uint32_t x = 1;
int32_t y = 1;
x << -1; /* is undefined, so is y << -1 */
x << 32; /* is undefined, so is y << 32 */
y << 31; /* shifting 1 into sign bit is also undefined */
((int32_t) -1) << 1; /* is undefined */
((int32_t) -1) >> 1; /* is implementation-defined */