present to create such a binary.

Most builds both compile source code and invoke the linker to create a
binary. When cgo is involved, the compile step already requires gcc, so
it is not problematic for the link step to require gcc too.

An important exception is builds using a pre-compiled copy of the
standard library. In particular, package net uses cgo on most systems,

	"strings"
	"testing"
	"unsafe"
)

// Test that the stack can be unwound through a call out and call back
// into Go.
func testCallbackCallersSEH(t *testing.T) {
	testenv.SkipIfOptimizationOff(t) // This test requires inlining.
	if runtime.Compiler != "gc" {
		// The exact function names are not going to be the same.
		t.Skip("skipping for non-gc toolchain")
	}
	if runtime.GOARCH != "amd64" {

		return false
	}

	size := b.uint64()
	if size != directory64EndLen-12 {
		t.Errorf("expected length of %d, got %d", directory64EndLen-12, size)
	}
	return true
}

// Zip64 is required if the total size of the records is uint32max.
func TestZip64LargeDirectory(t *testing.T) {
	if runtime.GOARCH == "wasm" {
		t.Skip("too slow on wasm")
	}
	if testing.Short() {
		t.Skip("skipping in short mode")

		if r < 0x20 || r > 0x7d || r == 0x5c {
			if !utf8.ValidRune(r) || (r == utf8.RuneError && size == 1) {
				return false, false
			}
			require = true
		}
	}
	return true, require
}

// prepare performs the bookkeeping operations required at the start of
// CreateHeader and CreateRaw.
func (w *Writer) prepare(fh *FileHeader) error {
	if w.last != nil && !w.last.closed {

		// OK
	default:
		p.errorf("DATA value must be an immediate constant or address")
		return
	}

	// The addresses must not overlap. Easiest test: require monotonicity.
	if lastAddr, ok := p.dataAddr[name]; ok && nameAddr.Offset < lastAddr {
		p.errorf("overlapping DATA entry for %s", name)
		return
	}
	p.dataAddr[name] = nameAddr.Offset + int64(sz)

			required: []string{"B", "D"},
			ok:       false,
			out:      "+A\n+C\n+E\n+F\n",
		},
		{
			name:     "feature removed",
			features: []string{"C", "A"},
			required: []string{"A", "B", "C"},
			ok:       false,
			out:      "-B\n",
		},
		{
			name:      "exception removal",
			features:  []string{"A", "C"},
			required:  []string{"A", "B", "C"},

				Modified: time.Date(2011, 12, 8, 10, 6, 8, 0, timeZone(0)),
				Mode:     0444,
			},
		},
	},
	{
		// created by Go, before we wrote the "optional" data
		// descriptor signatures (which are required by macOS).
		// Use obscured file to avoid Apple’s notarization service
		// rejecting the toolchain due to an inability to unzip this archive.
		// See golang.org/issue/34986
		Name:     "go-no-datadesc-sig.zip.base64",

	// To use sub-second resolution, specify the Format as PAX.
	ModTime    time.Time // Modification time
	AccessTime time.Time // Access time (requires either PAX or GNU support)
	ChangeTime time.Time // Change time (requires either PAX or GNU support)

	Devmajor int64 // Major device number (valid for TypeChar or TypeBlock)
	Devminor int64 // Minor device number (valid for TypeChar or TypeBlock)

			features = append(features, f2)
		}
	}

	bw := bufio.NewWriter(os.Stdout)
	defer bw.Flush()

	var required []string
	for _, file := range checkFiles {
		required = append(required, fileFeatures(file, needApproval(file))...)
	}
	for _, file := range nextFiles {
		required = append(required, fileFeatures(file, true)...)
	}
	exception := fileFeatures(filepath.Join(testenv.GOROOT(t), "api/except.txt"), false)

	return paxHdrs, nil
}

// readHeader reads the next block header and assumes that the underlying reader
// is already aligned to a block boundary. It returns the raw block of the
// header in case further processing is required.
//
// The err will be set to io.EOF only when one of the following occurs:
//   - Exactly 0 bytes are read and EOF is hit.
//   - Exactly 1 block of zeros is read and EOF is hit.