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Re: Which ObjC2.0 features are missing in the latest GCC?


From: Umberto Cerrato
Subject: Re: Which ObjC2.0 features are missing in the latest GCC?
Date: Tue, 26 Nov 2019 14:49:21 +0000

I would like to get involved in these choices... like name ideas etc. please 
make something more “open” (f.e. a poll/Doodle ...)

Also... you write a lot! Here on the mailing list.
IDK how you do to keep yourself up-to-date...

This is just a feedback from a new-subscriber point of view... I do not know if 
you can help me with this.

Best

> Il giorno 26 nov 2019, alle ore 15:43, Pirmin Braun <address@hidden> ha 
> scritto:
> 
> ah, what's in a name...
> 
> "Next" and "step" are from NeXTSTEP, an ancient Operating System from 1987, 
> running on stylish 680030 NeXT Hardware like the NeXTStation, no one knows 
> today
> 
> "GNU" is from GNU which is Not Unix so you get asked "what's so bad about 
> Unix?"
> 
> what will we have?
> 
> a modern Objective-C Ecosystem, comparable to iOS and XCode from Apple, the 
> well known market leader, blah blah
> 
> making it a perfect porting target for iOS applications to run on any cheap 
> laptop with any Linux distribution 
> 
> or for rapid development of stunning server applications and deployment on 
> all sorts of *ix operating systems and covering all hardware from the 
> Raspberry PI up to the AWS or Azure server farms
> 
> now, how to put this in a word?
> 
> On Tue, 26 Nov 2019 15:15:01 +0100
> Andreas Fink <address@hidden> wrote:
> 
>> 
>> 
>>> On 26 Nov 2019, at 15:06, H. Nikolaus Schaller <address@hidden> wrote:
>>> 
>>> 
>>>> Am 26.11.2019 um 11:09 schrieb Pirmin Braun <address@hidden>:
>>>> 
>>>> I'd suggest a fork, i.e. "Gnustep2" with LLVM, Clang, libobjc2 
>>> 
>>> just came to my mind: ClangSTEP?
>> 
>> 
>> what a tong breaker. FreeStep sounds better to me :)
>> Drop the "GNU" and break free.
>> 
>> 
>>> 
>>>> 
>>>> On Tue, 26 Nov 2019 04:55:43 -0500
>>>> Gregory Casamento <address@hidden> wrote:
>>>> 
>>>>> I'd really like some resolution on this topic.   There seem to be a lot of
>>>>> reasons for and against.
>>>>> 
>>>>> GC
>>>>> 
>>>>> On Mon, Nov 25, 2019 at 1:04 PM David Chisnall <address@hidden>
>>>>> wrote:
>>>>> 
>>>>>>> On 25 Nov 2019, at 14:07, H. Nikolaus Schaller <address@hidden> wrote:
>>>>>>> I am not sure that this is the only way to implement it.
>>>>>>> 
>>>>>>> First of all the callMethodOn returns some block which is a data
>>>>>> structure knowing that it should take the parameter x and do some 
>>>>>> function.
>>>>>>> Let's call it NSBlock. NSBlock can be an ordinary object like any other
>>>>>> so that it can follow the same memory management rules as used otherwise.
>>>>>> 
>>>>>> That’s shifting the goalposts somewhat.  It is not news that objects and
>>>>>> closures are equivalent.  Smalltalk implemented blocks as BlockClosure
>>>>>> objects, Ian Piumarta’s Composite Object-Lambda Architecture, and C++
>>>>>> lambdas (which are just shorthand for C++ objects that implement
>>>>>> `operator()`).  You can always express anything that uses blocks with
>>>>>> objects.
>>>>>> 
>>>>>> There are two issues:
>>>>>> 
>>>>>> 1. If you want to be compatible with existing APIs that use blocks, you
>>>>>> need to be ABI compatible with blocks.
>>>>>> 2. The reason that most languages that have objects also have blocks is
>>>>>> that the shorthand syntax is very convenient.
>>>>>> 
>>>>>> The following are roughly equivalent:
>>>>>> 
>>>>>> ```
>>>>>> @interface Delegate : NSObject
>>>>>> - (void)invoke;
>>>>>> - (instancetype)initWithCapture: (id)someObject;
>>>>>> @end
>>>>>> 
>>>>>> @implementation Delegate
>>>>>> {
>>>>>>      @private
>>>>>>      id obj;
>>>>>> }
>>>>>> - (instancetype)initWithCapture: (id)someObject
>>>>>> {
>>>>>>      if ((self = [super init]) == nil) return nil;
>>>>>>      obj = [someObject retain];
>>>>>>      return self;
>>>>>> }
>>>>>> - (void)invoke
>>>>>> {
>>>>>>      [obj doSomething];
>>>>>> }
>>>>>> - (void)dealloc
>>>>>> {
>>>>>>      [obj release];
>>>>>>      [super dealloc];
>>>>>> }
>>>>>> @end
>>>>>> 
>>>>>> // At construction site:
>>>>>> 
>>>>>> [[Delegate alloc] initWithCapture: x];
>>>>>> 
>>>>>> // At use site:
>>>>>> 
>>>>>> [delegate invoke];
>>>>>> ```
>>>>>> 
>>>>>> And this, with blocks:
>>>>>> 
>>>>>> ```
>>>>>> // At construction site:
>>>>>> 
>>>>>> ^() { [x doSomething]; };
>>>>>> 
>>>>>> // At use site:
>>>>>> 
>>>>>> delegate();
>>>>>> ```
>>>>>> 
>>>>>> At use, these are similar complexity for the programmer.  At the point of
>>>>>> construction, one is one line of code (two or three if you put lambda
>>>>>> bodies on their own lines), the other is 26.  As a programmer, I don’t 
>>>>>> want
>>>>>> to write 26 lines of code for a one-line callback.
>>>>>> 
>>>>>> In C++98 you could probably template that and provide a generic class 
>>>>>> that
>>>>>> took a struct containing the captures and a C function, so you’d get a 
>>>>>> lot
>>>>>> less boilerplate.  Assuming you had fudged ARC like this (as above, this
>>>>>> code is typed into a mail client and probably doesn’t compile):
>>>>>> 
>>>>>> ```
>>>>>> template<typename T>
>>>>>> struct ObjCObjectWrapper
>>>>>> {
>>>>>>      ObjCObjectWrapper(T x) : obj(objc_retain(x)) {}
>>>>>>      ObjCObjectWrapper(const ObjCObjectWrapper &other) :
>>>>>> obj(objc_retain(other.obj) {}
>>>>>>      ObjCObjectWrapper(ObjCObjectWrapper &&other) : obj(other.obj)
>>>>>>      {
>>>>>>              other.obj = nil;
>>>>>>      }
>>>>>>      ObjCObjectWrapper()
>>>>>>      {
>>>>>>              objc_release(obj);
>>>>>>      }
>>>>>>      operator=(T x)
>>>>>>      {
>>>>>>              objc_storeStrong(&obj, x);
>>>>>>      }
>>>>>>      T operator()
>>>>>>      {
>>>>>>              return obj;
>>>>>>      }
>>>>>>      private:
>>>>>>      T obj;
>>>>>> 
>>>>>> };
>>>>>> ```
>>>>>> 
>>>>>> You could then define a generic capture structure and invoke method like
>>>>>> this:
>>>>>> 
>>>>>> ```
>>>>>> template<typename Capture, typename Ret, typename... Args>
>>>>>> struct BlockImpl
>>>>>> {
>>>>>>      using invoke_t = Ret(*)(Capture &, Args...);
>>>>>>      void operator()(Args... args)
>>>>>>      {
>>>>>>              inv(capture, std::forward<Args>(args)…);
>>>>>>      }
>>>>>>      Block(Capture &&c, invoke_t fn) : capture(c), inv(fn) {}
>>>>>>      private:
>>>>>>      Capture capture;
>>>>>>      invoke_t inv;
>>>>>> };
>>>>>> ```
>>>>>> 
>>>>>> This is then generic and you could use it as follows:
>>>>>> 
>>>>>> ```
>>>>>> struct CaptureOneObject
>>>>>> {
>>>>>>      ObjCObjectWrapper<id> o;
>>>>>> };
>>>>>> void invoke(CaptureOneObject &c)
>>>>>> {
>>>>>>      [(id)c.o doSomething];
>>>>>> }
>>>>>> // At construction site:
>>>>>> std::function<void(void)> block(BlockImpl<CaptureOneObject, void>({x},
>>>>>> invoke));
>>>>>> // At use site:
>>>>>> block();
>>>>>> ```
>>>>>> 
>>>>>> I *think* you could get the same ABI as blocks if you worked on the
>>>>>> generic templated boilerplate a bit.
>>>>>> 
>>>>>> Of course, if you were using C++ then you could also write it using
>>>>>> lambdas as:
>>>>>> 
>>>>>> ```
>>>>>> // At construction site
>>>>>> ObjCObjectWrapper<id> capture(x);
>>>>>> auto block = [=capture]() { [(id)capture.o doSomething]; };
>>>>>> // At use site:
>>>>>> block();
>>>>>> ```
>>>>>> 
>>>>>> And with this you don’t need the invoke function or the capture class.
>>>>>> Again, much less boiler plate for users, though we don’t have ABI
>>>>>> compatibility with blocks.
>>>>>> 
>>>>>> If you were using ARC and C++, then this reduces even further to:
>>>>>> 
>>>>>> ```
>>>>>> auto block = [=]() { [x doSomething]; };
>>>>>> ```
>>>>>> 
>>>>>> And now we’re back with different syntax for the same thing, though with 
>>>>>> a
>>>>>> different ABI (I think Clang has support for implicitly converting C++
>>>>>> lambdas to blocks, but it’s been a few years since I tried)
>>>>>> 
>>>>>> David
>>>>>> 
>>>>>> 
>>>>>> 
>>>>> 
>>>>> -- 
>>>>> Gregory Casamento
>>>>> GNUstep Lead Developer / OLC, Principal Consultant
>>>>> http://www.gnustep.org - http://heronsperch.blogspot.com
>>>>> http://ind.ie/phoenix/
>>>> 
>>>> 
>>>> -- 
>>>> Pirmin Braun address@hidden +49 261 92199400 +49 174 9747584 
>>>> Geschäftsführer der Pirmin Braun GmbH www.pirmin-braun.de 
>>>> Im Palmenstück 4 - 56072 Koblenz - www.facebook.com/PB.ERP.Software
>>>> Registergericht: Koblenz HRB 26312 UStID: DE319238613 Steuernummer: 
>>>> 22/656/03918
>>> 
>>> 
>> 
>> 
> 
> 
> -- 
> Pirmin Braun address@hidden +49 261 92199400 +49 174 9747584 
> Geschäftsführer der Pirmin Braun GmbH www.pirmin-braun.de 
> Im Palmenstück 4 - 56072 Koblenz - www.facebook.com/PB.ERP.Software
> Registergericht: Koblenz HRB 26312 UStID: DE319238613 Steuernummer: 
> 22/656/03918

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