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A reviewer may now recognize that the operation should also be checked for overflow. This might not have been apparent in the original, noncompliant code example. For more information, see INT00-J. Ensure that integer operations do not result in overflow.

Noncompliant Code Example (Logical Right Shift)

In this noncompliant code example, the programmer prematurely optimizes attempts to optimize code by replacing a division with a right shift.

int x = -50;
x = x + 2;
x >>>= 2;

The >>>= operator is a logical right shift; it fills the leftmost bits with zeroes, regardless of the number's original sign. After execution of this code sequence, x contains a large positive number (specifically, 0x3FFFFFF3). Using logical right shift for division produces an incorrect result when the dividend (x in this example) contains a negative value.

Noncompliant Code Example (Arithmetic Right Shift)

In this noncompliant code example, the programmer attempts to correct the previous example by using an arithmetic right shift (the >>= operator) can replace division, as shown in the following example:

int x = -50;
x = x + 2;
x >>= 2;

However, the result is less maintainable than making the division explicit. Refer to guideline NUM04-J. Use shift operators correctly for examples of sign extension with respect to the shift operatorsAfter execution of this code sequence, x contains the value -13 rather than the expected -12. Arithmetic right shift truncates its results towards negative infinity; integer division truncates towards zero.

Compliant Solution (Right Shift)

In this compliant solution, the right shift is correctly replaced by division.

int x = -50;
x += 2
x /= 4;

Noncompliant Code Example

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NUM02-EX0: Bitwise operations may be used to construct constant expressions. As a matter of style, we recommend replacing such constant expressions with the equivalent hexadecimal constants; 0x1FFFF in this case.

int limit = 1 << 17 - 1; // 2^17 - 1 = 131071

NUM02-EX1: Data that is normally treated arithmetically may be treated with bitwise operations for the purpose of serialization or deserialization. This is often required for reading or writing the data from a file or network socket, . It may also be used when reading or writing the data from a tightly packed data structure of bytes.

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