On 04/08/2016 10:58, Martin Panter wrote:
> Martin Panter added the comment:
>
> Okay, so to be clear, I am assuming XLC supports all of the following fields, and uses unsigned bit fields by default:
>
> struct UNSIGNED_BITS {
>      unsigned int AU: 1;
>      int A: 1; /* Equivalent to unsigned int */
>      signed int AS: 1;
>      unsigned short MU: 1;
>      short M: 1; /* Equivalent to unsigned short; triggers warning */
> };
>
> and that it cannot compile the following:
>
> struct SIGNED_BITS {
>      signed short MS: 1; /* Not supported */
> };
>
> Attached is what I think a patch to resolve this would look like. However it needs a line in Modules/_ctypes/_ctypes_test.c completed to detect the compiler:
>
> #ifndef /* Something to identify XLC */
>
> Can you figure out a way to test for XLC (but not GCC, which the AIX buildbot uses),

I'll figure this out. HOWEVER, Just want to mention that both parts of 
C_Test are failing when using xlc (i.e., on "A" and "M"). Note line 40 
and 51.

(Have not done the compiler detect part yet, so it still returns 
something != 999)

    +33  class C_Test(unittest.TestCase):
    +34
    +35      def test_ints(self):
    +36          for i in range(512):
    +37              for name in "ABCDEFGHI":
    +38                  b = BITS()
    +39                  setattr(b, name, i)
    +40                  self.assertEqual(getattr(b, name), 
func(byref(b), name.encode('ascii')))
    +41
    +42      def test_shorts(self):
    +43          b = BITS()
    +44          name = "M"
    +45          if func(byref(b), name.encode('ascii')) == 999:
    +46              self.skipTest("Compiler does not support signed 
short bitfields")
    +47          for i in range(256):
    +48              for name in "MNOPQRS":
    +49                  b = BITS()
    +50                  setattr(b, name, i)
    +51                  self.assertEqual(getattr(b, name), 
func(byref(b), name.encode('ascii')))
    +52

======================================================================
FAIL: test_ints (ctypes.test.test_bitfields.C_Test)
----------------------------------------------------------------------
Traceback (most recent call last):
   File 
"/data/prj/python/git/xlc-python3-3.7/Lib/ctypes/test/test_bitfields.py", 
line 40, in test_ints
     self.assertEqual(getattr(b, name), func(byref(b), 
name.encode('ascii')))
AssertionError: -1 != 1

======================================================================
FAIL: test_shorts (ctypes.test.test_bitfields.C_Test)
----------------------------------------------------------------------
Traceback (most recent call last):
   File 
"/data/prj/python/git/xlc-python3-3.7/Lib/ctypes/test/test_bitfields.py", 
line 51, in test_shorts
     self.assertEqual(getattr(b, name), func(byref(b), 
name.encode('ascii')))
AssertionError: -1 != 1

----------------------------------------------------------------------

> and then try my patch out? Hopefully you see no more compiler warnings, test_ints() should now pass,
again - not done the changes to _ctypes_test.c yet - so maybe the 
test_ints() will pass after that.
>   and test_shorts() should be skipped.
>
> ----------
> keywords: +patch
> Added file: http://bugs.python.org/file44005/disable-signed-short.patch
>
> _______________________________________
> Python tracker <report@bugs.python.org>
> <http://bugs.python.org/issue27643>
> _______________________________________