}
				case testClose:
					err := tw.Close()
					if !equalError(err, tf.wantErr) {
						t.Fatalf("test %d, Close() = %v, want %v", i, err, tf.wantErr)
					}
				default:
					t.Fatalf("test %d, unknown test operation: %T", i, tf)
				}
			}

			if v.file != "" {
				want, err := os.ReadFile(v.file)
				if err != nil {
					t.Fatalf("ReadFile() = %v, want nil", err)
				}
				got := buf.Bytes()

			}
			buf.WriteByte(']')
		}

	case *types.TypeParam:
		// Type parameter names may change, so use a placeholder instead.
		fmt.Fprintf(buf, "$%d", typ.Index())

	default:
		panic(fmt.Sprintf("unknown type %T", typ))
	}
}

func (w *Walker) writeSignature(buf *bytes.Buffer, sig *types.Signature) {
	if tparams := sig.TypeParams(); tparams != nil {
		w.writeTypeParams(buf, tparams, true)
	}

func test1435(t *testing.T) {
	if syscall.Getuid() != 0 {
		t.Skip("skipping root only test")
	}
	if testing.Short() && testenv.Builder() != "" && os.Getenv("USER") == "swarming" {
		// The Go build system's swarming user is known not to be root.
		// Unfortunately, it sometimes appears as root due the current
		// implementation of a no-network check using 'unshare -n -r'.
		// Since this test does need root to work, we need to skip it.

---
title: "Go, Backwards Compatibility, and GODEBUG"
layout: article
---

<!--
This document is kept in the Go repo, not x/website,
because it documents the full list of known GODEBUG settings,
which are tied to a specific release.
-->

## Introduction {#intro}

Go's emphasis on backwards compatibility is one of its key strengths.
There are, however, times when we cannot maintain complete compatibility.

		// to an index into the r.fileList entry that we are
		// building. They are used to mark duplicate entries.
		files := make(map[string]int)
		knownDirs := make(map[string]int)

		// dirs[name] is true if name is known to be a directory,
		// because it appears as a prefix in a path.
		dirs := make(map[string]bool)

		for _, file := range r.File {
			isDir := len(file.Name) > 0 && file.Name[len(file.Name)-1] == '/'

</p>

<pre>
const (
	AAND = obj.ABaseARM + obj.A_ARCHSPECIFIC + iota
	AEOR
	ASUB
	ARSB
	AADD
	...
</pre>

<p>
This is the list of instructions and their spellings as known to the assembler and linker for that architecture.
Each instruction begins with an initial capital <code>A</code> in this list, so <code>AAND</code>
represents the bitwise and instruction,

	switch {
	case major == "0" && (minor == "0" || minor == "1"):
		is1x0 = false
	case major == "1" && minor == "0":
		is1x0 = true
	case major != "" || minor != "":
		return nil, nil // Unknown GNU sparse PAX version
	case hdr.PAXRecords[paxGNUSparseMap] != "":
		is1x0 = false // 0.0 and 0.1 did not have explicit version records, so guess
	default:
		return nil, nil // Not a PAX format GNU sparse file.
	}

		if !strings.HasSuffix(s, "\n") {
			s += "\n"
		}
		errBuf.WriteString(s)
	}
	for _, flag := range flags {
		switch flag {
		case "dynlink":
			ctxt.Flag_dynlink = true
		default:
			t.Errorf("unknown flag %s", flag)
		}
	}
	pList.Firstpc, ok = parser.Parse()
	obj.Flushplist(ctxt, pList, nil)
	if ok && !failed {
		t.Errorf("asm: %s had no errors", file)
	}

	errors := map[string]string{}

</li>
<li>
	At most one of the type parameters has a known type argument.
	In this case, the type parameters are <i>joined</i>:
	they both stand for the same type argument.
	If neither type parameter has a known type argument yet,
	a future type argument inferred for one the type parameters
	is simultaneously inferred for both of them.
</li>
<li>
	Both type parameters have a known type argument

		p.next()
		scale = p.parseScale(p.next().String())
	}
	return r1, r2, scale, true
}

// registerShift parses an ARM/ARM64 shifted register reference and returns the encoded representation.
// There is known to be a register (current token) and a shift operator (peeked token).
func (p *Parser) registerShift(name string, prefix rune) int64 {
	if prefix != 0 {
		p.errorf("prefix %c not allowed for shifted register: $%s", prefix, name)