Multiple return values

[Timon Gehr]

On 01/04/2012 12:09 AM, Manu wrote:
> Does returning a tuple give any ABI guarantees?  How can I be sure multiple return values will return in consecutive 
registers?

   * 1, 2 and 4 byte structs are returned in EAX.
   * 8 byte structs are returned in EDX,EAX, where EDX gets the most 
significant half.
   * For other struct sizes, the return value is stored through a hidden 
pointer passed as an argument to the function.



> What if the return types are of different types, a float and an int...
> can I expect each to return in their own register types respectively?

No.

> This needs to be defined and loosely guaranteed (within reason) so
> people can expect multiple return values to behave as expected on any
> architecture.

A possibility would be to allow TypeTuple return types.


>
> On 4 January 2012 01:02, Sean Kelly <sean at invisibleduck.org
> <mailto:sean at invisibleduck.org>> wrote:
>
>     It's easy enough with Tuple, though better language support would be
>     nice.
>
>     Sent from my iPhone
>
>     On Jan 3, 2012, at 2:40 PM, Manu <turkeyman at gmail.com
>     <mailto:turkeyman at gmail.com>> wrote:
>
>      > Why doesn't D support multiple return values like many other
>     modern languages?
>      >
>      > Clearly the same syntax as Go wouldn't work, but I'm sure a neat
>     and tidy syntax could be invented?
>      > I constantly want to be able to return x,y from a function, or
>     retVal,errorCode and I want the language to make some rough ABI
>     guarantees, like multiple return values will be returned in
>     consecutive registers, rather than a single return value register
>     like C/C++, avoiding the need to pass output addresses through ref
>     function parameters (slow!).
>
>