[Mono-list] C++/CLI compiler

[Daniel Lo Nigro]

This sounds like it'd be pretty handy for quite a few users :)

It might be worth posting this to the mono-devel mailing list as well.


On Sun, Dec 9, 2012 at 3:36 PM, João Matos <ripzonetriton at gmail.com> wrote:

> Hi.
>
> So I've been working for a bit on a C++/CLI compiler and I think it's came
> along enough that it makes sense to announce it.
>
> I started it because of the need to interop with existing C/C++ native
> code. I first tried extending Cxxi for a bit, but found some problems that
> cannot be solved with the approach of generating IL code at runtime. So I
> tried Microsoft's implementation C++/CLI and found it is a pretty nice
> extension of C++ that makes it play nice on .NET and started implementing.
> Since there is nothing like it for Mono (at least publicly), I started
> working on a new implementation of it above the Clang and LLVM platforms.
>
> The frontend (Clang) was extended to support the Ecma 372 (C++/CLI
> standard) additions to the type system, expressions and declarations, like
> handles, tracking references, CLI arrays, CLI properties and CLI generics.
> It then uses Cecil to import the metadata from DLLs that are introduced in
> the translation unit via #using.
>
> LLVM was also extended with a CIL backend based on the old MSIL LLVM
> backend. The old backend had some problems and had to be updated to compile
> with the new LLVM interfaces. It also only generated IL code from native
> code and had no support for calling .NET types. I later found out LLVM is
> not really that suited to an higher-level assembly language like IL so I
> also had to modify and extend Clang's IR gen to send some bits as metadata
> (LLVM does not have signedness support on its integer types, for instance).
> The backend at the moment generates ILasm text code that is assembled
> externally, but long term I'd really like to emit IL directly via Cecil.
>
> Here are some use cases where it might be useful:
>  1. Calling .NET libraries from native C++ (via calls to the Mono runtime
> for invocations)
>  2. Compiling existing C++ code to CIL code (of course you can also call
> .NET code in this case)
>  3. Introducing new .NET types via pure CIL C++ code
>  4. Calling native libraries from .NET types (seamless interop)
>
> At the moment only use case 2. is implemented and fully functional, though
> I am starting to work on the other use cases. 1. is especially important
> for bootstrapping on Linux (see below).
>
> Implemented CLI features:
>  + Handles
>  + Ref classes
>  + Value classes
>  + Properties
>  + Indexers
>  + Generics
>  + Arrays
>  + Parameter arrays (variadics)
>  + Attributes (WIP)
>
> Missing CLI features:
>  - Exceptions
>  - Delegates
>  - Events
>  - Static Constructors
>
> So you can that there are still quite a bit of things left to implement
> and some that are implemented need some love:
>
>  - Diagnostics and error handling needs a bit of work to be robust. It has
> not been tested that much yet.
>
>  - The generated code is really crap at the moment, LLVM is not that well
> suited to generate code for stack machines, but there are papers out there
> with stack optimization strategies that can be implemented to improve on
> this front.
>
>  - The compiler still has a bit of a bootstrapping problem, as it uses the
> existing MS C++/CLI to bootstrap. I don't expect this to be a big problem,
> since once Mono code-gen mode is added you will be able to call existing
> .NET libraries from native code (instead of generating IL) and it should
> work well on Linux too.
>
>  - It needs a linker to be able to compile multiple C++ translation units
> into just one .NET DLL. The strategy here is not fully clear to me, but I
> was thinking on using the newly-developed LLVM linker (lld) to do it, since
> it seems the best way forward. Another option would be trying to use
> il-repack.
>
> Somebody interested in helping out? Or maybe in sponsoring some features?
> There is a lot of work left to do :)
>
> Code is up at https://github.com/tritao/clang. There is still quite a bit
> of code left to commit so don't try to compile it yet. The rest of the code
> should be up in a day or two, along with instructions on how to compile it.
>
> --
> João Matos
>
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>
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