[pypy-commit] pypy default: Issue #2813

[arigo]

Author: Armin Rigo <arigo at tunes.org>
Branch: 
Changeset: r94456:4a06e23782cf
Date: 2018-04-28 04:24 +0200
http://bitbucket.org/pypy/pypy/changeset/4a06e23782cf/

Log:	Issue #2813

	Fix for ctypes: doing some operations before setting the _fields_ of
	a Structure would make and cache an _ffiargtype that says "opaque".

diff --git a/lib_pypy/_ctypes/array.py b/lib_pypy/_ctypes/array.py
--- a/lib_pypy/_ctypes/array.py
+++ b/lib_pypy/_ctypes/array.py
@@ -82,8 +82,11 @@
     def _CData_output(self, resarray, base=None, index=-1):
         from _rawffi.alt import types
         # If a char_p or unichar_p is received, skip the string interpretation
-        if base._ffiargtype != types.Pointer(types.char_p) and \
-           base._ffiargtype != types.Pointer(types.unichar_p):
+        try:
+            deref = type(base)._deref_ffiargtype()
+        except AttributeError:
+            deref = None
+        if deref != types.char_p and deref != types.unichar_p:
             # this seems to be a string if we're array of char, surprise!
             from ctypes import c_char, c_wchar
             if self._type_ is c_char:
@@ -120,6 +123,12 @@
                 value = self(*value)
         return _CDataMeta.from_param(self, value)
 
+    def _build_ffiargtype(self):
+        return _ffi.types.Pointer(self._type_.get_ffi_argtype())
+
+    def _deref_ffiargtype(self):
+        return self._type_.get_ffi_argtype()
+
 def array_get_slice_params(self, index):
     if hasattr(self, '_length_'):
         start, stop, step = index.indices(self._length_)
@@ -248,6 +257,5 @@
             _type_ = base
         )
         cls = ArrayMeta(name, (Array,), tpdict)
-        cls._ffiargtype = _ffi.types.Pointer(base.get_ffi_argtype())
         ARRAY_CACHE[key] = cls
         return cls
diff --git a/lib_pypy/_ctypes/basics.py b/lib_pypy/_ctypes/basics.py
--- a/lib_pypy/_ctypes/basics.py
+++ b/lib_pypy/_ctypes/basics.py
@@ -49,10 +49,13 @@
         else:
             return self.from_param(as_parameter)
 
+    def _build_ffiargtype(self):
+        return _shape_to_ffi_type(self._ffiargshape_)
+
     def get_ffi_argtype(self):
         if self._ffiargtype:
             return self._ffiargtype
-        self._ffiargtype = _shape_to_ffi_type(self._ffiargshape_)
+        self._ffiargtype = self._build_ffiargtype()
         return self._ffiargtype
 
     def _CData_output(self, resbuffer, base=None, index=-1):
diff --git a/lib_pypy/_ctypes/pointer.py b/lib_pypy/_ctypes/pointer.py
--- a/lib_pypy/_ctypes/pointer.py
+++ b/lib_pypy/_ctypes/pointer.py
@@ -70,7 +70,12 @@
         self._ffiarray = ffiarray
         self.__init__ = __init__
         self._type_ = TP
-        self._ffiargtype = _ffi.types.Pointer(TP.get_ffi_argtype())
+
+    def _build_ffiargtype(self):
+        return _ffi.types.Pointer(self._type_.get_ffi_argtype())
+
+    def _deref_ffiargtype(self):
+        return self._type_.get_ffi_argtype()
 
     from_address = cdata_from_address
 
diff --git a/lib_pypy/_ctypes/structure.py b/lib_pypy/_ctypes/structure.py
--- a/lib_pypy/_ctypes/structure.py
+++ b/lib_pypy/_ctypes/structure.py
@@ -160,6 +160,10 @@
             raise AttributeError("_fields_ is final")
         if self in [f[1] for f in value]:
             raise AttributeError("Structure or union cannot contain itself")
+        if self._ffiargtype is not None:
+            raise NotImplementedError("Too late to set _fields_: we already "
+                        "said to libffi that the structure type %s is opaque"
+                        % (self,))
         names_and_fields(
             self,
             value, self.__bases__[0],
diff --git a/pypy/module/test_lib_pypy/ctypes_tests/test_pointers.py b/pypy/module/test_lib_pypy/ctypes_tests/test_pointers.py
--- a/pypy/module/test_lib_pypy/ctypes_tests/test_pointers.py
+++ b/pypy/module/test_lib_pypy/ctypes_tests/test_pointers.py
@@ -272,3 +272,18 @@
         base = cast(d, c_void_p).value
         for i in [0, 1, 4, 1444, -10293]:
             assert cast(byref(c, i), c_void_p).value == base + i
+
+    def test_issue2813_fix(self):
+        class C(Structure):
+            pass
+        POINTER(C)
+        C._fields_ = [('x', c_int)]
+        ffitype = C.get_ffi_argtype()
+        assert C.get_ffi_argtype() is ffitype
+        assert ffitype.sizeof() == sizeof(c_int)
+
+    def test_issue2813_cant_change_fields_after_get_ffi_argtype(self):
+        class C(Structure):
+            pass
+        ffitype = C.get_ffi_argtype()
+        raises(NotImplementedError, "C._fields_ = [('x', c_int)]")