Debugging segmentation faults in the JVM on linux-powerpc

[John Paul Adrian Glaubitz]

Hi Severin!

On Mon, Jun 12, 2017 at 01:51:20PM +0200, Severin Gehwolf wrote:
> It smells a lot like the GCC issues we've run across when building with
> newer compilers in Fedora/RHEL.

That's something that I have been thinking of as well. Especially
since the problem goes away when building with

      --with-debug-level=slowdebug.

> Here is one example which turned out to be a GCC bug:
> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63341

Aha, thanks for the pointer.

> Others were UB in hotspot code:
> https://bugs.openjdk.java.net/browse/JDK-8078666
> 
> Which GCC version is this?

gcc version 6.3.0 20170516 (SVN r248076 from the 6 branch).

> Provided this is a GCC issue:
> 
> In order to figure out which new optimization might have caused this,
> I'd suggest to go through the list of new opto flags that are on by
> default in the new version and disable one by one.

Good idea, I will try that. Thanks!

> Once you know which opto flag causes it, you might be able to figure
> out which object file causes the problem with something like this:
> https://github.com/jerboaa/hotspot-tools-find-bad-object
> 
> It might be something else entirely.

Very good pointers. I will try what you have suggested.

Adrian

-- 
 .''`.  John Paul Adrian Glaubitz
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