Re: [PATCH, v2] Fortran: ordering of hidden procedure arguments [PR107441]

[Mikael Morin <morin-mikael@orange.fr>]

Le 02/11/2022 à 22:19, Harald Anlauf via Fortran a écrit :
> Am 02.11.22 um 18:20 schrieb Mikael Morin:
>> Unfortunately no, the coarray case works, but the other problem remains.
>> The type problem is not visible in the definition of S, it is in the 
>> declaration of S's prototype in P.
>>
>> S is defined as:
>>
>> void s (character(kind=1)[1:_c] & restrict c, integer(kind=4) o, 
>> logical(kind=1) _o, integer(kind=8) _c)
>> {
>> ...
>> }
>>
>> but P has:
>>
>> void p ()
>> {
>>    static void s (character(kind=1)[1:] & restrict, integer(kind=4), 
>> integer(kind=8), logical(kind=1));
>>    void (*<T63a>) (character(kind=1)[1:] & restrict, integer(kind=4), 
>> integer(kind=8), logical(kind=1)) pp;
>>
>>    pp = s;
>> ...
>> }
> 
> Right, now I see it too.  Simplified case:
> 
> program p
>    call s ("abcd")
> contains
>    subroutine s(c, o)
>      character(*) :: c
>      integer, optional, value :: o
>    end subroutine s
> end
> 
> I do see what needs to be done in gfc_get_function_type, which seems
> in fact very simple.  But I get really lost in create_function_arglist
> when trying to get the typelist right.
> 
> One thing is I really don't understand how the (hidden_)typelist is
> managed here.  How does that macro TREE_CHAIN work?  Can we somehow
> chain two typelists the same way we chain arguments?
> 
TREE_CHAIN is just a linked list "next" pointer like there is in the 
fortran frontend a "next" pointer in gfc_ref or gfc_actual_arglist 
structures.
Yes, we can chain typelists; the implementation of chainon in tree.cc is 
just TREE_CHAIN appending under the hood.

> (Failing that, I tried to split the loop over the dummy arguments in
> create_function_arglist into two passes, one for the optional+value
> variant, and one for the rest.  It turned out to be a bad idea...)
> 
Not necessarily a bad idea, but one has to be careful to keep linked 
lists synchronized with argument walking.

The most simple, I think, is to move the hidden_typelist advancement for 
optional, value presence arguments from the main loop to a preliminary loop.

I hope it helps.