This pattern appears in all the native compressors.
// Get members of ZlibCompressor
jobject clazz = (*env)->GetStaticObjectField(env, this,
The 2nd argument to GetStaticObjectField is supposed to be a jclass, not a jobject. Adding the JVM param -Xcheck:jni will cause "FATAL ERROR in native method: JNI received a class argument that is not a class" and a core dump such as the following.
#0 0x00007f02e4aef8a5 in raise () from /lib64/libc.so.6
#1 0x00007f02e4af1085 in abort () from /lib64/libc.so.6
#2 0x00007f02e45bd727 in os::abort(bool) () from /opt/jdk1.6.0_31/jre/lib/amd64/server/libjvm.so
#3 0x00007f02e43cec63 in jniCheck::validate_class(JavaThread*, _jclass*, bool) () from /opt/jdk1.6.0_31/jre/lib/amd64/server/libjvm.so
#4 0x00007f02e43ea669 in checked_jni_GetStaticObjectField () from /opt/jdk1.6.0_31/jre/lib/amd64/server/libjvm.so
#5 0x00007f02d38eaf79 in Java_org_apache_hadoop_io_compress_zlib_ZlibCompressor_deflateBytesDirect () from /usr/lib/hadoop/lib/native/libhadoop.so.1.0.0
In addition, that clazz object is only used for synchronization. In the case of the native method _deflateBytesDirect, the result is a class wide lock used to access the instance field uncompressed_direct_buf. Perhaps using the instance as the sync point is more appropriate?