This warning is the cause of several FAILs for libjava testsuite on alphaev56-unknown-linux-gnu [1]:

FAIL: natgetargssize.cc compilation
FAIL: natgetlocalvartable.cc compilation
FAIL: natgetstacktrace.cc compilation
FAIL: natevents.cc compilation
FAIL: natgetallthreads.cc compilation
FAIL: natgeterrorname.cc compilation
FAIL: natgetmethodname.cc compilation

These tests all fail during compile with following message:

In file included from /home/uros/gcc-svn/trunk/libjava/testsuite/libjava.jvmti/interp/natgetargssize.cc:3:

/home/uros/gcc-svn/trunk/libjava/testsuite/../classpath/include/jvmti.h: In member function 'jvmtiError _Jv_JVMTIEnv::SetEventNotificationMode(jvmtiEventMode, jvmtiEvent, __jobject*, ...)':

/home/uros/gcc-svn/trunk/libjava/testsuite/../classpath/include/jvmti.h:1242: warning: cannot pass objects of non-POD type 'struct va_list' through '...'; call will abort at runtime

output is:
In file included from /home/uros/gcc-svn/trunk/libjava/testsuite/libjava.jvmti/interp/natgetargssize.cc:3:

/home/uros/gcc-svn/trunk/libjava/testsuite/../classpath/include/jvmti.h: In member function 'jvmtiError _Jv_JVMTIEnv::SetEventNotificationMode(jvmtiEventMode, jvmtiEvent, __jobject*, ...)':

/home/uros/gcc-svn/trunk/libjava/testsuite/../classpath/include/jvmti.h:1242: warning: cannot pass objects of non-POD type 'struct va_list' through '...'; call will abort at runtime


FAIL: natgetargssize.cc compilation

The relevant part of jvmti.h reads:

--cut here--
  jvmtiError SetEventNotificationMode (jvmtiEventMode mode,
				       jvmtiEvent event_type,
				       jthread event_thread, ...)
  {
    va_list args;
    va_start (args, event_thread);
    jvmtiError result = p->SetEventNotificationMode (this, mode, event_type,
						     event_thread, args);
    va_end (args);
    return result;
  }
--cut here--

[1] http://gcc.gnu.org/ml/gcc-testresults/2008-12/msg02551.html