[Cython] Cython 0.17 beta 3 released - release candidate

[Stefan Behnel]

Stefan Behnel, 26.08.2012 11:36:
> Christoph Gohlke, 26.08.2012 10:03:
>> On 8/25/2012 6:51 AM, Stefan Behnel wrote:
>>> Christoph Gohlke, 25.08.2012 04:07:
>>>> On 8/24/2012 12:43 PM, Stefan Behnel wrote:
>>>>> Christoph Gohlke, 24.08.2012 07:20:
>>>>>> On 64 bit Python 2.7 and 3.2 with msvc9 compiler, python.exe crashes
>>>>>> during
>>>>>> `test_slice_assignment (memslice.__test__)`. I tested two computers. The
>>>>>> Windows executive can not identify in which specific module it
>>>>>> crashes, and
>>>>>> neither enabling faulthandler nor building with debug symbols gives any
>>>>>> useful information. Can anyone reproduce this? It seems compiler specific
>>>>>> since Python 3.3, which is using msvc10, does not crash.
>>>>>
>>>>> Hmm, yes, sounds like a problem with the compiler. Would be good to get
>>>>> this sorted out, but it's almost impossible to debug something like this
>>>>> from a distance.
>>>>
>>>> Maybe the following simple example is related. It fails (not crash) when
>>>> compiled with 64 bit msvc9, but does work with 32 bit msvc9 and msvc10 (32
>>>> and 64 bit):
>>>>
>>>> ```
>>>> from cython.view cimport array as cvarray
>>>> import numpy as np
>>>>
>>>> narr = np.arange(8 * 14 * 11).reshape((8, 14, 11))
>>>>
>>>> cdef int[:, :, ::1] a = narr
>>>> cdef int[:, :, :] b = a[2:8:2, -4:1:-1, 1:3]
>>>>
>>>> print narr[2:8:2, -4:1:-1, 1:3].shape
>>>> print b.shape[0], b.shape[1], b.shape[2]
>>>> ```
>>>>
>>>> On win-amd64-py2.x the shape of b is (3, 9, 3) but it should be (3, 9, 2)
>>>
>>> I'll leave that for the others to comment.
>>
>> This failure and the test crash disappear when auto-inlining is disabled,
>> e.g. using the `/Ob1` compiler switch
>> <http://msdn.microsoft.com/en-us/library/47238hez%28v=vs.100%29.aspx>
> 
> Thanks for figuring that out.
> 
> 
>> Is there a way to add a C pre-processor `#pragma` to a Cython generated C
>> file?
> 
> I don't think so, not in arbitrary places.
> 
> 
>> I tried `cdef void emit_pragma '#pragma auto_inline(off) //' ()` but
>> the pragma ends up inside the Python module init function, which fails to
>> compile with `error C2156: pragma must be outside function`.
> 
> As a quick fix, we could wrap (or just start) our utility code section with
> that pragma. It starts after all user code. According to the docs, the
> pragma only disables automatic inlining in the specific range, not
> explicitly requested inlining.
> 
> http://msdn.microsoft.com/en-us/library/ah08w5c3%28v=vs.71%29.aspx
> 
> We usually know what we consider worth inlining and what doesn't need to
> be. If we can find out what exact functions trigger this, we can start
> being more specific about where to enable the pragma, but I think it's ok
> to enable it on all utility code for now.
> 
> Could you figure out a suitable preprocessor guard that only enables it for
> the affected compilers?

A patch would essentially look like this:

diff -r 18fed0dec20e Cython/Compiler/Code.py
--- a/Cython/Compiler/Code.py   Sun Aug 26 00:54:01 2012 +0200
+++ b/Cython/Compiler/Code.py   Sun Aug 26 11:39:29 2012 +0200
@@ -893,6 +893,8 @@
             code.write('\n#line 1 "cython_utility"\n')
         code.putln("")
         code.putln("/* Runtime support code */")
+        code.putln("#pragma auto_inline(off)")
+        code.putln("")

     def finalize_main_c_code(self):
         self.close_global_decls()

Stefan