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

[Matt Rice]

On Mon, Nov 25, 2019 at 10:53 AM David Chisnall
<gnustep@theravensnest.org> wrote:
>
> On 25 Nov 2019, at 09:37, Gregory Casamento <greg.casamento@gmail.com> wrote:
> >
> > * C++, while this is not exclusive to clang, gcc doesn't support the latest 
> > version of C++.  Clang is extraordinarily good at optimization.
>
> I don’t think this is true.  We have a C++17 project that we test in CI with 
> GCC.  The only times that we experience problems are when we use some 
> non-standard attributes that GCC doesn’t support (but we also build with 
> Visual Studio, so we rarely find anything that we need that those two support 
> but GCC doesn’t, it’s only when we have something ELF-specific that’s a 
> problem).
>
> I don’t know how good GCC’s Objective-C++ support is (as I recall, 
> Objective-C and Objective-C++ in GCC aren’t just base-language + Objective-*, 
> so it isn’t necessarily a given that you get full C++17 support in GCC’s 
> Objective-C++), but using C++ smart pointers you can get a lot of ARC (at the 
> very least - and prior to ARC support, I did - you can implement smart 
> pointers that manage Objective-C retain / release and use them to hold 
> Objective-C objects in collections.

I had used ObjC++ before when embedding a c++ rendering engine in an
NSOpenGLView,
many years ago, but I don't recall anything specifically in the objc++
frontend that did anything but punt to either the objc or c++ backend.

What I do remember is that the debugging support is terrible!
It implements Dwarf with the language ObjC++, and then in the
debuginfo Classes in objc are mapped to dwarf's Object/Class thing,
and classes in C++ are mapped to the same Object/Class thing.

Apple's debugger tells the difference by looking at symbol mangling,
In particular their objc symbols contain +-[()]: characters, and it
can tell from the first character if it's objective-c or not.
A solution like that was never really acceptable for gdb.

So you generally had to set language to c++, or objc at every step.
This is very unlikely to have changed for gcc, is it any better on clang?