 4
)

func (d *digest) MarshalBinary() ([]byte, error) {
	b := make([]byte, 0, marshaledSize)
	b = append(b, magic...)
	b = byteorder.BeAppendUint32(b, uint32(*d))
	return b, nil
}

func (d *digest) UnmarshalBinary(b []byte) error {
	if len(b) < len(magic) || string(b[:len(magic)]) != magic {

	// Read and decode Plan 9 magic
	var magic [4]byte
	if _, err := r.ReadAt(magic[:], 0); err != nil {
		return nil, err
	}
	_, err := parseMagic(magic[:])
	if err != nil {
		return nil, err
	}

	ph := new(prog)
	if err := binary.Read(sr, binary.BigEndian, ph); err != nil {
		return nil, err
	}

	f := &File{FileHeader: FileHeader{
		Magic:       ph.Magic,
		Bss:         ph.Bss,

	var k pthreadkey
	err := g0_pthread_key_create(&k, 0)
	if err != 0 {
		abort()
	}

	const magic = 0xc476c475c47957
	err = g0_pthread_setspecific(k, magic)
	if err != 0 {
		abort()
	}

	for i, x := range tlsbase {
		if x == magic {
			*tlsg = uintptr(i * goarch.PtrSize)
			g0_pthread_setspecific(k, 0)
			return
		}
	}
	abort()

	out = put32be(out, b.offset)
	return out
}

const blobSize = 2 * 4

type SuperBlob struct {
	magic  uint32 // magic number
	length uint32 // total length of SuperBlob
	count  uint32 // number of index entries following
	// blobs []Blob
}

func (s *SuperBlob) put(out []byte) []byte {
	out = put32be(out, s.magic)
	out = put32be(out, s.length)
	out = put32be(out, s.count)
	return out
}

// Copyright 2012 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 p1

type Magic int

type T struct {
	x interface{}
}

func (t *T) M() bool {
	_, ok := t.x.(Magic)
	return ok
}

func F(t *T) {
	println(t)

	return b, nil
}

func (d *digest) UnmarshalBinary(b []byte) error {
	if len(b) < len(magic) || string(b[:len(magic)]) != magic {
		return errors.New("crypto/md5: invalid hash state identifier")
	}
	if len(b) != marshaledSize {
		return errors.New("crypto/md5: invalid hash state size")
	}
	b = b[len(magic):]
	b, d.s[0] = consumeUint32(b)
	b, d.s[1] = consumeUint32(b)
	b, d.s[2] = consumeUint32(b)

	var frames []fakeTimeFrame
	for len(x) != 0 {
		if len(x) < 4+8+4 {
			return nil, errors.New("truncated header")
		}
		const magic = "\x00\x00PB"
		if string(x[:len(magic)]) != magic {
			return nil, errors.New("bad magic")
		}
		x = x[len(magic):]
		time := binary.BigEndian.Uint64(x)
		x = x[8:]
		dlen := binary.BigEndian.Uint32(x)
		x = x[4:]
		data := string(x[:dlen])
		x = x[dlen:]

// license that can be found in the LICENSE file.

/*
 * Plan 9 a.out constants and data structures
 */

package plan9obj

// Plan 9 Program header.
type prog struct {
	Magic uint32 /* magic number */
	Text  uint32 /* size of text segment */
	Data  uint32 /* size of initialized data */
	Bss   uint32 /* size of uninitialized data */
	Syms  uint32 /* size of symbol table */
	Entry uint32 /* entry point */

	return b, nil
}

func (d *digest) UnmarshalBinary(b []byte) error {
	if len(b) < len(magic) || string(b[:len(magic)]) != magic {
		return errors.New("crypto/sha1: invalid hash state identifier")
	}
	if len(b) != marshaledSize {
		return errors.New("crypto/sha1: invalid hash state size")
	}
	b = b[len(magic):]
	b, d.h[0] = consumeUint32(b)
	b, d.h[1] = consumeUint32(b)
	b, d.h[2] = consumeUint32(b)