[foreign] RFR: record padding is not emitted correctly

[Maurizio Cimadamore]

Updated webrev - added file name to anon record name.

http://cr.openjdk.java.net/~mcimadamore/panama/padding_layout_v2/


On 14/06/18 15:37, Maurizio Cimadamore wrote:
> Hi,
> this is an overhaul of how jextract adds padding to record layouts - 
> the general strategy is this:
>
> 1) make sure that fields are emitted at the correct expected offset, 
> if not , add prefix padding
> 2) make sure that record size matches the expected one, if not add 
> trailing padding
>
> Note that (1) should onlyy apply to structs, not unions, as for 
> unions, you always restart from the base offset for each field; so, 
> assumption is, base offset should already be in sync because of outer 
> padding (if needed).
>
> To get there, the Utils::getRecordLayoutInternal now does a recursive 
> walk, as anonymous nested records must join the dance too.
>
> I also did a followup fix on the patch that Sundar sent yesterday; in 
> short, using Utils:getIdentifier doesn't always work. For typedefs it 
> does the right thing, but for anonymous records it just gives a random 
> blob of text mentioning the source location; I tweaked this so that if 
> I see that the output contains '::', I generate a synthetic string 
> "anon$xyz", where xyz is the offset in the source for that anon record.
>
>
> I also noted that when structs contain incomplete arrays (e.g.flexible 
> array members), clang fails to return correct offset for anything 
> inside the struct, and returns -2 instead. Right now I'm accepting it 
> (as did the old impl, and the one in the nicl branch), but I believe 
> it would be better to punt with an exception (after all the generated 
> layout will be all wrong) - but if I do so, the StructTest, which 
> contains an incomplete array, will fail. Opinions?
>
> Webrev:
>
> http://cr.openjdk.java.net/~mcimadamore/panama/padding_layout/
>
> Cheers
> Maurizio
>