// It strips leading common prefixes (like tv_ in tv_sec, tv_usec)
// converts names to upper case, and rewrites _ into Pad_godefs_n,
// so that all fields are exported.
func godefsFields(fld []*ast.Field) {
	prefix := fieldPrefix(fld)

	// Issue 48396: check for duplicate field names.
	if prefix != "" {
		names := make(map[string]bool)
	fldLoop:
		for _, f := range fld {
			for _, n := range f.Names {
				name := n.Name