Re: NullPointerException throwed when running GCJ

[majia gm <gmmajia@gmail.com>]

2010/12/30 David Daney <ddaney@caviumnetworks.com>:
> On 12/29/2010 12:01 AM, majia gm wrote:
>>
>> 2010/12/29 David Daney<ddaney@caviumnetworks.com>:
>>>
>>> Adding java@... as this is where java questions are handled.
>>>
>>> On 12/28/2010 07:05 AM, majia gm wrote:
>>>>
>>>> Hi, everyone.
>>>>
>>>> I'm porting GCJ to a non-mainstream platform, which is a RISC machine
>>>> with some similarity to ARM.
>>>> The GCC I'm using is version 4.4.2. I start the porting from ARM's code.
>>>>
>>>
>>> There is quite a bit of work involved in getting libgcj running on a new
>>> target.  One thing that is obvious from your stack trace is that the
>>> stack
>>> unwinding code is not decoding the instruction pointer properly. That
>>> would
>>> be one place to start.
>>>
>>> Unfortunatly, there isn't really one specific thing we can point you to.
>>>  You will probably have to step through things with GDB and make sure
>>> that
>>> are the target specific code is doing the right thing.
>>>
>>> The boehm-gc may need porting as well.  Actually I might start with
>>> boehm-gc, I think it has its own test suite, so it can be debugged
>>> separately.
>>>
>>> Then look at all the target specific code for a known working target
>>> (arm,
>>> mips, x86, etc...) and try to verify that your target code functions
>>> correctly.
>>>
>>> Good Luck,
>>> David Daney
>>>
>>>
>>>
>>>> When running the GCJ on the target platform, it mentioned that the ECJ
>>>> is needed. I don't know whether GCJ can live without ECJ, so I
>>>> donwload the latest ECJ jar file and recompiled.
>>>>
>>>> When running GCJ to compile a JAVA source file, I got the following
>>>> error.
>>>>
>>>> [root@localhost pxx]# gcj -C HelloWorld.java -v
>>>> Using built-in specs.
>>>> Target: unicore32-linux
>>>> Configured with: /home/vhome/FengYi/pxx/mydir/gcc-4.4.2/configure
>>>> --host=unicore32-linux --target=unicore32-linux --prefix=/usr
>>>> --build=i686-redhat-linux-gnu --enable-clocale=gnu --enable-shared
>>>> --enable-threads=posix --enable-__cxa_atexit --enable-languages=java
>>>> --with-gnu-ld --disable-libstdcxx-pch --disable-multilib
>>>> --with-pkgversion=UC4_1.0_gama_20101228
>>>> Thread model: posix
>>>> gcc version 4.4.2 (UC4_1.0_gama_20101228)
>>>> COLLECT_GCC_OPTIONS='-fsaw-java-file' '-C' '-v'
>>>> '-fbootclasspath=./:/usr/share/java/libgcj-4.4.2.jar' '-g1'
>>>> '-fsyntax-only' '-femit-class-files' '-S' '-o' 'NONE' '-shared-libgcc'
>>>>  /usr/libexec/gcc/unicore32-linux/4.4.2/ecj1 HelloWorld.java -g1
>>>> -fbootclasspath=./:/usr/share/java/libgcj-4.4.2.jar -g1 -fsource=1.5
>>>> -ftarget=1.5 -fzip-dependency /tmp/ccTF9EKh.zip
>>>> Exception in thread "main" java.lang.ExceptionInInitializerError
>>>>    at 0x1(Unknown Source)
>>>>    at 0x3(Unknown Source)
>>>>    at 0x5(Unknown Source)
>>>>    at 0x5(Unknown Source)
>>>>    at 0x5(Unknown Source)
>>>>    at 0x5(Unknown Source)
>>>>    at 0x5(Unknown Source)
>>>>    at 0xffffffffffffffff(Unknown Source)
>>>>    at 0x2(Unknown Source)
>>>>    at 0xffffffffffffffff(Unknown Source)
>>>>    at 0xffffffffffffffff(Unknown Source)
>>>> Caused by: java.lang.NullPointerException
>>>>    at 0x1(Unknown Source)
>>>>    at 0x5(Unknown Source)
>>>>    at 0x4(Unknown Source)
>>>>    ...9 more
>>>>
>>>>
>>>> Could anyone give me some hints on how could this happen?
>>>> I really appreciate you patience.
>>>>
>>>
>>>
>>
>> Hi, David.
>>
>> Thank you for your reply. It's very nice of you.
>>
>> When metioned to the stack unwinding code, do you mean the file
>> backtrace.h in libjava/sysdeps/arch? It seems some archs don't have
>> this file. And ARM has this file, but seems it takes over little
>> works.
>>
>
> Before java can work, you need to make sure that your GCC can correctly
> compile C and C++ code.  Specifically all GCC testsuite C and C++ tests that
> deal with exception handling must pass.
>
> libgcj as a normal part of its startup processing will throw and catch
> several exceptions.  If the exception handling machinery is not working you
> will never get to your programs main() method.
>
> Before trying to get your own programs working, you should be able to run
> the libjava testsuite and have the majority of the the tests pass.
>
>
>
>> Actually, the current status of my porting is as follows. I tried gij
>> successfully on the target to interpret a simple class file
>> HelloWorld.class which is compiled through a x86-gcj on a x86 machine.
>> And the gcj on the target also works well to compile the source file
>> HelloWorld.java into native executable file. But it fails to compile
>> HelloWorld.java into HelloWorld.class through gcj on the target. My
>> GCC version is 4.4.2, and the ecj I used is the latest.
>>
>> I found that when compiling Java sources into class file, the x86-gcj
>> use the jc1 instead of ecj.
>> The following two questions confusing me. Can gcj live without ecj?
>> What's the difference between ecj and jc1? I googled and got little.
>>
>
> ecj: .java -> .class
> jc1: .class -> .s (assembly)
> as:  .s -> .o (linkable object code)
> ld:  .o -> executable program.
>
> The gcj driver program runs the required sequence of these to obtain the
> requested result.
>
>> If you could give me some hints, I would really appreciate.
>>
>> Thank you.
>> Gmmajia
>>
>
>

Hi, David.

My target toolchain is cross build in a x86 machine. On my target
machine there's only executables and libs of the toolchain, but no
build tree.

To run the testsuite, it seems I cannot use 'make check'  when there's
no build tree. Must I rebuild the toolchian on the target?

Thank you.