| msg105374 - (view) |
Author: Daniel Stutzbach (stutzbach)  |
Date: 2010-05-09 06:38 |
| Using a UCS2 Python on a platform with a 32-bit wchar_t, the following code throws an exception (but should not): >>> ctypes.c_wchar('\u10000') Traceback (most recent call last): File "", line 1, in TypeError: one character unicode string expected The trouble is in the u_set() function in Modules/_ctypes/cfield.c. The corresponding u_get() function looks correct. On a UCS4 Python running on a system with a 16-bit wchar_t, u_set() will corrupt the data by silently truncating the character to 16-bits. For reference, Linux and Mac OS use a 32-bit wchar_t while Windows uses a 16-bit wchar_t. |
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| msg105656 - (view) |
Author: STINNER Victor (vstinner) * |
Date: 2010-05-13 21:10 |
| Support of characters outside the Unicode BMP (code > 0xffff) is not complete in narrow build (sizeof(Py_UNICODE) == 2) for Python2: $ ./python Python 2.7b2+ (trunk:81139M, May 13 2010, 18:45:37) >>> x=u'\U00010000' >>> x[0], x[1] (u'\ud800', u'\udc00') >>> len(x) 2 >>> ord(x) Traceback (most recent call last): ... TypeError: ord() expected a character, but string of length 2 found >>> unichr(0x10000) Traceback (most recent call last): ... ValueError: unichr() arg not in range(0x10000) (narrow Python build) It looks better in Python3: $ ./python Python 3.2a0 (py3k:81137:81138, May 13 2010, 18:50:51) >>> x='\U00010000' >>> x[0], x[1] ('\ud800', '\udc00') >>> len(x) 2 >>> ord(x) 65536 >>> chr(0x10000) '\U00010000' About the issue, the problem is in function u_set(). This function should use PyUnicode_AsWideChar() but PyUnicode_AsWideChar() doesn't support surrogates... whereas PyUnicode_FromWideChar() does support surrogates. |
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| msg105670 - (view) |
Author: STINNER Victor (vstinner) * |
Date: 2010-05-13 23:56 |
| Patch for Python3: - Fix PyUnicode_AsWideChar() to support surrogates (Py_UNICODE: 2 bytes, wchar_t: 4 bytes) - u_set() of _ctypes uses PyUnicode_AsWideChar() - add a test (skipped if sizeof(wchar_t) is smaller than 4 bytes) It's too late to fix Python2: 2.7 beta 2 was released (it doesn't support non BMP characters for chr()/ord()). TODO: - I'm not sure that my patch on PyUnicode_AsWideChar() works if sizeof(wchar_t)==2 - Test the patch on Windows - Check that it doesn't break other functions calling PyUnicode_AsWideChar() ctypes, _locale.strcoll() and time.strftime() use PyUnicode_AsWideChar(). time has interesting comments: /* This assumes that PyUnicode_AsWideChar doesn't do any UTF-16 expansion. */ if (PyUnicode_AsWideChar((PyUnicodeObject*)format, (wchar_t*)PyBytes_AS_STRING(tmpfmt), PyUnicode_GetSize(format)+1) == (size_t)-1) /* This shouldn't fail. */ Py_FatalError("PyUnicode_AsWideChar failed"); |
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| msg117567 - (view) |
Author: STINNER Victor (vstinner) * |
Date: 2010-09-29 00:21 |
| #9979 proposes to create a new PyUnicode_AsWideCharString() function. |
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| msg117568 - (view) |
Author: Daniel Stutzbach (stutzbach) |
Date: 2010-09-29 00:27 |
| I know enough about Unicode to have reported this bug, but I don't feel knowledgeable enough about Python's Unicode implementation to comment on your suggested solution. I'm adding the other people listed in Misc/maintainers.rst as interested in Unicode to the nosy list on this issue and the one you just linked to. |
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| msg117787 - (view) |
Author: STINNER Victor (vstinner) * |
Date: 2010-10-01 11:53 |
| Update the patch for the new PyUnicode_AsWideCharString() function: - use Py_UNICODE_SIZE and SIZEOF_WCHAR_T in the preprocessor tests - faster loop: don't use a counter + pointer, but only use pointers (for the stop condition) The patch is not finished: I have to implement "#elif Py_UNICODE_SIZE == 4 && SIZEOF_WCHAR_T == 2" case. |
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| msg117789 - (view) |
Author: STINNER Victor (vstinner) * |
Date: 2010-10-01 12:24 |
| Patch version 3: - fix unicode_aswidechar if Py_UNICODE_SIZE == SIZEOF_WCHAR_T and w == NULL (return the number of characters, don't write into w!) - improve unicode_aswidechar() comment |
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| msg117790 - (view) |
Author: STINNER Victor (vstinner) * |
Date: 2010-10-01 12:28 |
| I don't know how to test "if Py_UNICODE_SIZE == 4 && SIZEOF_WCHAR_T == 2". On Windows, sizeof(wchar_t) is 2, but it looks like Python is not prepared to have Py_UNICODE != wchar_t for is Windows implementation. wchar_t is 32 bits long on Linux and Mac OS X. So how can I test it? Or should we just drop support of "Py_UNICODE_SIZE == 4 && SIZEOF_WCHAR_T == 2"? |
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| msg117791 - (view) |
Author: Daniel Stutzbach (stutzbach) |
Date: 2010-10-01 12:44 |
| I, too, can't think of any platforms where Py_UNICODE_SIZE == 4 && SIZEOF_WCHAR_T == 2 and I'm not sure what the previous policy has been. Have you noticed any other code that would set a precedent? If no one else chimes in, perhaps ask on IRC or python-dev? |
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| msg117792 - (view) |
Author: Marc-Andre Lemburg (lemburg) * |
Date: 2010-10-01 12:46 |
| STINNER Victor wrote: > > STINNER Victor <victor.stinner@haypocalc.com> added the comment: > > I don't know how to test "if Py_UNICODE_SIZE == 4 && SIZEOF_WCHAR_T == 2". On Windows, sizeof(wchar_t) is 2, but it looks like Python is not prepared to have Py_UNICODE != wchar_t for is Windows implementation. > > wchar_t is 32 bits long on Linux and Mac OS X. So how can I test it? Or should we just drop support of "Py_UNICODE_SIZE == 4 && SIZEOF_WCHAR_T == 2"? You can tweak the Windows pyconfig.h to use UCS4, AFAIK, if you want to test drive this case. But it's probably easier to configure with "gcc -fshort-wchar" on Linux :-) Dropping support for this is not a good idea. |
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| msg117795 - (view) |
Author: Daniel Stutzbach (stutzbach) |
Date: 2010-10-01 13:01 |
| > You can tweak the Windows pyconfig.h to use UCS4, AFAIK, if you want to > test drive this case. I seem to recall seeing some other code that assumed Windows implied UCS2. Proceed with caution. ;-) > But it's probably easier to configure with "gcc -fshort-wchar" on > Linux :-) libc will still be using sizeof(wchar_t) == 4, though. Won't that cause Bad Things to happen when calling libc wide-character functions? |
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| msg117796 - (view) |
Author: Marc-Andre Lemburg (lemburg) * |
Date: 2010-10-01 13:06 |
| Daniel Stutzbach wrote: > > Daniel Stutzbach <daniel@stutzbachenterprises.com> added the comment: > >> You can tweak the Windows pyconfig.h to use UCS4, AFAIK, if you want to >> test drive this case. > > I seem to recall seeing some other code that assumed Windows implied UCS2. Proceed with caution. ;-) Probably, yes. I've never tried it myself. >> But it's probably easier to configure with "gcc -fshort-wchar" on >> Linux :-) > > libc will still be using sizeof(wchar_t) == 4, though. Won't that cause Bad Things to happen when calling libc wide-character functions? Sure, but this is just about testing an interface, not running applications :-) Here's what the GCC man-page has to say: -fshort-wchar Override the underlying type for wchar_t to be short unsigned int instead of the default for the target. This option is useful for building programs to run under WINE. Warning: the -fshort-wchar switch causes GCC to generate code that is not binary compatible with code generated without that switch. Use it to conform to a non-default application binary interface. |
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| msg117845 - (view) |
Author: STINNER Victor (vstinner) * |
Date: 2010-10-01 22:56 |
| Patch version 4: - implement unicode_aswidechar() for 16 bits wchar_t and 32 bits Py_UNICODE - PyUnicode_AsWideWcharString() returns the number of wide characters excluding the nul character as does PyUnicode_AsWideChar() For 16 bits wchar_t and 32 bits Py_UNICODE, I extracted the "as wide char" unicode functions into a small C file and compiled it with -fshort-wchar on Linux. |
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| msg117848 - (view) |
Author: STINNER Victor (vstinner) * |
Date: 2010-10-01 23:02 |
| Ooops, I lost my patch to fix the initial (ctypes) issue. Here is an updated patch: ctypes_nonbmp.patch (which needs aswidechar_nonbmp-4.patch). |
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| msg117866 - (view) |
Author: STINNER Victor (vstinner) * |
Date: 2010-10-02 11:17 |
| r85172 changes PyUnicode_AsWideCharString() (don't count the trailing nul character in the output size) and add unit tests. r85173 patches unicode_aswidechar() to supports non-BMP characters for all known wchar_t/Py_UNICODE size combinaisons (2/2, 2/4 and 4/2). I noticed that PyUnicode_AsWideChar() and PyUnicode_AsWideCharString() accept embeded nul characters. I don't know if it is a bug or an expected behaviour. Anyway, there is now a test for this case. |
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| msg117868 - (view) |
Author: STINNER Victor (vstinner) * |
Date: 2010-10-02 11:55 |
| r85174+r85177: ctypes.c_wchar supports non-BMP characters with 32 bits wchar_t => fix this issue (I commited also an unwanted change on _testcapi to fix r85172 in r85174: r85175 reverts this change, and r85176 fixes the _testcapi bug again) |
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| msg117869 - (view) |
Author: STINNER Victor (vstinner) * |
Date: 2010-10-02 11:59 |
| > r85173 patches unicode_aswidechar() to supports non-BMP characters > for all known wchar_t/Py_UNICODE size combinaisons (2/2, 2/4 and 4/2). Oh, and 4/4 ;-) |
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| msg117872 - (view) |
Author: Daniel Stutzbach (stutzbach) |
Date: 2010-10-02 13:15 |
| Thanks for working on this! Since this was a bugfix, it should be merged back into 2.7, yes? |
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| msg117882 - (view) |
Author: STINNER Victor (vstinner) * |
Date: 2010-10-02 15:29 |
| > Since this was a bugfix, it should be merged back into 2.7, yes? Mmmh, the fix requires to change PyUnicode_AsWideChar() function (support non-BMP characters and surrogate pairs) (and maybe also to create PyUnicode_AsWideCharString()). I don't really want to change such important function in a stable branch (Python2). Is it really important to support non-BMP characters for ctypes.c_wchar in Python2? I would like to say: if you want better unicode support, use Python 3. And Python 3.2 if it's possible :-) |
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| msg117883 - (view) |
Author: Daniel Stutzbach (stutzbach) |
Date: 2010-10-02 15:33 |
| Since I noticed the bug through source code inspection and no one has reported it occurring in practice, that sounds reasonable to me. |
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