Fix issue #3547: ctypes is confused by bitfields of varying integer types

Reviewed by Fredrik Lundh and Skip Montanaro.

Backport from trunk.

Lib/ctypes/test/test_bitfields.py

@@ -215,6 +215,21 @@ class BitFieldTest(unittest.TestCase):
                         ("b", c_ubyte, 4)]
         self.failUnlessEqual(sizeof(X), sizeof(c_byte))
 
+    def test_mixed_4(self):
+        class X(Structure):
+            _fields_ = [("a", c_short, 4),
+                        ("b", c_short, 4),
+                        ("c", c_int, 24),
+                        ("d", c_short, 4),
+                        ("e", c_short, 4),
+                        ("f", c_int, 24)]
+        # MS compilers do NOT combine c_short and c_int into
+        # one field, gcc does.
+        if os.name in ("nt", "ce"):
+            self.failUnlessEqual(sizeof(X), sizeof(c_int) * 4)
+        else:
+            self.failUnlessEqual(sizeof(X), sizeof(c_int) * 2)
+
     def test_anon_bitfields(self):
         # anonymous bit-fields gave a strange error message
         class X(Structure):

Misc/NEWS

@@ -86,6 +86,9 @@ Core and builtins
 Library
 -------
 
+- Issue #3547: Fixed ctypes structures bitfields of varying integer
+  sizes.
+
 - Issue #3762: platform.architecture() fails if python is lanched via
   its symbolic link.
 

Modules/_ctypes/cfield.c

@@ -163,7 +163,7 @@ CField_FromDesc(PyObject *desc, int index,
 		break;
 
 	case EXPAND_BITFIELD:
-		/* XXX needs more */
+		*poffset += dict->size - *pfield_size/8;
 		*psize += dict->size - *pfield_size/8;
 
 		*pfield_size = dict->size * 8;