RFR(S): 8219650: [Testbug] Fix potential crashes in new test hotspot gtest "test_print_hex_dump"

[Langer, Christoph]

Hi,

please review the following small test fix.

Bug: https://bugs.openjdk.java.net/browse/JDK-8219650
Webrev: http://cr.openjdk.java.net/~clanger/webrevs/8219650.0/

JDK-8217994 introduced a new gtest "test_print_hex_dump". This test calls os::print_hex_dump on a potentially unaligned address because the array that is dumped in the test is just placed on the stack. I try to avoid that by mallocing and hence getting a better aligned placement. Another minor issue is that the test should be run as TEST_VM, because it uses VM facilities such as ResourceMark.

We've observed a crash on a Solaris machine during jdk11u testing. I'll run the fix through our test system and if it passes and fixes the crash, I'll also request backporting to jdk12u and jdk11u.

Thanks
Christoph