Eric Abbott created HADOOP-10027:
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             Summary: *Compressor_deflateBytesDirect passes instance instead of 
jclass to GetStaticObjectField
                 Key: HADOOP-10027
                 URL: https://issues.apache.org/jira/browse/HADOOP-10027
             Project: Hadoop Common
          Issue Type: Bug
          Components: native
            Reporter: Eric Abbott
            Priority: Minor


http://svn.apache.org/viewvc/hadoop/common/trunk/hadoop-common-project/hadoop-common/src/main/native/src/org/apache/hadoop/io/compress/zlib/ZlibCompressor.c?view=markup

This pattern appears in all the native compressors.
    // Get members of ZlibCompressor
    jobject clazz = (*env)->GetStaticObjectField(env, this,
                                                 ZlibCompressor_clazz);

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.

(gdb) 
#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?



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