error messages, debug information, and object files. In practice,
parsing these is significantly less work and more robust than parsing
C source.

Cgo first invokes gcc -E -dM on the preamble, in order to find out
about simple #defines for constants and the like. These are recorded
for later use.

Next, cgo needs to identify the kinds for each identifier. For the
identifiers C.foo, cgo generates this C program:

	<preamble>

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

package asm

import (
	"internal/buildcfg"
	"strings"
	"testing"

	"cmd/asm/internal/arch"
	"cmd/asm/internal/lex"
	"cmd/internal/obj"
)

// A simple in-out test: Do we print what we parse?

func setArch(goarch string) (*arch.Arch, *obj.Link) {
	buildcfg.GOOS = "linux" // obj can handle this OS for all architectures.
	buildcfg.GOARCH = goarch

<p>
Slice expressions construct a substring or slice from a string, array, pointer
to array, or slice. There are two variants: a simple form that specifies a low
and high bound, and a full form that also specifies a bound on the capacity.
</p>

<h4>Simple slice expressions</h4>

<p>
For a string, array, pointer to array, or slice <code>a</code>, the primary expression
</p>

<pre>

// Copyright 2009 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 bytes

// Simple byte buffer for marshaling data.

import (
	"errors"
	"io"
	"unicode/utf8"
)

// smallBufferSize is an initial allocation minimal capacity.
const smallBufferSize = 64

//
//	_cgoIndexNN := a
//	_cgoNN := &cgoIndexNN[i] // with type conversions, if any
//
// to sb, and writes
//
//	_cgoCheckPointer(_cgoNN, _cgoIndexNN)
//
// to sbCheck, and returns true. If a is a simple variable or field reference,
// it writes
//
//	_cgoIndexNN := &a
//
// and dereferences the uses of _cgoIndexNN. Taking the address avoids
// making a copy of an array.
//

	switch *flags.Spectre {
	default:
		log.Printf("unknown setting -spectre=%s", *flags.Spectre)
		os.Exit(2)
	case "":
		// nothing
	case "index":
		// known to compiler; ignore here so people can use
		// the same list with -gcflags=-spectre=LIST and -asmflags=-spectrre=LIST
	case "all", "ret":
		ctxt.Retpoline = true
	}

	ctxt.Bso = bufio.NewWriter(os.Stdout)
	defer ctxt.Bso.Flush()

package asm

import (
	"cmd/asm/internal/lex"
	"strings"
	"testing"
	"text/scanner"
)

type exprTest struct {
	input  string
	output int64
	atEOF  bool
}

var exprTests = []exprTest{
	// Simple
	{"0", 0, true},
	{"3", 3, true},
	{"070", 8 * 7, true},
	{"0x0f", 15, true},
	{"0xFF", 255, true},
	{"9223372036854775807", 9223372036854775807, true}, // max int64
	// Unary
	{"-0", 0, true},

</p>

<h3 id="directives">Directives</h3>

<p>
The assembler uses various directives to bind text and data to symbol names.
For example, here is a simple complete function definition. The <code>TEXT</code>
directive declares the symbol <code>runtime·profileloop</code> and the instructions
that follow form the body of the function.

	}
	if err := scanner.Err(); err != nil {
		fmt.Fprintln(os.Stderr, "shouldn't see an error scanning a string")
	}
	// Output:
	// true
}

// Use a Scanner to implement a simple word-count utility by scanning the
// input as a sequence of space-delimited tokens.
func ExampleScanner_words() {
	// An artificial input source.

			s.start = 0
		}
		// Finally we can read some input. Make sure we don't get stuck with
		// a misbehaving Reader. Officially we don't need to do this, but let's
		// be extra careful: Scanner is for safe, simple jobs.
		for loop := 0; ; {
			n, err := s.r.Read(s.buf[s.end:len(s.buf)])
			if n < 0 || len(s.buf)-s.end < n {
				s.setErr(ErrBadReadCount)
				break
			}
			s.end += n
			if err != nil {