How to Detect Integer Overflow in Go?

Detecting Integer Overflow in Go

Integer overflow occurs when the result of an arithmetic operation exceeds the maximum or minimum value representable by the data type. In Go, integers are represented using signed or unsigned integers, with 32-bit and 64-bit being the most common.

To detect integer overflow, the "correct" way is to compare the result with the maximum or minimum value for the data type. For example, for 32-bit addition, overflow occurs if the sum of two positive integers exceeds the maximum value (2^31 - 1) or if the sum of two negative integers is less than the minimum value (-2^31).

Consider the following code:

a, b := 2147483647, 2147483647 // 32-bit integers
c := a + b

To check if c overflowed, we can compare it to the maximum 32-bit integer:

if c > math.MaxInt32 {
    // Integer overflow occurred
}

Similarly, for 64-bit addition, overflow occurs if the sum of two positive integers exceeds the maximum value (2^63 - 1) or if the sum of two negative integers is less than the minimum value (-2^63). The check would be:

if c > math.MaxInt64 {
    // Integer overflow occurred
}

An alternative approach is to use custom error handling. We can define an error variable and set it to nil if there's no overflow:

var errOverflow error

if right > 0 {
    if left > math.MaxInt32-right {
        errOverflow = errors.New("integer overflow")
    }
} else {
    if left < math.MinInt32-right {
        errOverflow = errors.New("integer overflow")
    }
}

Then, we can check the error variable after the operation:

if errOverflow != nil {
    // Integer overflow occurred
}

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