RFR(S): 8220348: [ntintel] asserts about copying unalinged array

[Doerr, Martin]

Hi,

I'd like to propose a fix for an old issue on 32 bit Windows (also for an 11u backport):
https://bugs.openjdk.java.net/browse/JDK-8220348

Some jdk native methods use jni_SetLongArrayRegion with a stack allocated buffer.
jni_SetLongArrayRegion uses Copy::conjoint_jlongs_atomic which requires jlongs to be 8 byte aligned (asserted).
However, Windows 32 bit only uses 4 byte alignment for jlong arrays by default.
I found such issues in the following files:
src/java.prefs/windows/native/libprefs/WindowsPreferences.c
src/java.security.jgss/share/native/libj2gss/GSSLibStub.c
I suggest to use __declspec(align(8)) there.

Webrev:
http://cr.openjdk.java.net/~mdoerr/8220348_ntintel_stack_align/webrev.00/
Please review.

I think using 8 byte alignment is not a disadvantage for 64 bit.

I guess there are still people interested in this platform with jdk14. Otherwise I could contribute it as 11u only fix.

Is there a better way to force 8 byte alignment for jlongs or jlong arrays on stack?
Best regards,
Martin

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