Bug#892153: Objective-C libraries (was: Bug#892153: marked as done (RFS: addresses-for-gnustep/0.4.8-3 [RC]))

[Yavor Doganov <yavor@gnu.org>]

Adam Borowski wrote:
> On Tue, Mar 06, 2018 at 08:28:17AM +0200, Yavor Doganov wrote:
> >  * Package name    : addresses-for-gnustep
> >    Version         : 0.4.8-3

> I don't understand ObjC library stuff well enough to adequately
> check these parts, but it's unlikely we'd get someone else who can
> review this... and you know what you're doing.

I'd be happy to explain the changes that raise questions.

I guess you refer to dropping the symbols files?  If so, please take a
look at lintian #749202.  If it's still unclear, let me give an
example with the smallest class in the Addresses framework:

@interface ADPublicAddressBook: ADAddressBook
{
  BOOL _readOnly;
  ADAddressBook *_book;
}

- initWithAddressBook: (ADAddressBook*) book
	     readOnly: (BOOL) ro;
@end

The symbol is just __objc_class_name_ADPublicAddressBook@Base.  Now,
imagine if a new upstream version 0.4.9 adds another instance method
-doSomething which is an API addition.  This API addition will not be
reflected in the symbols file and apps using the new -doSomething
method will still pick up the lax dependency on 0.4.6.  And as a
result will get an NSInvalidArgument exception (abort) if run with an
older version of the library.  This totally defeats the purpose of
using symbols files, which as I understand it is an enhancement of the
shlibs system to provide fine-grained dependencies.  Not only that
they are not fine-grained, they are simply wrong in this case.

If -initWithAddressBook:readOnly: is removed in a new version of the
library, that's an API/ABI break but again, it won't be reflected in
the symbols table.  In a C/C++ library you'll see a symbol
disappearing but it won't happen here.  So even the secondary reason
for using symbols files (detecting ABI breaks, although that's really
a weak test) is not applicable.

There's also the case that private classes and class categories also
get their own symbols (as there is no concept for "private" in
Objective-C, everything is exposed to the ObjC runtime).  These will
trigger spurious additions/removals of symbols when no public API is
involved at all.

> Uploaded.

Many thanks for sponsoring.