Hello again,
I managed to build my library using the the GNU linker
(ld -G -f /usr/lin/libdb.so -o libkeys.so) but another problem surfaced - I now get
java.lang.UnsatisfiedLinkError: /home/ams/work/keys/libkeys.so: undefined
symbol: GetStringUTFChars
I pass -Djava.library.path=/home/ams/work/keys which according to everything i read
should be sufficient. Besides, setting
LD_LIBRARY_PATH=/usr/local/java/jre/lib/i386/classic doesn't help either.
Any idea what is going on? TIA,
-a
Joi Ellis wrote:
> "Aaron M. Stromas" wrote:
> >
> > greetings,
> >
> > I need a little assistance with building a shared library for JNI under
> > Linux 2.2.
> > This is how I went about creating the library:
> >
> > compiling: g++ -I /usr/local/java/include
> > -I/usr/local/java/include/linux -shared -fPIC -o keys.o keys.c
> >
> > linking: gcc -shared -Wl,-soname,libkeys.so -o libkeys.so.0 keys.o -lc
> >
> > $ java -Djava.library.path=/home/ams/work/keys T
> > Exception in thread "main" java.lang.UnsatisfiedLinkError:
>/home/ams/work/keys/libkeys.so: keys.o: cannot open shared object file: No such file
>or directory
> > at java.lang.ClassLoader$NativeLibrary.load(Native Method)
> > at java.lang.ClassLoader.loadLibrary0(ClassLoader.java:1357)
> > at java.lang.ClassLoader.loadLibrary(ClassLoader.java:1281)
> > at java.lang.Runtime.loadLibrary0(Runtime.java:469)
> > at java.lang.System.loadLibrary(System.java:774)
> > at T.<clinit>(T.java:5)
> >
> > I have also tried another way of building the library (ld -G -f
> > /lib/libuuid.so.1 keys.o -o libkeys.so) but got the same error. I have
> > to mention that the native code accesses the libdb.so library which i
> > copied to /home/ams/work/keys. Why doesn't java find my library? TIA,
>
> I found that JNI code can compile and link without error and still be
> incorrect, and the only error you do get is the one above. I diagnose
> this with 'ldd -r /path/to/library/file' and see if there are any
> unresolved references that don't point to an existing library.
>
> Your library is looking for a routine "keys" which does not exist in
> that library, or any of the other .o files you sent through the linker.
>
> Here's bits of a Makefile with the gcc/library commands I use:
>
> JAVA_HOME=/usr/local/java/jdk1.2.2
> JAVA_INC= -I$(JAVA_HOME)/include -I$(JAVA_HOME)/include/linux
> #
> # gcc configurable compile options of interest
> # -H list include header names
> # -g debugging code enabled
> GCCOPT= -g
> LDOPT=-Xlinker -t -Xlinker -Map -Xlinker /tmp/linkmap
> GCCDEF=-DIP_SUPPORT -DUNIX
> LIBOUT=$(HOME)/lib
> SRC=$(PROJ)/src
>
> $(LIBOUT)/libjsystem.so: \
> $(SRC)/JNsApiSubsystemInterfaces.h \
> $(SRC)/JNsApiSubsystemInterfaces.c \
> $(CLASSES)/com/aravox/nsapi/subsystem/JNsApiSubsystemInterfaces.class
> - rm -f $@
> @echo Creating $@...
> gcc $(GCCOPT) $(GCCDEF) $(JAVA_INC) -I$(SRC) \
> $(LDOPT) \
> -shared -o $@ $(SRC)/JNsApiSubsystemInterfaces.c \
> $(LIBOUT)/lib*.so
> /home/joi/bin/anyUndefined $(LIBOUT)/lib*.so
>
>
> anyUndefined is a bash script which inspects the resulting .so for
> unresolved references and exits with an error code make will detect.
>
> #!/bin/bash
> tmp=/tmp/anyUndefined.$$
> ldd -r $1 >$tmp 2>&1
> echo "----------"
> cat $tmp
> echo "----------"
> if
> grep undefined $tmp;
> then
> exit 1
> else
> exit 0
> fi
>
> --
> Joi Ellis Software Engineer
> Aravox Technologies [EMAIL PROTECTED], [EMAIL PROTECTED]
>
> No matter what we think of Linux versus FreeBSD, etc., the one thing I
> really like about Linux is that it has Microsoft worried. Anything
> that kicks a monopoly in the pants has got to be good for something.
> - Chris Johnson
--
Aaron Stromas | "Tick-tick-tick!!!... ja, Pantani is weg..."
Oracle Corp | BRTN commentator
+1 703.708.68.21 | L'Alpe d'Huez
1995 Tour de France
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