Re: [PATCH 1/3] gdb: add inferior_target_stack_changed observer, use it to clear auxv cache

[Tom Tromey <tom@tromey.com>]

>> It seems like overall it would be better to have the auxv cache just be
>> some member of 'inferior'.  Then these indirections and observers
>> wouldn't be needed -- the inferior could just manage it directly.

Simon> I kind of like observers, it gives the impression that things are
Simon> decoupled... but yeah in practice it just adds unnecessary layers of
Simon> indirection.

I like them depending on the situation.  For me it's sort of like
attaching a registry entry.

If there are "optional" modules that need to attach data to a core data
structure (e.g., something arch-specific attaching to an objfile) then a
registry entry makes sense.  But for things that are inherit attributes
of an object, a registry entry would be sort of absurd.

I see observers the same way.  If two modules "should be" decoupled,
like if one is a core bit of gdb and another is some thing that might be
not compiled in, or only useful in some situations, then an observer is
a good way to convey state changes.

For auxv, IIUC, it's intended to always cache this data, which is
somewhat intrinsic to the inferior and the module must track some
aspects of the inferior's lifetime.  To me this says, just make some
auxv cache object as a field of inferior and let the inferior tell it
directly.

That said I wouldn't expect a change here since it's already written.
Just wouldn't object; and I guess it's worthwhile to try to articulate
the principle for new code.

thanks,
Tom