DMD compiler switch to set default extern() linkage?

[Alex Rønne Petersen]

On 05-04-2012 12:16, Dmitry Olshansky wrote:
> 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.

Right. I won't deny that the "D" calling convention is good, but 
supporting it is not practical.

>
> 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.

Good luck convincing the GCC guys to merge your D ABI patch. ;)

>
> 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.

Extend what?

>
>>
>> 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?
>>
>
>


-- 
- Alex