2.2.6 A Simple Example for Integer Overflows

What is integer overflow in C?

Integer overflow occurs when an arithmetic operation results in a value exceeding the maximum representable value for a given integer type, causing wrap-around behavior.

What is the maximum value for a 32-bit signed integer (int) in C?

2,147,483,647 (INT_MAX).

What happens when you add 1 to INT_MAX in C?

It wraps around to INT_MIN (-2,147,483,648) due to two’s complement representation.

How are signed integers stored in C?

Using two’s complement, where the leftmost bit (MSB) is the sign bit (0 for positive, 1 for negative).

How do you compute the two’s complement of a negative number?

Invert all bits and add 1.

What is the binary representation of -5 in a 4-bit system using two’s complement?

1011

What is the range of values a 4-bit signed integer can represent?

-8 to 7

What is the maximum value for a 32-bit unsigned integer (unsigned int) in C?

4,294,967,295 (UINT_MAX).

What happens when you add 1 to UINT_MAX in C?

It wraps around to 0 due to modular arithmetic.

What is the difference between signed and unsigned integer overflow?

Signed overflow causes wrap-around to negative values due to two’s complement, while unsigned overflow wraps around to 0.

How can you check for integer overflow before performing an addition?

Use if (x > INT_MAX - y) before adding y to x.

How can you prevent integer overflow in C?

- Use wider data types (long long int).

• Check limits before performing operations (limits.h).

• Enable compiler warnings (gcc -Wall -Wextra).

What is the effect of gcc -Wall -Wextra when compiling a C program?

It enables additional warnings, including possible integer overflow warnings.

What is the default behavior of C when integer overflow occurs?

Undefined behavior for signed integers; predictable wrap-around for unsigned integers.