Mail.app in macOS 10.11 and earlier used to check the plugins compatibility using the SupportedPluginCompatibilityUUIDs key in the plugin’s Info.plist. For example a Mail plugin would only be compatible with macOS 10.11.6 if its Info.plist contained the following:
<key>SupportedPluginCompatibilityUUIDs</key> <array> <string>71562B89-0D90-4588-8E94-A75B701D6443</string> </array> Mail.app version 10.0 in macOS Sierra (10.12) now uses a different key to check the plugins compatibility. It now requires a key with the format Supported%ld.%ldPluginCompatibilityUUIDs where %ld.
It might be useful in some cases to know if the MacOS kernel is running in the 32-bit or 64-bit (K64) mode. This is useful for example if you write an application like ‘System Profiler’ that displays the details of the currently running system:
Obviously this post only applies to intel machines running on Snow Leopard (see my previous post ‘Intel 64-bit summary’). To simplify the code, I assume that you compiled your application with the 10.
Since people are confused regarding Intel 64-bit, here is a brief summary of what can run on which Intel processor.
To run a 64-bit application, you obviously need a 64-bit processor. All the machines that Apple currently ships have a 64-bit processor.
Only the ‘Intel Core Solo’ and ‘Intel Core Duo’ processors are 32-bit. On such machines, you won’t be able to run 64-bit apps. The ‘Intel Core 2 Duo’ and ‘Xeon’ processors are 64-bit.