RFR: 8247910: Improve alignment and power-of-2 utilities using C++14

[Kim Barrett]

> On Sep 23, 2020, at 2:14 AM, Thomas Stüfe <thomas.stuefe at gmail.com> wrote:
> 
> Hi,
> 
> unfortunately this breaks my builds on Ubuntu 16.4. I am using gcc 5.4.0 which according to https://openjdk.java.net/groups/build/doc/building.html should still be an accepted compiler?
> 
> Creating hotspot/variant-server/libjvm/gtest/gtestLauncher from 1 file(s)
> In file included from /shared/projects/openjdk/jdk-jep387/source/src/hotspot/share/services/memTracker.hpp:85:0,
>                  from /shared/projects/openjdk/jdk-jep387/source/src/hotspot/share/precompiled/precompiled.hpp:60:
> /shared/projects/openjdk/jdk-jep387/source/src/hotspot/share/services/mallocTracker.hpp:190:78: error: size of array '_snapshot' is not an integral constant-expression
>    static size_t _snapshot[CALC_OBJ_SIZE_IN_TYPE(MallocMemorySnapshot, size_t)];

I don’t see anything here to indicate what platform this is for.  It’s not, by any chance, arm32?