[oe] [meta-java][PATCH] openjdk-8: make GCC6 happy

[Dan McGregor]

On 18 July 2016 at 01:51, Patrick Ohly <patrick.ohly at intel.com> wrote:
> Dan McGregor <danismostlikely <at> gmail.com> writes:
>> On 11 July 2016 at 05:29, Patrick Ohly <patrick.ohly <at> intel.com> wrote:
>> > Dan McGregor <danismostlikely <at> gmail.com> writes:
>> >> From: Daniel McGregor <daniel.mcgregor <at> vecima.com>
>> >>
>> >> GCC 6 sets the default C++ standard to C++14 and introduces dead store
>> >> elimination by default. OpenJDK 8 is not ready for either of these
>> >> changes, so set the C++ standard back to gnu++98 and disable dead
>> >> store elimination.
>> >>
>> >> Switched to using --with-extra-cflags, cxxflags, and ldflags. The added
>> >> patch fixes building when using those flags, and are needed to get
>> >> CFLAGS into the JDK build in the native case.
>> >
>> > Has anyone tested this on a host system where gcc is still 4.x, like 4.9.2
>> > on Debian Wheezy?
>> >
>> > I'm finding that -fno-lifetime-dse is also getting passed to the gcc used
>> > for compiling native binaries (obviously in openjdk-8-native, but also for
>> > some helper executables in openjdk-8). This then breaks the compilation
>> > because older gcc rejects that flag.
>> >
>> > I've briefly toyed with the patch below which worked for openjdk-8-native,
>> > but not for openjdk-8. I'm just going to work around it by staying on gcc
>> > 5.x and clearing these extra flags.
>> >
>> > I'm not familiar enough with the openjdk-8 build process to propose a better
>> > solution, but perhaps someone else has an idea?
>> >
> [...]
>> This regex doesn't work in the cross case because the version string
>> doesn't start with "gcc". It starts with '<target-triple>-gcc', so
>> that should be checked instead.
>>
>> I'll fiddle with this patch some more. It looks like a good short-term
>> solution to building OpenJDK on GCC 4 hosts.
>
> Thanks for taking this further. But please really test on such an older
> system, because the patch alone is not enough. Something also needs to
> be done when configuring openjdk-8 such that it uses different flags
> when invoking the host compiler (old gcc) and the target compiler (gcc 6).
>
> I haven't found a solution for that (not familiar enough with the Java
> build system).
>

Will-do. It's just somewhat difficult to find one for this. I'll maybe
generate a build machine based on CentOS or Debian. I wonder why it's
picking non-default CFLAGS for host tools though.

I'll keep poking.


> Bye, Patrick
>
> --
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