macros

#define MAX(a, b) \
  ({ __typeof__(a) _a = (a); \
      __typeof__(b) _b = (b); \
    _a > _b ? _a : _b; })

bitfields

<code c> #define BITMASK(bit_len, bit_shift) 1)-1) « (bit_shift)) </code<

1)
(1U « (bit_len