The D ecosystem in Debian with free-as-in-freedom DMD

[Matthias Klumpp via Digitalmars-d]

On Monday, 10 April 2017 at 23:27:35 UTC, Walter Bright wrote:
> On 4/10/2017 5:59 AM, Matthias Klumpp wrote:
>> You need to see here that D is not the center of the world and 
>> we will need to
>> make it work nicely with the rest of the system. The technical 
>> policies work for
>> everything else, so there is nothing that really justifies an 
>> exception for D
>> here (if 10% of Debian's code was written in D and the Debian 
>> D team was really
>> large we could maybe get one, but not the way it is now).
>> And tbh, I think finding a good solution here is entirely 
>> possible.
>
> I think it is possible, too, and thank you for your efforts 
> helping us do this.
>
> The ABI differences between the compilers is unfortunate, and 
> is largely the result of historical accident.
>
> The first problem is that my idea originally was for D to have 
> its own function calling convention, which would free us to 
> innovate to have a more efficient calling convention than the C 
> one. This hasn't panned out in practice, and ldc/gdc decided to 
> sensibly stick with the C ABI. At some point, we should just 
> crowbar dmd to generate the C ABI, but this has its own 
> problems - it'll break code that uses the inline assembler. No 
> obvious solution there.
>
> The next problem is that dmd occasionally changes the interface 
> to the D runtime. Or more accurately, with about every release. 
> This has not been an issue historically for us, as the two have 
> always been a matched set. I'm a lot less sure how to deal with 
> this. I also do not know how the gdc/lds druntime interfaces 
> differ.

Thank you very much for this context! It's really good to know 
why things are the way they are to properly understand the 
problem (I am no compiler developer and ABIs are not my expertise 
- as outsider to this I see pages like 
https://dlang.org/spec/abi.html though and wonder whether the 
incompatibilities are seen as an issue in the D community and 
whether there is a chance to address them before putting work 
into setting up infrastructure to rebuild the world on compiler 
updates).