[11u] RFR 8223186: HotSpot compile warnings from GCC 9

[Martin Balao]

Hi,

I'd like to propose an 11u backport of JDK-8223186 [1]:

Webrev.00:

 * http://cr.openjdk.java.net/~mbalao/webrevs/8223186/8223186.webrev.11u.00/

jdk/jdk patch does not apply cleanly because of the following conflicts:

 * src/hotspot/share/compiler/disassembler.cpp
  * 11u has JDK-8222079 [2] applied, which includes the changes
introduced by JDK-8223186 and a change that supersedes JDK-8223186 in
the _nm field. No change to apply in the 11u backport.

 * src/hotspot/share/gc/shared/ptrQueue.cpp
  * 11u does not have JDK-8154343 [3] applied, so the file is located in
src/hotspot/share/gc/g1/ptrQueue.cpp.
  * The 'strncpy' function fixed by JDK-8223186 is introduced by
JDK-8212826 [4] but the latter is not available in 11u. JDK-8212826 is
not fundamental or related to JDK-8223186, so I believe we should not
backport it at this time as its dependency. No change to apply in the
11u backport.

Testing: no regressions found while building with GCC 9.2.1 in my local
enviornment.

Thanks,
Martin.-

--
[1] - https://bugs.openjdk.java.net/browse/JDK-8223186
[2] - https://bugs.openjdk.java.net/browse/JDK-8222079
[3] - https://bugs.openjdk.java.net/browse/JDK-8154343
[4] - https://bugs.openjdk.java.net/browse/JDK-8212826