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Best way to detect integer overflow in C/C++

Oftentimes when I’ve coded something in C++ using large numbers I can’t tell when overflow is occurring, even if I am using something like a long long or other 64-bit data type. Is there an effective way to detect when overflow is occurring than witnessing erroneous values?

Answer 1

There may not be much that you would get from standard C++:

5 Expressions

4 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. [ Note: most existing
implementations of C++ ignore integer overflows. Treatment of division
by zero, forming a remainder using a zero divisor, and all floating
point exceptions vary among machines, and is usually adjustable by a
library function. —end note ]

Your best bet is to probably use the standard fixed width integer types defined in <cstdint> such as uint32_t.

Take a look at the <cerrno> header too for error codes such as EOVERFLOW. There are then the overflow_error/underflow_error classes from <stdexcept>.