[foreign] RFR 8217784: Ignore anonymous bitfields so they are handled as padding

[Maurizio Cimadamore]

Looks good by me - I suggest you also wait for Sundar's opinion, since 
he's fresh with this code

Maurizio

On 25/01/2019 21:24, Maurizio Cimadamore wrote:
> The patch is functionally good, I just wonder if it's too magic - e.g. 
> wouldn't be better if the record computer processed the anonymous 
> bitfield (so that the correct padding can be added) instead of relying 
> on the right thing to happen (which will be fragile if e.g. the impl 
> changes a bit) ?
>
> Maurizio
>
> On 25/01/2019 19:18, Jorn Vernee wrote:
>> Good catch. I kinda glossed over unions since I thought there would 
>> be no point in having anonymous bitfields in a union, since there is 
>> no need for padding - but on second thought, these could be used to 
>> manually widen the type. Any ways, the compiler seems to allow 
>> anonymous bitfields in unions, so it's good to support that as well.
>>
>> Updated webrev: 
>> http://cr.openjdk.java.net/~jvernee/panama/webrevs/8217784/webrev.01/
>>
>> Jorn
>>
>> Maurizio Cimadamore schreef op 2019-01-25 19:25:
>>> Looks good - but what happens with unions? I'm worried we'd get a
>>> similar failure there...
>>>
>>> Maurizio
>>>
>>> On 25/01/2019 13:52, Jorn Vernee wrote:
>>>> Hi,
>>>>
>>>> From the bug description:
>>>>
>>>> Jextract fails on the following example:
>>>>
>>>> ```
>>>> struct Foo {
>>>>     unsigned int x: 1;
>>>>     int :7;
>>>>     unsigned int y: 8;
>>>>     int :16;
>>>>     int z;
>>>> };
>>>> ```
>>>>
>>>> The current code tries to look up the second field, but because it 
>>>> has no name this throws an illegal field name error.
>>>>
>>>> ---
>>>>
>>>> I've fixed this by ignoring anonymous bitfields, since the 
>>>> StructLayoutComputer inserts padding automatically before the next 
>>>> field.
>>>>
>>>> Please review the following.
>>>>
>>>> Bug: https://bugs.openjdk.java.net/browse/JDK-8217784
>>>> Webrev: 
>>>> http://cr.openjdk.java.net/~jvernee/panama/webrevs/8217784/webrev.00/
>>>>
>>>> Thanks,
>>>> Jorn