[8u] RFR 8141491: Unaligned memory access in Bits.c

[Mikael Vidstedt]

Looks good. A few comments:

* src/share/classes/sun/misc/Unsafe.java

javadoc for copySwapMemory says “@since 9” which seems confusing at best.

The original change in jdk9 only added the new methods to the jdk internal Unsafe, while this back port adds them to sun.misc.Unsafe. I’ll leave it for somebody else to comment on the appropriateness of that.

* CopySwap.java test

You’ll probably want to back port the test covered by https://bugs.openjdk.java.net/browse/JDK-8149611 <https://bugs.openjdk.java.net/browse/JDK-8149611> as well. It was supposed to go in together with the fix.

Cheers,
Mikael

> On Nov 7, 2018, at 9:45 AM, David Buck <david.buck at oracle.com> wrote:
> 
> Hi!
> 
> May I please get a review of this straightforward backport from JDK 9 to JDK 8:
> 
> bug report:
> https://bugs.openjdk.java.net/browse/JDK-8141491
> 
> JDK 9 change sets:
> http://hg.openjdk.java.net/jdk9/jdk9/hotspot/rev/75f6573e9c44
> http://hg.openjdk.java.net/jdk9/jdk9/jdk/rev/13759d57abca
> 
> JDK 9 review thread:
> http://mail.openjdk.java.net/pipermail/nio-dev/2015-November/003365.html
> http://mail.openjdk.java.net/pipermail/nio-dev/2016-January/003496.html
> http://mail.openjdk.java.net/pipermail/nio-dev/2016-February/003522.html
> 
> JDK 8 webrevs (for review):
> http://cr.openjdk.java.net/~dbuck/8141491_jdk8_ver00/
> 
> The backport is almost line-for-line the same as the JDK 9 fix with the following exceptions:
> 
> - assertions / guarantees need to have their format strings wrapped with err_msg() [0]
> 
> - there is no need to "backout" of JDK-8140630 [1], which was never backported to JDK 8 in the first place.
> 
> This fix is urgently needed for JDK 8 built with newer versions of GCC.
> 
> Cheers,
> -Buck
> 
> [0] https://bugs.openjdk.java.net/browse/JDK-8080775
> [1] https://bugs.openjdk.java.net/browse/JDK-8140630

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