## Ports {#ports}

### Darwin {#darwin}

<!-- go.dev/issue/64207 -->
As [announced](go1.22#darwin) in the Go 1.22 release notes,
Go 1.23 requires macOS 11 Big Sur or later;
support for previous versions has been discontinued.

### Wasm {#wasm}

<!-- go.dev/issue/63718 -->
The `go_wasip1_wasm_exec` script in `GOROOT/misc/wasm` has dropped support

var (
	swigOnce sync.Once
	haveSwig bool
)

func mustHaveSwig(t *testing.T) {
	swigOnce.Do(func() {
		mustHaveSwigOnce(t)
		haveSwig = true
	})
	// The first call will skip t with a nice message. On later calls, we just skip.
	if !haveSwig {
		t.Skip("swig not found")
	}
}

func mustHaveSwigOnce(t *testing.T) {
	swig, err := exec.LookPath("swig")
	if err != nil {
		t.Skipf("swig not in PATH: %s", err)
	}

		}
	}
}

// Save various references we are going to need later.
func (f *File) saveExprs(x interface{}, context astContext) {
	switch x := x.(type) {
	case *ast.Expr:
		switch (*x).(type) {
		case *ast.SelectorExpr:
			f.saveRef(x, context)
		}
	case *ast.CallExpr:
		f.saveCall(x, context)
	}
}

// Save references to C.xxx for later processing.
func (f *File) saveRef(n *ast.Expr, context astContext) {

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>
	#line 1 "not-declared"

The expression <code>x</code> is evaluated and saved during the evaluation of the
method value; the saved copy is then used as the receiver in any calls,
which may be executed later.
</p>

<pre>
type S struct { *T }
type T int
func (t T) M() { print(t) }

t := new(T)
s := S{T: t}
f := t.M                    // receiver *t is evaluated and stored in f

	paxSize     = "size"
	paxUid      = "uid"
	paxGid      = "gid"
	paxUname    = "uname"
	paxGname    = "gname"
	paxMtime    = "mtime"
	paxAtime    = "atime"
	paxCtime    = "ctime"   // Removed from later revision of PAX spec, but was valid
	paxCharset  = "charset" // Currently unused
	paxComment  = "comment" // Currently unused

	paxSchilyXattr = "SCHILY.xattr."

// delim.
func (b *Buffer) ReadBytes(delim byte) (line []byte, err error) {
	slice, err := b.readSlice(delim)
	// return a copy of slice. The buffer's backing array may
	// be overwritten by later calls.
	line = append(line, slice...)
	return line, err
}

// readSlice is like ReadBytes but returns a reference to internal buffer data.
func (b *Buffer) readSlice(delim byte) (line []byte, err error) {

		cnt, _ := io.ReadFull(tr, []byte{0})
		if cnt > 0 && hdr.Typeflag != TypeReg {
			t.Errorf("ReadFull(...): got %d bytes, want 0 bytes", cnt)
		}
	}

	// File is crafted with 16 entries. The later 8 are identical to the first
	// 8 except that the size is set.
	if len(hdrs) != 16 {
		t.Fatalf("len(hdrs): got %d, want %d", len(hdrs), 16)
	}
	for i := 0; i < 8; i++ {
		hdr1, hdr2 := hdrs[i+0], hdrs[i+8]

		// See golang.org/issue/6563.
		pos := (*r.Expr).Pos()
		if x, ok := expr.(*ast.Ident); ok {
			expr = &ast.Ident{NamePos: pos, Name: x.Name}
		}

		// Change AST, because some later processing depends on it,
		// 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 {

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