enormous amount of work.

Cgo takes a different approach. It determines the meaning of C
identifiers not by parsing C code but by feeding carefully constructed
programs into the system C compiler and interpreting the generated
error messages, debug information, and object files. In practice,
parsing these is significantly less work and more robust than parsing
C source.

Using `panicnil=1` restores the behavior of Go 1.20 and earlier.

When compiling a work module or workspace that declares
an older Go version, the Go toolchain amends its defaults
to match that older Go version as closely as possible.
For example, when a Go 1.21 toolchain compiles a program,
if the work module's `go.mod` or the workspace's `go.work`
says `go` `1.20`, then the program defaults to `panicnil=1`,
matching Go 1.20 instead of Go 1.21.

//	{
//		outcode(int($1), &$2, int($4.Reg), &$6);
//	}
	ADDD	F1, F2, F3

//	LFCMP freg ',' freg
//	{
//		outcode(int($1), &$2, 0, &$4);
//	}
	CMPEQD	F1, F2


//
// WORD
//
	WORD	$1	// 00000001
	NOOP		// 00000000
	SYNC		// 0000000f

//
// NOP
//
//	LNOP comma // asm doesn't support the trailing comma.
//	{
//		outcode(int($1), &nullgen, 0, &nullgen);
//	}

		nr, nbytes, err := buf.ReadRune()
		if nr != r || nbytes != size || err != nil {
			t.Fatalf("ReadRune(%U) got %U,%d not %U,%d (err=%s)", r, nr, nbytes, r, size, err)
		}
	}

	// Check that UnreadRune works
	buf.Reset()

	// check at EOF
	if err := buf.UnreadRune(); err == nil {
		t.Fatal("UnreadRune at EOF: got no error")
	}
	if _, _, err := buf.ReadRune(); err == nil {

type Buffer struct {
	buf      []byte // contents are the bytes buf[off : len(buf)]
	off      int    // read at &buf[off], write at &buf[len(buf)]
	lastRead readOp // last read operation, so that Unread* can work correctly.
}

// The readOp constants describe the last action performed on
// the buffer, so that UnreadRune and UnreadByte can check for
// invalid usage. opReadRuneX constants are chosen such that

				err = ErrChecksum
			}
		}
	}
	r.err = err
	return
}

func (r *checksumReader) Close() error { return r.rc.Close() }

// findBodyOffset does the minimum work to verify the file has a header
// and returns the file body offset.
func (f *File) findBodyOffset() (int64, error) {
	var buf [fileHeaderLen]byte
	if _, err := f.zipr.ReadAt(buf[:], f.headerOffset); err != nil {

			Format:   FormatUSTAR,
		}},
	}, {
		// Generated by Go, works on BSD tar v3.1.2 and GNU tar v.1.27.1.
		file: "testdata/gnu-nil-sparse-data.tar",
		headers: []*Header{{
			Name:     "sparse.db",
			Typeflag: TypeGNUSparse,
			Size:     1000,
			ModTime:  time.Unix(0, 0),
			Format:   FormatGNU,
		}},
	}, {
		// Generated by Go, works on BSD tar v3.1.2 and GNU tar v.1.27.1.

</p>

<p>
This program starts a goroutine for every entry in the work list, but the
goroutines coordinate using the <code>limit</code> channel to ensure
that at most three are running work functions at a time.
</p>

<pre>
var limit = make(chan int, 3)

func main() {
	for _, w := range work {
		go func(w func()) {
			limit &lt;- 1
			w()
			&lt;-limit
		}(w)
	}

	case "s390x":
		return archS390x()
	case "wasm":
		return archWasm()
	}
	return nil
}

func jumpX86(word string) bool {
	return word[0] == 'J' || word == "CALL" || strings.HasPrefix(word, "LOOP") || word == "XBEGIN"
}

func jumpRISCV(word string) bool {
	switch word {
	case "BEQ", "BEQZ", "BGE", "BGEU", "BGEZ", "BGT", "BGTU", "BGTZ", "BLE", "BLEU", "BLEZ",

		if !isSpace(r) {
			break
		}
	}
	// Scan until space, marking end of word.
	for width, i := 0, start; i < len(data); i += width {
		var r rune
		r, width = utf8.DecodeRune(data[i:])
		if isSpace(r) {
			return i + width, data[start:i], nil
		}
	}
	// If we're at EOF, we have a final, non-empty, non-terminated word. Return it.
	if atEOF && len(data) > start {
		return len(data), data[start:], nil
	}