I just wanted to let everyone know that I have implemented D/Objective-C
for 64bit. Everything that worked for 32bit should work, except for
exceptions, which are not implemented yet.
Objective-C on 64bit uses the modern runtime, which is also the same
used on iOS. This means D/Objective-C should now be compatible with iOS
as well, at least in theory.
For those how don't know what D/Objective-C is. It is a language
extension to D making it ABI compatible with Objective-C. This means
it's possible to use Objective-C classes, methods, protocols
(interfaces) and so on, directly just as it's currently possible to do
with regular C functions.
Here's a recap of what's implemented, both for 32 and 64bit unless
* Instance and class methods
* Protocols (interfaces)
* Exceptions (only 32bit)
* Class references
* String literals
Some improvements that are really not part of Objective-C but are very
convenient to have in D :
* Inheriting selectors
* Automatically generated selectors
On the other hand, here a list of what's not implemented yet:
* Blocks (similar to delegates)
* Categories (class extensions)
* Any form of automatic memory management
* Exceptions (64bit)
* Vtable optimization (64bit)
Objective-C exceptions on 64bit is implemented using the same mechanism
as C++. I'm wondering if it would be possible for D (not just for this
extension) to adapt this mechanism as well. This would make D compatible
with both C++ and Objective-C exceptions on 64bit.
A DIP is available here  and the latest implementation is available