The simple answer is to use strtoul() instead. The longer answer is that even if all you needed was signed 32 bit integers or were happy with 31 bits for unsigned, the atoi() function is a poor fit for what you appear to be doing. As you have already noted, the atoi() function converts a … Read more
18,446,744,073,709,551,615 This number mentioned, 18,446,744,073,709,551,615, is actually 2^64 − 1. The important thing here is that 2^64-1 is essentially 0-based 2^64. The first digit of an unsigned integer is 0, not 1. So if the maximum value is 1, it has two possible values: 0, or 1 (2). Let’s look at 2^64 – 1 in … Read more
Because the integer overflows. When it overflows, the next value is Integer.MIN_VALUE. Relevant JLS If an integer addition overflows, then the result is the low-order bits of the mathematical sum as represented in some sufficiently large two’s-complement format. If overflow occurs, then the sign of the result is not the same as the sign of … Read more
As DK. points out, you don’t want wrapping semantics at the integer level: fn main() { let idx: usize = 0; let len = 10; let next_idx = idx.wrapping_sub(1) % len; println!(“{}”, next_idx) // Prints 5!!! } Instead, you want to use modulo logic to wrap around: let next_idx = (idx + len – 1) … Read more
I don’t know about studies and statistics, but yes, there are definitely optimizations taking this into account that compilers actually do. And yes, they are very important (tldr loop vectorization for example). Besides the compiler optimizations, there is another aspect to be taken into account. With UB you get C/C++ signed integers to behave arithmetically … Read more
In C#, it was a question of performance. Specifically, out-of-box benchmarking. When C# was new, Microsoft was hoping a lot of C++ developers would switch to it. They knew that many C++ folks thought of C++ as being fast, especially faster than languages that “wasted” time on automatic memory management and the like. Both potential … Read more
Math.addExact throws exception on overflow Since Java 8 there is a set of methods in the Math class: toIntExact(long) addExact(int,int) subtractExact(int,int) multiplyExact(int,int) …and versions for long as well. Each of these methods throws ArithmeticException if overflow happens. Otherwise they return the proper result if it fits within the range. Example of addition: int x = … Read more
This is not a bug. int.MinValue * -1 is 1 greater than int.MaxValue can hold. Thus, the number wraps around back to int.MinValue. This is basically caused by an integer overflow. Int32.MinValue: The value of this constant is -2,147,483,648 Int32.MaxValue: The value of this constant is 2,147,483,647 So, -2,147,483,648 * -1 = 2,147,483,648 which is … Read more
You misunderstand the reason for undefined behavior. The reason is not memory corruption around the integer – it will always occupy the same size which integers occupy – but the underlying arithmetics. Since signed integers are not required to be encoded in 2’s complement, there can not be specific guidance on what is going to … Read more
XOR will never go out of bounds because it combines bits and doesn’t create new bits where no bits were set before. The result 5 is correct. Look at the binary representation of your value and the XOR result 10 00001010 20 00010100 30 00011110 5 00000101 20 00010100 10 00001010 30 00011110 ————– 00000101 … Read more