UInt64 and "The operation overflows at compile time in checked mode" - CS0220?

Question

This feels like a stupid question, but I can't seem to see the answer. I have an UInt64, which is supposed to have a max value of UInt64.MaxValue 18446744073709551615 However, when I try to assign a modest-sized number, I get this overflow error of "The operation overflows at compile time in checked mode". If I wrap it in an "unchecked" block then it compiles, and runs as if this variable is zero: UInt64 value1 = 1073741824 * 8; // Compile error CS0220 UInt64 value2 = 8589934592; // Actual value - no error Why is this happenning?

Answer 1

I think that your compiler defaults to UInt32's for integer constants. When the compiler multiplies 1073741824 by 8, it overflows a UInt32 max value.

To fix the problem, you need to do something like put a "UL" (unsigned long) suffix at the end of constants that can overflow ... like 1073741824UL * 8UL.