[fpc-devel] Difficulty in specifying record alignment

[J. Gareth Moreton]

I'm going to have to keep trying.  So far that gets me the following 
(some debug lines I inserted into the compiler):

record UCOMPLEX.complex
- alignment = 8
- aggregatealignment = 8
- structalignment = 8
- size = 16

I was wrong about what I said about RECORDMIN=16... the alignment fields 
are still equal to 8, but it puts the byte offset of the 2nd field to 16.

There might be a bug in my vectorcall code that prevents the correct 
alignment (plus I need to double-check which alignment field is which).  
If there is a bug, I'll post a test and a patch to fix it.

Gareth aka. Kit


On 21/10/2019 20:53, Florian Klämpfl wrote:
> Am 21.10.19 um 21:42 schrieb J. Gareth Moreton:
>> On 21/10/2019 20:00, Florian Klämpfl wrote:
>>> What's the problem with
>>>
>>> {$push}
>>> {$codealign RECORDMIN=16}
>>> type complex = record
>>>                       re : real;
>>>                       im : real;
>>> end;
>>> {$pop}
>>>
>>> ?
>>
>> Hi Florian,
>>
>> I tried that, but that puts each individual field on a 16-byte boundary 
>
> Then do:
>
> {$push}
> {$codealign RECORDMIN=16}
> type dummyrec = record
>         b : byte;
> end;
>
> {$pop}
> type complex = record
>        case byte of
>           1 : (
>                       re : real;
>                       im : real
>               );
>           2 : (alignmentdummy : dummyrec);
> end;
>
> I thought I mentioned this trick even somewhere :)
>
>> parameters passed into the function may not be aligned (e.g. when 
>> deferencing a pointer on the heap after calling, say, 
>> "New(complex);"), hence why the compiler can only go by the 8-byte 
>> aggregate alignment.
>
> No. Data is guaranteed to be aligned at it's natural boundary when it 
> is passed without further information.
> _______________________________________________
> fpc-devel maillist  -  fpc-devel at lists.freepascal.org
> https://lists.freepascal.org/cgi-bin/mailman/listinfo/fpc-devel
>

-- 
This email has been checked for viruses by Avast antivirus software.
https://www.avast.com/antivirus