linking libc with JNI code on embedded Linux platform (GuruPlug) - linux

Question

I'm trying to compile a simple JNI application on an embedded Linux platform (a GuruPlug computer), but for some reason it's not linking to libc properly. The Java program I'm compiling is called Test.java:
public class Test {
static {
System.loadLibrary("Test");
}
public static void main(String[] args) {
new Test().printMessage();
}
public native void printMessage();
}
The implementation of printMessage() is in Test.c:
#include <jni.h>
#include <stdio.h>
#include "Test.h"
JNIEXPORT void JNICALL Java_Test_printMessage(JNIEnv *env, jobject obj)
{
printf("Message 123...\n");
}
I'm compiling Test.c with the following command on a bash shell:
gcc -g -shared -static -lc -Wl,-soname,libTest.so -I${JAVA_HOME}/include/ -I${JAVA_HOME}/include/linux/ Test.c -o libTest.so
When I run the above command, I get the error message "R_ARM_TLS_LE32 relocation not permitted in shared object". The full error message is:
/usr/bin/ld: /usr/lib/gcc/arm-linux-gnueabi/4.4.5/../../../libc.a(dl-tsd.o)(.text+0x18): R_ARM_TLS_LE32 relocation not permitted in shared object
Despite the error message, the JNI .so file is still written by the compiler, but running the Java application gives the following error message:
Exception in thread "main" java.lang.UnsatisfiedLinkError: /usr/lib/jni/libTest.so: /usr/lib/jni/libTest.so: unexpected reloc type 0x03
at java.lang.ClassLoader$NativeLibrary.load(Native Method)
at java.lang.ClassLoader.loadLibrary0(ClassLoader.java:1750)
at java.lang.ClassLoader.loadLibrary(ClassLoader.java:1675)
at java.lang.Runtime.loadLibrary0(Runtime.java:840)
at java.lang.System.loadLibrary(System.java:1047)
at Test.<clinit>(Test.java:3)
Could not find the main class: Test. Program will exit.
Does anybody have any idea how to go about fixing this? Admittedly, the above code is a toy example, but I need to get a real JNI library compiling on this platform, and the real JNI library depends on libc. I can't seem to solve this basic issue of linking libc with a JNI library. Any suggestions would be greatly appreciated.
Thanks!

Answer 1

gcc -g -shared -static -lc -Wl,-soname,libTest.so -I${JAVA_HOME}/include/ -I${JAVA_HOME}/include/linux/ Test.c -o libTest.so
There are several problems with the command line above:
the -shared and -static flags are mutually exclusive, and the second overrides the first
when linking shared libraries, you want -fPIC on most architectures
the -lc is in the wrong place (should follow your sources, not precede them), and is not necessary anyway: gcc will add it automatically
you don't strictly need the -soname either; it's just useless clutter
The correct command then is:
gcc -g -shared -fPIC -I${JAVA_HOME}/include -I${JAVA_HOME}/include/linux \
Test.c -o libTest.so