When you try to assign a value larger than the maximum possible integer for a given data type, an integer overflow occurs. This means the value exceeds the range that can be represented within the fixed number of bits allocated for that integer type.
What happens during integer overflow?
- Wraparound (Modulo behavior):
For unsigned integers, the value typically wraps around using modulo arithmetic. For example, if the maximum value for a 32-bit unsigned integer is 4,294,967,295, adding 1 results in 0. This is because the value "wraps around" to the beginning of the range
- Signed integer overflow:
For signed integers, overflow usually causes the value to wrap from the maximum positive value to the minimum negative value. For instance, in Java, incrementingInteger.MAX_VALUE(2,147,483,647) by 1 results in-2,147,483,648due to overflow
. This happens because the most significant bit is used as the sign bit in signed integers.
- Unexpected or undefined behavior:
Overflow can lead to unpredictable program behavior such as data corruption, incorrect calculations, or program crashes. In some cases, it can cause infinite loops or system instability
- Security implications:
Integer overflow can be exploited by attackers to cause buffer overflows, leading to unauthorized access or arbitrary code execution. This makes integer overflow a serious security vulnerability in software
- No spillover to adjacent memory:
The overflowed value does not "spill over" into the next memory location. Instead, the value stored in the allocated memory is truncated or wrapped within its size limit, without affecting adjacent memory addresses
Summary
- Assigning a value larger than the maximum integer causes overflow.
- The stored value wraps around modulo the maximum representable value.
- Signed integers wrap into negative values after overflow.
- Overflow can cause program errors, crashes, or security vulnerabilities.
- The overflow affects only the variable’s allocated memory and does not spill over to other memory locations.
This behavior depends on the programming language and hardware, but wraparound is the most common outcome
