Why Does My Go Code Experience an Overflow Error When Using Constants?

Cascading Constant Overflows in Go

When working with constants in Go, it's important to understand their type conversions to avoid potential overflows. Consider the following code snippet:

<code class="go">const (
    userid = 12345
    did = (userid &^ (0xFFFF <p>Compiling this code results in the following error:</p>
<pre class="brush:php;toolbar:false">constant -18446462598732840961 overflows int

To resolve this issue, we need to delve into the underlying type conversions that Go performs with constants.

Understanding Untyped Constants and Type Conversion

In the above code, the constant 0xFFFF

In our case, we're performing an AND operation (&) between the typed constant userid (which is an int) and the untyped constant 0xFFFF

Overflowing Integer Constants

The problem arises when we negate the untyped constant 0xFFFF

Using Int64 for Portability

To avoid this issue, we can use a larger integer type, such as int64, which has a higher range and can accommodate larger constant values.

<code class="go">const (
    userid int64 = 12345
    did = (userid &^ (0xFFFF <p>This change allows us to represent and manipulate constants within the constraints of the available integer types without encountering overflows.</p></code>

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