Linking D and Obj-C code into a Cocoa app proper? (Mac)

[Heywood Floyd]

Ok! Thanks for the advice! Great work on the plugin—it got me into D :)

/FH

Michel Fortin Wrote:

> On 2010-10-05 10:02:45 -0400, Heywood Floyd <soul8o8 at gmail.com> said:
> 
> > But, sometimes I get reeeaally weird bugs. I had one bug where if I 
> > added an empty function to a class in D I got EXC_BAD_ACCES (segfault). 
> > An empty function! Ie "void f(){}". Remove the function--it works. In 
> > the debugger, I got the impression maybe the stack has got messed up, 
> > but I don't know, the debugger just shows assembler code, and I don't 
> > have the proper skills.
> 
> It's hard to say without further details, but it could be that you're 
> not recompiling everything that uses the class where you add a 
> function. Unlike in Objective-C, adding a function to a D class breaks 
> most compiled code that uses that class (because you're adding an 
> offset to the virtual function table), so you need to recompile every D 
> module that uses that class (or a derived class).
> 
> Note that this is totally unrelated to having Objective-C code in the 
> same program.
> 
> 
> > This got really frustrating, needless to say, so I started playing 
> > around with the build settings. I switched from using LLVM 1.5 (for the 
> > obj-c code) to gcc 4.2. And now it magically seems to work!
> 
> Are you using D for Xcode? By doing that you basically force everything 
> to be recompiled, which solves problem described above.
> 
> 
> > [...]
> > 
> > == Question ==
> > How do you make D code and Obj-C code coexist? That is, I want to write 
> > a Cocoa-app that is mostly written in D, and with a little "glue"-code 
> > in Objective-C. How do you set that up? Is it even supposed to be 
> > possible?
> 
> It is totally possible, and not that hard. Communicating via `extern 
> (C)` functions should work well.
> 
> 
> > (And what could the bug above be? I know LLVM does link-time 
> > optimizations, and even run-time optimizations. Could it be that it 
> > messes things up?)
> 
> I doubt LLVM optimizations have anything to do with your problem. 
> Things to keep in mind when mixing Objective-C:
> 
> 1. Apple's Objective-C GC isn't supported by D, so you it's probably 
> safer to use manual memory management (retain/release) on the 
> Objective-C site.
> 
> 2. Exceptions are not compatible between the two runtimes. Throwing can 
> cause unexpected results when it unwinds stack frames in the other 
> language.
> 
> 
> -- 
> Michel Fortin
> michel.fortin at michelf.com
> http://michelf.com/
>