Menu
What is an integer overflow error? Why do i care about such an error? What are some methods of avoiding or preventing it?
347
In languages where integer overflow can occur, you can reduce its likelihood by using larger integer types, like Java's long or C's long long int. If you need to store something even bigger, there are libraries built to handle arbitrarily large numbers.
For example, if an integer data type allows integers up to two bytes or 16 bits in length (or an unsigned number up to decimal 65,535), and two integers are to be added together that will exceed the value of 65,535, the result will be integer overflow.
In computer programming, an integer overflow occurs when an arithmetic operation attempts to create a numeric value that is outside of the range that can be represented with a given number of digits – either higher than the maximum or lower than the minimum representable value.
In general, a data type overflow error is when the data type used to store data was not large enough to hold the data. Furthermore, some data types can only store numbers up to a certain size. An overflow error will be produced, for example, if a data type is a single byte and the data to be stored is greater than 256.
Integer overflow occurs when you try to express a number that is larger than the largest number the integer type can handle.
If you try to express the number 300 in one byte, you have an integer overflow (maximum is 255). 100,000 in two bytes is also an integer overflow (65,535 is the maximum).
You need to care about it because mathematical operations won't behave as you expect. A + B doesn't actually equal the sum of A and B if you have an integer overflow.
You avoid it by not creating the condition in the first place (usually either by choosing your integer type to be large enough that you won't overflow, or by limiting user input so that an overflow doesn't occur).
186
The easiest way to explain it is with a trivial example. Imagine we have a 4 bit unsigned integer. 0 would be 0000 and 1111 would be 15. So if you increment 15 instead of getting 16 you'll circle back around to 0000 as 16 is actually 10000 and we can not represent that with less than 5 bits. Ergo overflow...
In practice the numbers are much bigger and it circles to a large negative number on overflow if the int is signed but the above is basically what happens.
Another way of looking at it is to consider it as largely the same thing that happens when the odometer in your car rolls over to zero again after hitting 999999 km/mi.
44
If you love us? You can donate to us via Paypal or buy me a coffee so we can maintain and grow! Thank you!
Donate Us With
