I don't know what OSX does, and having methods of a mutable class (other than -copy...) return immutable instances is unusual/unintuitive, but from a performance point of view (because character sets can consume a lot of memory) it makes complete sense for these methods to return shared/singleton instances of immutable character sets.
> > On 18 Jul 2025 at 10:00, Riccardo Mottola <riccardo.mott...@libero.it> > wrote: > > > Hi, > > Frederik Seiffert wrote: > > I had changed these return types from id to NSCharacterSet in > > https://github.com/gnustep/libs-base/pull/501, because that is what > > the implementation returns by calling „copy“ on the created set before > > returning. This matches Apple platforms both in the implementation and > > header declaration. > > Oh, missed that one. This explain why these warnings are "new" (but the > code itself is the same). > I must then check what that call does on NSMutableCharacterSet on Apple > and see if we need another subclass method or there is some > inconsistency here. > Will comment or make a PR in case. > > Riccardo > >
