Re: [Jamvm-general] Jamvm seg faults on Mips ( Big endian )

[Robert L. <rob...@gm...>]

Hi,

On 2 August 2011 09:50, JediKnight <ver...@ya...> wrote:
>
> Hi Rob,
>
> Any pointers how to debug this ?
>

Debugging a JVM is not easy.  First thing to always do is disable the
(code-copying) JIT.  This is for two reasons.  If it now works the
problem is likely to be invalid code from the JIT.  You now have a
really tough debugging task!

If it still doesn't work the problem is in the rest of the VM.
Turning off the JIT makes debugging far easier, as the PC now points
to compiled C code rather than generated code, which confuses the
debugger.

On MIPS, the JIT is off by default in 1.5.4.  It is on in 1.6.0.

./configure --disable-int-inlining

Now run the executable in gdb.  Before you run anything you want to do:

handle SIGUSR1 nostop pass noprint

Otherwise gdb will stop whenever a thread is suspended by the VM (e.g.
for garbage collection).

Now run your program.  It should stop when the segv occurs, and you
should be able to get a backtrace.

This should be enough for getting on with.  You'll probably want to
poke about a bit, and print the values of various variables.  By
default JamVM is built with -O2 -g.  The -O2 can make debugging
harder, as some values will be optimised out by the compiler.  So at
this stage you might like to try disabling optimisation, e.g.:

./configure --disable-int-inlining CFLAGS=-g

Of course, everything will run much slower.

Rob.

> /JediKnight
>
> --
> View this message in context: http://old.nabble.com/Jamvm-seg-faults-on-Mips-%28-Big-endian-%29-tp32089143p32176070.html
> Sent from the JamVM mailing list archive at Nabble.com.
>
>
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