build crash after extending oopDesc

[Simmen David]

Hello
Thanks so far your help.
Moving the new field after the _mark field did not help.

The error still occurs when the build process tries to link hotspot.
Alltough the error message now difers a bit it occurs still at the same place

Here is the build output
Linking vm...
/usr/bin/objcopy --only-keep-debug libjvm.so libjvm.debuginfo
/usr/bin/objcopy --add-gnu-debuglink=libjvm.debuginfo libjvm.so
strip -g libjvm.so
[ -f libjvm.debuginfo ] || ln -s libjvm.debuginfo libjvm.debuginfo
zip -q -y libjvm.diz libjvm.debuginfo libjvm.debuginfo
rm -f libjvm.debuginfo libjvm.debuginfo
[ -f libjvm.diz ] || { ln -s libjvm.diz libjvm.diz; }
echo Linking launcher...
Linking launcher...
gcc -m32 -march=i586 -Xlinker -O1 -Wl,--hash-style=both  -Xlinker -z -Xlinker noexecstack -m32 -march=i586 -Xlinker -export-dynamic  -L `pwd` -o gamma launcher/java_md.o launcher/jli_util.o launcher/wildcard.o launcher/java.o -ljvm -lm -ldl -lpthread
make[6]: Leaving directory `/home/jdk/openjdku4/build/linux-i586/hotspot/outputdir/linux_i486_compiler2/product'
All done.
make[5]: Leaving directory `/home/jdk/openjdku4/build/linux-i586/hotspot/outputdir/linux_i486_compiler2/product'
cd linux_i486_compiler2/product && ./test_gamma
Using java runtime at: /usr/lib/jvm/java-6-openjdk/jre
#
# A fatal error has been detected by the Java Runtime Environment:
#
#  SIGSEGV (0xb) at pc=0x00000000, pid=6318, tid=1090440000
#
# JRE version: 6.0_24-b24
# Java VM: OpenJDK Server VM (23.2-b03 mixed mode linux-x86 )
# Problematic frame:
# C  0x00000000
#
# Failed to write core dump. Core dumps have been disabled. To enable core dumping, try "ulimit -c unlimited" before starting Java again
#
# An error report file with more information is saved as:
# /home/jdk/openjdku4/build/linux-i586/hotspot/outputdir/linux_i486_compiler2/product/hs_err_pid6318.log
#
# If you would like to submit a bug report, please visit:
#   http://bugreport.sun.com/bugreport/crash.jsp
#
Aborted (core dumped)
make[4]: *** [product] Error 134


and here the code
class oopDesc {
  friend class VMStructs;
 private:
  volatile markOop  _mark;
  jint NewField;
  union _metadata {
    wideKlassOop    _klass;
    narrowOop       _compressed_klass;
  } _metadata;


MfG David

-----Original Message-----
From: hotspot-dev-bounces at openjdk.java.net [mailto:hotspot-dev-bounces at openjdk.java.net] On Behalf Of Thomas Wuerthinger
Sent: Sunday, June 10, 2012 8:23 PM
To: Remi Forax
Cc: hotspot-dev at openjdk.java.net; Christian Thalinger
Subject: Re: build crash after extending oopDesc

Extensibility and flexibility are at least main goals of the Graal project. We are currently doing experiments around removing the restriction on the JIT by writing the interpreter in Java too. We will present our results at this year's JVM Language Summit.

- thomas


On 10.06.2012 12:55, Remi Forax wrote:
> I think Graal (the OpenJDK project) is nowadays close to the original 
> hotspot in term of hackability even if it's restricted to the JIT.
>
> Rémi
>
> Sent from my Phone
>
> ----- Reply message -----
> From: "John Rose" <john.r.rose at oracle.com>
> To: "Krystal Mok" <rednaxelafx at gmail.com>
> Cc: "hotspot-dev at openjdk.java.net" <hotspot-dev at openjdk.java.net>, 
> "Christian Thalinger" <christian.thalinger at oracle.com>
> Subject: build crash after extending oopDesc
> Date: Sat, Jun 9, 2012 09:37
>
>
> On Jun 8, 2012, at 11:51 AM, Krystal Mok wrote:
>
> > David,
> >
> > If this patch [1] resembles your change, then what I saw was that
> the VM would build all right, but would fail running test_gamma right 
> at the end of the build process.
> >
> > The problem was caused by arrayOopDesc::length_offset_in_bytes(), as
> noted [2]. test_gamma runs fine if I drop a .hotspotrc file specifying 
> -UseCompressedOops in it, which confirms the problem.
>
> Good analysis, Kris.
>
> What happens if you add the extraneous field after the _mark field?  I 
> think that would be more robust, although there is still likely to be 
> a bug tail.
>
> Here's an old war-story:  When the original Hotspot team brought their 
> prototype to Sun long ago, I was on the technical evaluation team.
>  One of my tests was to inject an extra field into class oopDesc. 
>  (Specifically, the field held a string representation of the thread 
> backtrace at the point of the object's allocation.  A crude allocation
> profiler!)  The system worked with a few edits and no further 
> adjustment.  This demonstrated to me that the software architecture 
> was robust and ready to evolve.
>
> (Things are different now.  The system is more than 10x larger.  It 
> contains multiple platform ports, two good JITs, instrumentation, 
> several GCs, and compressed pointers, none of which the prototype had.
>  I wish our system were still as malleable as it was when it was 
> young, but it's a different engineering problem today.)
>
> — John
>
> diff --git a/src/share/vm/oops/oop.hpp b/src/share/vm/oops/oop.hpp
> --- a/src/share/vm/oops/oop.hpp
> +++ b/src/share/vm/oops/oop.hpp
> @@ -62,6 +62,7 @@
>   friend class VMStructs;
>  private:
>   volatile markOop  _mark;
> +  intptr_t _extraneous;
>   union _metadata {
>     wideKlassOop    _klass;
>     narrowOop       _compressed_klass;
>