NullPointerException throwed when running GCJ

majia gm gmmajia@gmail.com
Wed Dec 29 08:01:00 GMT 2010


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.

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.

If you could give me some hints, I would really appreciate.

Thank you.
Gmmajia



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