ALI Files and Recompilation (GNAT Reference Manual)

#### 7.1.6 ALI Files and Recompilation ¶

- ALI files are always generated for predefined generic packages.
- Compiling a unit whose top-level name is `Ada`, `Interfaces`, or `System` as the main unit is permitted; the RM reserves these as hierarchical library-unit name prefixes, but the diagnostic is suppressed to let GNAT compile its own predefined library (`Ada.Text_IO`, `System.Storage_Elements`, etc.) as main units.