[foreign] RFR 8217664: jextract should check for error code returns from Type::getOffsetOf and Type::size

[Jorn Vernee]

Updated webrev for recent push: 
http://cr.openjdk.java.net/~jvernee/panama/webrevs/8217664/webrev.03/

Jorn

Jorn Vernee schreef op 2019-01-24 14:04:
> Hi,
> 
> jextract uses libclang functions to query the size of a type and
> offset of a field. The returned values are used for instance in layout
> calculations. But, these functions can also return error codes and
> there is currently no check for them. They are happily being used in
> the layout calculations, and this can cause some strange errors, or in
> some cases incorrect layouts are generated. To give an example:
> 
>     struct Foo {
>         int x;
>         void *list_of_data[];
>     };
> 
> The expected layout of this struct (which uses an incomplete/flexible
> array field) should be `[i32x32[0u64]]` but jextract instead generates
> `[i32[0u64]x32]`. This particular case is due to a bug in libclang
> where requesting the offset of a field in a type with a flexible array
> member always returns an incomplete type error, even though getting
> the offset of each fields should be possible. This error code (-2) is
> then used in the layout calculations and yields the incorrect result.
> 
> So I've added checking to the returned value of Type::size and
> Type::getOffsetOf and throwing an exception in case an error code is
> returned. I'm also explicitly checking for the flexible array case and
> throwing a UOE in that case. This also means I had to disable the
> flexible array jextract test [1]. The test was passing, but at least
> on Windows the wrong layout was being generated. Since we can not
> reliably compute padding for types with flexible arrays using the
> current method, I think it's better to throw an exception for now
> until we can find a workaround for this bug in libclang, or the bug
> gets fixed.
> 
> Using a type with a flexible/incomplete array member in the binder
> should still be fine of course, so I've added a separate test for
> that.
> 
> Please review the following.
> 
> Bug: https://bugs.openjdk.java.net/browse/JDK-8217664
> Webrev: 
> http://cr.openjdk.java.net/~jvernee/panama/webrevs/8217664/webrev.00/
> 
> Thanks,
> Jorn
> 
> [1] :
> http://hg.openjdk.java.net/panama/dev/file/c40a5a6dc24d/test/jdk/com/sun/tools/jextract/testStruct/struct.h#l85