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

[Aleksey Shipilev]

On 2/25/19 4:23 PM, Langer, Christoph wrote:
> I discussed that with Thomas. Maybe we should align the start address down to unitsize in
> os::print_hex_dump, instead of asserting.

Yup. It is also arguably better UX: no matter what the start address is, we would always "granulate"
the dumped memory the same way.

>> ...and print_hex_dump is supposed to be resilient, because I'd expect SafeFetch to handle
>> SIGBUS from unaligned accesses too. I see the signal handler for linux_x86 and solaris_x86
>> handle all signals, not only SEGVs. So, why did the test SIGBUS'ed? What a rabbit hole.
> 
> Good point, will see if we can figure out more. Interestingly, the test crashes on one Solaris
> machine (that tests jdk11u here), but not on another (where jdk/jdk is tested).

Also, Oracle testing presumably builds/runs/tests Solaris, and there were no bug reports about it.

It looks that test had caught a legit problem, and as such does not look like a testbug.

-Aleksey