Re: Which of the following PrimTyCons have a pointer-sized representations

On 11/12/12 21:31, Johan Tibell wrote:
> On Tue, Dec 11, 2012 at 1:02 PM, Simon Peyton-Jones
> <[email protected]> wrote:
>> |  >    data T = MkT !S
>> |  >            data S = MkS Int
>> |  >
>> |  > then my impl will unbox the S field of MkT because the result is only one field
>> |  wide, namely an Int.
>> |
>> |  Wouldn't Johan's have unboxed S too?  (if not, I misunderstood what he did)
>>
>> No, that would change the semantics!  We don't want to do that.
>
> I think Simon M meant that my change would have unpacked the field of
> *type* S in the MkT constructor. We must not unpack the field in the
> MkS constructor.

Correct, sorry for not being clear enough.

>> |  I'm happy to call this -funbox-strict-small-fields. However, I'd like
>> |  the documentation to talk about pointer-sized things as that, even
>> |  though a bit operational sounding, has a clear meaning in my mind.
>>
>> I'm somewhat inclined to *change* the current flag so that
>>
>>          -funbox-strict-fields means "unbox small fields"
>>          -funbox-all-strict-fields means "unbox ALL strict fields"
>
> Lets go with -funbox-small-strict-fields to avoid unnecessary
> breakages. If we end up enabling this flag by default eventually it
> doesn't really matter what the name is as people will never type it
> out explicitly.

+1

There are lots of users of the existing flag, we don't want to change 
its meaning.

Cheers,
	Simon