RFR: 8269120: Build failure with GCC 6.3.0 after JDK-8017163

[Thomas Schatzl]

On Tue, 22 Jun 2021 09:22:42 GMT, Aleksey Shipilev <shade at openjdk.org> wrote:

> One of my CI servers that carry GCC 6.3.0 fails after JDK-8017163 with:
> 
> 
> In file included from /home/buildbot/worker/build-jdkX-linux/build/src/hotspot/share/gc/g1/g1CardSetFreeMemoryTask.hpp:29:0,
>                  from /home/buildbot/worker/build-jdkX-linux/build/src/hotspot/share/gc/g1/g1CollectedHeap.hpp:31,
>                  from /home/buildbot/worker/build-jdkX-linux/build/src/hotspot/share/gc/g1/g1CollectedHeap.inline.hpp:28,
>                  from /home/buildbot/worker/build-jdkX-linux/build/src/hotspot/share/gc/g1/heapRegion.inline.hpp:31,
>                  from /home/buildbot/worker/build-jdkX-linux/build/src/hotspot/share/gc/g1/g1AllocRegion.inline.hpp:30,
>                  from /home/buildbot/worker/build-jdkX-linux/build/src/hotspot/share/gc/g1/g1AllocRegion.cpp:26:

What platform is still on GCC 6.3.0? It has been released in December 21, 2016 and actually the whole release series is apparently "no longer supported" according to the GNU homepage ([link](https://gcc.gnu.org/gcc-6/)). I kind of understand supporting still supported compilers, but officially unsupported ones with the last release 3 years ago (which is 6.5.0 btw)? 

Not having looked into the change too much, but there might be more similar trouble when implementing [JDK-8267834](https://bugs.openjdk.java.net/browse/JDK-8267834) when the JDK 17 release trouble dies down a bit, as `G1CardSetAllocator` and `BufferNode::Allocator` will be merged again...

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PR: https://git.openjdk.java.net/jdk/pull/4551