Int overflow on 32-bit systems

Question

This is my test function.

if -1 != cmp(2<<32, keys[2].Distance(keys[5])) {
        t.Errorf("2<<32 should be smaller")
    }

it results in the folllowing error

constant 8589934592 overflows int

Is it possible to make this work on a 32 bit system?

edit: also this is the Distance function for comparing keys

// Distance returns the distance metric in this key space
func (s *xorKeySpace) Distance(k1, k2 Key) *big.Int {
    // XOR the keys
    k3 := XOR(k1.Bytes, k2.Bytes)

    // interpret it as an integer
    dist := big.NewInt(0).SetBytes(k3)
    return dist
}

are you sure the golang version you're using is 64 bit? according to the docs on 64 bit go int should be 64 bit — Not_a_Golfer
– Not_a_Golfer, Commented Oct 3, 2014 at 19:54
I just checked on a 64 bit version of go and there's no problem with 2<<32 as an int — Not_a_Golfer
– Not_a_Golfer, Commented Oct 3, 2014 at 19:56
@sourcey Run go version , what is the output on your machine. — nos
– nos, Commented Oct 3, 2014 at 19:58
i might be on a 32 bit actually. go -v says 'go version go1.3.1 darwin/386'. Is it possible to make this work on a 32 bit system? — sourcey
– sourcey, Commented Oct 3, 2014 at 19:59
@sourcey can you modify your code to use int64 explicitly? if so - you're good to go. — Not_a_Golfer
– Not_a_Golfer, Commented Oct 3, 2014 at 20:00

OneOfOne · Accepted Answer · 2014-10-03 21:09:53Z

1

Make sure you work on an 64bit int, the best way is to ensure the size by using uint64

type Key int64 // or uint64

Assuming key is defined to be int, otherwise just change all your function signatures from int to int64.

edited Oct 3, 2014 at 21:09

answered Oct 3, 2014 at 20:00

OneOfOne

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