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.

			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 {