Debugging segmentation faults in the JVM on linux-powerpc

[Severin Gehwolf]

Hi,

On Fri, 2017-06-09 at 20:57 +0200, John Paul Adrian Glaubitz wrote:
> On 06/09/2017 07:54 PM, John Paul Adrian Glaubitz wrote:
> > On 06/09/2017 05:58 PM, John Paul Adrian Glaubitz wrote:
> > > I'll rebuild everything with --enable-debug --with-debug-level=slowdebug
> > 
> > Just rebuilding with "--with-debug-level=slowdebug", of course. Both options
> > are mutually exclusive.
> 
> Surprise, surprise. Building with "--with-debug-level=slowdebug" instead of
> "--with-debug-level=release" made the crash go away. Does gcc optimize too
> aggressively here?

It smells a lot like the GCC issues we've run across when building with
newer compilers in Fedora/RHEL.

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

Others were UB in hotspot code:
https://bugs.openjdk.java.net/browse/JDK-8078666

Which GCC version is this?

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.

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.

Cheers,
Severin