Bitwise shifts include left shift operations of the form shift-expression << additive-expression and right shift operations of the form shift-expression >> additive-expression. The integer promotions are performed on the operands, each of which has an integer type. The type of the result is that of the promoted left operand. If the value of the right operand is negative or is greater than or equal to the width of the promoted left operand, the behavior is undefined.
In almost every case, an attempt to shift by a negative number of bits or by more bits than exist in the operand indicates a bug (logic error). This is different than overflow, where there is simply a representational deficiency (see INT32-C. Ensure that operations on signed integers do not result in overflow).
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In C99, the CHAR_BIT macro defines the number of bits for the smallest object that is not a bit-field (byte). A byte, therefore, Consequently, a byte contains CHAR_BIT bits.
Non-Compliant Code Example (Left Shift, Unsigned Type)
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