Valgrind regression in "rpcrt4: Use abrtitrary pointer identifiers when marshalling pointers instead of using pointer values."?

[Dan Kegel]

This Valgrind error popped up for the first time today.
To reproduce, make sure you have an up to date valgrind
from svn, apply something like http://kegel.com/wine/valgrind/runtest.patch,
and do e.g.

$ cd dlls/rpcrt4/tests
$ RUNTEST_USE_VALGRIND=1 make server.ok

Reverting
http://source.winehq.org/git/wine.git/?a=commit;h=4bde42aaa20df0492e45a965ce05d4c20d36a62f
makes it go away, though I can't for the life of me see how.
Rob, can you have a look?

Syscall param socketcall.send(msg) points to uninitialised byte(s)
   at 0x40007F2: (within /lib/ld-2.7.so)
   by 0x4CEA13A: rpcrt4_conn_write (rpc_binding.h:171)
   by 0x4CEA006: RPCRT4_SendWithAuth (rpc_message.c:533)
   by 0x4CEA784: RPCRT4_Send (rpc_message.c:675)
   by 0x4CED074: process_request_packet (rpc_server.c:313)
   by 0x4CED34E: RPCRT4_process_packet (rpc_server.c:345)
   by 0x4CED422: RPCRT4_worker_thread (rpc_server.c:362)
   by 0x475F8C0: worker_thread_proc (threadpool.c:113)
   by 0x475D2A1: ??? (thread.c:128)
   by 0x475D329: call_thread_func (thread.c:383)
   by 0x475D58D: start_thread (thread.c:443)
   by 0x41754FA: start_thread (in /lib/tls/i686/cmov/libpthread-2.7.so)
   by 0x425FE5D: clone (in /lib/tls/i686/cmov/libc-2.7.so)
 Address 0x7f013870 is 24 bytes inside a block of size 49 alloc'd
   at 0x472C516: notify_alloc (heap.c:191)
   by 0x472C3DD: RtlAllocateHeap (heap.c:1231)
   by 0x4CE9E3C: RPCRT4_SendWithAuth (rpc_message.c:492)
   by 0x4CEA784: RPCRT4_Send (rpc_message.c:675)
   by 0x4CED074: process_request_packet (rpc_server.c:313)
   by 0x4CED34E: RPCRT4_process_packet (rpc_server.c:345)
   by 0x4CED422: RPCRT4_worker_thread (rpc_server.c:362)
   by 0x475F8C0: worker_thread_proc (threadpool.c:113)
   by 0x475D2A1: ??? (thread.c:128)
   by 0x475D329: call_thread_func (thread.c:383)
   by 0x475D58D: start_thread (thread.c:443)
   by 0x41754FA: start_thread (in /lib/tls/i686/cmov/libpthread-2.7.so)
   by 0x425FE5D: clone (in /lib/tls/i686/cmov/libc-2.7.so)
 Uninitialised value was created by a stack allocation
   at 0x496FBFB: IServer_get_filename (server_s.c:4697)