**Document:** N1817

**Summary**Harmonizing left-shift with C++14

It is not uncommon to see code such as:

`signed someint_t min_value = 1 << (CHAR_BIT * sizeof(someint_t));`

However, left-shifting a one bit into the sign bit is undefined behavior, despite the fact that the majority of (twos-complement) architectures handle it properly.

**Suggested Technical Corrigendum**

The result ofC++ addressed this in C++14 with DR1457 with identical wording modifications.`E1 << E2`

is`E1`

left-shifted`E2`

bit positions; vacated bits are filled with zeros. If`E1`

has an unsigned type, the value of the result is`E1 x 2`

, reduced modulo one more than the maximum value representable in the result type. If^{E2}`E1`

has a signed type and nonnegative value, and`E1 x 2`

is representable in the corresponding unsigned type of the result type, then that value, converted to the result type, is the resulting value; otherwise, the behavior is undefined.^{E2}