RFR: JDK-8202319: Fix compilation warnings in Solaris debug builds for DevStudio 12.6
kim.barrett at oracle.com
Tue May 1 00:42:40 UTC 2018
> On Apr 27, 2018, at 7:25 PM, David Holmes <david.holmes at oracle.com> wrote:
> We discussed this offline and Gary pointed out that, at least in the VMError case the attempt to SEGV by dereferencing zero is one of a specific number of crash inducing cases, others of which include trying to trigger SEGV at non-zero address and explicit signal raising. So changing the code to raise the signal directly is not really appropriate - and the code in VMError knows the attempt may not result in a crash.
> So I am okay with just disabling the compilation warnings for these two cases.
I feel pretty uncomfortable with code that is intentionally invoking
undefined behavior and expecting anything at all useful to come from
I think in the frame::oops_do_internal case, the code used when
CrashGCForDumpingJavaThread should use os::signal_raise, as suggested
by David. Except there is the problem that David diagnosed in
JDK-8139300, that OSX raise sends a signal to the main thread instead
of the current thread. I wonder if that is still true with our new
minimum supported OSX version? Man pages on my Mac say raise sends
the signal to the current thread. (And I'm surprised that bug was
fixed that way, rather than using os::signal_raise and making sure
that worked properly.)
In VMError::controlled_crash, not only is there no guarantee the write
will crash, there's also no guarantee the break will do anything
either. Since executing the write clearly invokes UB, the subsequent
break can be assumed to be unreachable, or demons may fly out your
But since both of these are !PRODUCT, I guess I'm okay with
suppressing the warning for now, as a way to move forward with the
compiler upgrade. However, I'd like the scope of that warning
suppression narrowed if possible, such as by moving it down to inside
the #ifndef PRODUCT protecting the test code. We don't need the
suppression for the entire file. For the frame case, does Solaris
support any sort of push/pop diagnostic control?
And it looks like there is further cleanup needed in these areas.
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