Index - O
| OS | GHC.Platform | 
| OSAIX | GHC.Platform | 
| OSDarwin | GHC.Platform | 
| OSDragonFly | GHC.Platform | 
| osElfTarget | GHC.Platform | 
| OSFreeBSD | GHC.Platform | 
| OSHaiku | GHC.Platform | 
| OSHurd | GHC.Platform | 
| OSKFreeBSD | GHC.Platform | 
| OSLinux | GHC.Platform | 
| osMachOTarget | GHC.Platform | 
| OSMinGW32 | GHC.Platform | 
| OSNetBSD | GHC.Platform | 
| OSOpenBSD | GHC.Platform | 
| OSQNXNTO | GHC.Platform | 
| OSSolaris2 | GHC.Platform | 
| osSubsectionsViaSymbols | GHC.Platform | 
| OSUnknown | GHC.Platform | 
| OverlappingInstances | GHC.LanguageExtensions | 
| OverloadedLabels | GHC.LanguageExtensions | 
| OverloadedLists | GHC.LanguageExtensions | 
| OverloadedStrings | GHC.LanguageExtensions |