RFR: 8239357: Revert gcc implementation of offset_of

[Erik Joelsson]

Build change looks good.

/Erik

On 2020-04-22 06:23, Kim Barrett wrote:
> Please review this change to undo the (small) portion of JDK-8238281
> [1] related to the HotSpot offset_of macro for gcc/clang.  That change
> should not have been made.  See CR for details.
>
> I did not reinstate the redefinition of offsetof; we shouldn't be
> using that macro, and having the warning enabled will catch
> questionable cases.  (I also considered but didn’t poison it.)
>
> CR:
> https://bugs.openjdk.java.net/browse/JDK-8239357
>
> [1] https://bugs.openjdk.java.net/browse/JDK-8238281
>
> Webrev:
> https://cr.openjdk.java.net/~kbarrett/8239357/open.00/
>
> Testing:
> mach5 tier1
>
> With a temporary change to use offsetof with a non-standard-layout class,
> verified the expected build failures occur with gcc and clang.
>