pointer bitwidth and int bitwidth are different

theano/compile/tests/test_pfunc.py

@@ -556,7 +556,7 @@ class Test_pfunc(unittest.TestCase):
     def test_default_updates_input(self):
         x = shared(0)
         y = shared(1)
-        if theano.gof.cmodule.local_bitwidth() == 32:
+        if theano.gof.cmodule.python_int_bitwidth() == 32:
             a = iscalar('a')
         else:
             a = lscalar('a')

theano/compile/tests/test_shared.py

@@ -16,7 +16,7 @@ class Test_SharedVariable(unittest.TestCase):
             assert shared(7, dtype='float64').type == Scalar('float64')
 
         else:
-            if theano.gof.cmodule.local_bitwidth()==32:
+            if theano.gof.cmodule.python_int_bitwidth() == 32:
                 assert shared(7).type == theano.tensor.iscalar, shared(7).type
             else:
                 assert shared(7).type == theano.tensor.lscalar, shared(7).type

theano/gof/cmodule.py

@@ -29,12 +29,24 @@ AddConfigVar('cmodule.mac_framework_link',
         BoolParam(False))
 
 def local_bitwidth():
-    """Return 32 for 32bit arch, 64 for 64bit arch"""
-    # Note - it seems from an informal survey of machines at scipy2010
-    # that platform.architecture is a reliable way to get the bitwidth
-    arch = platform.architecture()
-    bit_width = arch[0][:-3]
-    return int(bit_width)
+    """
+    Return 32 for 32bit arch, 64 for 64bit arch
+
+    By "architecture", we mean the size of memory pointers (size_t in C),
+    *not* the size of long int, as it can be different.
+    """
+    # Platform.architecture is not reliable on OS X with universal binaries
+    maxsize = sys.maxsize
+    return len('%x' % maxsize) * 4
+
+def python_int_bitwidth():
+    """
+    Return the bit width of Python int (C long int).
+
+    Note that it can be different from the size of a memory pointer.
+    """
+    maxint = sys.maxint
+    return len('%x' % maxint) * 4
 
 _logger=logging.getLogger("theano.gof.cmodule")
 _logger.setLevel(logging.WARNING)