ยง6.2.5, paragraph 9: A computation involving unsigned operands can never overflow, because a result that cannot be represented by the resulting unsigned integer type is reduced modulo the number that is one greater than the largest value that can be represented by the resulting type. Edit: Sorry, wrong reference, but the result is still pinned … Read more
-2147483648 is not a “number”. C++ language does not support negative literal values. -2147483648 is actually an expression: a positive literal value 2147483648 with unary – operator in front of it. Value 2147483648 is apparently too large for the positive side of int range on your platform. If type long int had greater range on … Read more
1. Detecting the overflow: x = a * b; if (a != 0 && x / a != b) { // overflow handling } Edit: Fixed division by 0 (thanks Mark!) 2. Computing the carry is quite involved. One approach is to split both operands into half-words, then apply long multiplication to the half-words: uint64_t … Read more
No, your 2nd code isn’t correct, but you are close: if you set int half = INT_MAX/2; int half1 = half + 1; the result of an addition is INT_MAX. (INT_MAX is always an odd number). So this is valid input. But in your routine you will have INT_MAX – half == half1 and you … Read more
This is due to integer overflow. When thisVal is very large and anotherVal is negative then subtracting the latter from the former yields a result that is bigger than thisVal which may overflow to the negative range.
is still overflow of these types an undefined behavior? Yes. Per Paragraph 5/4 of the C++11 Standard (regarding any expression in general): If during the evaluation of an expression, the result is not mathematically defined or not in the range of representable values for its type, the behavior is undefined. […] The fact that a … Read more
The historical reason is that most C implementations (compilers) just used whatever overflow behaviour was easiest to implement with the integer representation it used. C implementations usually used the same representation used by the CPU – so the overflow behavior followed from the integer representation used by the CPU. In practice, it is only the … Read more
If it overflows, it goes back to the minimum value and continues from there. If it underflows, it goes back to the maximum value and continues from there. You can check that beforehand as follows: public static boolean willAdditionOverflow(int left, int right) { if (right < 0 && right != Integer.MIN_VALUE) { return willSubtractionOverflow(left, -right); … Read more
How do I detect unsigned integer overflow?
Integer variables are stored as 16-bit (2-byte) numbers Office VBA Reference Long (long integer) variables are stored as signed 32-bit (4-byte) numbers Office VBA Reference So, the benefit is in reduced memory space. An Integer takes up half the memory that a Long does. Now, we are talking about 2 bytes, so it’s not going … Read more