[issue6068] ctypes is not correctly handling bitfields backed by 64 bit integers on Windows
Meador Inge mead...@gmail.com added the comment: I am closing this issue in favor of issue6493. This patch attached to this issue is incorrect. The proposed definition of BIT_MASK allows for undefined behavior when the number of bits shifted is 64 for a uint64. The patch in issue6493 handles this case correctly. -- nosy: +meador.inge resolution: - duplicate stage: patch review - committed/rejected status: open - closed superseder: - Can not set value for structure members larger than 32 bits ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue6068 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue6068] ctypes is not correctly handling bitfields backed by 64 bit integers on Windows
Vlad Riscutia riscutiav...@gmail.com added the comment: Ping? This also fixes 6493 (I believe in a cleaner way) -- ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue6068 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue6068] ctypes is not correctly handling bitfields backed by 64 bit integers on Windows
Vlad Riscutia riscutiav...@gmail.com added the comment: Changing title and type to better reflect issue. On Windows MSVC build, ctypes is not correctly setting bitfields backed by 64 bit integers if specifying custom width. Simple repro: from ctypes import * class X(Structure): _fields_ = [(a, c_ulonglong, 16), (b, c_ulonglong, 32), (c, c_ulonglong, 16)] s = X() s.b = 1 print(s.b) # this prints 0 Whenever field width goes over 32 bits, setting or getting value of the field in cfield.c will only look at last (actual size - 32) bits of the field. So if we have a field of 34 bits, only least significant 2 bits will be operated on. The above repro results in an (actual size - 32) = 0 bits so nothing is getting set with the assignement. This is not caught in unit test package because we have only this in test_bitfields.py: def test_ulonglong(self): class X(Structure): _fields_ = [(a, c_ulonglong, 1), (b, c_ulonglong, 62), (c, c_ulonglong, 1)] self.assertEqual(sizeof(X), sizeof(c_longlong)) x = X() self.assertEqual((x.a, x.b, x.c), (0, 0, 0)) x.a, x.b, x.c = 7, 7, 7 self.assertEqual((x.a, x.b, x.c), (1, 7, 1)) For 62 bit width, we will actually operate on last 30 bits but this test passes as 7 fits in those bits. If we would actually try to set it to 0x3FFF, result will be different than expected (0x3FFF). I will look into extending UT package with some tests that set full range of bits and check if they are actually being set correctly. This issue reproes with latest bits but only on Windows. Root cause seems to be BIT_MASK macro in cfield.c which is ifdef-ed to something different on Windows. I patched on my machine by removing the special treatment: @@ -429,12 +429,7 @@ #define LOW_BIT(x) ((x) 0x) #define NUM_BITS(x) ((x) 16) -/* This seems nore a compiler issue than a Windows/non-Windows one */ -#ifdef MS_WIN32 -# define BIT_MASK(size) ((1 NUM_BITS(size))-1) -#else -# define BIT_MASK(size) ((1LL NUM_BITS(size))-1) -#endif +#define BIT_MASK(size) ((1LL NUM_BITS(size))-1) /* This macro CHANGES the first parameter IN PLACE. For proper sign handling, we must first shift left, then right. Unittests still pass with this in place and now fields are handled correctly though I don't know why this was put in in the first place. Looking at file history it seems it was there from the start (from 2006). Could it be that it was addressing some MSVC bug which got fixed in the meantime? Things seem to be building and working fine now when using 1LL for shift. Also related to this I have doubts about the SWAP_8 macro which is similarly changed for MSVC, also in cfield.c. I am only able to build 32 bit version so I can't say whether this was put in place due to some x64 issue, maybe someone can check behavior on x64 build. If that's the case, maybe #ifdef should take that into account. -- nosy: +vladris title: support read/write c_ulonglong type bitfield structures - ctypes is not correctly handling bitfields backed by 64 bit integers on Windows type: feature request - behavior versions: +Python 3.3 -Python 3.2 ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue6068 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue6068] ctypes is not correctly handling bitfields backed by 64 bit integers on Windows
Terry J. Reedy tjre...@udel.edu added the comment: Vlad, thanks for delving into this. Your two header changes are contradictory. If this is a feature request, then it is 3.3 only. If this is a behavior (bug) issue, then 3.2 should be included ;-). 'higstar's second comment indicates 'feature', but I am not sure what 'integer field means in this context'. I am guessing that UT = 'unittest' Higstar, I see buried in your 3rd message the reference to Windows and 2.6. Please specify OS and version in initial messages. -- ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue6068 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue6068] ctypes is not correctly handling bitfields backed by 64 bit integers on Windows
Vlad Riscutia riscutiav...@gmail.com added the comment: Terry, I am kind of new to this so I might not have marked header correctly. Please feel free to fix it. This is 100% bug not feature request. Initial message was confusing because highstar thought Python has such bitfields as readonly and was asking for a feature to make them read-write. That is not the case, behavior is caused by a bug. By UT I mean unittest. I reproed this on 64bit Windows 7 on latest sources with x32 build (as I said, I don't have x64 build). -- ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue6068 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue6068] ctypes is not correctly handling bitfields backed by 64 bit integers on Windows
Changes by Terry J. Reedy tjre...@udel.edu: -- versions: +Python 2.7, Python 3.2 ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue6068 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue6068] ctypes is not correctly handling bitfields backed by 64 bit integers on Windows
Vlad Riscutia riscutiav...@gmail.com added the comment: Attached is addition to unittests which repro the issue. They will currently pass on Linux but fail on Windows. -- keywords: +patch Added file: http://bugs.python.org/file22447/issue6068_unittest.diff ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue6068 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue6068] ctypes is not correctly handling bitfields backed by 64 bit integers on Windows
higstar adr...@higstar.com added the comment: Issue was originally found on do sp2 on Python 2.6. Thanks Vlad, this rendered ctypes useless for my purposes, had to mask and shift myself. On Jun 25, 2011 8:32 AM, Vlad Riscutia rep...@bugs.python.org wrote: Vlad Riscutia riscutiav...@gmail.com added the comment: Attached is addition to unittests which repro the issue. They will currently pass on Linux but fail on Windows. -- keywords: +patch Added file: http://bugs.python.org/file22447/issue6068_unittest.diff ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue6068 ___ -- Added file: http://bugs.python.org/file22448/unnamed ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue6068 ___pIssue was originally found on do sp2 on Python 2.6.br Thanks Vlad, this rendered ctypes useless for my purposes, had to mask and shift myself./p div class=gmail_quoteOn Jun 25, 2011 8:32 AM, quot;Vlad Riscutiaquot; lt;a href=mailto:rep...@bugs.python.org;rep...@bugs.python.org/agt; wrote:br type=attributiongt; brgt; Vlad Riscutia lt;a href=mailto:riscutiav...@gmail.com;riscutiav...@gmail.com/agt; added the comment:br gt; brgt; Attached is addition to unittests which repro the issue. They will currently pass on Linux but fail on Windows.brgt; brgt; --brgt; keywords: +patchbrgt; Added file: a href=http://bugs.python.org/file22447/issue6068_unittest.diff;http://bugs.python.org/file22447/issue6068_unittest.diff/abr gt; brgt; ___brgt; Python tracker lt;a href=mailto:rep...@bugs.python.org;rep...@bugs.python.org/agt;brgt; lt;a href=http://bugs.python.org/issue6068;http://bugs.python.org/issue6068/agt;br gt; ___br/div ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue6068] ctypes is not correctly handling bitfields backed by 64 bit integers on Windows
Changes by Santoso Wijaya santoso.wij...@gmail.com: -- nosy: +santa4nt ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue6068 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue6068] ctypes is not correctly handling bitfields backed by 64 bit integers on Windows
Santoso Wijaya santoso.wij...@gmail.com added the comment: FWIW, I tested the patch on a 64-bit Python build and test_ctypes passes with the new unittest added. -- ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue6068 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue6068] ctypes is not correctly handling bitfields backed by 64 bit integers on Windows
R. David Murray rdmur...@bitdance.com added the comment: Adding our windows committers to nosy to see if this can be committed. -- nosy: +brian.curtin, r.david.murray, tim.golden stage: needs patch - patch review ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue6068 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue6068] ctypes is not correctly handling bitfields backed by 64 bit integers on Windows
Vlad Riscutia riscutiav...@gmail.com added the comment: Attaching patch as previous attachment is only unittest. I included change to SWAP_8 macro also as it looks like same issue and it will probably popup later. -- Added file: http://bugs.python.org/file22451/issue6068_patch.diff ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue6068 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
