My idea for seamless interop to C++

[Petar]

On Wednesday, 18 November 2020 at 14:04:36 UTC, Markus wrote:
> Hi there!
>
> For months I've been thinking on how to escape C++.
> Here are my thoughts about that matter:
> https://gitlab.com/qwertzui11/d-to-cpp/-/blob/master/README.md
>
> What do think about that idea. Is it worth a shot? I'm thinking 
> about implementing such a tool.
>
> Have fun,
> Markus

Kudos for the detailed comparison between the different C++ 
alternatives!

That said, I'm sorry to disappoint, but I don't think this would 
be a a viable approach (translating D source code to C++ (not 
just headers) while preserving the high-level structure). D is 
also a complex language (just the complexity is much less and 
much better managed compared to C++) and doing a semantically 
correct translation (while even preserving high-level concepts, 
such as OOP) would be quite hard. D's template system is more 
powerful (and more sane) than the one of C++, so you can't 
translate any D code that use templates basically (which is 
pretty much the whole standard and runtime library).

I believe there are 5 approaches / areas worth investing to:
1. dmd's built-in extern (C/C++) ABI and header generation [1] 
[6] [7] [8]
2. dpp [2]
3. dstep [3] (I really wish Atilla would collaborate with Jacob 
on merging dpp and dstep)
4. cling [4] - as far as I know Symmetry have build some sort of 
bridge between D and C++ based on this.
5. Calypso - using Qt from D is nothing sort of astonishing! 
Unfortunately all the work is done by single developer. If others 
would join, hopefully the project could progress much faster.

[1]: https://dlang.org/changelog/2.091.0.html#headers
[2]: https://github.com/atilaneves/dpp
[3]: https://github.com/jacob-carlborg
[4]: https://github.com/root-project/cling
[5]: https://wiki.dlang.org/Calypso

[6]: https://dlang.org/changelog/pending.html#dtoh-improvements | 
permalink: 
https://github.com/dlang/dmd/blob/82cbfec6c72a5ece1b2a9a72d18adcae145d10c7/changelog/dtoh-improvements.dd
[7]: https://dlang.org/changelog/2.094.0.html#cxx-header-modes
[8]: https://dlang.org/changelog/2.092.0.html#cpp_abi_tags

I'm curious to know more on your thoughts on dmd's dtoh.

You can find some sample generated code here:

Big example:
https://github.com/MoonlightSentinel/dmd/blob/ecce5075cbdef1e41b502ccfc01d188ecce4ebc6/src/dmd/frontend.h

Smaller examples:
https://github.com/MoonlightSentinel/dmd/blob/72e5188bd66e4bd8b23f12f0979d66e8354c7d2a/test/compilable/dtoh_cpp98_compat.d

https://github.com/MoonlightSentinel/dmd/blob/72e5188bd66e4bd8b23f12f0979d66e8354c7d2a/test/compilable/dtoh_enum.d

https://github.com/MoonlightSentinel/dmd/blob/72e5188bd66e4bd8b23f12f0979d66e8354c7d2a/test/compilable/dtoh_extern_type.d

https://github.com/MoonlightSentinel/dmd/blob/72e5188bd66e4bd8b23f12f0979d66e8354c7d2a/test/compilable/dtoh_functions.d