needCSize := f.CompressedSize == ^uint32(0)
	needHeaderOffset := f.headerOffset == int64(^uint32(0))

	// Best effort to find what we need.
	// Other zip authors might not even follow the basic format,
	// and we'll just ignore the Extra content in that case.
	var modified time.Time
parseExtras:
	for extra := readBuf(f.Extra); len(extra) >= 4; { // need at least tag and size

For example, here is a simple complete function definition. The <code>TEXT</code>
directive declares the symbol <code>runtime·profileloop</code> and the instructions
that follow form the body of the function.
The last instruction in a <code>TEXT</code> block must be some sort of jump, usually a <code>RET</code> (pseudo-)instruction.

</p>

<p>
Several backslash escapes allow arbitrary values to be encoded as
ASCII text.  There are four ways to represent the integer value
as a numeric constant: <code>\x</code> followed by exactly two hexadecimal
digits; <code>\u</code> followed by exactly four hexadecimal digits;
<code>\U</code> followed by exactly eight hexadecimal digits, and a
plain backslash <code>\</code> followed by exactly three octal digits.

			a.Offset = int64(r2)
			// Nothing may follow
			return
		}
		if p.arch.Family == sys.PPC64 {
			// Special form for PPC64: (R1+R2); alias for (R1)(R2).
			if prefix != 0 || scale != 0 {
				p.errorf("illegal address mode for register+register")
				return
			}
			a.Type = obj.TYPE_MEM
			a.Scale = 0
			a.Index = r2
			// Nothing may follow.
			return
		}
	}
	if r2 != 0 {

using a '#cgo pkg-config:' directive followed by the package names.
For example:

	// #cgo pkg-config: png cairo
	// #include <png.h>
	import "C"

The default pkg-config tool may be changed by setting the PKG_CONFIG environment variable.

For security reasons, only a limited set of flags are allowed, notably -D, -U, -I, and -l.
To allow additional flags, set CGO_CFLAGS_ALLOW to a regular expression

			for _, spec := range d.Specs {
				if s, ok := spec.(*ast.ImportSpec); ok && s.Path.Value == `"C"` {
					// Replace "C" with _ "unsafe", to keep program valid.
					// (Deleting import statement or clause is not safe if it is followed
					// in the source by an explicit semicolon.)
					f.Edit.Replace(f.offset(s.Path.Pos()), f.offset(s.Path.End()), `_ "unsafe"`)
				}
			}
		}
	}

	// Accumulate pointers to uses of C.x.

pkg syscall (netbsd-arm64-cgo), const O_NOCTTY = 32768
pkg syscall (netbsd-arm64-cgo), const ONOEOT = 8
pkg syscall (netbsd-arm64-cgo), const ONOEOT ideal-int
pkg syscall (netbsd-arm64-cgo), const O_NOFOLLOW = 256
pkg syscall (netbsd-arm64-cgo), const O_NOFOLLOW ideal-int
pkg syscall (netbsd-arm64-cgo), const O_NONBLOCK = 4
pkg syscall (netbsd-arm64-cgo), const O_NOSIGPIPE = 16777216
pkg syscall (netbsd-arm64-cgo), const O_NOSIGPIPE ideal-int

		for _, k := range nameKinds {
			if strings.HasPrefix(t, k+"_") {
				return true
			}
		}
	}
	return false
}

// rewriteCalls rewrites all calls that pass pointers to check that
// they follow the rules for passing pointers between Go and C.
// This reports whether the package needs to import unsafe as _cgo_unsafe.
func (p *Package) rewriteCalls(f *File) bool {
	needsUnsafe := false

pkg syscall (linux-386), const IN_CREATE ideal-int
pkg syscall (linux-386), const IN_DELETE ideal-int
pkg syscall (linux-386), const IN_DELETE_SELF ideal-int
pkg syscall (linux-386), const IN_DONT_FOLLOW ideal-int
pkg syscall (linux-386), const IN_EXCL_UNLINK ideal-int
pkg syscall (linux-386), const IN_IGNORED ideal-int
pkg syscall (linux-386), const IN_ISDIR ideal-int

// These tests run only on linux. The code being tested is
// not OS-specific, so it does not need to be tested on all
// operating systems.

// dangerousSlice returns a slice which is immediately
// preceded and followed by a faulting page.
func dangerousSlice(t *testing.T) []byte {
	pagesize := syscall.Getpagesize()
	b, err := syscall.Mmap(0, 0, 3*pagesize, syscall.PROT_READ|syscall.PROT_WRITE, syscall.MAP_ANONYMOUS|syscall.MAP_PRIVATE)