[8u] RFR: 8280963: Incorrect PrintFlags formatting on Windows

[Alex Kashchenko]

Hi,

Please review a fix to 8u-only Windows-specific problem with
-XX:+PrintFlags* output:

Bug: https://bugs.openjdk.java.net/browse/JDK-8280963

Webrev: https://cr.openjdk.java.net/~akasko/jdk8u/8280963/webrev.01/

Problem description on Stack Overflow by Andrei Pangin:
https://stackoverflow.com/a/63309395

The problem was fixed in jdk9 as part of JDK-8042893 [1], but this
jdk9 change [2] doesn't look like a good candidate for the 8u backport
according to 8u Best Practices [3]. Still the problem manifests itself
as a customer-visible bug on Windows because people do use
-XX:+PrintFlagsFinal to find out the actual flags picked up by JVM and
can be confused by unexpected zeros in the output. Proposed patch
cherry-picks the minimal change from JDK-8042893 commit [4].

Testing:

 - regression test is included with the proposed patch
 - checked that it builds on Windows 64-bit and 32-bit on VS2017 and VS2010
 - ran jtreg:hotspot/test/runtime on Windows and Linux


[1] https://bugs.openjdk.java.net/browse/JDK-8042893
[2] https://hg.openjdk.java.net/jdk9/jdk9/hotspot/rev/115188e14c15
[3] https://mail.openjdk.java.net/pipermail/jdk8u-dev/2020-June/012002.html
[4] https://hg.openjdk.java.net/jdk9/jdk9/hotspot/rev/115188e14c15#l53.1


-- 
-Alex