DMD compiler switch to set default extern() linkage?

[Dmitry Olshansky]

On 05.04.2012 13:49, Alex Rønne Petersen wrote:
> Hi,
>
> It is no secret that DMD is the only compiler in existence that follows
> the "D" calling convention (and even then, only on some platforms,
> seemingly?).

IMHO It's the only sane convention I've seen. C's default of caller-side 
cleanup adds nothing but a mess for years to clean up. And code size 
bloat for no good reason. I think it was just a "cool trick" to make 
printf work, bleh. And extern(D) still allows that.

Both GDC and LDC use the C calling convention of the
> platform by default (and don't even have options to use the "D" calling
> convention because their back ends don't support it at all).
>
> I'm writing a virtual machine. As far as I am concerned, the "D" calling
> convention adds nothing but complexity to the configuration support
> matrix. The calling convention situation across platforms is already
> utterly insane enough as it is. I would not have a problem with
> supporting the "D" calling convention if all compilers followed it. But
> they don't. And it is only specified for x86. Even in an ideal world,
> the "D" calling convention won't exist everywhere because it isn't
> intended to.
>
> So yes, we could just say "but eventually, those compilers should
> support it!".

Yup, let's stop being kids and copying whatever big ones are doing. 
Standards sort of happen like this:  people just start doing things 
differently, then others like it and follow suit and then it's all 
written on a bunch (virtual) paper with ISO number somewhere.

But realistically, it is not going to happen. Those
> compilers have no reason to implement yet another calling convention
> that is entirely specific to x86.

Extend it, I've seen some movement on ARM side.

>
> I don't think it's good that DMD forces all functions to use the "D"
> calling convention by default. However, I accept that it is an
> established situation, and changing is now is not an option.
>
> That said, I believe a compiler switch to set the default extern()
> linkage is not an unreasonable thing to ask for, e.g.: dmd -extern=C foo.d
>
> Thoughts?
>


-- 
Dmitry Olshansky