extern void _cgo_panic(void *, int);
extern void _cgo_allocate(void *, int);

void
callPanic(void)
{
	struct { const char *p; } a;
	a.p = "panic from C";
	crosscall2(_cgo_panic, &a, sizeof a);
	*(int*)1 = 1;

struct_, union_, or enum_, as in C.struct_stat.

The size of any C type T is available as C.sizeof_T, as in
C.sizeof_struct_stat.

A C function may be declared in the Go file with a parameter type of
the special name _GoString_. This function may be called with an
ordinary Go string value. The string length, and a pointer to the
string contents, may be accessed by calling the C functions

	size_t _GoStringLen(_GoString_ s);

pkg go/types, type SelectionKind int
pkg go/types, type Signature struct
pkg go/types, type Sizes interface { Alignof, Offsetsof, Sizeof }
pkg go/types, type Sizes interface, Alignof(Type) int64
pkg go/types, type Sizes interface, Offsetsof([]*Var) []int64
pkg go/types, type Sizes interface, Sizeof(Type) int64
pkg go/types, type Slice struct
pkg go/types, type StdSizes struct

a <a href="#Run_time_panics">run-time panic</a> occurs.
</p>

<h3 id="Size_and_alignment_guarantees">Size and alignment guarantees</h3>

<p>
For the <a href="#Numeric_types">numeric types</a>, the following sizes are guaranteed:
</p>

<pre class="grammar">
type                                 size in bytes

byte, uint8, int8                     1
uint16, int16                         2

#include <string.h>

#include "_cgo_export.h"

void
callback(void *f)
{
	// use some stack space
	volatile char data[64*1024];

	data[0] = 0;
	goCallback(f);
        data[sizeof(data)-1] = 0;
}

void
callGoFoo(void)
{
	extern void goFoo(void);
	goFoo();
}

void
IntoC(void)
{
	BackIntoGo();
}

void
Issue1560InC(void)
{
	Issue1560FromC();
}

	var buf Buffer
	n := 0
	for r := rune(0); r < NRune; r++ {
		size := utf8.EncodeRune(b[n:], r)
		nbytes, err := buf.WriteRune(r)
		if err != nil {
			t.Fatalf("WriteRune(%U) error: %s", r, err)
		}
		if nbytes != size {
			t.Fatalf("WriteRune(%U) expected %d, got %d", r, size, nbytes)
		}
		n += size
	}
	b = b[0:n]

	// Check the resulting bytes
	if !Equal(buf.Bytes(), b) {

		t.Errorf("%v", err)
		return
	}

	// For very large files, just check that the size is correct.
	// The content is expected to be all zeros.
	// Don't bother uncompressing: too big.
	if ft.Content == nil && ft.File == "" && ft.Size > 0 {
		if size != ft.Size {
			t.Errorf("%v: uncompressed size %#x, want %#x", ft.Name, size, ft.Size)
		}
		r.Close()
		return
	}

	var b bytes.Buffer

		{"DATA", "0", "expect two operands for DATA"},
		{"DATA", "(0), 1", "expect /size for DATA argument"},
		{"DATA", "@B(SB)/4,0", "expected '(', found B"}, // Issue 23580.
		{"DATA", "·A(SB)/4,0", "DATA value must be an immediate constant or address"},
		{"DATA", "·B(SB)/4,$0", ""},
		{"DATA", "·C(SB)/5,$0", "bad int size for DATA argument: 5"},
		{"DATA", "·D(SB)/5,$0.0", "bad float size for DATA argument: 5"},

	if got, want := NewReader(nil).Size(), DefaultBufSize; got != want {
		t.Errorf("NewReader's Reader.Size = %d; want %d", got, want)
	}
	if got, want := NewReaderSize(nil, 1234).Size(), 1234; got != want {
		t.Errorf("NewReaderSize's Reader.Size = %d; want %d", got, want)
	}
}

func TestWriterSize(t *testing.T) {
	if got, want := NewWriter(nil).Size(), DefaultBufSize; got != want {

import (
	"unicode/utf8"
)

var IsSpace = isSpace

const DefaultBufSize = defaultBufSize

func (s *Scanner) MaxTokenSize(n int) {
	if n < utf8.UTFMax || n > 1e9 {
		panic("bad max token size")
	}
	if n < len(s.buf) {
		s.buf = make([]byte, n)
	}
	s.maxTokenSize = n
}

// ErrOrEOF is like Err, but returns EOF. Used to test a corner case.
func (s *Scanner) ErrOrEOF() error {
	return s.err