One of the frameworks I use optionally supports a commercial library. If the library is present it enables support, if it isn't it just compiles without it. Th

One of the frameworks I use optionally supports a commercial library. If the library is present it enables support, if it isn't it just compiles without it. This is a nice feature since it avoids a lot of manual configuration. The downside is that support fails silently if the library is missing - since that is the expected case for most users.