Original bug report at https://bugzilla.redhat.com/show_bug.cgi?id=1174037
Additional informations at Issue #20160

Note that this was reproduced not only with separate libffi package but also with libffi bundled in python.
Reproduced with Python 2.7.9 but same issue should exists also in 3.4.x.

Richard Henderson provided fix in original bug report at bugzilla (attached).

Summary:
======================================================================
FAIL: test_struct_by_value (ctypes.test.test_win32.Structures)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/builddir/build/BUILD/Python-2.7.9/Lib/ctypes/test/test_win32.py", line 112, in test_struct_by_value
    self.assertEqual(ret.left, left.value)
AssertionError: -200 != 10
----------------------------------------------------------------------

(gdb) b ReturnRect
Function "ReturnRect" not defined.
Make breakpoint pending on future shared library load? (y or [n]) y
Breakpoint 1 (ReturnRect) pending.
(gdb) run test_win32.py
Starting program: /usr/bin/python test_win32.py
Missing separate debuginfos, use: debuginfo-install glibc-2.20.90-12.fc22.aarch64
[Thread debugging using libthread_db enabled]
Using host libthread_db library "/lib64/libthread_db.so.1".

Breakpoint 1, ReturnRect (i=0, ar=..., br=0x59b750, cp=..., dr=..., er=0x59b750, fp=..., 
    gr=<error reading variable: Cannot access memory at address 0xffff000000000000>)
    at /usr/src/debug/Python-2.7.9/Modules/_ctypes/_ctypes_test.c:552
552	    if (ar.left + br->left + dr.left + er->left + gr.left != left * 5)
(gdb) p fp
$1 = {x = 4396722194992, y = 5879632}
(gdb) p cp
$2 = {x = 15, y = 25}
(gdb)

Consider to apply a patch or update bundled libffi.