libgcj problem in FindClass with shared libraries.

abhishek desai
Wed Jun 3 10:51:00 GMT 2009

_Jv_RegisterClasses is called but only initially. Not after we call
FindClass. Also there is no call happening to dlsym after the library
is opened using dlopen in libdl. How are the symbols loaded then ?

On Wed, Jun 3, 2009 at 3:42 PM, Andrew Haley <> wrote:
> abhishek desai wrote:
>> I am using libgcj version 3.4.6 (I have to use this version of gcc and
>> libgcj) .
> Well, we can't fix it.  It is ancient history.
>> I have shared libraries with precompiled java clases and am
>> using JNI function call "(*env)->FindClass" to get the class. Tracing
>> through the _Jv_JNI_FIndClass I found that the dynamic library gets
>> loaded but the symbols are not loaded into the cache.
>> In the function call "jclass
>> gnu::gcj::runtime::VMClassLoader::findClass (jstring name)"
>> there is a call to "jboolean java::lang::Runtime::loadLibraryInternal
>> (jstring lib)" . This does the loading of the library by eventually
>> calling dlopen in libtdl.
>> After this call there is no call to access the symbol from the library
>> or to load it to the cache.
>> But the symbol is searched for in the cache using _Jv_FindClassInCache
>> which returns NULL. Is this a bug or I am missing something ? Need
>> help with getting the symbols loaded.
> You need to make sure that _Jv_RegisterClasses is being called when the
> shared library is loaded.  If it is, then the classes in the library will
> be found; if not, then you need to find out why not.
> Put a breakpoint on _Jv_RegisterClasses.  You should see it called once
> at startup, again when is loaded, and each time a shared library
> is loaded.
> Andrew.

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