Backed out changeset 0087e2aec9ef

Un-kill the ctypes backend.  Issue #282 for a justification.

1 files changed, 18 insertions, 12 deletions

diff --git a/cffi/api.py b/cffi/api.py
index 6d1eb48..eda7209 100644
--- a/cffi/api.py
+++ b/cffi/api.py
@@ -46,21 +46,20 @@ class FFI(object):
     '''
 
     def __init__(self, backend=None):
-        """Create an FFI instance.
-
-        The 'backend' argument is not used any more and must be set to None.
-        It is still present only so that 'FFI(None)' still works, and
-        for a few tests.
+        """Create an FFI instance.  The 'backend' argument is used to
+        select a non-default backend, mostly for tests.
         """
         from . import cparser, model
-
         if backend is None:
-            # You need the corresponding version of PyPy, or CPython
-            # with the '_cffi_backend' C extension module compiled.
+            # You need PyPy (>= 2.0 beta), or a CPython (>= 2.6) with
+            # _cffi_backend.so compiled.
             import _cffi_backend as backend
             from . import __version__
             assert backend.__version__ == __version__, \
                "version mismatch, %s != %s" % (backend.__version__, __version__)
+            # (If you insist you can also try to pass the option
+            # 'backend=backend_ctypes.CTypesBackend()', but don't
+            # rely on it!  It's probably not going to work well.)
 
         self._backend = backend
         self._lock = allocate_lock()
@@ -76,6 +75,8 @@ class FFI(object):
         self._init_once_cache = {}
         self._cdef_version = None
         self._embedding = None
+        if hasattr(backend, 'set_ffi'):
+            backend.set_ffi(self)
         for name in backend.__dict__:
             if name.startswith('RTLD_'):
                 setattr(self, name, getattr(backend, name))
@@ -83,10 +84,15 @@ class FFI(object):
         with self._lock:
             self.BVoidP = self._get_cached_btype(model.voidp_type)
             self.BCharA = self._get_cached_btype(model.char_array_type)
-        # attach these constants to the class
-        if not hasattr(FFI, 'NULL'):
-            FFI.NULL = self.cast(self.BVoidP, 0)
-            FFI.CData, FFI.CType = backend._get_types()
+        if isinstance(backend, types.ModuleType):
+            # _cffi_backend: attach these constants to the class
+            if not hasattr(FFI, 'NULL'):
+                FFI.NULL = self.cast(self.BVoidP, 0)
+                FFI.CData, FFI.CType = backend._get_types()
+        else:
+            # ctypes backend: attach these constants to the instance
+            self.NULL = self.cast(self.BVoidP, 0)
+            self.CData, self.CType = backend._get_types()
 
     def cdef(self, csource, override=False, packed=False):
         """Parse the given C source.  This registers all declared functions,