Re: Building a new Objective-C compiler?

[H. Nikolaus Schaller]

> Am 04.09.2024 um 00:21 schrieb Ethan C <echaroenpitaks@gmail.com>:
> 
> Hi everyone,
> 
>         Our recent discussion about whether we should switch to a newer 
> compiler has brought up an idea I've been thinking about for a while. 
> Objective-C was originally implemented as a preprocessor which emitted C 
> code. C++ was also originally implemented this way (Cfront), and Qt C++ is 
> still implemented as a preprocessor which emits C++ code. If we could make an 
> Objective-C 2.x compiler that emitted C code, we would unlock many benefits:
> 
> * We could add our own extensions to the Objective-C language rather easily 
> (think adding syntax support for traits)
> 
> * We could start using Objective-C features which were introduced after 
> Objective-C 2.0 without hacky stuff, such as blocks, lightweight generics, 
> etc., and allow GNUstep users on GCC-only platforms to use these too
> 
> * We could support compiler infrastructures other than GCC or LLVM, which 
> would mean that it would take less time to get to a working GNUstep system 
> when bootstrapping from scratch, and would make it easier for us to do things 
> that require C compiler support beyond what standard C or GNU C provide
> 
> * Our MSVC support would be much easier
> 
> * We could switch to libobjc2 for everything, which would give us typed 
> selectors and non-fragile ABI even on GCC-only platforms
> 
> I see a few options to do this:
> 
> * We write our own Objective-C-to-C compiler, perhaps using some code from 
> autogsdoc and the Objective-S compiler
> 
> * We heavily modify Portable Object Compiler (an Objective-C 1.0 transpiler 
> to C, with its own runtime library) to deal with Objective-C 2.0 and libobjc2
> 
> * We modify clang's `clang -rewrite-objc` to output standard C rather than 
> MSVC C++

You could also base it on:

https://git.goldelico.com/?p=mySTEP.git;a=tree;f=ObjC;hb=refs/heads/master

which parses ObjC (well, not yet perfectly) into an AST and allows to rewrite 
the AST as something else (backend).
The idea is to write this "transpiler" itself completely in ObjC-1.0 (for 
bootstrapping).
The other idea was rewrite ObjC code to PHP so that it runs in the mySTEP.php 
Web frontend framework.
Then you could write WebApps like desktop apps (NSApplication, NSWindow, 
NSButton, NSTableView etc.) without completely switching the paradigm like with 
WebObjects.

> 
> Finally, if we want to support compilers other than GCC, Clang, and MSVC, I 
> made a list of small C compilers here: 
> https://github.com/ethanc8/awesome-small-compilers/blob/master/SmallCCompilers.md.
>  These compilers could be useful to make sure that we're not depending on 
> buggy compiler behavior, and to give us a more hackable toolchain with which 
> to experiment with. We could also implement C extensions that we need much 
> easier than implementing them in GCC or LLVM, if it turns out the abilities 
> of GNU C and MSVC C17 or MSVC C++ aren't enough for us.
> 
> This seems like a lot of effort, but a lot of the work is already done for 
> us. I'm not sure if it will be worth it, but I think it will be, since it 
> will make it much easier to evolve the Objective-C language forward, support 
> other languages (like Objective-S) which run on top of libobjc2, and more.
> 
> Does anyone have any thoughts or opinions on this?
> 
>