JDK 9 build with GCC 6.1.1

[Kim Barrett]

> On Jun 25, 2016, at 9:57 AM, Yasumasa Suenaga <yasuenag at gmail.com> wrote:
> 
> Hi all,
> 
> This review request relates to [1].
> 
> I've tried to build OpenJDK 9 at Fedora 24 x64.
> Fedora 24 has GCC 6.1.1, and OpenJDK 9 build was failed.
> 
> I fixed build error and several issues (VM crash and internal error) as below:
> 
>  http://cr.openjdk.java.net/~ysuenaga/jdk9-for-gcc6/hotspot/

I've only done a quick skim of the proposed hotspot changes, not a
proper review.  Just in general, I'd rather review changes in chunks
that were logically related, which many of these aren't.  (Needed to
build and run with some new compiler doesn't make them related for
review purposes.)  And please provide some context.  Reviewers
shouldn't have to guess what problem is being solved by a given
change. Some of these still seem mysterious to me, even with the link
to build failures and crash dumps.

Some specific issues:

A couple of these were recently addressed by JDK-8157758.

Some of these are C++11 or later changes tripping up a code base
written for C++98/03.  A few months ago a change was made to
explicitly use -std=gnu++98 for exactly this reason (see JDK-8151841),
but that seems to have gotten lost in the transition to the new build
system (see JDK-8156980).  I would prefer that got fixed and these
kinds of issues be deferred to a future modernization project, where
some of them might involve something more principled than adding some
workaround casts, for example. (We've been doing string/identifier
whitespace separation for a while, though; I'd be fine with those,
other than being post-FC.)

Some of these appear to be just plain bug fixes, and I wonder why the
code is working now?  For example, the change at
src/share/vm/classfile/classLoaderData.cpp:145 seems suspicious.

Some of these are just cleanups, like
src/share/vm/oops/oop.inline.hpp:542, but it's post-FC.

> Does someone work for it?
> If no one works for it, I will file it to JBS and will send review request.

Certainly there should be CRs filed for these; the enhancements so
they don't get lost, and the crashes because they probably indicate
real bugs.

> For jdk repos, I've sent review request [2].
> 
> 
> Thanks,
> 
> Yasumasa
> 
> 
> [1] http://mail.openjdk.java.net/pipermail/jdk9-dev/2016-June/004494.html
> [2] http://mail.openjdk.java.net/pipermail/2d-dev/2016-June/007081.html