j += Index(s[start:], old)
		}
		w += copy(t[w:], s[start:j])
		w += copy(t[w:], new)
		start = j + len(old)
	}
	w += copy(t[w:], s[start:])
	return t[0:w]
}

// ReplaceAll returns a copy of the slice s with all
// non-overlapping instances of old replaced by new.
// If old is empty, it matches at the beginning of the slice
// and after each UTF-8 sequence, yielding up to k+1 replacements

	for typ, def := range typedef {
		if new := override[typ]; new != "" {
			if id, ok := def.Go.(*ast.Ident); ok {
				override[id.Name] = new
			}
		}
	}

	// Apply overrides.
	for old, new := range override {
		if id := goIdent[old]; id != nil {
			id.Name = new
		}
	}

	// Any names still using the _C syntax are not going to compile,
	// although in general we don't know whether they all made it

	f.Close()
	if err != nil {
		log.Fatal(err)
	}

	// <= go 1.7 doesn't embed the contentID or actionID, so no slash is present
	if !strings.Contains(id, "/") {
		log.Fatalf("%s: build ID is a legacy format...binary too old for this tool", file)
	}

	newID := id[:strings.LastIndex(id, "/")] + "/" + buildid.HashToString(hash)
	if len(newID) != len(id) {
		log.Fatalf("%s: build ID length mismatch %q vs %q", file, id, newID)
	}

[permitted by the Go 1 compatibility rules](/doc/go1compat).
Even so, Go provides a mechanism called GODEBUG to
reduce the impact such changes have on Go developers
using newer toolchains to compile old code.

A GODEBUG setting is a `key=value` pair
that controls the execution of certain parts of a Go program.
The environment variable `GODEBUG`
can hold a comma-separated list of these settings.

Such code should use a non-blocking receive instead.

These new behaviors are only enabled when the main Go program
is in a module with a `go.mod` `go` line using Go 1.23.0 or later.
When Go 1.23 builds older programs, the old behaviors remain in effect.
The new [GODEBUG setting](/doc/godebug) [`asynctimerchan=1`](/pkg/time/#NewTimer)
can be used to revert back to asynchronous channel behaviors

		// and also because -godefs mode still prints the AST.
		old := *r.Expr
		*r.Expr = expr

		// Record source-level edit for cgo output.
		if !r.Done {
			// Prepend a space in case the earlier code ends
			// with '/', which would give us a "//" comment.
			repl := " " + gofmtPos(expr, old.Pos())
			end := fset.Position(old.End())
			// Subtract 1 from the column if we are going to

	-gccgopkgpath path
		The -fgo-pkgpath option to be used with gccgo.
	-gccgo_define_cgoincomplete
		Define cgo.Incomplete locally rather than importing it from
		the "runtime/cgo" package. Used for old gccgo versions.
	-godefs
		Write out input file in Go syntax replacing C package
		names with real values. Used to generate files in the
		syscall package when bootstrapping a new target.
	-objdir directory

		in = in[:len(tt.in)]
		out := Replace(in, []byte(tt.old), []byte(tt.new), tt.n)
		if s := string(out); s != tt.out {
			t.Errorf("Replace(%q, %q, %q, %d) = %q, want %q", tt.in, tt.old, tt.new, tt.n, s, tt.out)
		}
		if cap(in) == cap(out) && &in[:1][0] == &out[:1][0] {
			t.Errorf("Replace(%q, %q, %q, %d) didn't copy", tt.in, tt.old, tt.new, tt.n)
		}
		if tt.n == -1 {

pkg syscall (darwin-arm64), const IP_OLD_FW_ADD = 50
pkg syscall (darwin-arm64), const IP_OLD_FW_ADD ideal-int
pkg syscall (darwin-arm64), const IP_OLD_FW_DEL = 51
pkg syscall (darwin-arm64), const IP_OLD_FW_DEL ideal-int
pkg syscall (darwin-arm64), const IP_OLD_FW_FLUSH = 52
pkg syscall (darwin-arm64), const IP_OLD_FW_FLUSH ideal-int
pkg syscall (darwin-arm64), const IP_OLD_FW_GET = 54

	if err != nil {
		t.Fatal(err)
	}
	for i, wt := range writeTests {
		testReadFile(t, src.File[i], &wt)
	}

	// make a new zip file copying the old compressed data.
	buf2 := new(bytes.Buffer)
	dst := NewWriter(buf2)
	for _, f := range src.File {
		if err := dst.Copy(f); err != nil {
			t.Fatal(err)
		}
	}
	if err := dst.Close(); err != nil {