AppletTalk.com Java discussions newsgroups   Archives   FAQ   Search   Memberlist   Usergroups   Register   Profile   Log in to check your private messages   Log in  Problem loading libs via /etc/ld.so.conf          AppletTalk.com Forum Index -> JVM, native methods and hardware View previous topic :: View next topic   Author Message Laurenz Albe Guest Posted: Wed Aug 02, 2006 6:46 pm    Post subject: Problem loading libs via /etc/ld.so.conf I am using Sun Java 1.4.2_05-b04 on a RedHat Enterprise Server 3 Linux machine, Kernel 2.4.21, glibc 3.2.3. I am trying to load the shared library that belongs to a native method. When Java is started with LD_LIBRARY_PATH=/path/to/lib java MyClass or java -Djava.library.path=/path/to/lib MyClass everything works fine. However, when I add /path/to/lib to /etc/ld.so.conf and run 'ldconfig', Java does not find the library when run as java MyClass and reports an UnsatisfiedLinkError. This happens only with Java, other programs find the libraries fine, and the loader shows the libraries correctly when queried with 'ldconfig -p'. Does anybody have an idea what is wrong? Thank you, Laurenz Albe Back to top Gordon Beaton Guest Posted: Wed Aug 02, 2006 7:46 pm    Post subject: Re: Problem loading libs via /etc/ld.so.conf On 02 Aug 2006 13:46:32 GMT, Laurenz Albe wrote: Quote: When Java is started with LD_LIBRARY_PATH=/path/to/lib java MyClass or java -Djava.library.path=/path/to/lib MyClass everything works fine. However, when I add /path/to/lib to /etc/ld.so.conf and run 'ldconfig', Java does not find the library when run as java MyClass and reports an UnsatisfiedLinkError. Some questions: What mechanism do you use to load the library in your code? When you tested the various ways of specifying the library location, did you leave the library in the same place the whole time? Does the library have dependencies on other dynamic libraries? ("readelf -d libFoo.so", look for NEEDED entries, or ldd -v). Does setting e.g. LD_DEBUG=libs tell you anything? Finally, please post the complete text of the error message. There is likely something we're both overlooking. /gordon -- [ don't email me support questions or followups ] g o r d o n + n e w s @ b a l d e r 1 3 . s e Back to top Ralf Ullrich Guest Posted: Thu Aug 03, 2006 2:31 pm    Post subject: Re: Problem loading libs via /etc/ld.so.conf Laurenz Albe wrote: Quote: When Java is started with LD_LIBRARY_PATH=/path/to/lib java MyClass or java -Djava.library.path=/path/to/lib MyClass everything works fine. However, when I add /path/to/lib to /etc/ld.so.conf and run 'ldconfig', Java does not find the library when run as java MyClass and reports an UnsatisfiedLinkError. Does anybody have an idea what is wrong? Are you even sure, that finding a JNI library* via the /etc/ld.so.conf mechanism is supported by the SUN JVM? The only docs I can find about this say, that the properties java.library.path and sun.boot.library.path will be used as search paths to find JNI libraries. And if you look into the Source of java.lang.ClassLoader you will see nothing else but these two paths are eventually used. cu * As you see, I try to make a difference between JNI libraries that are loaded via java.lang.System.load/loadLibrary and system libraries, that will be loaded automatically due to dependencies. Only the latter will be loaded via /etc/ld.so.conf mechanism, which is what you see when you tested it with programs other than the Java VM. Back to top Laurenz Albe Guest Posted: Thu Aug 03, 2006 4:47 pm    Post subject: Re: Problem loading libs via /etc/ld.so.conf Gordon Beaton <n.o.t (AT) for (DOT) email> wrote: Quote: When Java is started with LD_LIBRARY_PATH=/path/to/lib java MyClass or java -Djava.library.path=/path/to/lib MyClass everything works fine. However, when I add /path/to/lib to /etc/ld.so.conf and run 'ldconfig', Java does not find the library when run as java MyClass and reports an UnsatisfiedLinkError. Some questions: What mechanism do you use to load the library in your code? System.loadLibrary(String) Quote: When you tested the various ways of specifying the library location, did you leave the library in the same place the whole time? Yes. Quote: Does the library have dependencies on other dynamic libraries? ("readelf -d libFoo.so", look for NEEDED entries, or ldd -v). libc.so.6 (found in /lib/tls), nothing else. Quote: Does setting e.g. LD_DEBUG=libs tell you anything? Not really; all I can see is that the libraries loaded at Java startup (e.g. libpthread.so.0) are located in a different way than the libraries loaded from Java. The former produces several messages like trying file=./libpthread.so.0 while the latter does not output a 'trying' at all, it just says calling init: /home/laurenz/jni/libTest.so or nothing at all, depending on whether I set LD_LIBRARY_PATH or not. Quote: Finally, please post the complete text of the error message. There is likely something we're both overlooking. I will, and I also will post the complete sample, as it is very short. The problem occurs not only with this test program (so it is no bug of the test program). I have searched java.sun.com and elsewhere, but didn't find any clue. I wonder if it is a bug or 'expected behaviour'. Thanks for any hints, Laurenz Albe Error message: ============== Exception in thread "main" java.lang.UnsatisfiedLinkError: no Test in java.library.path at java.lang.ClassLoader.loadLibrary(ClassLoader.java:1517) at java.lang.Runtime.loadLibrary0(Runtime.java:788) at java.lang.System.loadLibrary(System.java:834) at Test.<clinit>(Test.java:7) Java source (Test.java): ======================== public class Test { static { System.loadLibrary("Test"); } public static native void main(String[] args); } Compiled with: ============== javac -g Test.java Native method source (Test.c): ============================== #include <jni.h> JNIEXPORT void JNICALL Java_Test_main (JNIEnv *a, jclass b, jobjectArray c) { } Compiled with: ============== gcc -Wall -o libTest.so -shared -Wl,-soname,libTest.so Test.c -static -lc Back to top Gordon Beaton Guest Posted: Thu Aug 03, 2006 6:52 pm    Post subject: Re: Problem loading libs via /etc/ld.so.conf On 03 Aug 2006 11:47:29 GMT, Laurenz Albe wrote: Quote: I have searched java.sun.com and elsewhere, but didn't find any clue. I wonder if it is a bug or 'expected behaviour'. Until now I thought that it was possible to load native libraries in Java using ld.so, i.e. without setting LD_LIBRARY_PATH or java.library.path. But after looking (rather cursively) at the J2SE sources it seems that Java needs to be able to find the actual file based on the contents of java.library.path (in turn derived from LD_LIBRARY_PATH), before passing the resulting absolute path to a native method that loads the library. This is unfortunate and IMO unnecessary, since dlopen() will search ld.so.cache if not given an absolute path. On the other hand if your library has dependencies on other shared libraries, those additional libraries must be loaded by ld.so, so the "normal" rules apply: put the path in ld.so.conf or LD_LIBRARY_PATH, i.e. java.library.path is not sufficient. /gordon -- [ don't email me support questions or followups ] g o r d o n + n e w s @ b a l d e r 1 3 . s e Back to top Laurenz Albe Guest Posted: Thu Aug 03, 2006 7:44 pm    Post subject: Re: Problem loading libs via /etc/ld.so.conf Ralf Ullrich <news (AT) jnana (DOT) de> wrote: Quote: Are you even sure, that finding a JNI library* via the /etc/ld.so.conf mechanism is supported by the SUN JVM? No; if I were sure, I wouldn't have asked. That's the information I would like to find. Do you have an idea where to start looking? Yours, Laurenz Albe Back to top Laurenz Albe Guest Posted: Thu Aug 03, 2006 7:47 pm    Post subject: Re: Problem loading libs via /etc/ld.so.conf Gordon Beaton <n.o.t (AT) for (DOT) email> wrote: Quote: Until now I thought that it was possible to load native libraries in Java using ld.so, i.e. without setting LD_LIBRARY_PATH or java.library.path. But after looking (rather cursively) at the J2SE sources it seems that Java needs to be able to find the actual file based on the contents of java.library.path (in turn derived from LD_LIBRARY_PATH), before passing the resulting absolute path to a native method that loads the library. This is unfortunate and IMO unnecessary, since dlopen() will search ld.so.cache if not given an absolute path. On the other hand if your library has dependencies on other shared libraries, those additional libraries must be loaded by ld.so, so the "normal" rules apply: put the path in ld.so.conf or LD_LIBRARY_PATH, i.e. java.library.path is not sufficient. Thank you for looking into that, your explanation seems reasonable and would explain the behaviour. I agree that this behaviour is unfortunate, because it breaks expected behaviour on Linux. Yours, Laurenz Albe Back to top Display posts from previous: All Posts1 Day7 Days2 Weeks1 Month3 Months6 Months1 Year Oldest FirstNewest First         AppletTalk.com Forum Index -> JVM, native methods and hardware All times are GMT Page 1 of 1   Jump to: Select a forum Java Newsgroups----------------Java DiscussionsWeb-based java games comp.lang.java 3D Graphics API's for Java Java: Support and criticism Java System Announcements comp.lang.java.api JavaBeans Java and CORBA Java and Databases comp.lang.java.developer Java GUI Toolkits Java Help comp.lang.java.javascript JVM, native methods and hardware comp.lang.java.misc Java Language Programming Security and Java comp.lang.java.setup Java Software Tools comp.lang.java.tech ibm.software.java.linux  Non-English Java Newsgroups----------------Java Language (German)Language Java (Français)Java (Italian)  You cannot post new topics in this forum You cannot reply to topics in this forum You cannot edit your posts in this forum You cannot delete your posts in this forum You cannot vote in polls in this forum Powered by phpBB © 2001, 2006 phpBB Group SEO toolkit © 2004-2006 webmedic.