Xojo already creates 64-bit apps for iOS. Soon, it will also create 64-bit apps for other platforms. I, for one, welcome our new 64-bit Overlords. After all, they’ll be bringing you increased performance and increased memory! Even better, there is not much you’ll have to do to create 64-bit versions of your existing Xojo apps.
UPDATE October 2015: Xojo Builds 64-bit Apps Now
At Xojo, we like to keep things simple. For many people, creating a 64-bit version of their app will involve going to the Inspector for the target OS and selecting “x86 64-bit” instead of “x86 32-bit” in the build settings and then clicking the Build button.
In all cases, this creates a separate 64-bit build of your app.
Some of your projects may use plugins. If so, you won’t be able to build that project as a 64-bit app until all the plugins it uses are first updated to 64-bit. We are working to update our plugin SDK so that plugin authors can get their plugins updated and available for testing.
Lastly, if your app uses Declares, you may find you have to update some of the data types. For example, for Cocoa apps the CGFloat type maps to Single on 32-bit systems, but Double on 64-bit systems. You may need to update Structures or Declares to account for that. You may also have to update parameters from Int32 to Integer or Ptr so that the parameter sizes change as expected when run on 32-bit and 64-bit systems.
Your app distribution is also affected a bit (pun intended) by the operating systems that you support. For OS X, you only need to make the 64-bit version available. All OS X releases currently supported by Xojo are already 64-bit only, so there is no reason to maintain a separate 32-bit app unless it has some feature that is not yet available for 32-bit apps.
For Windows, Microsoft still ships both 32-bit and 64-bit versions. So you’ll have to also have both 32-bit and 64-bit versions of your app available. Customers that are running a 64-bit version of Windows can run either the 32-bit or 64-bit versions of your app. But customers on a 32-bit version of Windows can only run a 32-bit version of your app.
On Linux, the situation is similar as both 32-bit and 64-bit versions of most distributions are commonly available. A difference is that most 64-bit distributions do not include the necessary libraries to run 32-bit apps. So your users will want to use the 32-bit version of your app on 32-bit Linux distributions and the 64-bit version of your app on 64-bit Linux distributions.
And remember, those of you with current Xojo Pro licenses get access to the Beta when it is available. If you’d like Beta access to test your apps early (and help us test as well), upgrade to Xojo Pro.