declarations and definitions. These may then be referred to from Go
code as though they were defined in the package "C". All names
declared in the preamble may be used, even if they start with a
lower-case letter. Exception: static variables in the preamble may
not be referenced from Go code; static functions are permitted.

See $GOROOT/cmd/cgo/internal/teststdio and $GOROOT/misc/cgo/gmp for examples. See

type (
	sparseDatas []sparseEntry
	sparseHoles []sparseEntry
)

// validateSparseEntries reports whether sp is a valid sparse map.
// It does not matter whether sp represents data fragments or hole fragments.
func validateSparseEntries(sp []sparseEntry, size int64) bool {
	// Validate all sparse entries. These are the same checks as performed by
	// the BSD tar utility.

		t.Fatal("addr2line output must have 2 lines")
	}
	funcname = f[0]
	pathAndLineNo := f[1]
	f = strings.Split(pathAndLineNo, ":")
	if runtime.GOOS == "windows" && len(f) == 3 {
		// Reattach drive letter.
		f = []string{f[0] + ":" + f[1], f[2]}
	}
	if len(f) != 2 {
		t.Fatalf("no line number found in %q", pathAndLineNo)
	}
	return funcname, f[0], f[1]
}

const symName = "cmd/addr2line.TestAddr2Line"

	AND	$1, ZR                              // fb0340b2ff031b8a
	ANDW	$1, ZR                              // fb030032ff031b0a
	// TODO: this could have better encoding
	ANDW	$-1, R10                            // 1b0080124a011b0a
	AND	$8, R0, RSP                         // 1f007d92
	ORR	$8, R0, RSP                         // 1f007db2

	ADD $-8589869055, R5            // 3fe0fffe63ff00017bff83e463ff00017cbf2a14 or 0602000138a50001

	//TODO: this compiles to add r5,r6,r0. It should be addi r5,r6,0.
	//      this is OK since r0 == $0, but the latter is preferred.
	ADD $0, R6, R5             	// 7ca60214

        //TODO: the assembler rewrites these into ADDIS $19, R5, Rx and ADD $-10617, Rx, Rx, but the test only sees the first ADDIS

<p>
The name <code>SP</code> always refers to the virtual stack pointer described earlier.
For the hardware register, use <code>R13</code>.
</p>

<p>
Condition code syntax is to append a period and the one- or two-letter code to the instruction,
as in <code>MOVW.EQ</code>.
Multiple codes may be appended: <code>MOVM.IA.W</code>.
The order of the code modifiers is irrelevant.
</p>

<p>
Addressing modes:
</p>

<ul>

		}
		if s[i+1] == c1 && Equal(s[i:i+n], sep) {
			return i
		}
		i++
		fails++
		if fails >= 4+i>>4 && i < t {
			// Give up on IndexByte, it isn't skipping ahead
			// far enough to be better than Rabin-Karp.
			// Experiments (using IndexPeriodic) suggest
			// the cutover is about 16 byte skips.
			// TODO: if large prefixes of sep are matching
			// we should cutover at even larger average skips,

	default:
		p.errorf("register list not supported on this architecture")
	}
}

func (p *Parser) registerListX86(a *obj.Addr) {
	// Accept only [RegA-RegB] syntax.
	// Don't use p.get() to provide better error messages.

	loName := p.next().String()
	lo, ok := p.arch.Register[loName]
	if !ok {
		if loName == "EOF" {
			p.errorf("register list: expected ']', found EOF")
		} else {

unicode_letter = /* a Unicode code point categorized as "Letter" */ .
unicode_digit  = /* a Unicode code point categorized as "Number, decimal digit" */ .
</pre>

<p>
In <a href="https://www.unicode.org/versions/Unicode8.0.0/">The Unicode Standard 8.0</a>,
Section 4.5 "General Category" defines a set of character categories.
Go treats all characters in any of the Letter categories Lu, Ll, Lt, Lm, or Lo

// It returns a [Writer] to which the file contents should be written.
// The file contents will be compressed using the [Deflate] method.
// The name must be a relative path: it must not start with a drive
// letter (e.g. C:) or leading slash, and only forward slashes are
// allowed. To create a directory instead of a file, add a trailing
// slash to the name.
// The file's contents must be written to the [io.Writer] before the next