test and fix for very large structure fields which were confused with bitfields

2 files changed, 16 insertions, 5 deletions

diff --git a/lib_pypy/_ctypes/structure.py b/lib_pypy/_ctypes/structure.py
index 26fabf7b01..1f56480f43 100644
--- a/lib_pypy/_ctypes/structure.py
+++ b/lib_pypy/_ctypes/structure.py
@@ -34,16 +34,18 @@ def names_and_fields(self, _fields_, superclass, anonymous_fields=None):
     for i, field in enumerate(all_fields):
         name = field[0]
         value = field[1]
+        is_bitfield = (len(field) == 3)
         fields[name] = Field(name,
                              self._ffistruct.fieldoffset(name),
                              self._ffistruct.fieldsize(name),
-                             value, i)
+                             value, i, is_bitfield)
 
     if anonymous_fields:
         resnames = []
         for i, field in enumerate(all_fields):
             name = field[0]
             value = field[1]
+            is_bitfield = (len(field) == 3)
             startpos = self._ffistruct.fieldoffset(name)
             if name in anonymous_fields:
                 for subname in value._names:
@@ -52,7 +54,7 @@ def names_and_fields(self, _fields_, superclass, anonymous_fields=None):
                     subvalue = value._fieldtypes[subname].ctype
                     fields[subname] = Field(subname,
                                             relpos, subvalue._sizeofinstances(),
-                                            subvalue, i)
+                                            subvalue, i, is_bitfield)
             else:
                 resnames.append(name)
         names = resnames
@@ -60,8 +62,8 @@ def names_and_fields(self, _fields_, superclass, anonymous_fields=None):
     self._fieldtypes = fields
 
 class Field(object):
-    def __init__(self, name, offset, size, ctype, num):
-        for k in ('name', 'offset', 'size', 'ctype', 'num'):
+    def __init__(self, name, offset, size, ctype, num, is_bitfield):
+        for k in ('name', 'offset', 'size', 'ctype', 'num', 'is_bitfield'):
             self.__dict__[k] = locals()[k]
 
     def __setattr__(self, name, value):
@@ -225,7 +227,7 @@ class StructOrUnion(_CData):
             field = self._fieldtypes[name]
         except KeyError:
             return _CData.__getattribute__(self, name)
-        if field.size >> 16:
+        if field.is_bitfield:
             # bitfield member, use direct access
             return self._buffer.__getattr__(name)
         else:
diff --git a/pypy/module/test_lib_pypy/ctypes_tests/test_structures.py b/pypy/module/test_lib_pypy/ctypes_tests/test_structures.py
index d0b06795e9..a0f9a208b4 100644
--- a/pypy/module/test_lib_pypy/ctypes_tests/test_structures.py
+++ b/pypy/module/test_lib_pypy/ctypes_tests/test_structures.py
@@ -424,6 +424,15 @@ class TestStructure(BaseCTypesTestChecker):
             sys.settrace(oldtrace)
             events = None
 
+    def test_large_fields(self):
+        # make sure that large fields are not "confused" with bitfields
+        # (because the bitfields use the higher bits of the "size" attribute)
+        Array = c_long * 8192
+        class X(Structure):
+            _fields_ = [('items', Array)]
+        obj = X()
+        assert isinstance(obj.items, Array)
+
 class TestPointerMember(BaseCTypesTestChecker):
 
     def test_1(self):